［ Basic Technologies ］

Development of Power Supply
Condition Monitoring TechnologyKeywords

Ryo Koshiya,
Yasuyuki Iwauchi,
Yoshihiro Hasegawa

Power supply, Condition monitoring technology, Preventative maintenance, Condition based maintenance

Abstract

For industrial machines, preventative maintenance done before the occurrence of a failure is essential. Time Based Maintenance (TBM) is currently themainstream in precautionary maintenance, while Condition Based Maintenance(CBM) has begun to attract attention due to the development of data sensing
technology and the social demand to lower maintenance costs and improve reliability. In many cases, among various machines and equipment, the power supply unit is equipped with service for life-limited components and parts andCondition Based Maintenance is required.
Against this background, we developed a power supply condition monitoring technology that utilizes data sensing technology, and also developed aprototype of a power supply system adding a condition monitoring function.

1 Preface
We offer a variety of industrial computers,
switching hubs, and related apparatus and equipment. Industrial machines are required to assure
many years of stable operation. To meet theserequirements, it is essential to perform preventative
maintenance for equipment.
Preventative maintenance formerly was donein the form of Time Based Maintenance (TBM) for
which maintenance is performed at the intervalsof the speciﬁed period. In recent years, however,sensing technology using sensors, and communication network advance has led to the developmentof Condition Based Maintenance (CBM) which has
attracted a lot of attention.
CBM is a maintenance approach for which
equipment conditions are continually monitored.
When any sign of malfunction is revealed, the necessary maintenance is carried out according to thedetected equipment conditions.
In order to estimate the life of the machine anddetermine maintenance times, the maintenanceintervals are shorter than the actual life of themachine. It is too costly to have a ﬁxed term. InTBM, maintenance timing is determined by predicting the remaining equipment life under projected
worst case conditions of use. Accordingly, maintenance timing is determined for a shorter life period

than the actual life span and is wasteful. On the contrary, CBM is carried out upon the discovery of asign of equipment malfunction. Such an approach
inevitably can lower unnecessary maintenancecosts and equipment availability can be improvedfor better facility management.
We are promoting the development of products
in support of CBM. We produced and evaluated a
prototype of a power supply unit where a condition
monitoring function is incorporated. In many cases,
since the power supply unit is an indispensable
component for all equipment, and it is equipped withan aluminum electrolytic capacitor which is alife-limited serviced component, its need for conditional monitoring is high. This paper introduces this
newly developed power supply condition monitoring
technology.

2 Outline of Power Supply Unit withCondition Monitoring Function
A prototype of a duplex power supply unit (“thispower supply unit” hereafter) was manufactured
and comes with a condition monitoring functionused for our industrial switching hub, MEIWAY
SW900. Fig. 1 shows the system conﬁguration of
the developed power supply unit and Table 1 shows
its speciﬁcations. Using the installed microcomputer,temperature and voltage data acquired from theMEIDEN REVIEW Series No.181 2021 No.109

Inputvoltage
AC85～
242 V

RectifiercircuitPower Factor
Correction(PFC) circuit

Outputvoltage
DC12 VDC/DC

3.1 Object of Condition Monitoring

Aluminum
electrolyticcapacitor
Power source circuit

Voltagemeasuring
circuitTemperature
sensorsMainmemorymini-USB

Fig. 1

Display
LED

Microcomputer

Nonvolatilememorymicro-SD

System Configuration of Developed Power
Supply Unit

Using the installed microcomputer, temperature sensors, andvoltage measuring circuit, conditions of the power source aremonitored.

Table 1 Specifications of Developed Power Supply Unit
Speciﬁcations are equivalent to those of the SW900. As an external interface to acquire condition monitoring data, a mini-USB
and micro-SD are loaded.
ItemSpecifications

Power source connector

3P inlet type

Input voltage range

AC85〜242 V

Rated output voltage

DC12 V

Rated output power

50 W

Operating temperature range −10〜55℃(during operation)
Withstanding voltage(Power source PrimarySecondary)AC2000 V for 1 minuteInsulation resistance(Power source PrimarySecondary)

DC500 V 5 MΩ or morePower source noise durability Rectangular impulse noise
2 kV, 50 ns/1 μs
MassApprox. 1.5 kg

External dimensions

W160 × H50 × D300 mm(Embossed parts excluded)

External interfacemini-USB × 1
micro-SD × 1

respective sensors are gathered and used to monitor the conditions in the power supply. The acquired
data can be obtained via a mini-USB or micro-SD.

103 Power Supply Condition Monitoring
TechnologyMEIDEN REVIEW Series No.181 2021 No.1

A capacitor used in the smoothing circuit of thepower supply is a large capacity and high voltage
resistance. In many cases, aluminum electrolytic
capacitors are used. The aluminum electrolytic
capacitor is subject to the reduction of its capacity
as a result of electrolyte evaporation.
In other words, it is a life service-limited component which deteriorate over time. The deterioration of an aluminum electrolytic capacitor, which isused as the smoothing capacitor, can cause malfunctions such as an increase in ripple voltage,instability of power source output, and output stoppage. Such a malfunction can lead to maloperationof equipment and functional stoppage. For this reason, we decided on this type of capacitor for condition monitoring.

3.2 Condition Monitoring Function
Three types of condition monitoring functions
have been provided to this power supply unit. Fig. 2
shows an example of CBM application of each monitoring function.

