IPE300 series engineering VFD Troubleshooting
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voltage endurance capability of the capacitor. Alternatively, you can use a magnet ring (Fe-based
nanocrystalline magnet rings are recommended). Put the power L/N line or +/- line of the upper
computer through the magnet ring in the same direction and wind 8 coils around the magnet ring.
7.7.3 Failure to stop and indicator shimmering due to motor cable coupling
Interference phenomenon
1. Failure to stop
In a VFD system where an S terminal is used to control the start and stop, the motor cable and control
cable are arranged in the same cable tray. After the system is started properly, the S terminal cannot
be used to stop the inverter.
2. Indicator shimmering
After the VFD is started, the relay indicator, power distribution box indicator, PLC indicator, and
indication buzzer shimmer, blink, or emit unusual sounds unexpectedly.
Solution
1. Check and ensure that the exception signal cable is arranged 20 cm or farther away from the
motor cable.
2. Add a safety capacitor of 0.1μF between the digital input terminal (S) and the COM.
3. Connect the digital input terminal (S) that controls the start and stop to other idle digital input
terminals in parallel. For example, if S1 is used to control the start and stop and S4 is idle, you
can try to short connect S1 to S4 in parallel.
Note: If the controller (such as PLC) in the system controls more than 5 VFDs at the same time
through digital input terminals (S), this scheme is not applicable.
7.7.4 Leakage current and interference on RCD
VFDs output high-frequency PWM voltage to drive motors. In this process, the distributed
capacitance between the internal IGBT of a VFD and the heat sink and that between the stator and
rotor of a motor may inevitably cause the VFD to generate high-frequency leakage current to the
ground. A residual current operated protective device (RCD) is used to detect the power-frequency
leakage current when a grounding fault occurs on a circuit. The application of a VFD may cause
misoperation of a RCD.
1. Rules for selecting RCDs
1) Inverter systems are special. In these systems, it is required that the rated residual current of
common RCDs at all levels is larger than 200 mA, and the VFDs are grounded reliably.
2) For RCDs, the time limit of an action needs to be longer than that of a next action, and the time
difference between two actions need to be longer than 20ms. For example, 1s, 0.5s, and 0.2s.
3) For circuits in VFD systems, electromagnetic RCDs are recommended. Electromagnetic RCDs
have strong anti-interference capability, and thus can prevent the impact of high-frequency leakage
current.
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