QT20.241, QT20.241-C1
24V, 20A, THREE PHASE INPUT

Q-Series

POWER SUPPLY
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3AC 380-480V Wide-range Input
Also Specified for 2-Phase Operation
Extra Long Lifetime
95% Full Load and Excellent Partial Load Efficiencies
Width only 65mm, Weight only 870g
50% BonusPower®, 720W for up to 4s
Active Power Factor Correction PFC
Active Filtering of Input Transients
Full Power Between -25°C and +60°C
Extremely Low Input Inrush Current Surge
DC-OK Relay Contact
Quick-connect Spring-clamp Terminals
3 Year Warranty

GENERAL DESCRIPTIONSHORT-FORM DATA

The most outstanding features of the DIMENSION QSeries DIN-rail power supplies are the extremely highefficiencies and the compact sizes which are achieved bya synchronous rectification and other unique design
details.

Output voltage
Adjustment range
Output current

Large power reserves of 150% support the starting ofheavy loads such as DC-motors or capacitive loads. In
many cases this allows the use of a unit from a lower
wattage class which saves space and money.
High immunity to transients and power surges as well as
low electromagnetic emission makes usage in nearly
every environment possible.
The integrated output power manager and virtually no
input inrush current make installation and usage simple
with no jumper and switches necessary. Diagnostics areeasy due to the DC-ok relay, a green DC-OK LED and thered overload LED.
Unique quick-connect spring-clamp terminals allow asafe and fast installation and a large international
approval package for a variety of applications makes
this unit suitable for nearly every application.

ORDER NUMBERS

DC 24V24 - 28V
20 – 17.5A
30 – 26A
Output power
480W
720W
Output ripple< 100mVpp
Input voltage
3AC 380-480V
Mains frequency
50-60HzAC Input current
0.79 / 0.65A
Power factor
0.94 / 0.95
AC Inrush current
3A peak
Efficiency
95.0 / 94.8%
Losses25.3 / 26.4W
Temperature range -25°C to +70°C
Derating
12W/°C
Hold-up time
22 / 22ms
Dimensions
65x124x127mm
Weight870g / 1.92lb

IND. CONT. EQ.

UL 508ZM1.WALL
ZM14.SIDE
UF20.241
YR40.241

continuous
short term (4s)continuous
short term (4s)20Hz to 20MHz±15%±6%
at 3x400 / 480Vac
at 3x400 / 480Vac
at 3x400 / 480Vac
at 3x400 / 480Vac
operational+60 to +70°C
at 3x400 / 480Vac
WxHxD

MARKINGSPower Supply QT20.241
24-28V Standard unit
QT20.241-C1 24-28V Unit with conformal
coated pc board
Accessory

nominalWall mount bracket
Side mount bracket
Buffer unit
Redundancy module

UL 60950-1

MarineApr. 2017 / Rev. 2.1 DS-QT20.241-EN
All parameters are typical values specified at 24V, 20A, 3x 400Vac, 50Hz, symmetrical mains voltages, 25°C ambient and aftera 5 minutes run-in time unless otherwise noted.
www.pulspower.com Phone +49 89 9278 0Germany

Class I Div 2

EMC, LVD

1/27

QT20.241, QT20.241-C1
24V, 20A, THREE PHASE INPUT

Q-Series

INDEX
Page
1. Intended Use .......................................................3
2. Installation Requirements...................................3
3. AC-Input...............................................................4
4. Input Inrush Current ...........................................5
5. DC-Input...............................................................5
6. Output .................................................................6
7. Hold-up Time.......................................................8
8. DC-OK Relay Contact ..........................................8
9. Efficiency and Power Losses................................910. Lifetime Expectancy and MTBF.........................10
11. Functional Diagram...........................................10
12. Terminals and Wiring........................................11
13. Front Side and User Elements...........................12
14. EMC....................................................................13
15. Environment ......................................................14
16. Protection Features ...........................................15
17. Safety Features ..................................................15
18. Dielectric Strength ............................................16
19. Approvals...........................................................16
20. Physical Dimensions and Weight......................17Page
21. Accessories ........................................................ 18
21.1. ZM1.WALL – Wall/Panel mounting..........18
21.2. ZM14.SIDE - Side Mounting Bracket........19
21.3. UF20.241 - Buffer module ........................20
21.4. YR40.241 - Redundancy Module..............20
22. Application Notes............................................. 21
22.1. Repetitive Pulse Loading..........................2122.2. Peak Current Capability ...........................22
22.3. External Input Protection.........................2222.4. Using only 2 Legs of a 3-Phase System ....23
22.5. Charging of Batteries ...............................23
22.6. Output Circuit Breakers............................24
22.7. Series Operation .......................................24
22.8. Parallel Use to Increase Output Power....25
22.9. Parallel Use for Redundancy ....................25
22.10. Inductive and Capacitive Loads................25
22.11. Back-feeding Loads ..................................26
22.12. Use in a Tightly Sealed Enclosure ............26
22.13. Mounting Orientations ............................27

The information given in this document is correct to the best of our knowledge and experience at the time of publication. If not
expressly agreed otherwise, this information does not represent a warranty in the legal sense of the word. As the state of ourknowledge and experience is constantly changing, the information in this data sheet is subject to revision. We therefore kindly ask
you to always use the latest issue of this document (available under www.pulspower.com). No part of this document may be
reproduced or utilized in any form without our prior permission in writing.
Some parts of this unit are patent by PULS (US patent No 091662,063, Des. 424,529, …).

TERMINOLOGY AND ABREVIATIONSPE andsymbolPE is the abbreviation for Protective Earth and has the same meaning as the symbol.

Earth, Ground

This document uses the term “earth” which is the same as the U.S. term “ground”.

T.B.D.

To be defined, value or description will follow later.

AC 400V

A figure displayed with the AC or DC before the value represents a nominal voltage withstandard tolerances included.
E.g.: DC 12V describes a 12V battery disregarding whether it is full (13.7V) or flat (10V)

400VacA figure with the unit (Vac) at the end is a momentary figure without any additional
tolerances included.

50Hz vs. 60Hz

As long as not otherwise stated, AC 230V parameters are valid at 50Hz mains frequency.

may

A key word indicating flexibility of choice with no implied preference.

shall

A key word indicating a mandatory requirement.

shouldA key word indicating flexibility of choice with a strongly preferred implementation.

Apr. 2017 / Rev. 2.1 DS-QT20.241-EN
All parameters are typical values specified at 24V, 20A, 3x 400Vac, 50Hz, symmetrical mains voltages, 25°C ambient and aftera 5 minutes run-in time unless otherwise noted.
www.pulspower.com Phone +49 89 9278 0Germany

2/27

QT20.241, QT20.241-C1
24V, 20A, THREE PHASE INPUT

Q-Series

1. INTENDED USEThis device is designed for installation in an enclosure and is intended for the general professional use such as inindustrial control, office, communication, and instrumentation equipment.
Do not use this power supply in equipment, where malfunction may cause severe personal injury or threaten humanlife.

2. INSTALLATION REQUIREMENTS
This device may only be installed and put into operation by qualified personnel.
This device does not contain serviceable parts.
The tripping of an internal fuse is caused by an internal defect.
If damage or malfunction should occur during installation or operation, immediately turn power off and send unit to
the factory for inspection.
Mount the unit on a DIN-rail so that the input terminals are located on the bottom of the unit. For other mounting
orientations see de-rating requirements in this document. See chapter 22.13.
This device is designed for convection cooling and does not require an external fan. Do not obstruct airflow and do
not cover ventilation grid (e.g. cable conduits) by more than 15%!
Keep the following installation clearances:
40mm on top,
20mm on the bottom,
5mm on the left and right sides are recommended when the device is loaded permanently with more than 50% of the
rated power. Increase this clearance to 15mm in case the adjacent device is a heat source (e.g. another power supply).
Caution: For use in a controlled environment according to CSA 22.2 No 107.1-01.

