Fast Starting Method using both Inverter and Delta-Star
Starter for Weaving Machine Drive Systems
Masakazu Kato, Koji Orikawa, and Jun-ichi Itoh

Noboru Saitoh

Department of Electrical Engineering
Nagaoka University of Technology
Niigata, Japan
katom@stn.nagaokaut.ac.jp

Department of Engineering
HOKUETSU DENKEN Co.,Ltd
Niigata, Japan
noboru-saitoh@post.hdnet.co.jp

Abstract— This paper proposes a fast accelerating method forthe weaving machine drive system, which an open winding of theinduction motor is used and connected in series to an inverter
and a switching unit. Generally, the star(Y)-delta() switching
method is used in the start-up mode in order to suppress therush current in general applications. However, in weaving
machine, the rush current is required in the start-up mode inorder to increase starting torque. If the starting torque is notenough to the induction motor, deficiencies of fabric cloth whichis called “start-up marks” will happen[1]. We proposes the Y switching method that achieve high rush current in order toincrease starting torque for weaving machine drive system.
From the experimental results, the start-up time of the proposedsystem is kept to the same as the direct power grid connection.
In addition, rush current of the proposed system is decreased to37.7% comparing to the direct power grid connection.

I.

INTRODUCTION

Weaving machines are generally driven by induction
motors because of a preferable low cost structure. Generally
the induction motor is connected directly to the power grid,and then an inverter is applied in order to improve the driving
efficiency of the weaving machine [2]. However, the driven of
inverter results that the start-up time of weaving machine
becomes slower because the rush current in the start-up can besuppressed by the inverter. The quality of the fabric cloth
which is produced by the weaving machine decreases due tothe slow start-up time. In order to increase a starting torque ofthe motor, the inverter needs to output larger voltage to themotor.

connection is used to increase the voltage of the primarywiring of the motor at the start-up of the weaving machine.
When the speed of the weaving machine reaches the desired
value (rated speed), the motor wiring is switched to Y connection. As a result, the proposed method can achieve afast accelerating time equivalent to that is achieved from thedirect power grid connection.
II.

CHARACTERISTICS OF THE WEAVING MACHINE

A. System configuration
Fig. 1 shows the system configuration of the weaving
machine, which is driven by the inverter. The induction motor
and the weaving machine are connected to the pulley. Thus,
the weaving machine becomes the conveyed power of theinduction motor due to the V-belt connection. Fig. 2 shows theexternal appearance of the weaving machine (JW-832C). The

V beltVdc

Weaving
MachineIM

INV

pulleyiu iv iw
Controller

wr_det Speed
sensorFig. 1 System configuration of the weaving machine, which isdriven by an inverter.

One simple way to increase the output voltage of theinverter is the use of a boost converter into the weaving
machine drive system [3]. However, the large voltage is only
required for the starting period of the motor. Taking accountof the conduction loss from the boost converter, the overall
efficiency of power conversion becomes worse.
This paper proposes a fast accelerating method for theweaving machine drive system by connecting the inverter anda switching unit to an open winding induction motor. -

Fig. 2 The weaving machine (JW-832C).

The weaving machine has a speed sensor on the load side.
Therefore, the speed detection includes the slip of the belt
from the pulley. As a result, the control performance becomesworse because the slip of the induction motor is not adjusted
properly to the slip of the belt. Overall, the efficiency of theweaving machine is further reduced.
B. Load characteristics of the weaving machine
Fig. 3 shows the load characteristic of the weaving
machine. The load of the weaving machine changes rapidly
because of a cam is connecting between the weaving machine
and the induction motor. Therefore, a variable of loads occurs
in a short cycle in according to the motor rotation frequency.
On the other hand, the maximum load torque is 1.5 times of
the rated motor torque. In addition, the recovery torque isapplied to the induction motor at approximately 50% of the
rated motor torque. Also, the load torque changes at around 10
Hz because the cam moves twice each time the pulley moves
once.
III.

1 rotation = 100 ms
2.02

Torque Load[p.u.]

ratio of the pulley between the induction motor and thewaving machine = 81:186 in this test case. The rated speed of
the induction motor is 1415 r/min, and the rated speed of theweaving machine is 653 r/min based on the pulley ratio andthe rated speed of the induction motor.

