Experimental Verification on Precise Calorimetric Power Loss Measurement
Using Two Chambers
Atsushi Nigorikawa* Yuki Nakata* Koji Orikawa* Jun-ichi Itoh**Nagaoka University of Technology
Abstract:- In this paper, the low cost Calorimetric Power Loss Measurement (CPLM) system for a high efficiency converter isproposed. The CPLM uses the heat quantity is generated by loss of the power converter. The proposed system is constructed at alow cost without the thermostatic chambers which cause a high cost of the CPLM system. The method for measurement of thepower loss by the temperature rise with the loss of power converter is discussed. The experimental results confirmed themaximum error of power loss is 8% when the loss of power converter is 5W. This system can achieve that the measurement error
rate is within 10%.
Keywords: Calorimetric determination, Power loss analysis, Thermostatic chamber

1. Introduction
Recently, the power converters become relatively high efficiency
due to the advanced semiconductor devices and magneticmaterials[1]. The power loss analysis of the power converter
becomes difficult in terms of the measurement error because of thepower losses decrease drastically. One of the loss measurement
methods is to measure the input and output power using a power
measurement instrument (EPM). However, this method has a risk
including much error because the ratio of the power loss into
output and input power is very small and full scale error of themeasurement range cannot neglect to measurement results. On theother hand, the other loss measurements method using the heat
quantity of the power converter is known as Calorimetric Power
Loss Measurement (CPLM)[2]. This method can reduce themeasurement error because this method can measure only power
loss. Therefore, this method provides higher accuracy than theEPM. This system uses the thermostatic chambers for the precise
measurement of heat quantity. However, thermostatic chambers
are high cost structure.
In this paper, the low cost CPLM system using two chambers isproposed. The proposed system uses two simple chambers insteadof thermostatic chambers. The validity of the proposed system isconfirmed by the experiment using the prototype.

Fig. 1 System configuration of CPLM using two chambers.

container B. The sensitivity error of the temperature sensor wascorrected in the control circuit. When the temperature in thecontainer B reaches the command value that is the saturated
temperature in the container A, the heat generation from the heaterin the container B equals to the heat generated from the power
converter in the container A. In this way, the power consumptionof the heater equals to the power loss of the power converter.
The room temperature and heat discharge for the two chambers
must be the same in order to obtain high accuracy measurement
results in the proposed system. Therefore, in this paper, thedevelopments of the measurement system will be discussed fromthe theoretical formula of the temperature rise in next chapter.

2. CPLM system using two chambers

3. Theoretical discussion

Fig. 1 shows the control block diagram of the proposed system
which is composed by two chambers and a heater. The chambers,
which are made from insulator materials, are illustrated as thecontainer A and container B in Fig. 1. A measured power converter
is placed in the container A. The temperature in the container A
rise due to the power losses generated from the power converter.
The temperature in the container A saturates when the amount ofheat dissipation from heater equals to the amount of heatdissipation from the container surface.
The temperature in the container B is controlled by a feedback
control using the PI regulator. It should be noted that the air in thecontainer B is heated by a heater, which is controlled by the buckconverter. The temperature in the container A is set to thecommand of the PI regulator which controls the temperature in the© 200● The Institute of Electrical Engineers of Japan.

The power converter is put and works in the container A. Thetemperature of the air in the container A rise, due to the heat
quantity by the power loss of the power converter. The air in thecontainer A is circulated by a fan in order to even out thetemperature in the container A. When the inner volume of thecontainer A is V (m3), the density of the air is ρ (kg/m3), thespecific heat of air is cp (J/gK), the temperature of the air in thecontainer A is Tin (K) and the heat quantity (Qin) can derive fromρ cp VdTin= Qin − Q R − Qcooldt(1)

where, Qin is the heat quantity from the power converter to the airin the container A and Qcool is the heat discharge from thecontainer A. Then QR and Qcool can be expressed as1

TITLEρ cp V(Q ⋅ R + T ) − TambdTin
T −TT −T= Qin − R in − in amb = Qin − in r indt
RrRambRTable 1 Derivation result.

