Motor rating for VFD 1

[MarTech1]

I have an ABB 30kw VFD ACS550 380V, I am in the process of specifying a motor, can I use a standard 30kw motor or would I need an increased motor kW rating ie 37kW. What do I need to consider?

 

[itsmoked]

Look for a VFD rated motor as that will do more for you than a straight 37kW.

The VFD does things with voltage that can be improved/protected with a VFD motor but that isn't generally improved in just a higher kW.

Keith Cress
Flamin Systems, Inc.-

http://www.flaminsystems.com

 

[edison123]

The magnet wire of the winding will have a different insulation (Dual coated called amide-imide) for a VFD rated motor. The standard motors will not have such insulation and hence not fit for VFD use.

 

[Skogsgurra]

If you are buying a new motor in the 30 kW range I think that most manufacturers will sell you a "VFD hardened" motor. If you are going to use an old, existing motor you have better check that the insulation can take the PWM voltage. Some can, some can not. Putting a small du/dt filter between inverter and motor is a good idea. Then you can use any motor.

Power rating: Before PWM, it was common practice to use overrated motor because the harmonics contents in motor voltage was quite high. Modern inverters do not give you that problem. So you should not need to overrate the motor.

But then, there is the cooling that usually get worse when speed is reduced. So, if you plan to run below half speed with a shaft mounted cooling fan, you had better check with the manufacturer. Which is a good idea in any case.

Also: Remember the bearing problems. They can be quite nasty in this power range. Especially with floating loads.

Gunnar Englund

http://www.gke.org

--------------------------------------
100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...

 

[elmotor]

Your drive 30 kW, giving maximum nominal output current of appr. 60A, which determines your maximum load. Why would you like to use 37 kW motor? I think that stator winding temp. rise is not a problem and you are not in Ex -area?

Consider following things:

1. Constant or quadratical torque
2. Speed range.In very low frequencies,some IR-compensation might be needed and at high speeds, ie. above fwp., especially friction and windage losses will be increased significantly. Keep in mind also lubrication intervals.
3. Usually at voltages below 500 V, special wire or special insulation is not needed. Recommendations varies.
4. Insulated N-end bearing could be worthwhile,even they are not always recommended for motors in this range.

 

[elmotor]

Oops, because it was my first time in this forum, it happened as for young men... for sure you know what I mean.

Additionally pay attention in cabling and grounding to avoid bearing currents.

 

[DickDV]

You should size your motor based on the load torque-speed profile. And, as stated, use an inverter rated motor as to insulation. In the US, that would mean a motor rated to MG1 Part 31, in my opinion.

You must also consider cooling issues if the motor is to be operated loaded below about 1/3 speed. You may have to switch to an auxiliary-cooled motor if you are operating heavy loads at slower speeds. Your motor manufacturer can give you speed-load profiles for your motor.

Finally, given the motor's continuous current at the expected continuous load plus the motor's peak current at the load's peak torque requirement, check your drive to be sure you have enough ampacity both continuous and short-term peak to cover the motor's requirements. If the drive has more, you are ok. If the drive has less, the drive is not big enough for the job. If the drive has exactly what your motor needs, why then, you are having an incredibly lucky day!