10.15.4. Commissioning the mains failure control
Commissioning should be executed with motors without load:
1. Let the motor rotate with a rated frequency of 100 %.
2. Disable the inverter and measure the time until the motor has reached standstill.
• The time can be measured with a stop watch or similar.
• If a motor encoder is connected to the inverter and set as feedback system for the
motor control, this signal can be output at the analog output and measured with an
oscilloscope.
3. Set the acceleration time for the voltage setpoint in 0x2D66:006 (P721.06) to approx.
1/10 of the time measured before.
4. Set the switch-off time n 0x2D66:007 (P721.07) to the time measured before.
Fine adjustment of the mains failure control
For the fine adjustment, you must repeat the following points several times:
1. An end frequency as low as possible should be reached before the inverter reaches
the error threshold for undervoltage:
• Increase the proportional gain of the DC-bus voltage controller in 0x2D66:003
(P721.03).
• Reduce the reset time of the DC-bus voltage controller in 0x2D66:004 (P721.04).
2. If, during the mains failure control, monitoring for overvoltage in the DC bus is
triggered:
• Increase the reset time again in 0x2D66:004 (P721.04) until monitoring is not
triggered anymore.
• If required, additionally reduce the voltage setpoint in 0x2D66:005 (P721.05) onto
which the DC-bus voltage is to be controlled.
3. Increasing the delay time or reducing the braking torque is only possible to a limited
extent:
• Increasing the acceleration time in 0x2D66:006 (P721.06) reduces the initial braking
torque and simultaneously increases the deceleration time.
• Increasing the reset time of the DC-bus voltage controller in 0x2D66:004 (P721.04)
reduces the braking torque and simultaneously increases the deceleration time. If
the reset time is too high, the inverter reaches the error threshold for undervoltage
before standstill is reached. From this point on, the motor is not guided anymore.
Signal flow DC-bus voltage controller
① Current DC-bus voltage
② Internally generated frequency setpoint that is transferred to the motor control in
case of an active mains failure control.
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