(2)

where, TR is the inner temperature of power converter, Rr is thethermal resistance from inside of the power converter to themeasurement point of the room temperature, Tamb is the ambienttemperature, Ramb is the thermal resistance of the container A, R isthe total thermal resistances.
Eq. (2) is then transformed with Laplace transformation andpresented asQ  R  T (s ) T(3)
ρ c V (s T (s ) − T ) = in 1 − r  − in − ambpinos R RsR

where, To is the initial temperature in the container A. The heat
quantity of the power converter is assumed the step input. Eq (3)solves the Tin, and then it is applied with inverse Laplacetransformation, which is shown in Eq. (4).
  R  T
1Tin = R Qin 1 − r  + amb  ⋅ 1 − exp −t ρRRcVRp  (4)1t
+ To exp − ρ cp V R 
Fig. 2 PI control result.

If the parameters are known except Qin, Eq. (4) is differentiatedand translated logarithmically to Eq. (5).
R Qin − Rr Qin + Tamb − To1(5)ln T ' = ln−t( )inρ cp V Rρ cp V R

As a result, the Qin can derive by Eq. (5) before temperature
becomes saturated.

4. Experiment results4.1 Identification of the thermal resistanceFor testing, a heater is used instead of the power converter. The
power converter runs in the container A. The thermal resistances
are identified from the experimental results of the temperature risein the container A. Those experimental containers are made fromfoam cartons. The volume of the container is V = 3.17×10-2m3(inner dimension of container; long 44.7cm, width 32.2cm, height22.0cm). The error rate set up within 10%.
From Eq. (4), the permissible temperature deviation range (∆T) is
derived substituting with the permissible power consumption
range, and the thermal resistances are obtained. Table 1 shows thethermal resistances and the permissible temperature deviation
range. From Table 1, if the power consumption is small, thecontrol of the temperature should be accurate. When the power
consumption is 5W, the allowance of the temperature deviation is±0.6 degrees Celsius.

Fig. 3 Measurement error rate.

rate of the power consumption can be within 10% in the proposedsystem.
In theory, when the temperature deviation of the container A andcontainer B is 0 degrees Celsius, the measurement error became
0% in this system. However, there are measurement errors in theexperimental results. This reason is the difference of ambient
temperature between the container A and the container B.

5. Conclusion
Abstract:- In this paper, the low cost CPLM system for a highefficiency converter is proposed. The CPLM uses the heat quantity
is generated by loss of the power converter. The proposed system
is constructed at a low cost without the thermostatic chambers
which cause a high cost of the CPLM system. The method formeasurement of the power loss by the temperature rise with theloss of power converter is discussed. The experimental results
confirmed the maximum error of power loss is 8% when the lossof power converter is 5W. This system can achieve that themeasurement error rate is within 10%.

4.2 Evaluation of the proposed system
The measurement accuracy is evaluated using the prototype. The
power consumption of a heater in container B is evaluated toward
the power loss of the power converter. The temperatures of air in
the two containers are affected by the same ambient temperature
because two containers are put in same place.
Fig. 2 shows the experimental result of the temperature control
by using PI when the power consumption of power converter is5W. From Fig. 2, it is conforms that the temperature in thecontainer B is equaled to the temperature in the container A byusing PI control.
Fig. 3 shows the measurement error rate of the power
consumption of the power converter. From Fig. 3, it is conforms
that the maximum error of power loss is 8% when the power
consumption of power converter is 5W. The measurement error

References
(1)

(2)

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Calorimetric for Power Loss Measurement”, Annual Conference of I.E.E. ofJapan, Industry Applications Society, pp.I-363-I-366 (2011)
D. Christen, U. Badstuebner, J. Biela, J.W.Kolar : “Calorimetric Power Loss
Measurement for Highly Efficient Converters”, I PEC2010, pp1438-1445(2010)