ABB 615 Series ANSI, Technical Manual

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1MAC050144-MB C
Section 4
Protection functions
615 series ANSI 217
Technical Manual
measured current exceeds the breakdown torque level, that is, above the set limit. The
operation characteristic is definite time.
The function contains a blocking functionality. It is possible to block function outputs,
timers or the function itself, if desired.
4.1.12.4 Operation principle
The function can be enabled and disabled with the Operation setting. The corresponding
parameter values are Enable and Disable.
The operation of the stalled motor protection can be described using a module diagram.
All the modules in the diagram are explained in the next sections.
Figure 102: Functional module diagram
Level detector
The measured phase currents are compared to the set Pickup value . The TRMS values of
the phase currents are considered for the level detection. The timer module is enabled if at
least two of the measured phase currents exceed the set
Pickup value .
Timer
Once activated, the internal
PICKUP
signal is activated. The value is available only
through the Monitored data view. The time characteristic is according to DT. When the
operation timer has reached the
Trip delay time value, the
TRIP
output is activated.
When the timer has elapsed but the motor stall condition still exists, the
TRIP
output
remains active until the phase currents values drop below the Pickup value , that is, until
the stall condition persists. If the drop-off situation occurs while the trip time is still
counting, the reset timer is activated. If the drop-off time exceeds the set
Reset delay time ,
the trip timer is reset.
The timer calculates the pickup duration value PICKUP_DUR which indicates the
percentual ratio of the pickup situation and the set trip time. The value is available through
the Monitored data view.
4.1.12.5 Application
The motor protection during stall is primarily needed to protect the motor from excessive
temperature rise, as the motor draws large currents during the stall phase. This condition
causes a temperature rise in the stator windings. Due to reduced speed, the temperature
also rises in the rotor. The rotor temperature rise is more critical when the motor stops.
TRIP
Level
detector
BLOCK
I_C
Timer
t
I_A
I_B