1.0 p.u. = 14.8 Nm

1.5
1.5
1
1.0
0.5
0.5

00
-0.5
-0.5

-1.0
-1

00

0.05

50

0.1
100

0.15

150

0.2
200

Time[ms]
Fig. 3 Load characteristic of a weaving machine. A variableof loads occurs in a short cycle in according to the motor
rotation frequency.

Start-up mode
Y connection
IM

MC_Y : ON,MC_Δ : OFFuvw

INTRODUCTION OF TWO SWITCHING METHOD FORWEAVING MACHINE

Fig. 4 shows a general switching method which is called Y-  switching method using a switching unit. Induction motors
are generally started by a switching unit. The switching unit isa magnetic contactors switch unit. MC_Y is the switch unit for
Y-connection, and MC_ is the switch unit for -connection.
The Y-connection is used in the start-up mode in order tosuppress the rush current into the induction motor in generalapplication which is a large capacity.

Switching
Rated speed statusuvw

Table 1 shows the difference between Y- switching
method and -Y switching method. Generally, Y-connection
is used in the start-up mode in order to suppress the rushIM connection
MC_Y : OFF,MC_Δ : ON

Fig. 4 A general switching method that is called
Y -  switching method.

Table 1. Comparison of Y switching method with -Y switching method: Vn_, In_ and Tn_ are rated voltage, rated
current and rated torque at steady operation of Y- switching method, respectively, Vn_Y, In_ Y and Tn_ Y are rated voltage,
rated current and rated torque at steady operation of -Y switching method, respectively
VoltageChangeof primary wiring Rushof wiring connection in start-up mode current

Y- switching
method(General method)

Changefrom Y to 

-Y switching
method(Using this paper)

Changefrom  to Y

Vn _Δ
3

3 Vn _ Y

Starting
torqueApplication

Purposeof using this method

Suppression of the rush current
Large capacityinorder to prevent burnout of
3
3 induction motors the induction motor.
Increase of the rush current andstarting torque in order to preventany deficiencies due to lower
acceleration of start up mode.
(Note that, there is little possibility ofWeaving
3In_Y 3Tn_Y machines
burnout of the induction motor in startI n _Δ

Tn _Δ

up mode of weaving machine. Because
the time of current flowing is shorter
than another applications due to thestart-up time is several one hundred
millisecond.)current. However, for weaving machines, the -connection isused to increase starting torque. During the -connection, thevoltage which is applied to the primary wiring of the motor isthe square root of three times the voltage that can be achieved
from Y-connection. The applied voltage is three times as large
as the Y-connection torque according to (1). That is, thestarting torque of the -connection is equivalent to the threetimes that can be achieved from the Y-connection. As a result,the -connection enables fast accelerating of the motor.
IV.

FAST ACCELERATING METHOD OF THE WEAVING
MACHINE BY USING -Y SWITCHING METHOD

the Y-connection. As a result, the -connection enables fast
accelerating, furthermore, since the switching unit are twomagnetic contactors (MC), no additional losses during thesteady state operation.
V.

HIGH EFFICIENCY CONTROL AND RESTART METHODFOR INDUCTION MOTOR

A. High efficiency control
Fig. 7 shows the T-Itype equivalent circuit of theinduction motor. The high efficiency control method adjusts
the exciting current in according to the load torque. Once the

The relationship between the motor torque T and the motor
input voltage V1 is indicated in (1).
3w1 Lm ( R2 / s )V1
2

T 





2

Boost converter
Grid

2

u

2

 R1 R2
w L R (1)2
 w1 L1 L2  M 2    1 1 2  w1 L2 R1 

s
 s




Vdc

Fig. 6 shows the proposed configuration of the weaving
machine drive system. The inverter and the switching unit
(which is a magnetic contactors switch unit, MC_ is theswitch unit for -connection, and MC_Y is the switch unit for
Y-connection) are connected in series to the open winding
induction motor. In order to achieve fast acceleration, theprimary side wiring of the motor is first connected as a connection, MC_ is turned ON, and MC_Y is turned OFF.
After the motor reaches the rated speed, the primary sidewiring of the motor is then converted to the Y-connection,
MC_ is turned OFF, and MC_Y is turned ON. Note that the
Y-connection is used in the start-up mode in general in orderto suppress the rush current in general application. However
for weaving machine, the -connection is used to increase
starting torque. During the -connection, the voltage which isapplied to the primary wiring of the motor is one over thesquare root of three of the voltage that can be achieved from
Y-connection, that is three times as large as the Y-connection
torque according to (1). That is, the starting torque of the connection is equivalent to the three that can be achieved fromIMw

