we are having slipring induction motor for crane application using rotor resistances for their torque. suppose i use drives for these motors what should i have to do for rotor resistances. please give me a proper solution
Specific drives are not necessary. General purpose drives are often used for slipring motors. The rotor resistors and associated control system is removed and the sliprings are shorted together. The stator windings of the slipring motors will probably not be able to withstand the voltage stress due to the voltage spikes caused by the fast switching of the PWM output waveform. That will require output dv/dt filters to be added. Drive suppliers are familiar with the problem and have appropriate filters available. The slipring motors are probably capable of higher starting torque than the drive can provide. If that high starting torque is needed, you will probably need to replace the motors. Edit 1 If the slipring motor is providing braking, the drive will need to be equipped with braking. AC drives can be equipped to provide braking by motor regeneration to dynamic braking resistors or to the power source. Edit 2 This is motor probably drives the hoist motion of the crane and must have a friction brake to hold the load in a stationary position. The drive will need provisions to coordinate the release and application of the brake with the starting and stopping of the motor by the drive. You should try to find a local drive supplier that is a specialist in hoist applications or is at least familiar with hoist drive application requirements.
your question is hard to understand but i believe any of the ac drives will work with an induction motor. go to the manufacturer's web site and look up the specs on the drive you are interested in.
This is common on crane upgrades to short out the rotor and use a drive. There are specific drives for cranes but I have never seen a specific drive for a wound rotor motor. The standard crane drive is used. You may have a concern about the motors if they have not been rewound recently since voltage spike from the drive may damage insulation of anything lower than class F. Most re-winders use class H.
