Planning the electrical installation
74
Alternative 3: When you have selected to use the scalar motor control mode in the
drive, open the contactor as follows:
1. Give a stop command to the drive.
2. Open the contactor.
WARNING! When you have the default motor control mode (DTC) in use, never
open the output contactor while the drive rotates the motor. The DTC motor control
operates extremely fast, much faster than it takes for the contactor to open its
contacts. When the contactor starts opening while the drive rotates the motor, the
DTC will try to maintain the load current by immediately increasing the drive output
voltage to the maximum. This will damage, or even burn the contactor completely.
Implementing a bypass connection
If bypassing is required, employ mechanically or electrically interlocked contactors
between the motor and the drive and between the motor and the power line. Ensure
with the interlocking that the contactors cannot be closed simultaneously.
Follow this control sequence:
1. Stop the drive.
2. Stop the motor.
3. Open the contactor between the drive and the motor.
4. Close the contactor between the motor and the power line.
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