WARNING

Risk of electrical shock, fire, personal injury or death.

- Do not use the power supply without proper grounding (Protective Earth). Use the terminal on the input block forearth connection and not one of the screws on the housing.
- Turn power off before working on the device. Protect against inadvertent re-powering.
- Make sure that the wiring is correct by following all local and national codes.
- Do not modify or repair the unit.
- Do not open the unit as high voltages are present inside.
- Use caution to prevent any foreign objects from entering the housing.
- Do not use in wet locations or in areas where moisture or condensation can be expected.
- Do not touch during power-on, and immediately after power-off. Hot surfaces may cause burns.
Notes for use in hazardous location areas:
The QT20.241 is suitable for use in Class I Division 2 Groups A, B, C, D locations.
WARNING EXPLOSION HAZARDS!
Substitution of components may impair suitability for this environment. Do not disconnect the unit or operate thevoltage adjustment unless power has been switched off or the area is known to be non-hazardous.
A suitable enclosure must be provided for the end product which has a minimum protection of IP54 and fulfils therequirements of the EN 60079-15:2010.

Apr. 2017 / Rev. 2.1 DS-QT20.241-EN
All parameters are typical values specified at 24V, 20A, 3x 400Vac, 50Hz, symmetrical mains voltages, 25°C ambient and aftera 5 minutes run-in time unless otherwise noted.
www.pulspower.com Phone +49 89 9278 0Germany

3/27

QT20.241, QT20.241-C1
24V, 20A, THREE PHASE INPUT

Q-Series

3. AC-INPUTThe unit is optimized to operate on a three phase system. An operation on only two legs of a three-phase system ispossible with slightly different parameters. See chapter 22.4 for details.
AC input
AC input range
Suitable mains systems
Allowed voltage L to Earth
Input frequency
Turn-on voltage
Shut-down voltage

max.
nom.
typ.
typ.

3AC 380-480V
3x 323-552Vac
TN, TT, IT
400Vac50–60Hz3x 263Vac
3x 242Vac

Input current
Power factor*)
Start-up delay
Rise time

typ.
typ.
typ.
typ.
typ.

3AC 400V
0.79A
0.94
350ms
30ms
40ms

3AC 480V
0.65A
0.95
290ms
30ms
40ms

Turn-on overshoot

max.

500mV

500mV

Wide-range input
Continuous operation
Line (L) must not be earthed (grounded)
Continuous, IEC 60664-1±6%
Steady-state value, load independent, see Fig. 3-1
Steady-state value, load independent, see Fig. 3-1

At 24V, 20A, see Fig. 3-3
At 24V, 20A, see Fig. 3-4
See Fig. 3-2
At 24V, 20A, only resistive load see Fig. 3-2
At 24V, 20A, resistive load with anadditional 20mF capacitor
See Fig. 3-2

The power factor is the ratio of the true (or real) power to the apparent power in an AC circuit.

Fig. 3-1 Input voltage range

POUT

Fig. 3-2 Turn-on behavior, definitions

Input
Voltage

Rated input range

Turn-onShut-down

L1 L2 L3

- 5%

OutputVoltage

VIN
242V 263V

323V

Start-up
delay

552VacFig. 3-3 Input current vs. output load at 24V

Fig. 3-4 Power factor vs. output load at 24V

Input Current, typ.

0.8A
0.7
0.6
0.5
0.4
0.3
0.2
0.1

c
Va
00
4
c
3x 80Va43x1.0Power Factor, typ.

3x
480Vac

0.95
0.9
0.85

3x
400Vac0.8
Output Current

0
2

4

6

Rise
Time

8 10 12 14 16 18 20A

Overshoot

*)

nom.
min.

Output Current

0.75
2

4

6

8 10 12 14 16 18 20A

Apr. 2017 / Rev. 2.1 DS-QT20.241-EN
All parameters are typical values specified at 24V, 20A, 3x 400Vac, 50Hz, symmetrical mains voltages, 25°C ambient and aftera 5 minutes run-in time unless otherwise noted.
www.pulspower.com Phone +49 89 9278 0Germany

4/27

QT20.241, QT20.241-C1
24V, 20A, THREE PHASE INPUT

Q-Series

4. INPUT INRUSH CURRENT
The power supply is equipped with an active inrush current limitation circuit, which limits the input inrush current
after turn-on and after short input voltage interruptions to a very low value.

Inrush current*)
Inrush energy
Inrush delay
*)

max.
typ.
max.
typ.

3AC 400V
10Apeak
3Apeak
1A2s
270ms

3AC 480V
10Apeak
3Apeak
1A2s
220ms

Over entire temperature range
Over entire temperature range
Over entire temperature range

The charging current into EMI suppression capacitors is disregarded in the first microseconds after switch-on.

Fig. 4-1 Typical turn-on behavior at nominal
load and 25°C ambient temperature
Input Current 2A/DIV

InrushDelay
Input Voltage 1000V/DIV

Output Voltage

5. DC-INPUT
Do not operate this power supply with DC-input voltage.
Investigate using the QTD20.241 instead for DC-input voltages.

Apr. 2017 / Rev. 2.1 DS-QT20.241-EN
All parameters are typical values specified at 24V, 20A, 3x 400Vac, 50Hz, symmetrical mains voltages, 25°C ambient and aftera 5 minutes run-in time unless otherwise noted.
www.pulspower.com Phone +49 89 9278 0Germany

5/27

QT20.241, QT20.241-C1
24V, 20A, THREE PHASE INPUT

Q-Series

6. OUTPUT
Output voltage
Adjustment range
Factory settingLine regulation
Load regulation
Ripple and noise voltage
Output current – continuous
Output current – up to 4s*)
Output power – continuous
Output power – up to 4s*)
BonusPower® time
BonusPower® recovery time
Overload behavior
Short-circuit current**)

Output capacitance
*)

**)
***)

nom.
min.
max.
typ.
max.
max.
max.
nom.
nom.
nom.
nom.
nom.
nom.
typ.
typ.

24V
24-28V
30V***)
24.1V
10mV
100mV
100mVpp
20A
17.5A
30A
26A
480W
720W*)
4s
7s

min.
max.
min.
max.
max.
typ.

cont. current
20A
23A
30A
34A
25A
950μF

Guaranteed
At clockwise end position of potentiometer±0.2%, at full load, cold unit
At 3x 323-552Vac voltage change
Static value, 0AÆ20A
20Hz to 20MHz, 50Ohm
At 24V, see Fig. 6-1
At 28V, see Fig. 6-1
At 24V, see Fig. 6-1 and Fig. 6-2
At 28V, see Fig. 6-1 and Fig. 6-2
At 24-28V
At 24-28V
Duration until the output voltage dips, see Fig. 6-2
Overload free time to reset power manager, see Fig.
6-3
See Fig. 6-1
Continuous, load impedance 50mOhm, see Fig. 6-1
Continuous, load impedance 50mOhm, see Fig. 6-1
Short-term (4s), load impedance 50mOhm, see Fig. 6-1
Short-term (4s), load impedance 50mOhm, see Fig. 6-1
Continuous, load impedance <10mOhm
Included in the power supply

BonusPower®, short term power capability (up to typ. 4s)
The power supply is designed to support loads with a higher short-term power requirement without damage or shutdown. The shortterm duration is hardware controlled by an output power manager. This BonusPower® is repeatedly available. Detailed information
can be found in chapter 22.1. If the power supply is loaded longer with the BonusPower® than shown in the bonus-time diagram (seeFig. 6-2), the max. output power is automatically reduced to 480W.
Discharge current of output capacitors is not included.
This is the maximum output voltage which can occur at the clockwise end position of the potentiometer due to tolerances. It is notguaranteed value which can be achieved. The typical value is about 28.5V.

