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magnetic (instantaneous) tripping. In most cases we would want the intermediate circuit
breaker (CB03) to respond thermally to a short in Load 2, but with a shorter delay than that
of CB01.
In order to protect the UPS's bypass contactor and also the main input of the UPS, for all
scenarios including short circuit, Gamatronic recommends the following:
•
The circuit breaker that feeds the bypass input line and the circuit breaker feeding the
main input of UPS shall have no magnetic protection delay, or a maximum magnetic
protection delay of 50 msec. This ensures that the circuit breaker will interrupt the short
circuit before any damage can be done to the static switch contactor and the UPS
modules. If you choose to use a time-delay circuit breaker on the bypass input line,
recommended rating of the breaker is approximately six (6) times the maximum bypass
input current.
•
When using a circuit breaker with delayed magnetic protection, the ability of the cables
and the rest of the infrastructure to withstand a short circuit must be taken in account.
Table 6 on page 24 provides recommend ratings for the circuit breakers and/or switches on
the UPS's input and output lines.
Ratings of circuit breakers and cables connected to the UPS must comply with applicable
local and national electrical codes at the installation site.
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POWER + SA: 20, 30, and 40 kVA, Release 2.1
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