Using Power Factor Compensation Capacitors With The Drive - ABB ACS880-37 Hardware Manual

Using power factor compensation capacitors with the
drive
Power factor compensation is not needed with AC drives. However, if a drive is to be
connected in a system with compensation capacitors installed, note the following
restrictions.
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 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, make sure 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 the
motor
We recommend to install a safety switch between the permanent magnet synchronous
motor and the drive output. The switch is needed to isolate the motor during any
maintenance work on the drive.
Protecting the contacts of relay outputs
Inductive loads (relays, contactors, motors) cause voltage transients when switched off.
The relay contacts on the drive control unit are protected with varistors (250 V) against
overvoltage peaks. In spite of this, it is highly recommended that inductive loads are
equipped with noise attenuating circuits (varistors, RC filters [AC] or diodes [DC]) in order
to minimize the EMC emission at switch-off. If not suppressed, the disturbances may
connect capacitively or inductively to other conductors in the control cable and form a risk
of malfunction in other parts of the system.
Install the protective component as close to the inductive load as possible. Do not install
protective components at the relay outputs.
Guidelines for planning the electrical installation 87