Question

Given: 100kVA single phase transformer, Z=1.5%

Primary: 480V 2 wire

Secondary: 120/240V 3 wire

Install the above transformer to serve a branch circuit panelboard. The panelboard will be located 10' from the transformer. The primary side raceway is PVC and the secondary raceway is EMT. All calculations will conform to applicable NEC regulations. The primary side, overcurrent protection device, will be chosen based on the next available standard size of the full load amps of the transformer. The secondary side, overcurrent protection device, will be chosen based on the size of the panelboard.

Provide the following information:

1) Full load primary amps

2) Full load secondary amps

3) Standard NEMA panelboard required

4) Transformer primary protection (See specifications above)

5) Transformer secondary protection (See specifications above)

6) Primary wire size (THWN 75°C)

7) Primary equipment grounding conductor size

8) Secondary wire size (THWN 75°C)

9) Conduit size for primary feeders (Schedule 40 PVC)

10) Conduit size for secondary feeders (EMT)

11) Grounding Electrode Conductor size

12) Secondary Bonding Jumper Size

13) Available Short Circuit amps at the transformer

14) Available Short Circuit amps at the panelboard (L – L)

15) Available Short Circuit amps at the panelboard (L – N)

Answer 1

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