Connection
3.3 Mounting Power Modules
Frequency inverter
Operating Instructions, 08.10. 2008, t.b.d.
39
Avoiding electromagnetic disturbances
The frequency inverters are designed for operation in industrial environments where high
values of electromagnetic noise and disturbances are expected. Generally, correct
installation guarantees safe, reliable and disturbance-free operation. If difficulties do arise,
then please note the following guidelines.
Required measures
●
Ensure that all of the devices in the cabinet are well-grounded using short grounding
cables with high cross-sections, connected to a common grounding point or a grounding
bar.
●
Ensure that every control device (e.g. a PLC) connected to the frequency inverter is
connected to the same ground or the same grounding point as the frequency inverter
through a short cable with a large cross-section.
●
Connect the return ground of the motors, which are controlled from the frequency
inverters, directly at the ground connection (PE) of the associated frequency inverter.
●
Flat cables are preferred as they have a lower impedance at higher frequencies.
●
The cable ends must be cleanly terminated and it must be ensured that unshielded
cables are as short as possible.
●
The control cables must be routed separately from the supply cables. Power and control
cables should cross at a 90° angle.
●
If at all possible, use shielded cables to connect the control circuit.
●
Ensure that the contactors in the cabinet have the necessary interference suppression
components; either using an RC circuit for AC contactors or using "free-wheeling diodes"
for DC contactors, whereby the noise suppression elements should be connected at the
coils. Varistor suppressors are also effective. This is important if the contactors are
controlled from the frequency inverter relay.
●
Use shielded cables for the motor connections, and ground the shielding at both ends
using cable clamps.