CG Drives & Automation 01-7492-01r1 149
11.4.2 Process Protection [420]
Submenu with settings regarding protection functions for
the AC drive and the motor.
Low Voltage Override [421]
If a dip in the mains supply occurs and the low voltage
override function is enabled, the AC drive will automatically
decrease the motor speed to keep control of the application
and prevent an under voltage trip until the input voltage
rises again. Therefore the rotating energy in the motor/load
is used to keep the DC link voltage level at the override level,
for as long as possible or until the motor comes to a
standstill. This is dependent on the inertia of the motor/load
combination and the load of the motor at the time the dip
occurs, see fig. 123.
Fig. 123 Low voltage override
Rotor locked [422]
With the rotor locked function enabled, the AC drive will
protect the motor and application when this is stalled whilst
increasing the motor speed from standstill. This protection
will coast the motor to stop and indicate a fault when the
Torque Limit has been active at very low speed for more
than 5 seconds.
Motor lost [423]
With the motor lost function enabled, the AC drive is able
to detect a fault in the motor circuit: motor, motor cable,
thermal relay or output filter. Motor lost will cause a trip,
and the motor will coast to standstill, when a missing motor
phase is detected during a period of 500 ms. The detection
time during DC-start is 50 ms and during Fast-start 10 ms.
Overvolt control [424]
Used to switch off the overvoltage control function when
only braking by brake chopper and resistor is required. The
overvoltage control function, limits the braking torque so
that the DC link voltage level is controlled at a high, but
safe, level. This is achieved by limiting the actual
deceleration rate during stopping. In case of a defect at the
brake chopper or the brake resistor the AC drive will trip for
“Overvoltage” to avoid a fall of the load e.g. in crane
applications.
421 Low Volt OR
Default: On
Off 0
At a voltage dip the low voltage trip will
protect.
On 1
At mains dip, AC drive ramps down until
voltage rises.
NOTE: During the low voltage override the LED trip/
limit blinks.
NOTE: LVO and OVC are not active in torque mode.
Override
level
Low Volt.
level
422 Rotor Locked
Default: Off
Off 0 No detection
On 1
AC drive will trip when locked rotor is
detected. Trip message “Locked Rotor”.
423 Motor lost
Default: Off
Off 0
Function switched off to be used if no
motor or very small motor connected.
Trip 1
AC drive will trip when the motor is
disconnected. Trip message “Motor Lost”.
Start 2
Test for disconnected motor will only be
performed during start routine.
NOTE: Overvoltage control should not be activated if
brake chopper is used.
424 OverVolt Ctl
Default: On
Off 0 Overvoltage control off
On 1 Overvoltage control activated
NOTE: LVO and OVC are not active in torque mode.
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