MOOG
ID
No.:
CB40859-001
Date:
02/2018
MSD Servo Drive - Device Help
29
4 Power Stage
If the power does not return, the drive will theoretically decelerate all the way to a
stop. Within this context, there will be a specific speed below which it will not be
possible to maintain the DC link voltage any longer even with the maximum motor
(brake) current. This will result in an undervoltage shutdown.
Mode 2
Power failure bridging with power return detection. The system will not start up
again.
Same as mode 1, except the system will not start up again if the power returns. Error
34-1 will always be triggered once the power returns.
Mode 3
Fastest possible speed reduction without power return detection.
In terms of configuring the power failure detection limits, the requirements listed for
mode 1 apply here as well. The voltage setpoint is yielded by adding P 701[17] - u_
bc_on (braking chopper threshold) and P 2942[1] - POWF_VRef. After a power
failure is detected, the controller will control the voltage so that it reaches the
configured setpoint. This setpoint will be considerably higher than the power failure
detection limit, which will technically ensure that it will not be possible to detect the
return of power. This mode is characterized by the fact that the DC link voltage is
typically raised all the way over the braking chopper threshold, resulting in the
braking energy being converted into braking resistance. Accordingly, the drive will
decelerate as quickly as possible.
Mode 4
Only with expanded VFC functionality.
specific DC link threshold values (based on the operating mode). The corresponding
details are described in the description for each individual mode. The controller will
ensure that the configured voltage setpoint is not fallen below as a result of motor
deceleration. If, however, the instantaneous DC link voltage becomes higher than
the setpoint (e.g. due to the power returning), there will be no control intervention,
i.e. the motor will not be accelerated regardless.
4.2.3 Modes
Mode 1
Power failure bridging with power return detection. The system will start up again if
the power returns within a configurable period of time.
The power failure detection limit is formed by adding together P 701[12] - u_zkoff
(Software shut-off limit for detection of DC link undervoltage) and P 2942[0] -
POWF_Von. It should be considerably higher than the shutdown limit (default setting
= 40 V).
Likewise, the voltage setpoint is yielded by adding P 701[12] - u_zkoff and P 2942
[1] - POWF_VRef. The voltage setpoint must be lower than the detection limit so that
it will be possible to detect when the power returns. Moreover, it should be
considerably higher than the shutdown limit (default setting = 20 V).
After a power failure is detected, the controller will control the voltage so that it
reaches the configured setpoint. If a power return is detected within the time period
set in P 2943[0] - CON_POWF_RetTime, the drive will return to its original control
state. If power returns after the aforementioned time period has already elapsed,
error 34-1 will be triggered. If P 2943[0] - CON_POWF_RetTime is set to 65535,
there will be no time limit for the drive to return to its original control state after power
returns.
