Wound Motor

[bob14]

Hi All,

I understand that starting a wound motor with the rotor short circuited will develop a very high locked rotor current and a very poor locked rotor torque. How detrimental could it be on the integrity of the rotor's insulation?

Best Regards.

Bob

[marke]

Hello Bob

It depends on the load that you are starting.

While you are operating at very high slip, frequency high, rotor speed low, the rotor current will be very high resulting in a very high I²R loss in the rotor and of course, lots of heat.

If you consider the full speed kinetic energy of the driven load, then that energy must be dissipated in the rotor circuit during start. Wound rotors are not designed to dissipate much energy and rely on the externally connected resistors to dissipate the slip losses during start. - expect to burn out the rotor if it is shorted during start on anything other than a Variable Frequency Drive!!