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Years ago I worked in a plant that had home made portable motor heaters. We hooked them to the motor T leads at the starter and the unit passed current through the motor windings to keep the windings warm. We used them on motors that did not have resistance heaters built in the motor.(The heater was hooked up only after the starter was locked out and the T leads were disconnected from the starter.)Now what I am looking for is a schematic for a similar unit. The only thing I am for sure of is that it had a large capacitor bank in it I will say aprox 20 and it did operate on 480 volts . Has anyone ever seen a similar unit THANKS HYPRESS

 
There are controllers for off-cycle stator heating that are intended for fixed installation, but may be applicable to portable use. Two links.. www.motortronics.com/products/otpr.html www.ab.com/en/epub/catalogs/12768/229240/229258/229579/print.html
Not familiar with a capacitor method, but low-voltage transformers and starter interlocking have been detailed in 1970s-era IEEE Industry Applications transactions.




[This message has been edited by Bjarney (edited 08-29-2004).]