3.2.1 Estimated Lifetime Calculating Function
For the aluminum electrolytic capacitor, its
deterioration speed can differ according the operating conditions such as ambient temperature andapplied voltage level. Ambient temperature, in particular, can be a major cause.
The estimated lifetime under each operating
condition can be obtained by Arrheniusʼ lifetime
computation formula. In order to attain highly accurate lifetime estimation, however, it is necessary toperform computation based on actual conditions ofuse. For this power supply unit, we therefore used atemperature sensor and a voltage measuring circuitin order to measure the ambient temperature andapplied voltage for the aluminum electrolytic capacitor. This unit is provided with a function to calculate
the estimated lifetime under actual operating conditions.
The temperature sensor is mounted the aluminum electrolytic capacitor. High-accuracy temperature measurement can be conducted by making
adequate amendment of measured data. Throughthe measurement of temperature and applied voltage during a determined period, it is possible to
make lifetime estimation in accordance with varia-Power supply unit
Temperature
sensor

Smoothingcircuit
Aluminum
electrolyte
capacitor

Voltagemeasuring
circuit

MaintenanceAmbient
temperature
measurement

Estimated lifetime output
derived from ambient
temperature and applied
voltage

Estimated
lifetime
calculation
function

Applied voltage
measurement

Maintenance performed
within the scope of
estimated lifetime
MaintenancePower supply unit
Smoothingcircuit
Aluminum
electrolyte
capacitor

Fig. 2

Seculardeterioration

Ripplevoltage
increased

Ripple voltage
monitoring
function

Alarming output generated
when ripple voltage exceeds
threshold level

CapacitanceloweredCapacitancemonitoring
function

Alarming output generated
when capacitance is lowered
below threshold level

Example of CBM Application

Estimated lifetime is calculated based on ambient temperature and applied voltage. Based on ripple voltage and capacitance acquired
from the data output, an alarming sound output is generated.

tions in operating conditions.

3.2.2 Ripple Voltage Monitoring Function
If deterioration is caused in an aluminum electrolytic capacitor of the smoothing circuit, an equivalent series resistance becomes high and ripple
voltage is increased. Since this power supply unit isprovided with a voltage ripples monitoring function,an alarm sounding function is available when themeasured ripple voltage exceeds the threshold levelof the error judging criterion. For ripple voltage
measurement, measuring accuracy can be improved by making a ﬁlter adjustment in the voltage
measuring circuit.

Table 2 Comparison of Condition Monitoring Functions
Advantages and disadvantages of the respective condition monitoring functions are shown.
Condition
monitoring
function
Estimated
lifetime
calculation
function

Advantages

Disadvantages

・Remaining lifetime ・Indirect monitoring(Estimated lifetime)clear

Ripple voltage ・Direct monitoring
monitoringof deterioration
function・Remaining lifetime unclear

・Direct monitoringof deterioration・Remaining lifetime unclear
・Detection is enabled only
if the power source is OFF

Capacitancemonitoring
function

3.2.3 Static Capacity Monitoring Function
Since the aluminum electrolytic capacitor
accompanies the lowering of capacitance due todeterioration over time, the rate of deterioration canbe monitored by monitoring the capacitance.
Utilizing this factor, this power supply unit is provided with a capacitance monitoring function. While
the power supply is turned off, the discharge time of
the aluminum electrolytic capacitor is measured bya microcomputer so that the capacitance can becalculated based on the measured discharge time.
If the calculated capacitance exceeds the thresholdlevel of the error judgment criterion, the occurrenceof a failure is notiﬁed by sound alarming.

3.2.4 Comparison of Condition Monitoring
Functions
Table 2 shows a comparison of three types ofcondition monitoring functions. Although the estimated lifetime calculating function is based on indirect monitoring of deterioration, it has the advantagethat the estimated lifetime can be made concisely.
While in the case of other two types of condition
monitoring functions, the lifetime cannot be estimated accurately. These two functions, however candetect variations in ripple voltage and capacitanceresulting from deterioration. Accordingly, deterioration in objective components and parts can be monitored directly and the related information can bereported before the occurrence of equipment failure. If these three types of condition monitoring
functions are used in combination, condition monitoring becomes possible with higher reliability.

3.2.5 Graphical User Interface (GUI)
Fig. 3 shows a GUI screen that displays thecurrent conditions being monitored. Connected witha Personal Computer (PC) through mini-USB, theestimated lifetime, ripple voltage, and capacitanceof an objective capacitor are displayed.
MEIDEN REVIEW Series No.181 2021 No.1

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4 Postscript

Fig. 3GUI Screen

It is possible to examine the estimated lifetime of aluminum electrolytic capacitor, capacitance, and applied ripple voltage.

This paper introduced the outlined features ofour power supply condition monitoring technology
developed for the CBM of industrial equipment.
When this expertise is applied to regular monitoringof power supply conditions, the maintenance cost
can be reduced by extending the maintenancecycle. It also prevents the loss of function due topower failure of the equipment. In doing so, it canimprove the reliability of the system.
In the future, we will utilize condition monitoring
technology to reduce maintenance costs and produce the product with high reliability.
・microSD is the registered trademark of SD Association.
・USB is the registered trademark or service mark of USB
Implementers Forum.
・All product and company names mentioned in this paper are
the trademarks and/or service marks of their respective owners.

12MEIDEN REVIEW Series No.181 2021 No.1