Open rotor versus locked rotor current for wound rotor motor 1

[eeprom]

Hello,
I have a wound rotor motor, 75 Hp. On start up, the stator coils are energized with the rotor stationary. Then a drum switch is used to allow rotor current and thereby start the motor. The stator draws very little current while the rotor is open circuited. But if I were to remove the rotor from the motor frame and then energize the circuit, I would destroy the windings. What is the difference here? Why doesn't the open rotor destroy the stator?

thanks
EE

 

[electricpete]

The difference in the two scenario’s is the presence or absence of rotor iron. When present it decreases the reluctance of the magnetic circuit and therefore increases the magnetizing reactance and limits the magnetizing current.

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[eeprom]

That makes sense. Thanks.