Apr. 2017 / Rev. 2.1 DS-QT20.241-EN
All parameters are typical values specified at 24V, 20A, 3x 400Vac, 50Hz, symmetrical mains voltages, 25°C ambient and aftera 5 minutes run-in time unless otherwise noted.
www.pulspower.com Phone +49 89 9278 0Germany

6/27

QT20.241, QT20.241-C1
24V, 20A, THREE PHASE INPUT

Q-Series

Fig. 6-1 Output voltage vs. output current, typ.
Output Voltage

28V

Adjustment Range

A

B

24
20
16

A Continuously

12

B Short-term (4s)available

A

B

BonusPower840

Output Current

0

5

10

15

20

25

30

35A

Fig. 6-2 Bonus time vs. output power

Fig. 6-3 BonusPower® recovery time

Bonus Time

5s

max.

4

100%

min.

3

t

2
OutputVoltage10110Limitation by
Power Manager

Power
DemandRecovery Time
Bonus Power disabled

Bonus
Time

Output Power

120

130

140

t

150

160%

The BonusPower® is available as soon as power comes on and after the end of an output short circuit or output
overload.
Fig. 6-4 BonusPower® after input turn-on

Fig. 6-5 BonusPower® after output short

Short ofOutput

Input
Voltage

OutputVoltage
OutputVoltage150%
Output
Power

100%

Bonus
Power

Output
Power

150%

Bonus
Power

100%

Apr. 2017 / Rev. 2.1 DS-QT20.241-EN
All parameters are typical values specified at 24V, 20A, 3x 400Vac, 50Hz, symmetrical mains voltages, 25°C ambient and aftera 5 minutes run-in time unless otherwise noted.
www.pulspower.com Phone +49 89 9278 0Germany

7/27

QT20.241, QT20.241-C1
24V, 20A, THREE PHASE INPUT

Q-Series

7. HOLD-UP TIME
Hold-up Time3AC 400V
44ms
36ms
22ms
18ms

typ.
min.
typ.
min.

Fig. 7-1 Hold-up time vs. input voltage

3AC 480V
44ms
36ms
22ms
18ms

At 24V, 10A, see Fig. 7-1
At 24V, 10A, see Fig. 7-1
At 24V, 20A, see Fig. 7-1
At 24V, 20A, see Fig. 7-1

Fig. 7-2 Shut-down behavior, definitions

Hold-up Time

50ms

L1 L2 L3

24V, 10A, typ.

40

24V, 10A, min.

Input
Voltage30
24V, 20A, typ.

20

24V, 20A, min.

10

Hold-up Time

Input Voltage

0
320

360

400

- 5%

OutputVoltage4403x480Vac

8. DC-OK RELAY CONTACT
This feature monitors the output voltage, which is produced by the power supply itself. It is independent of a back-fed
voltage from a unit connected in parallel to the power supply output.
Contact closes
Contact opens

As soon as the output voltage reaches the adjusted output voltage.
As soon as the output voltage dips more than 10% below the adjusted output voltage.
Short dips will be extended to a signal length of 250ms. Dips shorter than 1ms will be ignored.
As soon as the output voltage exceeds 90% of the adjusted voltage.
max.
60Vdc 0.3A, 30Vdc 1A, 30Vac 0.5A
Resistive loadmin.
1mA at 5Vdc
Min. permissible load
See dielectric strength table in section 18.

Contact re-closes
Contact ratings
Isolation voltage

Fig. 8-1 DC-ok relay contact behavior
VOUT = VADJ
10%

<
1ms

open

closed>1ms

0.9* VADJ

250ms

open

closedApr. 2017 / Rev. 2.1 DS-QT20.241-EN
All parameters are typical values specified at 24V, 20A, 3x 400Vac, 50Hz, symmetrical mains voltages, 25°C ambient and aftera 5 minutes run-in time unless otherwise noted.
www.pulspower.com Phone +49 89 9278 0Germany

8/27

QT20.241, QT20.241-C1
24V, 20A, THREE PHASE INPUT

Q-Series

9. EFFICIENCY AND POWER LOSSES
Efficiency
Average efficiency*)

typ.
typ.

3AC 400V
95.0%
94.2%

Power losses

typ.
typ.
typ.

8.2W
14.5W
25.3W

*)

3AC 480V
94.8%
93.6%
10.0W
16.0W
26.4W

At 24V, 20A
25% at 5A, 25% at 10A, 25% at 15A and
25% at 20A
At 24V, 0A (no load)
At 24V, 10A (half load)
At 24V, 20A (full load)

The average efficiency is an assumption for a typical application where the power supply is loaded with 25% of the nominal load for 25%of the time, 50% of the nominal load for another 25% of the time, 75% of the nominal load for another 25% of the time and with 100%of the nominal load for the rest of the time.

Fig. 9-1 Efficiency vs. output current at 24V,
typ.

Fig. 9-2 Losses vs. output current at 24V, typ.

Efficiency

Power Losses

96%
95
94
93
92
91
90
89
88

30W
25
20
(a) 3x 400Vac(b) 3x 480Vac

(a)

15

(a) 3x 400Vac(b) 3x 480Vac

(b)
(a)

10

(b)

5
Output Current

4

6

8

10

12

14

16

Output Current0
18 20A

Fig. 9-3 Efficiency vs. input voltage at 24V,
20A, typ.
Efficiency

0

2

4

6

8 10 12 14 16 18 20A

Fig. 9-4 Losses vs. input voltage at 24V, 20A,
typ.
Power Losses

95.4%

27W

95.2

26.5

95.0

26.0

94.8

25.5

94.6

25.0

94.4

24.5
Input Voltage

94.2
350

400

450

Input Voltage

24.0

500 3x550Vac

350

400

450

500 3x550Vac

Apr. 2017 / Rev. 2.1 DS-QT20.241-EN
All parameters are typical values specified at 24V, 20A, 3x 400Vac, 50Hz, symmetrical mains voltages, 25°C ambient and aftera 5 minutes run-in time unless otherwise noted.
www.pulspower.com Phone +49 89 9278 0Germany

9/27

QT20.241, QT20.241-C1
24V, 20A, THREE PHASE INPUT

Q-Series

10. LIFETIME EXPECTANCY AND MTBF
Calculated lifetime expectancy*)

MTBF**) SN 29500, IEC 61709
MTBF**) MIL HDBK 217F

3AC 400V
495 000h *)175 000h *)297 000h *)105 000h
1 194 000h
690 000h
389 000h
284 000h

3AC 480V
485 000h *)171 000h *)299 000h *)106 000h
1 159 000h
670 000h
371 000h
271 000h

At 24V, 10A and 25°C
At 24V, 10A and 40°C
At 24V, 20A and 25°C
At 24V, 20A and 40°C
At 24V, 20A and 25°C
At 24V, 20A and 40°C
At 24V, 20A and 25°C; Ground Benign GB25
At 24V, 20A and 40°C; Ground Benign GB40*)

The calculated lifetime expectancy shown in the table indicates the minimum operating hours (service life) and is determined by the
lifetime expectancy of the built-in electrolytic capacitors. Lifetime expectancy is specified in operational hours and is calculated according
to the capacitor’s manufacturer specification. The manufacturer of the electrolytic capacitors only guarantees a maximum life of up to 15
years (131 400h). Any number exceeding this value is a calculated theoretical lifetime which can be used to compare devices.
**) MTBF stands for Mean Time Between Failure, which is calculated according to statistical device failures, and indicates reliability of adevice. It is the statistical representation of the likelihood of a unit to fail and does not necessarily represent the life of a product.
The MTBF figure is a statistical representation of the likelihood of a device to fail. A MTBF figure of e.g. 1 000 000h means thatstatistically one unit will fail every 100 hours if 10 000 units are installed in the field. However, it can not be determined if the failed unit
has been running for 50 000h or only for 100h.

