Cable size for Motors 1km away from controller 1

[SAMBOY]

I will install a 100HP 3Phase 60Hz 440V Induction Type motor 1 kilometer away from the Motor Control Center (Using Wye Delta starter). I'm planning to use 6 sets of 3x200mm sq Copper Wire. Is it sufficient, under or over design? Need your suggestions. Thanks



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[mc5w]

A 440 volt motor at that distance is rather impractical. If your utility service is that far away you need to put your wye delta started right at the motor so that your 6 sets of conductor will be fully paralleled to control voltage drop. At this distance you need more like 1,000 amp wiring.

Is this motor a submersible pump that is way down in a mine? An application that is that far away from the controller is almost always done using a 2,300 volt or 4,000 volt motor with an autotransformer reduced voltage starter or a medium voltage soft starter. A wye delta starter WILL NOT work 1 kilometer away from the motor.

Mike Cole, mc5w@earthlink.net

 

[SAMBOY]

Mike,

The motor will be installed on a jetty 1000 meters away from the shoreline (location of the controller). The problem is, it was already purchased.

If the wye-delta starter is not possible, then we have to provide a power generating set near the motor.

Thanks a lot.

 

[mc5w]

To what extent can the controller be hardened against harsh weather out at the far end of the jetty where the motor is? If you are really worried about driving rain getting into the controller then location at the shoreline is not any better than location way out on the jetty.

What kind of load does this motor drive?

Are you locating the controller at the shoreline merely to save on service entrance equipment? If so, you are better off buying another fusible switch or circuit breaker and putting the controller at the motor.

Even if you try to brute force this with seven 1000 amp conductors ( 50% equipment ground plus 50% neutral because of the distance ) the cable capacitance will tend to cause the motor to act as an induction generator during the starting transition and during shut down. This could cause severe overvoltages when starting and stopping and also could create a large current spike when doing the wye delta transition. You may need rather hefty metal oxide varistor surge suppressors at both the motor and controller. You would need 12 at each end ( 6 phase to neutral and 3 across each winding and the other 3 across the wye contacts.

Also, in this application THWN conductors will have very high capacitance when wet. You will need to use XHHW ( cross linked polyethylene ) or EPDM conductor insulation because it will have less capacitance when wet.