66 Planning the electrical installation
Alternative 2: When you have selected to use the default motor control mode (DTC) and
motor ramp stop in the drive, open the contactor as follows:
1. Give a stop command to the drive.
2. Wait until the drive decelerates the motor to zero speed.
3. Open the contactor.
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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