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Overtemperature protection and termistors

As a standard, HDD motors are equipped with over temperature protection. The protection consists of three PTC thermistors in series, one for each phase. The PTC thermistors are manufactured according to norms DIN 44081 and DIN 44082. According to these norms, the resistance for a single thermistor at room temperature is in the range of 20 Ohms – 250 Ohms. For three thermistors in series, the total room temperature resistance is typically between 150 Ohms – 300 Ohms (50 Ohms – 100 Ohms per thermistor). It can be as high as 750 Ohm without indicating malfunction.

The PTC thermistors have a switch temperature of 150 C. When T < 145 C, R < 550 Ohm for each thermistor (R < 1650 Ohms for the whole triplet), and when T > 155 C, R > 1330 Ohm for each thermistor (R < 4990 Ohms for the whole triplet). The resistance should be measured with a d.c. voltage no greater than 2.5V. More detailed information about the PTC resistors can be found here.

As an option, HDD motors can be equipped with a temperature measurement device of type KTY84-130. Detailed information about this device can be found here. The resistance of the KTY device depends continuously on the temperature, as described in the document KTY84-130 that can be downloaded on the left side.

Name Type Description Information
A Resolver 7 V input, 1 pole pair, 0.5 transf. ratio  
D Resolver 9 V input, 1 pole pair, 0.3 transf. ratio  
EC Endat 2.1 singleturn 32 lines (19 bits) per rev. ECI 119
ED Endat 2.2 singleturn 32 lines (19 bits) per rev. EBI 135
EE Endat 2.2 singleturn, SIL2 25 bits per rev. ECN 1325
EF Endat 2.2 multiturn, SIL2 25 bits per rev. ECN 1337
EH Endat 2.2 32 lines (19 bits) per rev. ECI 119
EM Endat 2.1 multiturn 512 lines per rev. EQN 1325
EN Endat 2.1 multiturn 2048 lines per rev. EQN 1325
EO Sincos, commutation signal 2048 lines per rev. ERN 1387
EP Endat 2.2 battery buffered multiturn 18 bits per rev. EBI 1135
EQ Endat 2.1 singleturn 18 bits per rev. ECI 1118
ES Endat 2.1 singleturn 512 lines per rev. ECN 1313
ET Endat 2.1 singleturn 2048 lines per rev. ECN 1313  
EV Endat 2.2 singleturn 19 bits per rev. ECI 1319
EW Endat 2.2 multiturn 19 bits per rev. EQI 1331
EY Endat 2.2 singleturn 18 bits per rev. ECI 1118
SS Hiperface Sincos singleturn 1024 lines per rev. Electrically equivalent to SRS50
SM Hiperface Sincos multiturn 1024 lines per rev. Electrically equivalent to SRM50
SC Hiperface Sincos singleturn 50mm hollow shaft 64 lines per rev. Electrically equivalent to SEK90