motor perfomance on over speed

[ram14375]

sir,

we have got a 2.2 kw motor 415v 4.85 amps Full load sqcage gearised motor operated by v/f drive for driving packer unit.Now at the drive we have set for 50hz(rated frq) and the motor is drawing around 2.8 amps.

 

we want to increase the speed upt to 60hz.

what will be the torque and how about the motor perfomance

thanks

ram

[marke]

Hello ram

 

Unfortunately, without further information on the operation of the machine, I can not predict the load at 60Hz, but there is no harm in trying it. I would slowly increase the speed and provided that the current does not exceed the rating of the motor or the inverter, you should be OK.

 

Above rated speed, the motor is "power limited" which means that as the speed is increased, the power rating remains the same. This is due to the limitation caused by the supply voltage. The drive should be increasing the voltage with the frequency increase in order to maintain the v/Hz ratio, but it can not lift the voltage above the incoming line voltage. The voltage limit causes the flux in the iron to reduce with increasing frequency, resulting in a reducing torque capacity with speed.

 

With a 2.2KW motor, it is probable that it is star connected for 415 volts.

If you needed more that 2.2KW at 60Hz, it may be possible to rewire the motor in delta and set the drive up for a rated output voltage at 50Hz of 230 volts. If you do this, then the drive which is fed by 415 volts, can continue to lift the output voltage with frequency.

 

Best regards,

[ram14375]

sir,

The motor is gearised type and it is used for driving packer(for cement industry).which supplies cement through spouts and it rotates at 5rpm for 50 hz.

 

hence on the driven side only the rpm will increase .

 

 

u have said the motor is power limited above base freq.is that means it can be operated up to the rated motor kw(in our case 2.2kw).since the load current is now only 2.8 amps case the motor kw will be now 1.732x415x 2.8 x 0.78 around 1.56 kw.

can i load the motor up to the full load current of the motor.

 

thanks

ram

[marke]

Hello ram

 

Yes that is correct, you can load up to the current rating of the motor.

 

Best regards,