11. FUNCTIONAL DIAGRAM
Fig. 11-1 Functional diagram

L1
L2
L3

OutputVoltage
Regulator
Input Filter
Input Rectifier
Inrush LimiterTransient Filter

Temperature
Shutdown

PFC
Converter

OutputPower
Manager

OutputOverVoltage
Protection

Power
Converter

OutputVoltage
Monitor

OutputFilterVOUT++
Overload
LED
DC-ok
LED

DC ok
Relay

DC-ok
Contact

Apr. 2017 / Rev. 2.1 DS-QT20.241-EN
All parameters are typical values specified at 24V, 20A, 3x 400Vac, 50Hz, symmetrical mains voltages, 25°C ambient and aftera 5 minutes run-in time unless otherwise noted.
www.pulspower.com Phone +49 89 9278 0Germany

10/27

QT20.241, QT20.241-C1
24V, 20A, THREE PHASE INPUT

Q-Series

12. TERMINALS AND WIRING
The terminals are IP20 Finger safe constructed and suitable for field and factory wiring.
All terminals
Quick-connect spring-clamp terminals
Max. 6mm2Max. 4mm2Max. AWG10
Max. 2.8mm (including ferrules)
Typ. 10mm / 0.4inch
Not applicableNot applicable

Type
Solid wire
Stranded wire
American Wire Gauge
Wire diameter
Wire stripping length
Screwdriver
Recommended tightening torqueInstructions:a) Use appropriate copper cables that are designed for minimum
operating temperatures of:
60°C for ambient up to 45°C and
75°C for ambient up to 60°C minimum
90°C for ambient up to 70°C minimum.
b) Follow national installation codes and installation regulations!
c) Ensure that all strands of a stranded wire enter the terminal
connection!
d) Do not use the unit without PE connection.
e) Ferrules are allowed.

1. Insert the wire

2. Snap the lever

To disconnect wire: same procedure
vice versa

Daisy chaining:
Daisy chaining (jumping from one power supply output to the next) is allowed as long as the average output current
through one terminal pin does not exceed 27A. If the current is higher, use a separate distribution terminal block asshown in Fig. 12-2.
Fig. 12-1 Daisy chaining of outputs

Power
SupplyPower
Supply

+ + -

+ + -

-

Output-OutputFig. 12-2 Using distribution terminals

Distribution
Terminals
Load
+

-

Power
SupplyPower
Supply

+ + -

+ + -

-

Output-OutputLoad+-max 27A
continuous!

Apr. 2017 / Rev. 2.1 DS-QT20.241-EN
All parameters are typical values specified at 24V, 20A, 3x 400Vac, 50Hz, symmetrical mains voltages, 25°C ambient and aftera 5 minutes run-in time unless otherwise noted.
www.pulspower.com Phone +49 89 9278 0Germany

11/27

QT20.241, QT20.241-C1
24V, 20A, THREE PHASE INPUT

Q-Series

13. FRONT SIDE AND USER ELEMENTS
Fig. 13-1 Front sideA

Input Terminals (Quick-connect spring-clamp terminals)
L1, L2, L3 Line input...PE (Protective Earth) input
Output Terminals (Quick-connect spring-clamp terminals, two pins
per pole)+
Positive output–
Negative (return) output
C Output Voltage Potentiometer
Multi turn potentiometer;
Open the flap to set the output voltage.
Factory set: 24.1V at full output current
D DC-OK LED (green)
On, when the voltage on the output terminals is >90% of theadjusted output voltage.
E Overload LED (red)- On, when the voltage on the output terminals is <90% of theadjusted output voltage, or in case of a short circuit in the output.
- On, when the unit has switched off due to over-temperature.
- Input voltage is always required
F DC-OK Relay Contact (Quick-connect spring-clamp terminals)
The DC-OK relay contact is synchronized with the DC-OK LED.
See chapter 8 for details.
B

Indicators, LEDs:

Overload LED

DC-OK LED

DC-OK Contact

Normal mode
During BonusPower®
Overload (Vout < 90%)
Output short circuit
Temperature Shut-down
No input power

OFF
OFF
ON
ON
ON
OFF

ON
ON
OFF
OFF
OFF
OFF

ClosedClosed
Open
Open
Open
Open

Apr. 2017 / Rev. 2.1 DS-QT20.241-EN
All parameters are typical values specified at 24V, 20A, 3x 400Vac, 50Hz, symmetrical mains voltages, 25°C ambient and aftera 5 minutes run-in time unless otherwise noted.
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12/27

QT20.241, QT20.241-C1
24V, 20A, THREE PHASE INPUT

Q-Series

14. EMCThe power supply is suitable for applications in industrial environment as well as in residential, commercial and lightindustry environment without any restrictions.
All results assume a three phase operation of the power supply.
EMC Immunity
Electrostatic discharge
Electromagnetic RF field
Fast transients (Burst)

Surge voltage on input
Surge voltage on output
Surge voltage on DC-OK
Conducted disturbance
Mains voltage dips
(Dips on three phases)
Mains voltage dips
(Dips on two phases)

Voltage interruptions
Voltage sags

Powerful transients

According to generic standards: EN 61000-6-1 and EN 61000-6-2
EN 61000-4-2
Contact discharge
8kV
Criterion A
Air discharge
15kV
Criterion A
EN 61000-4-3
80MHz-2.7GHz
20V/m
Criterion A
EN 61000-4-4
Input lines
4kV
Criterion A
Output lines
2kV
Criterion A
DC-OK signal (coupling clamp)
2kV
Criterion A
EN 61000-4-5
L1 Æ L2, L2 Æ L3, L1 Æ L3
2kV
Criterion A
L1 / L2 / L3 Æ PE
4kV
Criterion A
EN 61000-4-5+Æ500V
Criterion A+ / - Æ PE
1kV
Criterion A
EN 61000-4-5
DC-OK signal Æ PE
1kV
Criterion A
EN 61000-4-6
0.15-80MHz
20V
Criterion A
EN 61000-4-11
0% of 380Vac (0Vac)
0Vac, 20ms
Criterion A,
0% of 480Vac (0Vac)
0Vac, 20ms
Criterion A
EN 61000-4-11
40% of 380Vac (152Vac)
200ms
Criterion A
40% of 480Vac (192Vac)
200ms
Criterion A
70% of 380Vac (266Vac)
500ms
Criterion A
70% of 480Vac (336Vac)
500ms
Criterion A
EN 61000-4-11
0Vac
5000msCriterion C
SEMI F47 0706
Dips on two phases according to section 7.2. of the SEMI F47 standard
1000msCriterion A
80% of 380Vac (304Vac)
500ms
Criterion A
70% of 380Vac (266Vac)
50% of 380Vac (160Vac)
200ms
Criterion A
VDE 0160
Over entire load range
1550V, 1.3ms
Criterion A

Criterions:
A: Power supply shows normal operation behavior within the defined limits.
C: Temporary loss of function is possible. Power supply may shut-down and restarts by itself. No damage or hazards for the power supply
will occur.

EMC Emission
Conducted emission
input lines
Conducted emission
output lines

According to generic standards: EN 61000-6-3 and EN 61000-6-4
EN 55011, EN 55022, FCC Part 15, CISPR 11, CISPR 22
Class B
IEC/CISPR 16-1-2, IEC/CISPR 16-2-1

12dB higher than average limits
for DC power port according to
EN 61000-6-3**)Class B
Fulfilled for class A equipment
Fulfilled*)

Radiated emission
EN 55011, EN 55022
Harmonic input current
EN 61000-3-2
Voltage fluctuations, flicker EN 61000-3-3This device complies with FCC Part 15 rules.
Operation is subjected to following two conditions: (1) this device may not cause harmful interference, and (2) thisdevice must accept any interference received, including interference that may cause undesired operation.

