ABB Drive Issue

1. You do not indicate if the drive alarm is for the motor temperature or the drive temperature, the drive is monitoring both.

2. If it is the motor temperature, you do not indicate if there are temperature sensors inside of the motor that are feeding the information to the drive, or if the drive is calculating (estimating) the temperature solely based on current.

3. Using an IR camera or scanner on the exterior housing of a motor to try to determine the winding temperature is like trying to bake a cake using the thermostat for your whole house to control the oven temperature; useless other than if the cake is already on fire and burning the kitchen down. In other words, it is not telling you anything useful.

Stop panicking, slow down and be more thorough. If the drive is tripping on motor over temperature but has no thermal sensors connected, it is telling you that the motor duty cycle is likely too high, for example you are starting and stopping too often or accelerating and decelerating too quickly. If there are sensors, and they are RTDs, then you likely have a problem in the motor, maybe a failing winding, bad bearings or a broken rotor bar (assuming here that it is an AC motor). If the thermal sensor is just a thermistor (more likely if it goes directly into the drive), then it may just be a bad connection or a loose wire, and thermistors are not good at analog temperature measurement, they are threshold devices. So if it is doing it's job correctly, you have a serious motor problem and the drive is preventing a fire long before the outer motor housing shows signs of stress.

Thanx Mr. JRAEF

This is actually motor temperature which drive monitors. and per winding we have 1 thermistor for motor temperature monitoring. External Exhaust Fan was used to lower the temperature but 1 degree celcius rise occurred after every 5 minutes and it got tripped eventually.We restarted and it run normally for 2 hours then it again tripped with over temperature and Then its 24 Vdc supply was reset and its temperature was gradually became normal.

Best Regards,

Is this DC drive or AC?

ABB has a thermistor relay L505 optional for ACS800 drive.

The ACS800 can also use the +24VDC voltage supply connected to DI6. The drive stops the motor if the PTC thermistor resistance exceeds 4kohms. Are you using DI6?

You can also use the analog (current)output and an analog input to measure the temperature - if you have the correct PTC thermistor.

There are different thermistors with different "knees" in the characteristic - do you have the correct one (programmed)? Is it around 1.5K at 30C ambient - when the motor has been sitting unused for several hours?

There is also a Motor thermal model Over temperature mode that is independent of the thermistor - does it trip at the same point?

Have you checked the RMS current to the motor? Is it over NP value?

Is this a force vent motor? Do you have adequate cooling? I have seen blower motors connected with the wrong rotation and the cooling is poor.

Are you running slow with a fan cooled motor (not force vented)?

Thermistors are not very good at relaying temperature values, they are better at simply proving information to something else that a specific temperature has been reached. They do so by the fact that they resist a change in resistance until the temperature level they are designed for causes the resistance to suddenly increase rapidly. When that resistance increases, the sensing device indicates that it needs to trip. Unfortunately, a bad connection or failing conductor will ALSO increase the resistance in the circuit, which can be easily misinterpreted as a temperature increase.

Dear Guru/JRAEF,

Thanx for contribution. Actually this is ac drive and we are not using DI6 with +24 Vdc.One more thing I could not mention it was not paper roll rather it was Chiller Roll where by mistake some chilled water was pouring because of some manual valve got opened. So torque of the drive rose to the point that its temperature passed the limit of tripping.After its water was drained, the motor temperature became normal and it is still running normal today.

Best Regards,

Was that an internally chilled roll, with a siphon to drain the water?

On a paper machine I have seen dryer cans with excess water condensate causing overload of the section.

Another time a chilled size press roll flooded and caused overload of the section.

If you do not need the OL current to accelerate the section, you can set the current limit to 100%, When something silly happens like an open valve, the section will slow down but not trip out. Additionally if you need the OL current to accelerate you can program from your PLC OL current levels for the accel, then clamp it back to 100%. I use this technique on Dryer sections that have very large inertia but low running current requirements. A trip of the motor and drive causes too much down time and a maintenance call to reset.