t9jrt7homas61
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I have a 480 volt primary and a 480v/277v secondary. The input amps and output amps are the same (273 amps)Do I have to have primary and secondary overcurrent protection
If the facility 'service' voltage is ungrounded, corner grounded, or high resistance grounded L-N loads are not allowed, so a 480-480Y/277 transformer is employed to create an isolated 4-wire system (usually for lighting).
I have a 480 volt primary and a 480v/277v secondary. The input amps and output amps are the same (273 amps)Do I have to have primary and secondary overcurrent protection
We use the 480-480/277 transformers to feed lighting circuits. We see several advantages:
1. Able to use High Resistance Grounding on the main 480 power systems.
2. 3-Phase, 3-Wire saves the neutral on the large feeders to MCC's and switchboards.
3. Transformer reduces short circuit current on lighting circuit, dropping the arc flash level and increasing safety.
4. Lower short circuit allows use of less expensive lighting panel circuit breakers.
5. Process loads and lighting loads are kept on separate panels. An electrician trying to find or kill a lighting circuit doesn?t dump the plant.
Can we call it tertiary winding transformer ?
No, a tertiary winding transformer would have another winding, not just the two in a 480-480/277 transformer.
For instance, see the 110kV/25kV/10kV transformer in this article http://siemens.siprotec.de/download...rotection_of_three_winding_Transformer_en.pdf