*)
Tested with constant current loads, non pulsing**) Restrictions apply for applications in residential, commercial and light-industrial environments, where local DC power networks according
to EN 61000-6-3 are involved. No restrictions for all kinds of industrial applications.
Apr. 2017 / Rev. 2.1 DS-QT20.241-EN
All parameters are typical values specified at 24V, 20A, 3x 400Vac, 50Hz, symmetrical mains voltages, 25°C ambient and aftera 5 minutes run-in time unless otherwise noted.
www.pulspower.com Phone +49 89 9278 0Germany

13/27

QT20.241, QT20.241-C1
24V, 20A, THREE PHASE INPUT

Q-Series

The power supply has three converters with three different switching frequencies
included. One is nearly constant. The others are input voltage and load dependent.
100kHzResonant converter, nearly constant
30kHz to 90kHz
Boost converter, load dependent
40kHz to 220kHz
PFC converter, input voltage and load dependent

Switching Frequencies
Switching frequency 1
Switching frequency 2
Switching frequency 3

15. ENVIRONMENT
Operational temperature*)
Storage temperature
Output de-rating
Humidity**)Vibration sinusoidal
Vibration random
Shock
Altitude-25°C to +70°C (-13°F to 158°F)-40 to +85°C (-40°F to 185°F)
12W/°C
5 to 95% r.H.
2-17.8Hz: ±1.6mm; 17.8-500Hz: 2g
2 hours / axis
0.5m²(s³)
2 hours / axis
30g 6ms, 20g 11ms
3 bumps / direction, 18 bumps in total
0 to 2000m (0 to 6 560ft)
2000 to 6000m (6 560 to 20 000ft)

Reduce output power according Fig. 15-1
For storage and transportation
60-70°C (140°F to 158°F)
IEC 60068-2-30
IEC 60068-2-6
IEC 60068-2-64
IEC 60068-2-27

Without any restrictions
Reduce output power or ambient
temperature, see Fig. 15-2
IEC 62103, EN 50178, overvoltage category II
30W/1000m or 5°C/1000m> 2000m (6500ft), see Fig. 15-2
III
IEC 62103, EN 62477-1, altitudes up to 2000m
II
For altitudes from 2000m to 6000m
2
IEC 62103, EN 62477-1, not conductive
The unit does not release any silicone or other LABS-critical substances and is suitable foruse in paint shops.

Altitude de-rating
Over-voltage category
Degree of pollution
LABS compatibility*)

Operational temperature is the same as the ambient or surrounding temperature and is defined as the air temperature 2cm below theunit. Curves and figures for operation on only 2 legs of a 3-phase system can be found in chapter 22.4.
**) Do not energize while condensation is present.

Fig. 15-1 Output current vs. ambient temp.
Allowed Output
Current at 24V

Fig. 15-2 Output current vs. altitude
Allowed Output
Current at 24V

30A

for typ. 4s

25

30A

20

continuous

15

20

continuous

15

10

10

5

5

0
-25

for typ. 4s

25

Ambient Temperature

0

20

40

A

A... Tamb < 60°C
B... Tamb < 50°C
C... Tamb < 40°C

0

2000

C

Altitude0
60 70°C

B

4000

6000m

Apr. 2017 / Rev. 2.1 DS-QT20.241-EN
All parameters are typical values specified at 24V, 20A, 3x 400Vac, 50Hz, symmetrical mains voltages, 25°C ambient and aftera 5 minutes run-in time unless otherwise noted.
www.pulspower.com Phone +49 89 9278 0Germany

14/27

QT20.241, QT20.241-C1
24V, 20A, THREE PHASE INPUT

Q-Series

16. PROTECTION FEATURES
Output protection
Output over-voltage protection

Degree of protection
Penetration protection
Over-temperature protection
Input transient protection
Internal input fuse*)

Electronically protected against overload, no-load and short-circuits*)
typ. 32Vdc
In case of an internal power supply defect, a redundantmax. 35Vdc
circuit limits the maximum output voltage. The output
shuts down and automatically attempts to restart.
IP 20
EN/IEC 60529> 3.5mm
E.g. screws, small partsyes
Output shut-down with automatic restart
MOV (Metal Oxide Varistor)
Not included

In case of a protection event, audible noise may occur.

17. SAFETY FEATURES
Input / output separation*)
Class of protection
Isolation resistancePE resistance
Touch current (leakage current)

*)

SELV
PELV
I
> 500MOhm< 0.1Ohm
typ. 0.44mA / 0.94mA
typ. 0.62mA / 1.31mA
max. 0.54mA / 1.12mA
max. 0.78mA / 1.62mA

IEC/EN 60950-1
IEC/EN 60204-1, EN 62477-1, IEC 62103, IEC 60364-4-41
PE (Protective Earth) connection required
Input to output, 500Vdc
At 3x400Vac, 50Hz, TN-,TT-mains / IT-mains
At 3x480Vac, 60Hz, TN-,TT-mains / IT-mains
At 3x440Vac, 50Hz, TN-,TT-mains / IT-mains
At 3x528Vac, 60Hz, TN-,TT-mains / IT-mains

double or reinforced insulation

Apr. 2017 / Rev. 2.1 DS-QT20.241-EN
All parameters are typical values specified at 24V, 20A, 3x 400Vac, 50Hz, symmetrical mains voltages, 25°C ambient and aftera 5 minutes run-in time unless otherwise noted.
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15/27

QT20.241, QT20.241-C1
24V, 20A, THREE PHASE INPUT

Q-Series

18. DIELECTRIC STRENGTH
The output voltage is floating and has no ohmic connection to the ground. Type and factory tests are conducted by
the manufacturer. Field tests may be conducted in the field using the appropriate test equipment which applies thevoltage with a slow ramp (2s up and 2s down). Connect all phase terminals together as well as all output poles before
conducting the test. When testing, set the cut-off current settings to the value in the table below.
Fig. 18-1 Dielectric strength

Type test
Input
L1
L2
L3

D
Output

Earth
C

+
-

A
2500Vac

B
3000Vac

C
500VacD
500VacFactory test

5s

2500Vac

2500Vac

500Vac

500VacField test

5s

2000Vac

2000Vac

500Vac

500Vac> 10mA> 10mA> 30mA> 1mA

Cut-off current setting
B

A

DC-ok
B*)

60s

To fulfil the PELV requirements according to EN 60204-1 § 6.4.1, werecommend that either the + pole, the – pole or any other part ofthe output circuit shall be connected to the protective earthsystem. This helps to avoid situations in which a load starts
unexpectedly or can not be switched off when unnoticed earth
faults occur.

B*) When testing input to DC-OK ensure that the max. voltage between DC-OK and the output is not exceeded (column D). We recommend
connecting DC-OK pins and the output pins together when performing the test.

19. APPROVALSEC Declaration of Conformity

IEC 60950-1 2nd Edition

UL 508IND. CONT. EQ.

UL 60950-1, 2nd Edition

ANSI / ISA 12.12.01-2007(Class I Div 2)
SEMI F47

MarineEAC TR Registration

The CE mark indicates conformance with the- EMC directive and the- Low-voltage directive
CB Scheme,
Information Technology Equipment
Applicable for altitudes up to 2000m.
Listed for use as Industrial Control Equipment;
U.S.A. (UL 508) and Canada (C22.2 No. 107-1-01);
E-File: E198865
Recognized for use as Information Technology Equipment,
Level 5; U.S.A. (UL 60950-1) and Canada (C22.2 No. 60950-1);
E-File: E137006 Applicable for altitudes up to 2000m.
Recognized for use in Hazardous Location Class I Div 2 T4Groups A,B,C,D systems; U.S.A. (ANSI / ISA 12.12.01-2007) andCanada (C22.2 No. 213-M1987)
SEMI F47-0706 Ride-through compliance for thesemiconductor industry. Full SEMI range compliance (Dips on
two phases: 304Vac for 1000ms, 266Vac for 500ms and 190Vac
for 200ms, Pout < 480W)
GL (Germanischer Lloyd) classified and ABS (American Bureau
for Shipping) PDA Environmental category: C, EMC2 Marineand offshore application
Registration for the Eurasian Customs Union market(Russia, Kazakhstan, Belarus)

