Transformer tapping query

We have a ten 1000kVA transformers on site.
They transform the 3 phase 11kV phase to phase supply down to an average of
about 425V phase to phase.
Most of our plant is designed to operate at 400V phase to phase (230V phase to neutral)
If we adjust the tappings of the transformer to give us 400V phase to phase (230V phase to neutral), I believe we can expect a substantial reduction in energy consumption.
Our plant consists of extrusion lines & weaving looms, so we have many direct on line 3 phase induction motors, & dc drives/motors.
Has anybody tried this method to reduce energy consumption, & if so what was the result ?
TIA
woodglass...
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woodglass wrote:

I don't think I'd bother,although your average of 425 v on a 400 v nominal system is 6% high and would not be within customary tolerance for North American utilities. Measure this frequently and see if it's really the case, or did you happen to measure during a lunch break when all the machinery was shut down? Do you have power factor correction in the plant and is it regulating properly? Is the 11 kv also high?
Induction motors tend to be constant power loads - a voltage reduction won't necessarily proportionately reduce power. Similarly for dc drives, these will have control circuits on them to match the motor output to the load and speed required; all that will happen is that the motor drives will phase back a little bit, but you won't see an energy reduction.
You may see some reduction in incandescent lamp energy consumption ( and less light, but fewer bulb changes). This would be a small part of your load in any case, and likely your plant has fluorescent lamps or HID lamps that regulate for small changes in voltage also.
Check with your local electrical supply utility and see if their customer service representative can help you - they will likely have some programs to help you conserve energy, and can point at other things you may do to improve energy efficiency.
Bill
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| I don't think I'd bother,although your average of 425 v on a 400 v | nominal system is 6% high and would not be within customary tolerance | for North American utilities.
It's about the same increase as using 120V appliances from USA on 127V in Mexico.
I would agree the OP really doesn't need to do much with the voltage to do energy concervation. Only the resistive and psuedo-resistive loads need to be attended to (e.g. heating elements w/o controls, and incandescent lights). All the rest should draw less current resulting in less wiring losses. Any incandescent lights that can be changed to FL/HID should be. Everything else is a matter of figuring out smarter ways to use electrical energy.
If he were 6% low, then I might have suggested getting it raised.
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