64 Guidelines for planning the electrical installation
Using a contactor between the drive and the motor
Implementing the control of the output contactor depends on how you select the drive to
operate. See also section Implementing a bypass connection on page 64.
When you have selected to use
• vector control mode and motor ramp stop,
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.
When you have selected to use
• vector control mode and motor coast stop; or scalar control mode,
open the contactor as follows:
1. Give a stop command to the drive.
2. Open the contactor.
WARNING! When the vector control mode is in use, never open the output
contactor while the drive controls the motor. The vector control operate extremely
fast, much faster than it takes for the contactor to open its contacts. When the
contactor starts opening while the drive controls the motor, the vector control 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. Make sure
with interlocking that the contactors cannot be closed simultaneously. The installation must
be clearly marked as defined in IEC/EN 61800-5-1, subclause 6.5.3, for example, “THIS
MACHINE STARTS AUTOMATICALLY”.
WARNING! Never connect the drive output to the electrical power network. The
connection may damage the drive.
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