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Ward Leonard DC control:


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Ward Leonard DC control:

 

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The crane and the face shovel have one thing in common, Ward Leonard motor control.

 

The face shovel has three generators driven by a single 3.3kV 300HP squirrel cage motor. This as you can probably imagine is a fairly hefty lump of machinery, the motor generator set forms a part of the shovels rear counter weight. The three control exciters are driven by a separate motor and the constant voltage exciter has a motor all to itself. Starting the main set was by an autotransformer oil switch, all the ancillary drives started all at once via a DOL starter.

 

On the cranes there was a single 250HP squirrel cage motor started DOL, it drove the main generator and both the exciters.

 

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The cranes only have one DC motor for the main hoist, the auxiliary hoists were AC. The motor generator is on the overhung platform. On this set the motor, generator, control exciter and constant voltage exciter shared a common bedplate. The drive was started DOL.

 

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This is a very much simplified animation. I’ve missed out the delightfully named “suicide shunt”. Basically this momentarily reverses the control exciter field to kill any residual magnetism. Without this a small current would be allowed to flow in the generator field causing the motor to creep.

 

A favorite trick of both the crane and shovel drivers was to “accidentally” start two MG sets at the same time causing the feeder breakers to open. No power equals a longer meal break.

 

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