• Starts per hour block;
• Anti-Backspin block;
• Thermal block (from thermal model); and
• External starting block
When any of Anti-Backspin, thermal, and external blocks are on, the general blocked flag
will be set. The TBS and SPH can turn on the general blocked flag only if the motor is not
in a cold start sequence; NOCS block can not cause the general blocked flag to be set.
4.2.12
Forced Starting
It is recommended that the user wires the general blocked output to the motor trip circuit
for preventing the motor from starting under these blocked conditions. If the user
chooses not to do this for their applications, a Forced Starting flag will be set when the
motor is started with the blocked conditions. This flag can only be reset manually through
PowerPort-E or from the front panel.
4.2.13
Trips and Trip Bypass
If any of the motor protective functions operate while the motor starts or runs, the
protective device can open its trip contact if so configured. It may also open its trip
contact after a stop is recognized if any jogging function time limit is blocking the next
start. In either case, the protective device expects that the contactor has opened in
response and that no current flows.
If the protective device senses noticeable current for more than about a second whenever
it is tripped, it sets a Trip Bypass flag. This means that the relay blocking of the contactor
has been circumvented by the user to start the motor. If the current fails to stop when the
protective device trips a running motor, it may be because of a User trip bypass or
because of a stuck contactor.
Consider the possibility of backup protection for a contactor opening failure. Configure
one of the output relays to pick up for a trip bypass. Connect the contact to trip an
upstream breaker. This protects the motor from damage in case of a stuck contactor (at
the cost of interrupting other loads connected to the same breaker).
4.2.14
Zero Speed Switch (ZSS ON or OFF)
ZSS enables the function that verifies if the motor begins to physically spin after a start. It
requires a zero-speed switch (digital switch) on the motor, which is closed at rest and
opens as the rotor reaches (5%-10%) its normal speed. Connect the zero-speed switch
contact to one of the protective device Digital Inputs. If the contact fails to open
within »LRT/2« (one-half of locked-rotor time) after a start, the relay trips with a zero-
speed switch trip message.
This protection is always useful, but is essential if the Long Acceleration Time (LAT)
function setting is used.
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EMR-3MP0
4 Protective Elements
4.2 Motor Starting and Control Module
