20

POWERTHERMISTORThe POWER THERMISTOR is a device forsuppressing inrush current to an electriccircuit. Circuits including electric bulbs orcapacitors induce a inrush current morethan 100 times the normal current when thecircuit switch is turned on. The POWERTHERMISTOR in the circuits protectselectric equipments from being damagedby limiting the inrush current.

MARK is a NEW POWER THERMISTORfeaturing smaller size and larger energycapacity to meet severe requirements ininrush current suppression.There is the tendency of miniturization inlow power switching power supply, andMARK is effectively applicable for theneeds, though the camparatively largersized fixed resistors (ceramic coat) areused now.

Application

How to use the power thermistor

The power thermistor will suppress inrush currentwhich is caused by a capacitor, filament for a bulb,inverter for fluorescent lamp, a heater and etc., alsowill control fan motor speed of cooler for electriccircuit.Especially MARK was developed to use for powersupply of TV, VCR instead of cement resistor.

Accordingly, suitable thermistors are 6D-22, 5D-18and 8D-18, and if we consider in the points of smalltime constant which means a small size and largeeffect for suppressive current which means largerated zero-power resistance, 8D-18 is the mostsuitable one.

Use the following circuit in the power supply for 100Vand 200V.

The most suitable power thermistor for the abovecircuit is required to fulfill the following terms andconditions.1. The permissible current at ambient temperature of 558C should be over 2A.2. The thermistor resistance for suppressive current which becomes below 30A should be over 4.2 ohm from the under-mentioned formula.

2t8

SW

VE

IO

C L

Input voltage : AC 100V610%Steady state current : 2ACapacitor : 2000mFAmbient temperature : Max.558CSuppressive current : Max.30A at 258C

SW1

SW2

C2

C1

VE L

2 VE31.1 30.5RC1R25

RC : Intial resistance value in the circuit is 1 ohm (100V/100A)R25 : Rated zero-power resistance at 258C3. Max. capacitance shall be over 2000mF at AC 100V.

SW2 : ON (200V), OFF (100V)

2t8

2t8

21

Thermal time constantIf ambient temperature of a thermistor is changedto T1 from T2 suddenly, temperature of the thermistorchanges slowly.The time constant means the time when temperatureof the thermistor reaches 63% of the temperaturedifference.

Maximum permissible currentIf the maximum permissible current flows to athermistor at 258C, temperature of the thermistorrises to 2008C, (1608C). When ambient temperature isabove 258C, the maximum permissible current shall beover reduced as the maximum permissible currentreduction curve.

Reliability tests

Dry heat testMARK

Test sample is exposed in air at 2008C for 1,000hours. DR25/R25 620%Damp heat testTest sample is exposed in atmosphere of 95%RH at408C for 1,000 hours. DR25/R25 610%Load testTest sample is applied the maximum rating currentin air at 258C for 1,000 hours. DR25/R25 620%Change of temperatureTest sample is given 10 times of the followingtemperature cycle, 2408C for 30 minutes room temperature for 5minutes 2008C for 30 minutes room temperature for 5minutes.DR25/R25 610%

Residual resistanceIf current is flowed through a thermistor, any heatwill be generated in the thermistor by which itsresistance will be decreased, however, a decreaseof a resistance will be stabilized at a saturationresistance value which is determined by impressedelectric power and a dissipation constant. Theresidual resistance value means maximumsatulation resistance value when the maximumpermissible current is flowed through the thermistor.

Temperature coefficientThe temperature coefficient of a thermistor isexpressed by the following equation ;

Dissipation factorIf small voltage is applied to a thermistor, smallcurrent will flow which produce enough heat in thethermistor. Dissipation factor is electric powerwhich make 18 C raise by heat in a thermistor.

Resistance-temperature characteristicsThe theoretical characteristics of a thermistor is expressed by following equation.

P is applied electric power.Dt is rised temperature of the thermistor.

