Buck Boost Transformer Application

[ajob]

I came across an applicATION FOR BUCK bOOST TRANSFORMER. I need to provide power for a 240 volt sewage pump motor. The available source is 208 volt single phase. More clearly 208 volt 2-phase with neutral feeding a panelboard. I was told by the pump manufacturer technical expert that I can boost 208 to 240 and supply the motor.

The motor control panel need 120 volt power.

Is it okay to bring the neutral required for the motor control panel from 208/ 3 wire source (panelboard) and phase from output leg of boost transformer)

I was told by the pump manufacturer technical expert that, that is how the internal wiring is done in the pump control panel. Does it violate NEC 2002?

Please e-mail the reply to me.

 

[scott thompson]

Re: Buck Boost Transformer Application

I know you want the reply by E-Mail, but just want to see what other with more "NEC Savy" will say (if this is Okee-Dokee per the good book!):

If I understand your post, it appears you need to boost 1? 208 up an additional 32 volts, to 1? 240 VAC for an Induction Motor. Unsure what size Motor (H.P.) you have, so for an example I'll use a 1 H.P. Motor.
Along with the 240 VAC Motor circuit, you also need 120 VAC for control circuit.

Two options:

1: Drive a 500 VA 120/240?16/32 Isolated Transformer - connected as Voltage Boosting, Series connected windings, via a 20 or 30 amp 208 VAC 2 wire circuit (from a 2 pole breaker).
Also bring a Grounded (Neutral) Conductor from the same Panel.
Use one of the Ungrounded Conductors, along with the Grounded Noodle, for the Control Circuit. Tap Ungrounded Conductor from "Line" side of Boost Transformer. Run all Ungrounded Conductors through a 3 pole disconnect switch.

or;

2: Using the same setup as above (except the Grounded Noodle), tap in a Control Transformer on the Motor Feeder Circuit. Tap on "Load" side of Disconnect.

Does this sound OK, or just silly

Scott35