Eaton EMR-4000 Installation, Operation And Maintenance Manual page 439

Start Limits
Because motor starting consumes a considerable amount of thermal energy compared to its normal load conditions, the
number of starts in a given time period must be monitored and controlled. The protective device has three functions
that contribute to the start limits monitoring. These are:
TBS (Time between Starts);
•
SPH (Starts per Hour); and
•
NOCS (Number of Cold Starts).
•
Most motors can tolerate some number of consecutive cold starts before the time between starts is enforced. The
protective device treats a start as the first in a sequence of cold starts if the motor has been stopped for at least the
time period that is the greatest of one hour and TBS. Subsequent starts are treated as additional cold starts in the
same sequence, only if they run no more than ten minutes, until the set number of cold starts is reached. Once the
motor is in the cold starting sequence, it will ignore TBS and SPH limits. The cold start sequence will be terminated if
the motor has run for more than ten minutes for a cold start before it exhausts NOCS, then starts after this are subject
to time and count limits imposed by TBS and SPH. If the motor reaches the NOCS limit in a cold start sequence,
NOCS block flag will be set and TBS will start to time. When TBS reaches its limit while the NOCS block flag is still set,
the cold start sequence will be terminated and the NOCS block will be released. Meanwhile, the SPH will start to count
at the last start in the complete cold start sequence.
Stop Cycle
The run cycle continues until the motor current level falls below the Stop Current Threshold setting current on all three
phases. Then a stop is declared. The start limits (also referred as Jogging start limits) and the anti-backspin time delay
(ABS) are checked. If blocking conditions exist, the protective device can be configured to block a motor from starting.
Remaining jogging block times are displayed and counted down, indicating how long to wait. If there are no such
starting block conditions in effect, the protective device is ready for a new start.
Anti-Backspin Delay Time (ABS)
ABS sets the time in seconds before a motor restart is permitted after a trip or stop condition. This function can be set
to OFF.
This function is used with a motor driving a pump working into a head, or any other load that tends to spin in a reverse
direction (backspin) when the motor is de-energized. It blocks starting during the time when the motor might be rotating
in reverse following a trip. Also, this function may be used simply to set idle time (time between stop and start) before a
restart is permitted.
External Start Blocking
A motor can be blocked through a digital input. If this feature is enabled, the User must make sure that both the Motor
Start and Digital Input modules are configured properly.
EMR-4000
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IM02602009E
439