Brief Analysis of Frequency Converter Wiring Rules
The machine cable should be routed independently of other cables. The motor cables of several drives can be routed in parallel one after the other. It is recommended that motor cables, input power cables and control cables be installed in different racks to avoid long-distance parallel running of motor cables and other cables, thereby reducing electromagnetic interference caused by transient output voltage of the inverter.
When the control cables and power cables must be crossed, the crossing angle should be 90 degrees.
There must be a good electrical connection between the cable ducts and between the cable ducts and the ground electrode. Aluminum slot systems can be used to improve local voltage equalization.
General rules for selection of power cables Size the mains (input power) and motor cables according to local regulations: the cables must be able to withstand the load current of the drive. • Under continuous use conditions, the cable should withstand a temperature of at least 70°C. Quad cables are allowed as power cables, but symmetrical shielded cables are recommended. When the PE conductor and the phase conductor are made of the same metal, in order to ensure the conductivity of the PE conductor, the recommendations in the table below must be followed.
All control cables must be shielded cables.
The transmission line of the analog signal should use a double-shielded twisted pair. This cable is also recommended for use on transmission lines for pulse-coded signals. Different analog signals should be routed separately and not share a common return line.
It is best to use double-shielded cables for low-voltage digital signal lines, or use single-shielded multi-pair twisted pairs.
Separate shielded cables should be used for analog and digital signals.
Relay control signals, if their voltage does not exceed 48V, can use the same cables as digital input signals. It is recommended to use twisted pair wires for the relay control signal. Do not share the same multi-core cable for 24VDC and 115/230VAC signals.
DTC control mode is used in most cases, while SCALAR control mode is recommended in the following cases:
- For multi-motor drives, ie when the number of motors connected to the drive is uncertain.
- When the rated current of the motor is less than 1/6 of the rated current of the inverter.
When the frequency converter is not connected to the motor, but is used for testing purposes only.