ABB ACS850-04 series, Hardware Manual

Page: 65 / 164

Planning the electrical installation
65
If there are power factor compensation capacitors in parallel with the three phase
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, ensure that the connection steps are low enough not
to cause voltage transients that would trip the drive.
3. Check 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.
Implementing a safety switch between the drive and motor
It is recommended to install a safety switch between the permanent magnet motor
and the drive output. The switch is needed to isolate the motor during any
maintenance work on the drive.
Using a contactor between the drive and the motor
Arrange the control of the output contactor by applying one of the alternatives
described below.
Alternative 1: When you have selected to use the default motor control mode (DTC)
and motor coast stop in the drive, open the contactor as follows:
1. Give a stop command to the drive.
2. Open the contactor.
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.