Apr. 2017 / Rev. 2.1 DS-QT20.241-EN
All parameters are typical values specified at 24V, 20A, 3x 400Vac, 50Hz, symmetrical mains voltages, 25°C ambient and aftera 5 minutes run-in time unless otherwise noted.
www.pulspower.com Phone +49 89 9278 0Germany

16/27

QT20.241, QT20.241-C1
24V, 20A, THREE PHASE INPUT

Q-Series

20. PHYSICAL DIMENSIONS AND WEIGHT
Width
HeightDepth

WeightDIN-Rail
Housing material
Installation clearances

65mm 2.56’’124mm 4.88’’127mm 5.0’’
The DIN-rail height must be added to the unit depth to calculate the total required
installation depth.
870g / 1.92lb
Use 35mm DIN-rails according to EN 60715 or EN 50022 with a height of 7.5 or 15mm.
Body: Aluminium alloy
Cover: zinc-plated steel
See chapter 2

Fig. 20-1 Front viewFig. 20-2 Side viewApr. 2017 / Rev. 2.1 DS-QT20.241-EN
All parameters are typical values specified at 24V, 20A, 3x 400Vac, 50Hz, symmetrical mains voltages, 25°C ambient and aftera 5 minutes run-in time unless otherwise noted.
www.pulspower.com Phone +49 89 9278 0Germany

17/27

QT20.241, QT20.241-C1
24V, 20A, THREE PHASE INPUT

Q-Series

21. ACCESSORIES
21.1. ZM1.WALL – WALL/PANEL MOUNTINGThis bracket is used to mount the QT20 power supply on a wall/panel without utilizing a DINRail.
The two aluminum brackets and the black plastic slider of the unit have to be detached, so thatthe steel brackets can be mounted.

Fig. 21-1 Wall/panel mounting

Fig. 21-2 Mounting Dimensions - Wall mounting bracket

Apr. 2017 / Rev. 2.1 DS-QT20.241-EN
All parameters are typical values specified at 24V, 20A, 3x 400Vac, 50Hz, symmetrical mains voltages, 25°C ambient and aftera 5 minutes run-in time unless otherwise noted.
www.pulspower.com Phone +49 89 9278 0Germany

18/27

QT20.241, QT20.241-C1
24V, 20A, THREE PHASE INPUT

Q-Series

21.2. ZM14.SIDE - SIDE MOUNTING BRACKETThis bracket is used to mount the QT20 power supply sideways with or without utilizing a DINRail.
The two aluminum brackets and the black plastic slider of the unit have to be detached, so thatthe steel brackets can be mounted.
For sideway DIN-rail mounting, the removed aluminum brackets and the black plastic slider need
to be mounted on the steel bracket.

Fig. 21-3
Side mounting without DINrail brackets

Fig. 21-4
Side mounting with DIN-railbrackets

Fig. 21-5
Mounting Dimensions
Side mounting bracket

Apr. 2017 / Rev. 2.1 DS-QT20.241-EN
All parameters are typical values specified at 24V, 20A, 3x 400Vac, 50Hz, symmetrical mains voltages, 25°C ambient and aftera 5 minutes run-in time unless otherwise noted.
www.pulspower.com Phone +49 89 9278 0Germany

19/27

QT20.241, QT20.241-C1
24V, 20A, THREE PHASE INPUT

Q-Series

21.3. UF20.241 - BUFFER MODULE
This buffer unit is a supplementary device for DC 24V power supplies. It delivers power
to bridge typical mains failures or extends the hold-up time after turn-off of the AC
power. In times when the power supply provides sufficient voltages, the buffer unit
stores energy in the integrated electrolytic capacitors. In case of mains voltage fault, thisenergy is released again in a regulated process.
The buffer unit does not require any control
wiring. It can be added in parallel to the load
circuit at any given point. Buffer units can be
added in parallel to increase the output ampacityor the hold-up time.

Power
SupplyAC

BufferUnit(s)

Load

+
-

DC

21.4. YR40.241 - REDUNDANCY MODULEThe YR40.241 redundancy module is equipped with two input channels (20A each), which
are individually decoupled by utilizing MOSFET technology. The output current can go as
high as 40A.
Using MOSFET instead of diodes reduces the heat generation and the voltage drop
between input and output. The YR40.241 does not require an additional auxiliary voltage
and is self-powered even in case of a short circuit across the output.
Due to the low power losses, the unit is very slender and only requires 36mm width on the
DIN-rail.

Fig. 21-7 Typical N+1 Redundant configuration for 60A with two dual
redundancy modules and four power supplies

Fig. 21-6 Typical 1+1 Redundant configuration for
20A with one dual redundancy module und two
power supplies

FailureMonitorFailureMonitor++ - -

DC24V,20A OK

QT20.241+ - + -

Input Input
2
1

YR40.241

Redundancy
Module++ - -++ - -

QT20.241

QT20.241

DC24V,20A OK

DC24V,20A OK

OutputL1 L2 L3 PE+-+ - + -

Input Input
2
1

YR40.241

Redundancy
Module++ - -++ - -

QT20.241

QT20.241

DC24V,20A OK

DC24V,20A OK

OutputL1 L2 L3 PE

L1 L2 L3 PE+-

L1 L2 L3 PE

L1 L2 L3 PE+ - + -

Input Input
2
1

YR40.241

Redundancy
ModuleOutput+-++ - -

DC24V,20A OK

QT20.241

L1 L2 L3 PE

20A
Load

I

L1
L2
L3
PE

I

I

I

I

60A
Load

I

I

I

I

I

I

I

I

I

I

I

I

I

L1
L2
L3
PE

Apr. 2017 / Rev. 2.1 DS-QT20.241-EN
All parameters are typical values specified at 24V, 20A, 3x 400Vac, 50Hz, symmetrical mains voltages, 25°C ambient and aftera 5 minutes run-in time unless otherwise noted.
www.pulspower.com Phone +49 89 9278 0Germany

20/27

QT20.241, QT20.241-C1
24V, 20A, THREE PHASE INPUT

Q-Series

22. APPLICATION NOTES
22.1. REPETITIVE PULSE LOADING
Typically, a load current is not constant and varies over time. This power supply is designed to support loads with ahigher short-term power demand (=BonusPower®). The short-term duration is hardware controlled by an output
power manager and is available on a repeated basis. If the BonusPower® load lasts longer than the hardware
controller allows it, the output voltage will dip and the next BonusPower® is available after the BonusPower® recovery
time (see chapter 6) has elapsed.
To avoid this, the following rules must be met:a) The power demand of the pulse must be below 150% of the nominal output power.
b) The duration of the pulse power must be shorter than the allowed BonusPower® time. (see output section)c)
The average (R.M.S.) output current must be below the specified continuous output current.
If the R.M.S. current is higher, the unit will respond with a thermal shut-down after a period of time. Use themaximum duty cycle curve (Fig. 22-2) to check if the average output current is below the nominal current.
d) The duty cycle must be below 0.75.
Fig. 22-1 Repetitive pulse loads, definitions

Fig. 22-2 Max. duty cycle curve

P0 = 10%
P0 = 50%
P0 = 75%

Duty Cycle

PPEAK TPEAK

T0

0.75

max.
150%

0.6

100%

0.4
P0 = 100%

0.2

P0

PPEAK

0
100

P0
PPEAK
T0
TPEAK

Example:Base load (W)Pulse load (above 100%)
Duration between pulses (s)Pulse duration (s)110DutyCycle =

T0 =

120

130

140

150%

Tpeak
Tpeak + T0

Tpeak - (DutyCycle x Tpeak)
DutyCycle

A load is powered continuously with 240W (= 50% of the rated output load). From time to time a peak
power of 720W (= 150% of the rated output load) is needed for 1 second.
The question is: How often can this pulse be supplied without overloading the power supply?
- Make a vertical line at PPEAK = 150% and a horizontal line where the vertical line crosses the P0 = 50%
curve. Read the max. duty cycle from the duty cycle-axis (= 0.37)- Calculate the required pause (base load) length T0:- Result: The required pause length = 1.7s

