Motor Sizes 1

[pilts]

I have an apllication, where we I will be installing 4off 380kW pump motors. Initially it was assumed that these motors would be fed at 415 50Hz.
Can anyone suggest at what point it becomes economically viable to opt for H.V. (3.3kV or 6.6kV) drives as opposed to 415V.
The cabling itself is not really a problem as the route lengths are relatively short (i.e. <30M). However the feeding transformer will need to be in the order of 3MVA to cope with the other on site loads. This in itslef is a problem as 11/0.433kV 3MVA transformers are non-standard.

Thanks

 

[jbartos]

Suggestions:
1. Power plant generating stations often use a rule:
1a. 250hp and up 4160V 60Hz 3ph for squirrel-cage induction motor power supply and full-voltage across the motor terminal starts
1b. Below 250hp 480V 60Hz 3ph for squirrel-cage induction motor power supply and possibly reduced voltage across the motor terminal starts
2. However, the 480V AC 3phase power supply may power squirrel-cage induction motors up to 600hp
Reference: Smeaton R. W., &quot;Switchgear and Control Handbook,&quot; Second Edition, McGraw-Hill Book Company, 1987, page 9-9 Table 3b &quot;Standard Voltages for Large Polyphase Induction Motors.&quot;