Leakage Current And Interference On Rcd - INVT Goodrive300-21 Series Operation Manual

Goodrive300-21 integrated machine for air compressor
 Indicator shimmering
After the inverter is started, shimmering, flickering or abnormal noise occurred to below devices:
a) Relay indicator
b) Indicator of distribution box
c) PLC indicator
d) Indicating buzzer
Solution:
 Check and ensure that the exception signal cable is arranged 20 cm or farther away from the
motor cable.
 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.
D.4 Leakage current and interference on RCD
Inverters output high-frequency PWM voltage to drive motors. In this process, the distributed
capacitance between the internal IGBT of an inverter and the heat sink and that between the stator
and rotor of a motor may inevitably cause the inverter 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
inverter may cause misoperation of a RCD.
Rules for selecting RCDs
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 inverters are grounded reliably.
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.
For circuits in inverter systems, electromagnetic RCDs are recommended. Electromagnetic RCDs
have strong anti-interference capability, and thus can prevent the impact of high-frequency leakage
current.
Electronic RCD
Low cost, high sensitivity, small in volume,
susceptible to voltage fluctuation of the grid
and ambient temperature,
anti-interference capability.
Electromagnetic RCD
Requiring highly sensitive, accurate, and stable
zero-phase sequence current transformer, using
permalloy high-permeability materials, complex
and weak process, high cost, not susceptible to voltage
fluctuation of the power supply and ambient
temperature, strong anti- interference capability.
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Common EMC problems and solution