Motor Over Load Issue

The motor overload must be set no higher than the rating plate on the motor if the motor is to survive without burnout.

Any impact on running the motor 24/7/365 must be checked with its manufacturer. It seems that at the moment it won't do this without occasional overload tripping.

If the overload trips while it has been correctly set then the process conditions are causing the overload. It is the process that determines the load that the motor "sees", and the current it draws while the load is present. So the cause of the trip may not even be electrical at all.

If you have a thermal imager or laser thermometer I'd take the starting temperature of the overload. I'd check it every 15 minutes or so while reading amp draw. I suspect your overload could be defective.

You might also check to see if you have access to a "peak" current meter. It will record the largest current you are seeing.

Running a motor very close to its rating leaves no margin for error. An increase in the density of what you are pumping may be enough to overload the motor.

But more likely, the mechanics of the system, such as bearings may overheat and add to the load. They will be hot or noisy just before the overload trips and then they will cool. A majority of "electrical failures" are really mechanical failures.

The very first thing I would check is the current BALANCE between the 3 phases. Many, if not most, solid state overload protection units now include pahse current imbalance protection (sometimes whether you know it or not). What it will do is detect a current imbalance and bias the OL protection curve LOWER than you will think it is from the setting. This is to compensate for the added motor heating that will be the result of negative sequence currents created because of the imbalance.

So in other words if you have a setting of 28A, the biasing of the OL curve due to the imbalance may be lowering that trip pickup point to 22A or 23A, so when you are running at 26.5A you have what THE OLR thinks is an overload condition. It's a very common occurance now with SSOLs and many people are unaware of it. It's actually not a bad feature, you just need to understand what is happening. Phase current imbalances generally are the result of some of the things you have already eliminated, but also any VOLTAGE imbalance has an exponential effect on the current imbalance. So if you do show a current imbalance, check the voltages as well, that may be the root cause.

If you can, correct the current and/or voltage imbalance and the problem may go away. If not, you may have to live with it. I am not familiar with the GE 501 series unit, but most likely you can either adjust the phase current imbalance protection feature or even disable it if you are so inclined. You should however understand the consequences first. A small amount of current imbalance heats up the motor windings faster than a standard OL protection curve is designed for, so you can significantly decrease the motor life by running in an imbalanced condition over time.

you need to set the overload to 110%, set the overload delay timer, current unbalance to 1 second as a start and see if that does it.

do you have a recorder you can fit to the motor/controller, to record, running current etc? Or see if the motor controller can "Trend" what is happening, that is record over 24 hours exactly what the motor does.

You need more information to make an educated decision, however try increasing the delay timers to see if that helps, if not then call the manufacturer for advice.

Just by the way, could you have made a typing error on the relay part number? I cannot find any reference to a Multilin Motor Manager "501". There is an MM2, MM3, MM200 and MM300 series, but nothing that starts with a 5. The only Multilin product that has a "501" in it is a modification number for a PQM Power Quality METER, which is NOT an overload relay so it would not trip at all, it would just indicate to you that you have a problem. If that's what you have, that may be the problem!

Also by the way, the Multilin relays are set to the motor nameplate FLC, then there is a separate programmable pick-up point and all manner of delay settings that can accommodate virtually any starting scenario. If you used it "out of the box" without knowing how to properly commission it, that may be a contributing factor as well.

May i know Insulation class of motor and Running temperatures of motor and relay