where, w is the angular velocity of the motor primary side
[rad/s], R1 is the primary resistance [], R2 is the secondary
resistance [], L1 is primary inductance [H], L2 is secondary
inductance [H], M is mutual inductance [H], and s is the slip.
According to (1), the motor torque is increased with theincrement of the voltage to the motor.
Fig 5 shows the circuit structure with an inverter and aboost converter. One simple way to increase the output
voltage is the use of a boost converter into the weaving
machine drive system The boost converter is connected at theDC bus in order to increase the inverter output voltage. The
operation of the boost converter can be classified into twomode; in mode I, the DC bus voltage is boosted-up so that theinverter can deliver high output voltage during theaccelerating time. In mode II, the output voltage of the boost
converter is regulated to the same level of the DC bus voltage
since the high voltage is not required in steady state operation.
However, in either of the operation modes, the power loss isincreased because the switching devices in boost converter
generate conduction loss.

v

RectifierInverterFig. 5. Circuit structure with an inverter and a boost
converter.

Switching
Unit
Grid

MC_Δ

Vdc

u
v
w

MC_Y
x
y
z

Rectifier Inverter

IM(a) The proposed system configuration.

Y- switching (General method)①Y connection② connection
u
u
i
3i
v
Z
vuv
vuv Z
v

v

w

w

3v

②Y connection① connection
-Y switching (Using this paper)(b) The switching method of proposed system.
Fig. 6. The proposed system configuration.
The primary side wiring of the motor is first connected as a-connection.

iq

i1
R1

l1

R2
Rc

M

l2

id

Fig.7 . T-type steady state equivalent circuit.

1 s
R2
s

exciting current is controlled and decreased, the copper loss
can be decreased at the same time. Then, the copper loss Plossof Fig. 6 is given by
w 2 M 2  2 2PLoss  3R1  R2 iq   R1  1
id  (2)
Rc  

Then, the torque current iq is given by (3)TT......................................................... (3).
Mi d
The copper loss Ploss is substituted the equation (3). In
addition, the exciting current id is differentiated. Then, thecondition which achieves that the differential value of id iszero is calculated. Therefore, the id_min at the minimum copper
loss is given by
iq 

2d

Rm 



w1 2 M 2
Rc............................................................. (4)However, the frame position error occurs between the
motor control frame (d-q) and the controller frame (d’-q’).
In Fig. 8, if the phase of the controller frame is leadcompared with the motor control frame, then  will be
subtracted into eq to compensate the frame position error.
Additionally, if the phase of the motor control frame is leadcompared with the controller frame, then  will be added into
the eq to compensate the control frame error. The equations(7) and (8) show the d-axis and q-axis components of thecounter electromotive force which is observed on the control
frame. In addition, the compensated value of w1 is shown by(9), where, Kpem is the compensation gain of the axis error, 2n
is the rated secondary magnetic flux.
d ed  vd   R1  L
id  w1L iq ............................ (7)
dt 

d 

eq  vq   R1  L
iq  w1L id ............................. (8)
dt 


 eq

2

dPlossT  1 6R1  R2   3  6R1  R2 id  0 (5)did M  idR1  R2 T............................................ (6)R1  Rm M
The exciting current at the minimum copper loss changes
in according to the load torque shown by (3). Therefore, thehigh efficiency control method controls the exciting current
according to the load torque. As a result, the copper loss andthe iron loss are decreased. In this paper, the iron loss is notconsidered for simplicity.
id _ min  4

B. Speed sensor-less control
Fig. 8 shows the block diagram of a speed sensor-lessvector control. Weaving machines have a speed sensor on theload side. Therefore, the speed detection includes the slip ofthe V-belt from the pulley. As a result, the control
performance becomes worse because the slip of the induction
motor is not adjusted properly to the slip of the belt. Overall,the efficiency of the weaving machine is further reduced. Inorder to eliminate the effect of the slip, the system iscontrolled by speed-senseless vector control [4] [5] [6].
Fig. 9 shows the definition of the control frames.  is therotation angle of the motor control frame, * is the rotation
angle of the controller frame to adjust the motor control frame
equals to the controller axis, w1 is the angular frequency of *and the primary angular frequency of the vector control
method and w1 is the sum of the rotation angular velocity wr
and the slip angular frequency ws, and is the counterelectromotive force, and 2 is the secondary magnetic flux.
The vector control method assigns the secondary magnetic
flux into the d-axis, i.e. the vector control method assigns thecounter electromotive force into the q-axis. When thecontroller frame corresponds to the motor control frame, the qaxis component of the counter electromotive force becomeszero. In other words, if the q-axis component becomes zero bycontrolling , then the controller axis is corresponded to themotor control frame. This is because the angler frequency w1
is obtained by the integral  wr can be estimated.