New Power Thermistor MARK

1.2

1.1

1.0

0.9

0.8

0.7

0.6

0.5

0.4

0.3

0.220 30 40 50 60 70 80 90 100 110 120 130 140 150 160 170 180 190 200

Ambient temperature (8C)

Cur

rent

der

atin

g ra

tio

Power Thermistor

1.2

1.1

1.0

0.9

0.8

0.7

0.6

0.5

0.4

0.3

0.22010210 0 30 40 50 60 70 80 90 100 110 120 130 140 150 160

Ambient temperature (8C)

Temperature (8C)

Res

ista

nce

chan

ge r

atio

Cur

rent

der

atin

g ra

tio

D TYPE

W TYPE

2 ( % / 8 C)T2

B

25 exp B T1R1

R1 is the zero-power resistance at absolute temperature T1

R2 is the zero-power resistance at absolute temperature T2R2

1T2

1

5 (mW/ 8 C)dDtP

MARK B : 3150K

Dry heat testPOWER THERMISTOR

Test sample is exposed in air at 1608C for 1,000hours. DR25/R25 610%Damp heat testTest sample is exposed in atmosphere of 95%RH at408C for 1,000 hours. DR25/R25 610%Load testTest sample is applied the maximum rating currentin air at 258C for 1,000 hours. DR25/R25 610%Change of temperatureTest sample is given 10 times of the followingtemperature cycle, 2308C for 30 minutes room temperature for 5minutes 1608C for 30 minutes room temperature for 5minutes.DR25/R25 610%

B is constant which depends on the material used tomake the thermistor. Unless otherwise specified, allvalues of B are determined from measurements madeat 258C and 858C.

2000.01

0.1

1.0

10

100

160 100 50 25 2250Temperature (8C)

Res

ista

nce

chan

ge r

atio

MARK B : 2900K

2000.01

0.1

1.0

10

100

160 100 50 25 2250Temperature (8C)

Res

ista

nce

chan

ge r

atio

Power Thermistor B : 3250K

0.02

0.03

0.05

0.1

0.2

0.3

0.5

1.0

2.0

3.0

5.0

10.0

20.0

160 100 50 25 2300

.5

.5

.5

.5

.5

.5

.5

.5

22

Part number

Taping

Dimensions

5 D 11 T3C (F2)-

Shape D : Disk typeElement diameter : f11

Resistance at 258C : 5V

Washer type

4 W 25-

Shape W : Washer typeElement diameter : f25

Resistance at 258C : 4V

D

F

hL

d

d

D T

H25

min

.

T

5D-11DU

f 0.8Tin-platedcopperwire

5D-11DU

1. Straight lead type 2. Forming lead type

W W0 W

1

W2

L

H1

P

P1

PO fD0

t1

t

Dh

F1

28 max. 29 max.

(11)

23 max.

f 335

18

35 m

ax.

(12)

Disk typeDisk type

Washer type

UL approved (Disk type)

File No. E92669

Thermistor type device

Canadian Standards (Disk type)

File No. CA97673-1

Class 7950 30 NTC Thermistor

R

Part No.R25

(V)B value

B25/85

(K)

Dissipation factor

(mW/ 8C)

Specifications (Disk type)

Maximumenegy

J(W-s)

Maximumrating

currentat 258C

(A)

Residualresistance

(V)

Thermaltime

constant(s)

Ratingtemp(8C)

Maximum capacitance(mF)

3D-224D-226D-224D-185D-188D-18

10D-185D-138D-13

16D-135D-118D-11

10D-1110D-916D-922D-7

3615%4615%6615%4615%5615%8615%

10615%5615%8615%

16615%5615%8615%

10615%10615%16615%22615%

325065%325065%325065%

325065%325065%325065%325065%325065%325065%

325065%325065%325065%325065%325065%325065%325065%

40.050.080.09.0

11.018.022.04.06.0

12.04.06.07.02.04.01.0

5.44.73.94.13.83.12.83.42.71.93.32.62.42.21.71.4

0.1370.1820.2740.1820.2280.3650.4560.2280.3650.7300.2280.3650.4560.4560.7301.003

29.830.732.422.824.627.228.220.120.321.419.019.820.117.217.415.7

1301602201001201501505565

105507075405030

8,50011,00017,0002,0002,5004,1005,000

9001,4002,800

9001,4001,800

510820310

5,9007,600

11,8001,3501,7002,8003,400

620970

1,900620970

1,250350560210

1,4701,9002,950

34043071086015024048015024031080

14050

1,7002,2003,500

410510840

1,03018028057018028037010016060

AC100V AC120V AC220V AC240V

230;160230;160230;160

230;160230;160

230;160230;160

230;160

230;160230;160230;160230;160230;160230;160230;160230;160

Taping

D-7D-9D-11D-13

1561

3061

960.5 1660.5 7.560.5 460.3 0620.660.31560.3 3.7560.7 1811.0 20.5 3max. 1.6max.1max.5min.

P P0 P1 W W0 W1 W2 H1 L F1 fD0 t t1 Dh

D-7D-9D-11D-13D-18D-22

9.5max.11max.14max.16max.21max.25max.

