electrostatic transformers
- Thread starter blt
- Start date
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- Location
- Lockport, IL
- Occupation
- Retired Electrical Engineer
Re: electrostatic transformers
Why have that transformer at all? Why not just connect the motors to the upstream panel? Do you need to isolate the primary from the secondary, perhaps for reasons of harmonic distortion?
If you are asking whether it is necessary to provide a neutral to a distribution system for which all loads are 3-phase and none uses the neutral, the answer is that it isn't.
Why have that transformer at all? Why not just connect the motors to the upstream panel? Do you need to isolate the primary from the secondary, perhaps for reasons of harmonic distortion?
If you are asking whether it is necessary to provide a neutral to a distribution system for which all loads are 3-phase and none uses the neutral, the answer is that it isn't.
rcwilson
Senior Member
- Location
- Redmond, WA
Re: electrostatic transformers
IMO -A 480V delta to 480/277 wye transformer can provide some advantages:
1. Reduces fault current, especially if the upstream 480V system is fed by a large transformer (2500 kVA). The lower fault current may allow panels and breakers with lower short circuit ratings (=cheaper). Arc flash hazard may be reduced also.
2. Makes coordination of ground fault protection easier. A ground fault on the 480/277V side will only be seen as a phase-phase load on the upstream 480V system. This allows the upstream GF tripping devices to be set to trip faster.
These advantages have to be weighed against the disadvantages: additional kW losses, additional voltage drop on motor starting, plus the added transformer, secondary protection and panel and the space they take.
IMO -A 480V delta to 480/277 wye transformer can provide some advantages:
1. Reduces fault current, especially if the upstream 480V system is fed by a large transformer (2500 kVA). The lower fault current may allow panels and breakers with lower short circuit ratings (=cheaper). Arc flash hazard may be reduced also.
2. Makes coordination of ground fault protection easier. A ground fault on the 480/277V side will only be seen as a phase-phase load on the upstream 480V system. This allows the upstream GF tripping devices to be set to trip faster.
These advantages have to be weighed against the disadvantages: additional kW losses, additional voltage drop on motor starting, plus the added transformer, secondary protection and panel and the space they take.
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