ABB PSTX Series Installation And Commissioning Manual page 87

7.11 Motor braking
Stand still brake
Stand still brake prevents a motor from spinning when
in standstill condition. It can be activated through IO,
fieldbus or as a pre-start function.
Dynamic brake
Dynamic brake is an intelligent variant of DC brake
starting with a period of dynamic braking followed by a
switch to DC brake. During the dynamic brake the firing
angle and thyristor firing sequence are continuously
recalculated depending on operating conditions. During
DC brake these are pre-determined. The reason for
switching to DC brake is because it is effective at
low speed but ineffective at high speed. During both
dynamic- and DC-brake the kinetic energy of the motor is
converted to heat that is dissipated in the rotor.
Motor braking with Softstarter is not an exact science.
Trial and error testing is required to find the optimal
parameter values.
WARNING
Braking exerts a lot of stress on the thyristors so
from a thermal perspective a brake shortly after a
start can be counted as two consecutive starts.
If the brake strength is set to a too large value
the internal thyristor overload fault or electronic
overload protection can trip.
INFORMATION
Using a Softstarter to brake the motor will cause
noise and vibrations just like any other braking
method. If a fast stop time is required the brake
strength will have to be set to a large value which
will result in increased noise and vibration.
INFORMATION
Parameter 07.03 (Dynamic brake strength) and
07.04 (DC brake strength) are the ones that
affect the motor deceleration time. Parameter
07.02 (Motor brake time) only works as a
timeout. The goal should be to choose the lowest
possible braking strength and still fulfill the user's
deceleration time requirements.
INFORMATION
To use Dynamic brake set parameter 02.02 (Stop
mode) to Dynamic brake.
INFORMATION
An external PTC or PT100 sensor to monitor the
motor temperature is recommended.
How to use
7.11.2.1
Parameter 7.3 (Dynamic brake strength) and 7.4
(DC brake strength) are the ones that affect the
motor deceleration time. Parameter 7.2 (Motor
brake time) only works as a timeout.
be to choose the lowest possible braking strength and
still fulfill the user's deceleration time requirements.
1. Set parameter 2.2 (Stop mode) to Dynamic brake.
2. Set parameter 7.2 (Motor brake time) to be equal to the
desired stop time.
3. Set parameter 7.3 (Dynamic brake strength) to
40%.
4. Set parameter 7.4 (DC brake strength) to 40%.
5. Perform the first test and do two measurements:
6. Check if motor deceleration time is longer or shorter
than desired.
7. Optional configuration: It can be heard when the DC
brake is activated, the motor will sound different then. If
DC brake is activated too soon (before the motor speed
is below the value specified by parameter 7.5), increase
parameter 7.6 (DC brake switch delay time) by 5-10s and
try again.
8. Optional configuration: If it takes too long time for the
motor to decelerate when DC brake is active, increase the
motor brake time by 10s and increase only parameter 7.4
(DC brake strength) by 10% and try again.
9. Optional configuration: One of the digital inputs In0, In1
or In2 can be configured as "Cancel brake". When a logic
high (flank) is detected, the motor brake will be cancelled.
7.11.2.2
motor?
Depends on the moment of inertia of the motor and load.
Field test example: Motor: 61A, 400V, 50Hz; Load: Fan,
large flywheel. With stop mode equal to no ramp, the
deceleration time was 1min.
With stop mode equal to dynamic brake and dynamic
brake strength and DC brake strength equal to 40%, the
deceleration time was 30s.
With dynamic brake strength and DC brake strength equal
to 50%, the deceleration time was 20s.
The goal should
1SFC132081M0201 | Installation and commissioning manual | Functions
5.1 Time it takes for the motor to decelerate
from full speed to the value specified by
parameter 7.5 (DC brake switch speed threshold,
default value is 28%).
5.2 Time it takes for the motor to decelerate
from full speed to near zero speed.
6.1 If deceleration time is longer than desired,
increase dynamic brake strength and DC brake
strength by 10% and try again. Continue like this
until the actual stop time is equal to the desired
stop time.
6.2 If deceleration time is shorter than desired,
decrease dynamic brake strength and DC brake
strength by 10% and try again. Continue like this
until the actual stop time is equal to the desired
stop time.
How long time does it take to stop the
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