5.5 kW motor on 11 kW drive

Hello.

We tried running a backup motor on a micromaster 430.

The micromaster is rated at 11kW and the motor is rated at 5.5 kW.

While the motor was running on a contactor it was drawing 13.5A

When we started it on the drive it was drawing 16A at 15Hz and it wouldn't go above 15Hz even though the minimum frequency on the drive was set to 30Hz. I guess the drive overcurrent triggered.

My question is why was the motor drawing so much current and can you run a 5.5Kw motor on a 11kW drive?

The drive was programmed for a 5.5kW with factory reset before commissioning.

Thanks for any answers.

AutoGen_3369369

Hello.

We tried running a backup motor on a micromaster 430.

The micromaster is rated at 11kW and the motor is rated at 5.5 kW.

While the motor was running on a contactor it was drawing 13.5A

When we started it on the drive it was drawing 16A at 15Hz and it wouldn't go above 15Hz even though the minimum frequency on the drive was set to 30Hz. I guess the drive overcurrent triggered.

My question is why was the motor drawing so much current and can you run a 5.5Kw motor on a 11kW drive?

The drive was programmed for a 5.5kW with factory reset before commissioning.

Thanks for any answers.

 You do not say what the mechanical load is?

A DOL starter, this will run up to synchronous speed with a high torque start, the overload will ignore short term over currents. Any mechanical resistance then will be ignored during acceleration. 

The inverter drive will ramp up with a relatively slow acceleration, the current monitoring will be quick and accurate and will respond to any over current during this time. this may be the reason the drive has gone into current limit.

If you can come back with some detail regarding the mechanical load we can then advise.

Pump, fan, auger, conveyor, or screen for example, may give a clue to what you have seen.

AutoGen_3369369

Hello.

We tried running a backup motor on a micromaster 430.

The micromaster is rated at 11kW and the motor is rated at 5.5 kW.

While the motor was running on a contactor it was drawing 13.5A

When we started it on the drive it was drawing 16A at 15Hz and it wouldn't go above 15Hz even though the minimum frequency on the drive was set to 30Hz. I guess the drive overcurrent triggered.

My question is why was the motor drawing so much current and can you run a 5.5Kw motor on a 11kW drive?

The drive was programmed for a 5.5kW with factory reset before commissioning.

Thanks for any answers.

 Hello,

To me sounds that nominal motor values are not correctly entered into drive. Anyway:

Motor or any load does not draw as you say Current, it draws Power, so please provide info about your voltage on the motor during measurement. What is motor connection, delta or star, please paste here motor plate, saying just 1 number 5.5 does not describe motor as an Load at all. To fully describe nominal motor values you really need a lot more. For heater is enough to say just power.

Best Regards Soble 

Thank you both for the answers. Thank you for correcting my wrongly used terms.

We are talking about a submersible pump. It is about 20 meters deep. I don't have the plate. But I found online specifications.

Unfortunately I do not know the voltage during measurement, just the amperage.

I can only say that it happened during ramping up and that the pump wouldn't go up to maximum speed because of frequency limiting. (At least that's how I understood the problem)

If you need some more information I will try to provide.

Thank you for your time.

My. Response would be to lift the current and power settings to stop the current limit being tripped.

Run the motor to full speed and use the inverter to monitor the running current, this will allow you to see what is happening.

It is possible that the pump is ok, and the system, that is the static and dynamic pressures are creating the problem. Now with inverter acting as a useful monitor, investigate any valve which will restrict the flow, it is possible that the pump is operating on the incorrect part of the pump curve, for example, if a valve is available to restrict flow close it progressively and record findings. Looking for the control setting which permits the pump to operate over its full range.

After this investigation, the system will be re commissioned to respect the pump motor which is in use.

Note:

This is a centrifugal submersible pump, these devices need to operate between minimum and maximum speeds, and must accelerate to this working band as soon as possible. Extended operation of a submersible pump lifting a head of water, at low speed will damage the pump bearings, only operation within the permitted ’window’ is acceptable.

I hope this works out for you, come back if I can help further.