AB motor thermistor problem

[Ramsri]

Hi all,


I am facing E-4 Error continuously in Ultra 5000 Servo drive. I think the Motor(MPL series motor) thermistor damaged but there is no high temperature acutally in the motor. While discussing with the supplier he told me i need to go for another one motor. Since it is a temperature high indication, How can i bypass the error and run. I dont have any software to modify. Can anyone suggest me to do in Bypassing the Error without software modification???

Ram

 

[Valley Ind]

Ramsri,

I wouldn't suggest running without motor thermal protection, but to check the thermistor you could put a resistor in its place. Select an ohms value that will match the thermistor at 70 to 100 DegF.

But don't do anything that will void the warranty.

 

[jraef]

So how are you so confident that there is no high temperature in the motor? Does it read as high resistance through the thermistor circuit when the motor is off and has been sitting on the bench for an hour? If so, then yes, the thermistor is likely bad, or the wire going to it, same difference. A thermistor is a PTC device, meaning Positive Temperature Coefficient of resistance; as the temperature rises, so does the resistance of the thermister. The circuit inside of the drive is dropping a voltage across that resistor and as the resistance increases, the voltage decreases. If the wire breaks or goes to ground, that ALSO drops the voltage to the circuit and the drive reads it the same. So before you ASSume tht the thermistor itself is bad, make sure there is just not a loose connection or broken wire.

Then, if you are determining that there is no high temperature because you cannot feel anything on the outside, that too is a mistake. It takes a while for winding or rotor heat to make it to the exterior case and build up to where you feel it as hit, but inside of the motor, the hot spot can be right next to the thermistor and it can be detected much earlier. Then because it shuts down the drive, by the time you get to it, that heat has dissipated on the case surface and you don't feel it.

So if you are reading a high resistance in the circuit, you KNOW that it is not just because the wire is broken or there is a loose terminal somewhere, and the motor has been sitting idle for more than the motor cooling time constant, then you must have a bad thermistor and you can put a properly sized resistor in it's place temporarily (you might try just jumping out the circuit, but some drives detect that as a short). You will not have thermal protection for that motor however.

 

[alan_505]

I thought that the thermals in the MPL motors were just a switch.
So you could bridge the switch out at the encoder wiring.
You would need to check the manual to see which wires to bridge.


Alan

 

[jraef]

I thought that the thermals in the MPL motors were just a switch.
So you could bridge the switch out at the encoder wiring.
You would need to check the manual to see which wires to bridge.


Alan

Actually that's a good point. The input of the Ultra5000 is for a thermistor, but the MPL motor only has a basic thermal switch, not a thermistor.