T0=

- Max. repetition rate = pulse +pause length = 2.7s

Tpeak - (DutyCycle x Tpeak)
DutyCycle=

1s - (0.37 x 1s)
0.37= 1.7sMore examples for pulse load compatibility:
PPEAK
720W
720W
600W

P0
480W
0W
240W

TPEAK
1s
1s
1s

T0
>25s
>1.3s
> 0.75s

PPEAK
720W
720W
720W

P0
240W
240W
240W

TPEAK
0.1s
1s
3s

T0
>0.16s
>1.6s>4.9s

Apr. 2017 / Rev. 2.1 DS-QT20.241-EN
All parameters are typical values specified at 24V, 20A, 3x 400Vac, 50Hz, symmetrical mains voltages, 25°C ambient and aftera 5 minutes run-in time unless otherwise noted.
www.pulspower.com Phone +49 89 9278 0Germany

21/27

QT20.241, QT20.241-C1
24V, 20A, THREE PHASE INPUT

Q-Series

22.2. PEAK CURRENT CAPABILITY
The power supply can deliver peak currents (up to several milliseconds) which are higher than the specified short term
currents.
This helps to start current demanding loads. Solenoids, contactors and pneumatic modules often have a steady state
coil and a pick-up coil. The inrush current demand of the pick-up coil is several times higher than the steady-state
current and usually exceeds the nominal output current (including the BonusPower®). The same situation applies whenstarting a capacitive load.
The peak current capability also ensures the safe operation of subsequent circuit breakers of load circuits. The loadbranches are often individually protected with circuit breakers or fuses. In case of a short or an overload in one branch
circuit, the fuse or circuit breaker need a certain amount of over-current to open in a timely manner. This avoids
voltage loss in adjacent circuits.
The extra current (peak current) is supplied by the power converter and the built-in large sized output capacitors of
the power supply. The capacitors get discharged during such an event, which causes a voltage dip on the output. The
following two examples show typical voltage dips:
Fig. 22-4 Peak load with 4x the nominal
current for 5ms, typ.

Fig. 22-3 Peak load with 2x the nominal
current for 50ms, typ.

OutputVoltage

24V

OutputVoltage

24V

18V

16.5V

80A

40A

OutputCurrent

0A

OutputCurrent

0A
2ms/DIV

20ms/DIV

40A Peak load (resistive) for 50ms
Output voltage dips from 24V to 18V.

80A Peak load (resistive) for 5ms
Output voltage dips from 24V to 16.5V.

Please note: The DC-OK relay triggers when the voltage dips more than 10% for longer than 1ms.

Peak current voltage dips

typ.
typ.
typ.

from 24V to 18Vfrom 24V to 19V
from 24V to 16.5V

At 40A for 50ms, resistive load
At 80A for 2ms, resistive load
At 80A for 5ms, resistive load

22.3. EXTERNAL INPUT PROTECTION
The unit is tested and approved for branch circuits up to 15A (U.S.A.) and 16A (IEC). An external protection is only
required if the supplying branch has an ampacity greater than this. Check also local codes and local requirements. In
some countries local regulations might apply.
If an external fuse is necessary or utilized, minimum requirements need to be considered to avoid nuisance tripping of
the circuit breaker. A minimum value of 6A B- or 3A C-Characteristic breaker should be chosen.

Apr. 2017 / Rev. 2.1 DS-QT20.241-EN
All parameters are typical values specified at 24V, 20A, 3x 400Vac, 50Hz, symmetrical mains voltages, 25°C ambient and aftera 5 minutes run-in time unless otherwise noted.
www.pulspower.com Phone +49 89 9278 0Germany

22/27

QT20.241, QT20.241-C1
24V, 20A, THREE PHASE INPUT

Q-Series

22.4. USING ONLY 2 LEGS OF A 3-PHASE SYSTEM
L1
L2
L3
PE

No external protection devices are required to protect against a phase-loss
failure.
This power supply can also be permanently operated on two legs of a 3phase system. However, it is not recommended for this power class since thesupplying 3-phase network can become unbalanced.

Power Supply

AC
L1
L2
open

The output power must be reduced according to the curves below when
operation on only two legs of a 3-phase system. A long-term exceeding ofthese limits will result in a thermal shut-down of the unit.

L3

DC

EMC performance, hold-up time, losses and output ripple differ from a three phase operation. Therefore, checksuitability of your individual application.
Such use is not included in the UL approval. Additional tests might be necessary when the complete system has to beapproved according to UL 508 or UL60950-1.
Fig. 22-5
Output current vs. ambient temperature 2-phase operation

Fig. 22-6
Hold-up time – 2-phase operation

Allowed Output Current at 24V

Hold-up Time for Use on only Two Legs of aThree Phase System

30A

50ms

for typ. 4s

25
20

24V, 10A, min.

continuous

B A

15
10

30

20

40

24V, 20A, min.

10

Ambient Temperature

024V, 20A, typ.

20

A... 2x 460 to 552Vac
B... 2x 340 to 460Vac

5
0
-25

24V, 10A, typ.

40

Input Voltage

060 70°C

320

360

400

440

2x480Vac

22.5. CHARGING OF BATTERIESThe power supply can be used to charge lead-acid or maintenance free batteries. (Two 12V batteries in series)
Instructions for charging batteries:a)b)

Set output voltage (measured at no load and at the battery end of the cable) very precisely to the end-of-charge
voltage.
End-of-charge voltage

27.8V

27.5V

27.15V

26.8V

Battery temperature

10°C

20°C

30°C

40°C

Use a 25A circuit breaker (or blocking diode) between the power supply and the battery.

c)Ensure that the output current of the power supply is below the allowed charging current of the battery.

d)Use only matched batteries when putting 12V types in series.

e)

The return current to the power supply (battery discharge current) is typ. 16mA when the power supply isswitched off (except in case a blocking diode is utilized).

Apr. 2017 / Rev. 2.1 DS-QT20.241-EN
All parameters are typical values specified at 24V, 20A, 3x 400Vac, 50Hz, symmetrical mains voltages, 25°C ambient and aftera 5 minutes run-in time unless otherwise noted.
www.pulspower.com Phone +49 89 9278 0Germany

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QT20.241, QT20.241-C1
24V, 20A, THREE PHASE INPUT

Q-Series

22.6. OUTPUT CIRCUIT BREAKERS
Standard miniature circuit breakers (MCB’s or UL1077 circuit breakers) are commonly used for AC-supply systems andmay also be used on DC branches.
MCB’s are designed to protect wires and circuits. If the ampere value and the characteristics of the MCB are adapted to
the wire size that is used, the wiring is considered as thermally safe regardless of whether the MCB opens or not.
To avoid voltage dips and under-voltage situations in adjacent 24V branches which are supplied by the same source, afast (magnetic) tripping of the MCB is desired. A quick shutdown within 10ms is necessary corresponding roughly tothe ride-through time of PLC's. This requires power supplies with high current reserves and large output capacitors.
Furthermore, the impedance of the faulty branch must be sufficiently small in order for the current to actually flow.
The best current reserve in the power supply does not help if Ohm’s law does not permit current flow. The following
table has typical test results showing which B- and C-Characteristic MCBs magnetically trip depending on the wire crosssection and wire length.
Fig. 22-7 Test circuit

Power Supply

AC

MCB

+
Wire length

DC S1... Fault simulation switch

*)

Load

+
S1

Maximal wire length*) for a fast (magnetic) tripping:
0.75mm²
1.0mm²1.5mm²2.5mm²
29m
39m
56m
86m
C-2A
26m
34m
49m
76m
C-3A
16m
21m
29m
46m
C-4A
3m
5m
7m
8m
C-6A
1m
2m
2m
3m
C-8A
1m
1m
1m
1m
C-10A

B-6A
B-10A
B-13A
B-16A

18m
4m
3m
1m

23m
6m
5m
1m

31m
7m
6m
1m

54m
13m
11m
2m

Don’t forget to consider twice the distance to the load (or cable length) when calculating the total wire length (+ and – wire).

