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4.5.7 An electrical interlock shall be provided to ensure the isolation switch does not open with
the control power transformer under load. This interlock shall be designed such that during
switch opening, the transformer secondary is disconnected prior to the opening of the switch
blades. Also, during switch closing, the switch blades must close before the secondary load is
reconnected.
4.5.8 An electrical interlock shall be provided to prevent the vacuum contactor from being closed
using external test power unless the isolation switch is fully opened and the secondary of the
normal control power transformer is disconnected from the control circuit to prevent backfeeding
the transformer.
5. Ratings
5.1 Controllers shall be rated as follows:
5.1.1 Interrupting Ratings
- Contactor 7.2kA @ 6.6kV Max.
- Controller 50kA RMS Sym. @ 5.0kV Max.
200MVA @ 2.3kV
350MVA @ 4.0kV
400MVA @ 4.6kV
5.1.2 Continuous Current Ratings
N-1 Enclosure (Ventilated) 720A
N-1 Enclosure (Non-ventilated) 650A
N-12, 3, 3R Enclosure 600A
5.1.3 Horsepower Ratings - Induction Motors (Approximate)
@2.3kV@4.2kV
N-1 Enclosure (Ventilated) 3000 5500
N-1 Encl. (Non-ventilated) 2750 5000
N-12, 3, 3R Enclosure 2500 4500
5.1.4 Short Time Current Ratings
4320A - 30 seconds
10,800A - 1 second
5.1.5 Impulse Voltage Withstand
60kV
1.2 x 50 microsecond wave
Rev. 5, 2/16/1999