WARNING!
Do not connect power factor compensation capacitors or harmonic filters to the
motor cables (between the drive and the motor). They are not meant to be used
with AC drives and can cause permanent damage to the drive or themselves.
If there are power factor compensation capacitors in parallel with the input of the drive:
1. Do not connect a high-power capacitor to the power line while the drive is connected.
The connection will cause voltage transients that may trip or even damage the drive.
2. If capacitor load is increased/decreased step by step when the AC drive is connected
to the power line, make sure that the connection steps are low enough not to cause
voltage transients that would trip the drive.
3. Make sure that the power factor compensation unit is suitable for use in systems
with AC drives, ie, harmonic generating loads. In such systems, the compensation
unit should typically be equipped with a blocking reactor or harmonic filter.
Controlling a contactor between drive and motor
The control of the output contactor depends on how you use the drive, that is, which
motor control mode and which motor stop mode you select.
If you have the DTC motor control mode and the motor ramp stop mode selected, use
this operation sequence to open the contactor:
1. Give a stop command to the drive.
2. Wait until the drive decelerates the motor to zero speed.
3. Open the contactor.
If you have the DTC motor control mode and the motor coast stop, or scalar control
mode selected, open the contactor as follows:
1. Give a stop command to the drive.
2. Open the contactor.
WARNING!
When the DTC motor control mode is in use, never open the output contactor
while the drive controls 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 controls the motor, the DTC 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
82 Guidelines for planning the electrical installation
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