Unknown Thermistor in GE 600 HP DC Motor

[jktwn]

We recently had a GE 600HP DC motor suffer overheating and destruction when the cooling air intake became blocked by debris. During the the investigation it was discovered that the motor overtemperature devices (thermistor - GE p/n 36A172828BBG01) were not configured to work with the Siemens drive. This goes back to when the line was installed.

Our problem is that GE will not divulge thermistor information that would allow us to correctly program the Siemens drive. The only information they will provide is that the "Trip Temperature" is 140/130 C. Has anyone else had problems with GE getting the information you need and has anyone found a solution. We have to get the OT working and really don't want to redesign.

thanks,
Wayne

 

[ozmosis]

Wayne
Depending on the type of Siemens DC drive, most of them will accept a positive temperature sensor or a negative temperature sensor. Certainly the 6RA24 Siemens DC drive will, you just have to make sure the parameter (P146) is set accordingly.
I would go back to GE and ask if it is a PTC or NTC.

 

[jktwn]

According to GE it is a PTC with R=600 Ohms.

 

[ozmosis]

I just double checked the settings (in P146) you can make in the drive for "R" where R is the ohms at nominal response temperature. P146 can be set to 600ohms, 1200ohms, 1330ohms and 2660ohms. Jumper XJ101 will determine pos or neg.

 

[ozmosis]

So, if it is a 6RA24, then set P146=4 to enable a fault or set P146=3 if you just want a warning at 600ohms.

 

[jktwn]

sed2developer,

The Siemens drive is a model 6RA7091. Talked with our in-house technical person and he found the relavent parameters for this drive to configure it for a PTC 600 ohm thermistor.

We popped the peckerhead on the motor and found that the 3 thermistors in the motor are wired in series. This doesn't seem right since the drive is looking for a 600 ohm thermistor connection. Any thoughts on this?

Thanks for the help on this.

 

[DickDV]

Sure these aren't thermostats with an opening temp of 130/140C?

 

[stardelta]

I dont know if this information will help or not but according to British Standards the switching temperature of Thermistors should be identifiable by the colour of the leads. It may give you some help. See the link.

http://www.aev.co.uk/motorprotectionthermistors.htm

 

[ozmosis]

Showing my age with the 6RA24. The following link is for the 6RA70:

http://www.sea.siemens.com/drives/product/acdc/dcm/drdcmman.html

 

[oftenlost]

If this is a standard GE DC motor, it has thermal switches epoxied on the interpole coil extension. These are usually about three eights of an inch mounted on a heat sink and epoxied to the interpole copper. These are normally closed switches set for about 115 C