1 Jun Watanabe 2015.6.29 R&D status of highly efficient Stirling-type cryocooler for superconducting drive motor J Watanabe, T Nakamura, S Iriyama, T Ogasa,

1Jun Watanabe 2015.6.29

R&D status of highly efficient Stirling-type cryocooler for superconducting drive motor

J Watanabe, T Nakamura, S Iriyama,

T Ogasa, N Amemiya(Kyoto University, Japan);

Y Ohashi(AISHIN SEIKI Co.,Ltd , Japan)

CEC/ICMC 2015

June 29-July 4 2015

JW Marriott Starr Pass Resort & Spa,

Tucson, Arizona

Outline

1. Background and objective

2. Specifications of developed compressor

3. Analytical and experimental method

4. Results and discussion

5. Development and test of pulse-tube cryocooler

6. Conclusion




Advantages・ High efficiency thanks to synchronous rotation・ High torque density・ Stable Rotation

High Temperature Superconductor Induction/Synchronous Machine

HTS-ISM

Target ;Drive motor for the next generation electric vehicle

Direct-drive without transmission gears


Fig.1 Schematic diagram of direct-derived power train system

インバータバッテリー

制御ユニット

小型冷凍機

HTS-ISM

インバータバッテリー

制御ユニット

小型冷凍機

HTS-ISMHTSISM

InverterBattery

Controlunit

Cryocooler


Necessary functions of the cryocooler for HTS-ISM system

・ High efficiency ・ Light weight・ Robustness against vibration

Development of highly efficient Stirling-type cryocooler

Development of linear actuator-type compressor


Input 3000 W

Coil Wire diameter 1.6 mm

Turn number of coil 210

DC resistance 0.6 Ω

Rated stroke length ±10 mm

Piston diameter 40 mm

Table1 Specifications of compressor

Fig.2 Schematic diagram of compressor

Outer yokeInner yoke

Compression zone

Piston

Flexure bearingPermanent magnet

Coil

Moving magnet type linear actuator

2. Specifications of the developed actuator

Outer yoke

Coil

Shaft

Permanent magnet


Finite element method analysis model

SN

SN

x

r

Analysis by commercial software(JMAG-Designer )Ⓡ

Stator

(Analysis conditions) External circuit : Single-phase current source Mover motion : Forced displacement

Inner yoke

Fig.3 Axisymmetric analysis model of the linear actuator


Mover


Non-linear spring characteristic of the flexure bearingOrifice effect between

piston and cylinderα

Pressure changes in Stirling-cycle space

Dumping of the drive coilRigidity of the electromagnetic force….etc

tnaxxfxfxfdt

dxx

dt

xdm

nn sin))()()(())(( 3212

2

)(1 xf

)(2 xf

)(),( 3 xfx

Mover(piston+motor)

Electrical input :Sinusoidal wave

Fig.4 Analysis model of the actuator

Electromagnetic field analysis code coupled with kinetic equation




8

Experimental method under no-load condition

Fig.5 Schematic diagram of experiment under no-load condition

Fig.6 Photograph of compressor assembly

1Φ 200 V

Laser displacement Compressionzone

Linear actuatorLinear actuator Laser displacementsensor

Voltage controledinverter

sensor

Voltage controlled inverter

Compression - zone


Pressure gaugeNeedle valve

Laser displacement sensor

Buffer tank

　 Load test of the compressor with He gas

Fig.7 Photograph of experimental system under load condition V

P

0Fig.9 PV work

Fig.8 Laser displacement sensor

Pressure

Volume


10

(c) Current(a) Displacement

xa=5 mm

(b) Voltage

xa=10 mm

Drive frequency 42 Hz, Displacement 5 mm, 10 mm (experimental results)

In case of xa=10 mm, the current waveform was distorted.

Detailed examination by analysis

The power factor was decreased because phase of the current waveform lagged.

Jun Watanabe 2015.6.29


Fig.10 Experimental results under no-load condition

11

0

1

2

3

4

5

0 42 84 126 168 210 252

xa =1.55 mmxa =3.34 mmxa =5.06 mmxa =6.88 mmxa =8.65 mmxa =10.1 mm

Cu

rre

nt I

(A

)

Frequency f (Hz)

Fig.11 Power spectrum of current waveform

The FFT analysis of the current waveform →Third harmonic component was highly included

Current waveform obtained by superimposing the third harmonic

0

50

100

150

200

250

0 2 4 6 8 10 12

MeasuredAnalyzed (fundamental wave)Analyzed (harmonic wave)

Eff

ect

ive

po

we

r P

(W

)

Displacement amplitude xa (mm)

0

20

40

60

80

100

120

0 2 4 6 8 10 12

MeasuredAnalized (fundermental wave)Analized (harmonic wave)

Vo

ltag

e V

(V

)


