Klixon Motor Overtemperature Protection

Not unreasonable to expect it to work. In a motor of that size I would expect a series connected temperature sensor in each of the stator windings. To be honest for all sensors to fail seems unlikely, I would look to the external controls.

The klixon shut the motor down.

There were both Klixon and Thermistors installed in the motor.

The thermistors had not been wired up.

The klixon did shut the motor down, but not before permanent damage. There was one klixon in the top shunt field, one thermistor in the same coil, and one thermistor in the interpole. Armature and pole face and interpole coils are OK. Shunt field is toasted.

Do you know for sure there even is a Kilxon? It's not automatic. In addition, a "Klixon" is usually a power interrupt device and is wired in series with the field power. It may have had thermistors, which are not in series with the power, they need a thermistor monitoring device outside of the motor in the control system, as TonyS indicated. If you assumed those were Klixons and they were thermistors, that right there might be your problem.

It was for sure a Klixon in the shunt field.

The two thermistors had not been wired up.

The klixon was wired into a DC drive that shutdown the system.

I would really like to know the IEC definition of the protection it was to provide.

IEC 600434-5 does not show up in a Wikipedia list of current IEC standards. You sure of that number?

List of IEC current standards...

60034-5 and -11 appear to be the ones of note...expensive to get a read through copy!

http://webstore.iec.ch/webstore/webstore.nsf/mysearchajax?Openform&key=60034&sorting=&start=11&onglet=1

Your wright in assuming the Klixon over tempt. device should have tripped before permanent damage is incurred. Have you at any time had time to check the performance of the klixon unit? Just as you never fine time to clean the filters of the cooling air fan, you might have assumed all is well with the klixon temperature unit. The klixon modules are mostly unreliable when exposed to hazardous conditions, particularly in abnormal ambient temperature areas. The room temperature where the driver or control panel is installed is of vital importance to the performance of klixons. More so there is nothing wrong in having a double protection such that the motor can also trip on Over current. Take Care.

Installed for 3 months.

Air inlet at com end, outlet at drive end.

Pole face windings and commutator windings are OK.

Thermo about midway along shunt coil. As you can see the drive end was much hotter than com end, mid coil was somewhere in between. Therefore insulation was damaged at drive end by the time the thermo opened.