KT-420-4 // PDF Download
59
6.4
Safety chain
In case of safety relevant faults (such as exceeding maximum high pressure or overstress of the motor), the fre-
quency inverter must immediately be switched off. For this emergency switching off, a customary electronic regula-
tion is not sufficient. Suitable safety measures are e.g. a main contactor between the frequency inverter and motor,
which can immediately cut off the current supply.
A more advantageous option is a frequency inverter with safe torque off (STO) (e.g. BITZER VARIPACK) with ap-
proved integrated connection in the safety chain according to EN61800-5-2.
6.5
Power factor correction
Frequency inverters generate a low displacement reactive power, therefore a power factor correction is usually not
necessary – it may even have a negative effect. Overcompensation may lead to voltage peaks that can damage
electrical components.
6.6
Residual current circuit breakers
Failing internal components may cause the frequency inverter to generate high-energy direct current in the entire
protective earth conductor system that is not detected by standard residual current circuit breakers. Thus, in the
power connection, a residual current circuit breaker should either be omitted, or a suitable one be used.
DANGER
Danger of death due to electric shock by protective earth conductor system and earthed machine housings!
Carefully select and mount residual current circuit breakers.
Check the protective earth conductor system.
If a residual current circuit breaker is to be integrated in the power connection, it must be sensitive to all current
types (type B). This type is capable of detecting residual direct currents.
6.7
Line start permanent magnet motor (LSPM motor)
Compressors equipped with a line start permanent magnet motor (LSPM motor) can be identified by the letters "U"
and "L" added to the type designation (e. g. 6CTEU-50LK). The built-in permanent magnets generate a non-negli-
gible magnetic field which, however, is shielded by the compressor housing.
Fig. 19: Warning and prohibition signs on a compressor with permanent magnet motor
Safety signs attached to the compressor
WARNING
Strong magnetic field!
Keep magnetic and magnetizable objects away from compressor!
Persons with cardiac pacemakers, implanted heart defibrillators or metallic implants: maintain a clearance
of at least 30 cm!
