problems of instability due to overhauling of the load.
c.
Provide controller fault protection so that a single or three
phase short circuit at the controller terminals or inverter
commutation failure will not result in damage to power circuit
components.
Provide overload protection so that motor and
controller are protected against operating overloads.
d.
Provide adjustable time delay undervoltage protection so that
motors will continue to operate during momentary voltage
fluctuation or loss of voltage. Time adjustment shall be zero to
5 seconds. Provide for orderly shutdown on undervoltage
conditions exceeding the time delay interval.
e.
Provide adjustable timed linear acceleration and deceleration.
f.
Provide volts/hertz control to prevent motor overheating
throughout the speed range.
g.
Provide door interlocks to prevent opening of enclosure doors
unless power is disconnected.
h.
Controllers shall be self protecting and shall provide orderly
shutdown for, but not limited to, the following conditions:
(1)
Loss of input power
(2)
Undervoltage
(3)
Sustained gradual overload
(4)
Fault or large instantaneous overload
(5)
Overtemperature
(6)
Failure of ventilating system
(7)
Overvoltage
(8)
Control circuit failure
i.
Provide contacts for remote annunciation of shutdown or abnormal
condition.
j.
Electrical
bypass: Provide each controller with manual isolation
and bypass
switching. The switch shall be manually operated with
controller
deenergized. Switch shall be two position with
provisions
for locking the switch in either position.
(1) Normal position: Bypass shall be open and the controller
shall be connected to the supply circuit and the load.
(2) Bypass position: Bypass shall be closed and controller shall
be electronically isolated from the supply and the load.
Isolating contacts shall be located so that it is possible to
verify by visual inspection that the contacts are open and the
controller is electrically isolated. In the bypass position the
motor shall be operated at constant speed and controlled from the
air circuit breaker. Provide auxiliary contacts that close in the
SECTION 15502N
Page 154
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