Current Transformer and Current Input
28 RTHC-SVD01B-EN
7. Momentary Power Loss. Power losses of 2.5 line cycles (.042
seconds) or longer will be detected and cause the unit to shut-
down. The unit shall be disconnected from the line within 6 line
cycles of detection. If enabled, Momentary Power Loss shall be
active anytime the compressor is running. MPL shall not be active
on wye-delta starters from the initial start signal through transition.
Once the Transition Complete input is satisfied MPL is active.
8. Current overload starting. In the starting mode, the overload pro-
tection is the maximum acceleration time. If the motor is in a
locked rotor condition or the currents do not drop below 85% RLA
within the maximum acceleration time, a diagnostic will be called.
In the run mode, a ‘time-to-trip’ curve is looked at to determine if a
diagnostic should be called.
9. Current overload running. UCP2 continuously monitor compres-
sor current to provide running overcurrent and locked rotor pro-
tection. Overcurrent protection shall be based on the phase with
the highest current. It shall trigger a manually resettable diagnos-
tic shutting down the affected compressor and associated refrig-
erant circuit when the current exceeds a specified time trip curve.
The compressor overload shall be based on unit RLA.
Overload Must Hold = 102% RLA
Overload Must Trip in 20 +0 -3 seconds = 112% RLA
Note: The above gives a nominal 20 second must trip point of 107%
RLA.
Overload Must Trip in 1.5 seconds = 140% RLA (Nominal)
Figure 4-1.Current Limit
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