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S3 PROTECTION
6–60
I
is the equivalent motor heating current per-unit on an FLA base. However, the value of
eq
I
is limited in this equation, to 8.0, in order to prevent the overload from acting as an
eq
instantaneous element, and responding to short circuits.
For example, a motor with a stall current (also known as locked rotor current) of 8 times its
FLA, with a Curve Multiplier of 7, if stalled from a cold state, would trip in:
This would respect a Safe Stall Time Cold of 10 seconds.
339 MOTOR PROTECTION SYSTEM – INSTRUCTION MANUAL
CHAPTER 6: SETPOINTS
Eq. 6
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