I would like to know whether HT motors can be used as Bidirectional application i.e whether the HT motors can be rotated in both the directions if the application demands. If anyone is using so for any application, please mention the application and the control method.

 

Of course, but frequency of reversal and moment of inertia of all rotating elements must be carefully evaluated!

The application I am most familiar with is crane and hoist duty.

Regards,
Phil Corso, PE
Boca Raton, FL
[[email protected]] ([email protected]) {[email protected]}

 

Thanks for your comments. Please elaborate what are the factors to be considered for such application. Please also let me know the ratings (KW and Voltage) of the HT motors you have used in such type of application.

 

My only recollection was that they were in the 1 MW range and about 3kV. More importantly, they were not 2-pole machines.

There is a simple reason why the "standard" design motor probably shouldn't be used in reversing service.... starting duty. If you start
it, wait for it to coast to a stop, and then start it again in reverse, you are limited to two to three starts per hour. If the duty is much
more severe, then success is dependent on the motor's ability to adequately absorb the effects of heat produced during acceleration.

Typically, the larger the motor, the lower its capability regarding the handling of the kinetic-energy requirements: a) acceleration; b)
plugging to a stop; and c) reversal. These operations produce heat in both the stator and rotor of the machine.

Obvious key factors in the total heat produced are system inertia, and the square of speed change (hence my earlier caveat about the number of poles). Less obvious, but no less important are the ratio of stator to rotor resistance, and the motor's design torque-speed characteristic.

As an example, consider a motor capable of accelerating a given load, then one-unit of heat (Ha) is produced. Most large motors are designed
for about 3 Ha, hence the limits on frequency of starts! However, during a plug-stop (from full speed to stop) the loss is about 3 times Ha. And, during a complete reversal up to 4 times Ha is produced. Thus, you can see why starting-duty must be thoroughly examined!

If you have additional application detail, I may be able to provide additional insight.

Regards,
Phil Corso, PE
Boca Raton, FL
[[email protected]] ([email protected]) {[email protected]}