22.7. SERIES OPERATIONPower supplies of the same type can be connected in series for higher output
voltages. It is possible to connect as many units in series as needed, providing
the sum of the output voltage does not exceed 150Vdc. Voltages with apotential above 60Vdc are not SELV any more and can be dangerous. Suchvoltages must be installed with a protection against touching.

Unit A

Avoid return voltage (e.g. from a decelerating motor or battery) which isapplied to the output terminals.

Unit B

AC

DC

+
Load

AC

Keep an installation clearance of 15mm (left / right) between two power
supplies and avoid installing the power supplies on top of each other. Do not
use power supplies in series in mounting orientations other than the standard
mounting orientation (input terminals on the bottom of the unit).

+
-

DC

+
-

-

Pay attention that leakage current, EMI, inrush current, harmonics will increase when using multiple power supplies.

Apr. 2017 / Rev. 2.1 DS-QT20.241-EN
All parameters are typical values specified at 24V, 20A, 3x 400Vac, 50Hz, symmetrical mains voltages, 25°C ambient and aftera 5 minutes run-in time unless otherwise noted.
www.pulspower.com Phone +49 89 9278 0Germany

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QT20.241, QT20.241-C1
24V, 20A, THREE PHASE INPUT

Q-Series

22.8. PARALLEL USE TO INCREASE OUTPUT POWER
Unit A

Power supplies from the same series (Q-Series) can be paralleled to increase
the output power. The output voltage shall be adjusted to the same value(±100mV) or the units can be left with the factory settings.

AC

If more than three units are connected in parallel, a fuse or circuit breakerwith a rating of 25A is required on each output. Alternatively, a diode or
redundancy module can also be utilized.

DC

+
-

Unit BAC

Keep an installation clearance of 15mm (left / right) between two power+
supplies and avoid installing the power supplies on top of each other. Do
not use power supplies in parallel in mounting orientations other than theDCstandard mounting orientation (input terminals on the bottom of the unit)
or in any other condition where a derating of the output current is required (e.g. altitude, above 60°C, …).

+
Load

-

Pay attention that leakage current, EMI, inrush current, harmonics will increase when using multiple power supplies.

22.9. PARALLEL USE FOR REDUNDANCYPower supplies can be paralleled for redundancy to gain higher system availability. Redundant systems require acertain amount of extra power to support the load in case one power supply unit fails. The simplest way is to put two
power supplies in parallel. This is called a 1+1 redundancy. In case one power supply unit fails, the other one is
automatically able to support the load current without any interruption. Redundant systems for a higher power
demand are usually built in a N+1 method. E.g. five power supplies, each rated for 20A are paralleled to build a 80A
redundant system. For N+1 redundancy the same restrictions apply as for increasing the output power, see also
chapter 22.8.
Please note: This simple way to build a redundant system does not cover failures such as an internal short circuit in
the secondary side of the power supply. In such a case, the defective unit becomes a load for the other power supplies
and the output voltage can not be maintained any more. This can be avoided by utilizing redundancy modules, whichhave decoupling devices (diodes or MOSFETs) included. Further information and wiring configurations can be found inchapter 21.4.
Recommendations for building redundant power systems:
a)
b)
c)

Use separate input fuses for each power supply. A separate source for each supply when possible increases thereliability of the redundant system.
Monitor the individual power supply units. Therefore, use the DC-OK relay contact of the QT20 power supply.
It is desirable to set the output voltages of all units to the same value (± 100mV) or leave it at the factory setting.

22.10. INDUCTIVE AND CAPACITIVE LOADSThe unit is designed to supply any kind of loads, including capacitive and inductive loads.

Apr. 2017 / Rev. 2.1 DS-QT20.241-EN
All parameters are typical values specified at 24V, 20A, 3x 400Vac, 50Hz, symmetrical mains voltages, 25°C ambient and aftera 5 minutes run-in time unless otherwise noted.
www.pulspower.com Phone +49 89 9278 0Germany

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QT20.241, QT20.241-C1
24V, 20A, THREE PHASE INPUT

Q-Series22.11. BACK-FEEDING LOADS
Loads such as decelerating motors and inductors can feed voltage back to the power supply. This feature is also called
return voltage immunity or resistance against Back- E.M.F. (Electro Magnetic Force).
This power supply is resistant and does not show malfunctioning when a load feeds back voltage to the power supply.
It does not matter whether the power supply is on or off.
The maximum allowed feed-back-voltage is 34Vdc. The absorbing energy can be calculated according to the built-in
output capacitor which is specified in chapter 6.

22.12. USE IN A TIGHTLY SEALED ENCLOSURE
When the power supply is installed in a tightly sealed enclosure, the temperature inside the enclosure will be higher
than outside. In such situations, the inside temperature defines the ambient temperature for the power supply.
The following measurement results can be used as a reference to estimate the temperature rise inside the enclosure.
The power supply is placed in the middle of the box, no other heat producing items are inside the box
Enclosure:
Load:
Input:
Temperature inside enclosure:
Temperature outside enclosure:
Temperature rise:

Rittal Typ IP66 Box PK 9519 100, plastic, 180x180x165mm
24V, 16A; (=80%) load is placed outside the box
3x 400Vac
55.9°C (in the middle of the right side of the power supply with a distance of 2cm)
24.9°C
31.0K

Apr. 2017 / Rev. 2.1 DS-QT20.241-EN
All parameters are typical values specified at 24V, 20A, 3x 400Vac, 50Hz, symmetrical mains voltages, 25°C ambient and aftera 5 minutes run-in time unless otherwise noted.
www.pulspower.com Phone +49 89 9278 0Germany

26/27

QT20.241, QT20.241-C1
24V, 20A, THREE PHASE INPUT

Q-Series

22.13. MOUNTING ORIENTATIONSMounting orientations other than all terminals on the bottom require a reduction in continuous output power or alimitation in the maximum allowed ambient temperature. The amount of reduction influences the lifetime expectancyof the power supply. Therefore, two different derating curves for continuous operation can be found below:
Curve A1
Curve A2

Recommended output current.
Max allowed output current (results in approximately half the lifetime expectancy of A1).

Fig. 22-8
Mounting
Orientation A(Standardorientation)

Output Current
OUTPUT

20A
16
12
8
4
0
10

Power
SupplyINPUT

Fig. 22-9
Mounting
Orientation B(Upside down)

20

30

50

60°C

50

60°C

40

INPUT

20A
16
12
8
4
0
10

A2
A1

Ambient Temperature

20

30

40

Power
SupplyOUTPUT

Output Current

20A
16
12
8
4
0
10

A2
A1

Ambient Temperature

20

30

50

40

60°C

Output Current

OUTPUT

Power
Supply

INPUT

20A
16
12
8
4
0
10

A2
A1

Ambient Temperature

20

30

50

40

60°C

INPUT

Power
SupplyOutput Current

OUTPUT

Fig. 22-12
Mounting
Orientation E(Horizontal ccw)

Ambient Temperature

Output Current

Fig. 22-10
Mounting
Orientation C(Table-top
mounting)

Fig. 22-11
Mounting
Orientation D(Horizontal cw)

A1

20A
16
12
8
4
0
10

A2
A1

Ambient Temperature

20

30

40

50

60°C

Apr. 2017 / Rev. 2.1 DS-QT20.241-EN
All parameters are typical values specified at 24V, 20A, 3x 400Vac, 50Hz, symmetrical mains voltages, 25°C ambient and aftera 5 minutes run-in time unless otherwise noted.
www.pulspower.com Phone +49 89 9278 0Germany

27/27