Cable and wiring method for determining the distance between the inverter and the motor
The distance between the inverter and the motor should be as short as possible. This reduces the ground capacitance of the cable and reduces the interference of the emission source. The longer the cable, the greater the voltage drop. Long cables will cause the voltage output from the inverter to the motor to decrease, affecting the performance of the motor. Generally speaking, the inverter manufacturer will provide a recommended maximum cable length.
Calculate the voltage drop according to the cable specifications and load current to ensure that the voltage drop is within the allowable range (usually not more than 2-3% of the inverter output voltage).
Long-distance cables increase the risk of electromagnetic interference and affect surrounding electronic equipment. Shielded cables and correct grounding methods should be used to reduce electromagnetic interference. Therefore, shielded cables should be used for control cables, shielded cables should be used for power cables, or all cables from the inverter to the motor should be shielded with conduits.
The motor cable should be routed independently of other cables, with a minimum distance of 500mm. At the same time, the motor cable should be avoided from being routed parallel to other cables for a long distance, so as to reduce the electromagnetic interference caused by the rapid change of the inverter output voltage. If the control cable and the power cable cross, they should be crossed at a 90-degree angle as much as possible. Even in the control cabinet, the analog signal lines related to the inverter and the main circuit lines need to be routed separately.
It is best to use shielded twisted pair cables for analog signal lines of the inverter, and shielded three-core cables (whose specifications are larger than those of ordinary motor cables) for power cables or follow the user manual of the inverter.
Grounding of the inverter
Correct grounding of the inverter is an important means to improve system stability and suppress noise. The smaller the grounding resistance of the inverter’s grounding terminal, the better. The cross-section of the grounding wire should not be less than 4mm and the length should not exceed 5m. The grounding of the inverter should be separated from the grounding point of the power equipment and cannot be shared. One end of the shielding layer of the signal line is connected to the grounding terminal of the inverter, and the other end is floating. The inverter and the control cabinet are electrically connected.
In short, the distance between the inverter and the motor should take into account the convenience of installation and maintenance, and try to avoid complex installation problems caused by long-distance wiring. The distance between the inverter and the motor should be convenient for daily maintenance and repair, and avoid maintenance difficulties caused by excessive cable length. Choose low-capacitance, well-shielded cables to reduce electromagnetic interference and harmonic reflections. Inverter and motor manufacturers usually provide recommended maximum cable lengths and wiring recommendations in technical manuals, which should be strictly followed. When in doubt about a specific application, consult the manufacturer’s technical support team for expert advice.