(a) Effective power (b) Voltage

Agreement between experimental and analysis results

Reason for the current waveform distortion

Fundamental only

Third harmonic superimposed

Fig.12 Experimental and analysis results under no-load condition



12

-200

-150

-100

-50

0

50

100

150

200

0 0.005 0.01 0.015 0.02 0.025

xa =1.55 mmxa =3.34 mmxa =5.05 mmxa =6.88 mmxa =8.65 mmxa =10.1 mm

I

Co

unt

er

elec

trom

otiv

e f

orce

Es

(V)

Time t (s)

Fig.13 Analysis results of counter-electromotive force

(a) Waveform (b) Effective value

The counter-electromotive force in the case of forced displacement (analysis results)

→ Distortion of the waveform caused by nonlinear B-H curve

0

20

40

60

80

100

0 2 4 6 8 10 12

Co

unte

r e

lect

rom

otiv

e fo

rce

Es

(V)


Out of the linearDistortion


4. Results and discussionC

ou

nte

r-e

lect

rom

otiv

e f

orc

e E

s

(V)

Co

un

ter-

ele

ctro

mo

tive

fo

rce

Es

(V)


0

1000

2000

3000

4000

5000

6000

0 5 10 15 20

Input powerMechanical output

Po

wer

P (

W)

Current I (A)

0

0.2

0.4

0.6

0.8

1.0

0 5 10 15 20

EfficiencyPower factor

Current I (A)

Output characteristics (analysis results)

　　　　　　　　　　　 Fig.14 Output characteristics (analysis results)

→ 　 Possibility of high efficiency and power factor

Displacement 10.0 mm, Frequency 58 Hz, Current - displacement phase difference 90 °


Mechanical output2495 W

Efficiency 90 %

Power factor 0.83

Po

we

r P

(W

)

200

400

600

800

1000

1200

Effective power

Work

Pow

er P

(W)

small largeValve aperture

Frequency 59 Hz Pressure 2.5 MPa 　 Input 200 V


Fig.15 Experimental results under load condition

(a) 　 Input power and PV work (b) 　Displacement

(c) 　 Efficiency and power factor

Next target: ・ Improvement of efficiency

0

0.2

0.4

0.6

0.8

1

Efficiency

Power factor


・ Comparison of analysis results


3

4

5

6

7

8

Displacement (left)

Displacement (right)

Dis

pla

cem

ent

x(m

m)


・ Test at the rated displacement

Po

we

r P

(W

)

Dis

pla

cem

en

t x

(m

m)

5. Development and test of the pulse-tube cryocooler


ｚ

Heat exchanger

Cold stage

Pulse-tube

Hot stage

Fig.16 Photograph of pulse-tube cryocooler

Cooling test of the pulse-tube cryocooler coupled with the compressor

sensor

Heat exchanger

1Φ 400 V

Laser displacement

Buffer tank

Copper pipe

Compressionzone Linear actuatorLinear actuator

Laser displacement

sensor

sensorPressure

Variable voltageinverter

Cold stage

Pulse tube

sensor


Buffer tank volume

3485 cm3

(1 gal)

Copper pipe length

2 m

Evaluation of pulse-tube cryocooler at 77 K

Fig.17 Schematic diagram of experiment of pulse-tube cryocooler

Table2 Specifications of buffer unit


Voltage controlled inverter

Compression - zone

Pressure 2.5 MPa, Input 160 V, Operational temperature 77 K


Fig.18 　 Experimental results of pulse-tube cryocooler

Output 31.603 W COP 0.0276

(a) Input power and PV work (b) Cryocooler output (c) COP

Next target: Re-try of cooling test with the improved compressor 　

0.01

0.015

0.02

0.025

0.03

48 49 50 51 52 53 54 55

COPCO

P

Frequency f (Hz)

15

20

25

30

35

48 49 50 51 52 53 54 55

Heater output

Po

we

r P

(W

)

Frequency f (Hz)

0

200

400

600

800

1000

1200

1400

48 49 50 51 52 53 54 55

Effective powerWork

Po

we

r P

(W

)

Frequency f (Hz)



6. Conclusion

・　 Development of linear actuator-type compressor for cryocooler

・　 Agreement between experimental and analytical results by considering the nonlinear B-H curve of the iron core

・　 Modeling the linear actuator by the use of electromagnetic field analysis code coupled with kinetic equation

・　 Obtaining analytical results which show possibility of high efficiency as well as high power factor

・ Conducting cooling test of the pulse-tube cryocooler


Future plan

・ Experiment at the rated displacement and development of analysis code considering thermodynamics of He gas 　・ Development of Stirling-type cryocooler for HTS-ISM system 　

6. Conclusion

1 Jun Watanabe 2015.6.29 R&D status of highly efficient Stirling-type cryocooler for superconducting drive motor J Watanabe, T Nakamura, S Iriyama, T Ogasa,

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