8max.9max.8max.

13max.15max.18max.20max.26max.30max.

15max.17max.20max.22max.28max.32max.

360.2

661

3.560.57.561

1061

5max.

6max.

D T H h F L d

AC100V AC120V AC220V AC240V

Part No.R25

(V)B value

B25/85

(K)

Dissipation factor

(mW/ 8C)

Specifications (Washer type)

Maximumenegy

J(W-s)

Maximumrating

currentat 258C

(A)

Residualresistance

(V)

Thermaltime

constant(s)

Ratingtemp(8C)

Maximum capacitance(mF)

*4 Time when thermistor temperature reaches 63.2% of the temperature difference. The value is measured in the air.

6W-22

4W-25

6.0615% 325065%

325065%4.0615%

80

50

6.1

7.8

0.153

0.102

34.0

36.2

220

160

230;200

230;200

17,000 11,800 3,500 2,950

11,000 7,600 2,200 1,900

*1 *2 *3 *4

*1 R25 : Rated zero-power resistance value at 258C.

*2 B value : determined by rated zero-power resistance at 258C and 858C.

*3 Residual resistance is the maximum value when maximum rating current is applied.

Forming leadTaping

*1 *2 *3 *4

23

Part number

Taping

Dimensions

M 5R1 07 C

Element diameter : f7

Mark Resistance at 258C : 5.1V

1. Straight lead type

W W0 W

1

W2

L

H1

P

P1

PO fD0

t1

t

Dh

F1

UL approved

File No. E92669

Thermistor type devices

DD

25 m

in.

25m

in.

3.0 min.

dd

H0H5R110

1N5R1101N

D

3.0 min.

d

H0

5R1101N

T

3.56

0.75

Part No.R25

(V)B value

B25/85

(K)

Dissipation factor

(mW/ 8C)

Specifications (Disk type)

Maximumenegy

J(W.s)

Maximumrating

currentat 258C

(A)

Residualresistance

(V)

Thermaltime

constant(s)

Ratingtemp(8C)

Maximum capacitance(mF)

AC100V AC120V AC220V AC240V5.1610%8.2610%

10.0610%12.0610%16.0610%22.0610%2.2610%3.0610%3.9610%5.1610%8.2610%

10.0610%1.0610%2.0610%3.0610%3.9610%5.1610%

315065%315065%

315065%

4.63.63.33.63.12.67.46.45.65.74.54.1

11.98.68.37.46.5

0.180.300.360.240.430.590.080.110.110.140.220.270.040.070.080.080.14

17.017.217.217.517.818.018.919.219.519.219.920.122.023.423.624.524.7

290065%

315065%

315065%

290065%315065%

290065%

290065%290065%

290065%

315065%315065%

315065%290065%290065%

20253025304040454540506065908095

110

240;200

240;200240;200240;200240;200240;200240;200240;200240;200

240;200240;200240;200240;200240;200240;200240;200240;200

270380470380550660

1,1301,1901,3001,0001,0801,1302,5802,9002,1302,3602,500

80110140110160190330350380290320330760860630700740

6090

11090

130160280290320250270280640720530590620

M5R107M8R207M10007M12007M16007M22007M2R210M3R010M3R910M5R110M8R210M10010M1R014M2R014M3R014M3R914M5R114

2.02.83.43.64.04.88.28.68.07.27.88.2

18.021.015.017.018.0

400560680560800960

1,4601,7201,8801,4401,5601,6403,7204,2003,0803,4003,600

Taping

960.5 1660.5 7.560.5 460.2 0620.660.31560.3 3.7560.7 1811.0 20.5 3max. 1.5max.1max.5min.

P P0 P1 W W0 W1 W2 H1 L F1 fD0 t t1 Dh

D T H H0 dM...07M...10M...14

7.5619.5max.13max.17max.

12max.17max.20.5max.

15max.19.5max.22.5max.

6max.

1561

3061

M...07M...10M...14

*1 R25 : Rated zero-power resistance value at 258C.

*2 B value : determined by rated zero-power resistance at 258C and 858C.

*3

T3C : Clinch leadD : Straight leadCS : Clinch short

Taping

2. Clinch lead type 3. Clinch short lead type

Lead wire f0.8Soldered copper wire

Residual resistance is the maximum value when maximum rating current is applied.

*1 *2 *3 *4

*4 Time when thermistor temperature reaches 63.2% of the temperature difference. The value is measured in the air.