Guidelines for planning the electrical installation 91Using power factor compensation capacitors with thedrivePower factor compensation is not needed with AC drives. However, if a drive is to beconnected in a system with compensation capacitors installed, note the followingrestrictions.WARNING! Do not connect power factor compensation capacitors or harmonicfilters to the motor cables (between the drive and the motor). They are not meantto be used with AC drives and can cause permanent damage to the drive orthemselves.If there are power factor compensation capacitors in parallel with the three phase input ofthe 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 connectedto the power line, make sure that the connection steps are low enough not to causevoltage transients that would trip the drive.3. Check that the power factor compensation unit is suitable for use in systems with ACdrives, ie, harmonic generating loads. In such systems, the compensation unit shouldtypically be equipped with a blocking reactor or harmonic filter.Implementing a safety switch between the drive and themotorWe recommend to install a safety switch between the permanent magnet synchronousmotor and the drive output. The switch is needed to isolate the motor during anymaintenance work on the drive.Protecting the contacts of relay outputsInductive loads (relays, contactors, motors) cause voltage transients when switched off.The relay contacts on the drive control unit are protected with varistors (250 V) againstovervoltage peaks. In spite of this, it is highly recommended that inductive loads areequipped with noise attenuating circuits (varistors, RC filters [AC] or diodes [DC]) in orderto minimize the EMC emission at switch-off. If not suppressed, the disturbances mayconnect capacitively or inductively to other conductors in the control cable and form a riskof malfunction in other parts of the system.Install the protective component as close to the inductive load as possible. Do not installprotective components at the relay outputs.
