Fux

Hi,

I know that the maximum rated torque of a motor is limited to the rated speed of the motor. Above nominal speed, particularly when a VSD is used, the iron core saturates to a point that the maximum torque starts decreasing. I would like to determine the point of saturation. Any document or link would be appreciated.

Bob

Tandem

Dear Mark,

I posted a query some couple of months ago and I have been through all my posts but unfortunately could not locate it. You did reply to my query at that time. My post at that time was the necessity to phase align rotors for tandem application. I understand that this holds true for synchronous but not for induction ones. Grateful to refresh my memory relative to this query.

Thanks and best regards.

Bob

Vsd

Hi,

I am commissioning a VSD driving a conveyor. The VSD is struggling to pick up the load at standstill and is operating in current limit particularly when the conveyor is loaded. I have got a 4 pole motor on the conveyor and my intention is to replace it with a 6 pole one. However, I am not at all convinced that this will work. My feeling is that the motor is not able to break away the load at very low speed. The drive is operating in open loop mode. I understand that the 6 pole motor would provide a better starting torque but my worry is that would it be enough to start the loaded conveyor. I have also tried to con the drive by inputting a bigger motor(200 kW) in the configuration but this did work in some occassions but again with the conveyor fully loaded, the drive ran in current limit mode.The installed motor is a 160 k W one.
Any comment !
Bob

Motor

Hi,

I have go a 90 kW immersed pump which was working trouble free before. We just started to get overload conditions on this pump. The FLC of the motor is 160 Amps. The current measured on the three phases are 165 A, 150 A and 148 A. The imbalance tends to increase with increased laod
There is no voltage imbalance. I suspect something is wrong with the motor.
Any omment.

Bob

Vsd

Hi,

I just switched from one 600 k W VSD to a 900 k W one. The 600 k W was used on a V/F mode and the motor, a 600 k W 400 V one, was working within it`s current range. The 900 k W drive is configured on the direct torque control algorithm and the motor is drawing constantly much more than the rated current of the motor within the speed range but the k W rating is not exceeded. I belive that the 900 k W drive is underfluxing the motor !
Any comment !

Bob