w1  sgn(eq )  2 d K pem2 d * e  ................................. (9)2 n d C. Restart Method for Induction Motor
When the motor wirings is switching from -connection to
Y-connection, the system requires a dead time period. During
the dead time period, both MCs are turned off. Therefore, theprimary current of the motor becomes zero in the dead time
period. Since the primary current is zero, it is necessary torestart the weaving machine from the free-run state. In the
speed-senseless control, there is a possibility that the rushcurrent is generated in the motor which will damage the motor[7] [8]. The q-axis current controller is preferable with highId * +

Vd*
-

+

ACR

-

Decouplingω r* +

Iq * +

ASR

-

V*
+ + q

ACR

-

1
s


uvw
⇒dq

iu
iv
iw

Calculate Vd
counteruvw
Vangulare electromo q ⇒dqfrequency q tive force

vu
vv
vw

Id
Iq

Calculate
slip

ŵr

-

Calculate

ωlpf

+

vu*
dq⇒ vv*
uvw vw*

LPF

ω1 primary ed

Fig. 8. Block diagram of a speed sensor-less vector control.

q’

b

q

d’-q’:Controler asiseeq

d-q:Control frame

ω1

2d

d’ ab:Stater axis

2
ed





d

*

a

Fig. 9. Relationships among the controller frame and motor
control frame in the sensor-less vector control.

gain to reduce the rush current.
VI.

THERMAL ANALYSIS

Table 2 shows the induction motor parameters. Fig. 10shows a simulation result of primary current of a motor. In the
proposed method, inrush current is generated in the motor inorder to achieve first starting. The inrush is required whilestart-up period of the weaving machine. The cost of theinverter is increased due to the rush current.

between 300 ms and 320 ms. From the result, the differential
value of the q-axis current for the vector control with speed
sensor is approximately within 1.0 p.u.. On the other hand, inthe sensor-less vector control, the differential value of the qaxis current is within 1.6 p.u.. The fluctuation of the q-axis
current is also equivalent to the torque fluctuation. As a result,
it is seen that there is a possibility that the thread will be cut
by a large torque fluctuation. However, based on the
Table.2 Induction motor parameters.

Fig. 11 shows the rise of junction temperature Tj. The
analysis conditions are; the DC link voltage in the inverter is
560 V, and primary current of the motor shown in Fig. 10. It isnoted that the case temperature is 80 degrees. The results
show that higher rate current of IGBT module provides
smaller Tj. Tj of IGBT is 28.4 degrees and Tj of FWD is
5.7 degrees when the rate current of IGBT module is one –half of maximum of inrush current. If the rush current is twiceas large as the rate current of a IGBT module, the junction
temperature is less than a storage temperature of a IGBT
module. Therefore, the propose method has no problem ofcost up.

Parameter
Poles
Rated power
Rated voltage
Rated current
Rated frequency
Rated speed
Primary resistance R1Secondary resistance R2
Primary leakage inductance l1Secondary leakage inductance l2
Mutual inductance M
Excitation current I0
Inertia moment Jm
Rated acceleration timeVII. EXPERIMENTAL VERIFICATIONS

iu
iv
iw

10

30
20
Time [ms]50

40

Fig. 10. Simulation result of primary current of a motor

250
200

6MBI50VA-120-50

15
12

FWD

9

150
100
50

IGBT

6MBI150VX 6MBI180VX-120-50-120-50

6MBI75VW-120-75

0
0

150
50
100
Rated current of IGBT module [A]

6
3

0
200

Fig. 11. Rise of junction temperature. Tj of IGBT is 28.4
degrees and Tj of FWD is 5.7 degrees when the ratecurrent of IGBT module is one – half of maximum of inrush
current.

.

