Menu Item Description
10 RTHC-SVD01B-EN
2-5. Start to Transition Timing Logic
For ElectroMechanical Staters, the Start-to-Transition timing and logic
will be based on the motor current decreasing to below 85% RLA. At
this time UCP2 times out 1.5 seconds and then transitions. The excep-
tion to this rule is a Fixed Minimum Transition Time of 1.6 seconds; the
starter shall never be transitioned at less than 1.6 seconds from start. If
at 1.6 seconds the current is less than 85% RLA, UCP2 transitions
immediately.
For Solid State Starters, the phase currents cannot be expected to rise
above 85 percent RLA prior to 1.6 seconds following the closing of the
“Start” contact and remain above 85 percent RLA until the compressor
motor has come up to speed. The “Up-to-Speed” contact operation
cannot be tied to the motor currents falling below 85% RLA. Therefore,
regardless of motor current, the “Up-to-Speed” contact closure input is
expected to close before the Maximum Acceleration Timer times out,
otherwise an MMR diagnostic occurs.
The Starting Overload is a timing function based on the Maximum Time
to Transition permitted for a particular motor; this criteria requires that
the motor can withstand a locked rotor condition for a particular starting
method for the Maximum Transition Time. Therefore, UCP2 provides
field adjustable Maximum Acceleration Timers. If the starter is not tran-
sitioned within the Timer Setpoint, there are two possible outcomes
based on a Second Setting:
1. The starting sequence is aborted, the starter is de-energized, and a
Latching Diagnostic (MMR) is generated.
2. The starter is transitioned (“thrown across the line”) and an Infor-
mational Diagnostic (IFW) is generated.
UCP2 also provides a setting to either “Shutdown” or “Transition” the
Starter if the Maximum Acceleration Timer Times out.
The items that can be set in UCP2 are:
Located in Service Settings, Machine Configuration Group (+-+-+-)
• Maximum Acceleration Timer #1 (2- 64)
• Maximum Acceleration Timer #2 (191 - 253)
• Acceleration Time Out Action (shutdown, transition)
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