Tj of FWD [℃]

Fig. 13 shows the relationship between maximum rushcurrent and start-up time based on three different conditions
which is the direct power grid connection, inverter operation
only and inverter with the MC switching unit. The maximum
rush current is reduced to 42.0% comparing to the direct
power grid connection to the inverter. However, the start-up
time is also increased to 56.3%. In contrast, the maximum
rush current is reduced to 37.7% comparing the direct power
grid connection to the inverter with switching unit. Meanwhile
the start-up time can maintain equivalent to the direct power
grid connection.
Fig. 14 shows the maximum variation of the q-axis current
waveforms when the start-up sequence of the weaving
machine is repeated by10 times. The primary side wiring of
the motor changes from -connection to Y-connection

160
120
80
40
0
-40
-80
-120
-160
0

Tj of IGBT [℃]

Fig. 12 shows the acceleration characteristics of theweaving machine, which is obtained from the following
controls, (i) the direct power grid with Y-connection(Ystarting), (ii) the direct power grid connection with a -Yswitching unit (-Y starting), (iii) the inverter with the vector
control method, (iv) the inverter with the direct torque control(DTC) method [9], (v) the inverter with the -Y swathing unit
(Proposed method) and (vi) the proposed method with sensorless vector control. The results show that the start- up time of
-Y starting is approximately 80 ms. On the other hand, thestart- up time of the vector control and DTC is approximately
125 ms, respectively. The results clearly demonstrated that the
proposed method can achieve the accelerating time similar tothat of the direct power grid connection (-Y starting).

Primary Current of motor [A]The experimental conditions are; the DC link voltage in
the inverter is 560 V, and the rated speed of the induction
motor is 1415 r/min. The experimental vilifications were
implemented on the weaving machine JW-832C shown in Fig.
2.

Value
4
2.2 kW
380 V
5.4 A
50 Hz
1500 r/min
2.74 
2.98 
6.1 mH
5.4 mH
190 mH
3.5 A
0.0163 kgm2
173 ms125msThe primary side wiring of the motor

80ms

1.0

Proposed method

Δ connection of directly

q axis current [p.u.]

Motor speed[p.u.]

1.2

1.5

connected to the power grid

0.8

Proposed method(sensor-less vector control)

0.6

Vector control
0.4
DTC
0.2
0

200

Time[ms]

Start-up time [ms]140120
Inverter + Switching unit
(sensorless vector control)

56.3%

80
60

37.7%

Direct power
grid connection

Improvement

40

-1.0

5

10

15

300

differential value in the q-axis current for the sensor-lessvector control which is approximately 30% at the time of startup, it can be concluded that the weaving machine is unlikely
to stop.
Fig. 15 shows the driving efficiency of the weaving
machine based on the direct power grid connection, the vector
control with speed sensor of weaving machine, and the speedsensor-less control. The driving efficiency of the weaving
machine was calculated by the number of weft thread for theused power. The driving efficiency of the vector control withthe speed sensor is the same as that of the direct power gridconnection. On the other hand, the driving efficiency of the
speed sensor less control is improved by approximately 3.6%
more than that of the direct power grid connection.

330

×103
29.0

3.6%

28.5
28.0
27.5
27.0

Vector control
with speed sensor
of weaving machine

Speed sensor
less control

approximately 3.6% more than that of the direct power gridconnection.
REFERENCES
[1]

[2]

[3]
[4]
[5]

[6]

VIII. CONCLUSION
In this paper, the effectiveness of the proposed methods
was validated experimentally. The start-up time of the
proposed system is the same as the direct power gridconnection. In addition, the rush current of the proposedsystem is decreased to 37.7% comparing to that of the direct
power grid connection. If the rush current is twice as large as
the rate current of a IGBT module, the junction temperature isless than a storage temperature of a IGBT module. The driving
efficiency of speed-sensor-less control is improved by

320

310

Fig. 15. The driving efficiency of the weaving machine
based on the direct power grid connection, the vector
control and the speed-sensor-less control.

20

Inrush current [p.u.]
Fig. 13. Relationship between maximum rush current and startup time for each control. The maximum rush current is reducedby 37.7%.

1.6p.u.

Vector control
with speed sensor
of weaving machine

Direct power
grid connection

200

Speed sensor
less control-0.5

Driving efficiency[pick/kWh]Fig. 12. Relationship between maximum inrush current andstart-up time for each control. The Propose method can achieve
the accelerating time similar to that of the direct power gridconnection (-Y starting).

100

1.0p.u.
0

Fig. 14 The maximum variation of the q-axis current waveforms
when the start-up sequence of the weaving machine is repeatedby10 times.

connected to the power grid100

Y connection

0.5

-1.5
290

Y connection of directly

Change from  connection
to Y connection

 connection

1.0

[7]

[8]

[9]

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