Goodrive300-01 inverter for air compressor Common EMC problems and remedies
-93-
How to select RCD:
Due to the specialty of inverter system, it is required that the rated residual operating current should
be above 200mA for regular RCDs at all levels, and the inverter must be grounded with proper
technics.
As for the setting time of RCD, the time limit of preceding action should be longer than the secondary
action and time gap between them should be set to a value larger than 20ms eg 1s, 0.5s and 0.2s.
It is recommended to use electromagnetic RCD for the electrical circuit of inverter system. Such RCD
carries strong anti-interference capacity to prevent the RCD from being affected by high frequency
leakage current.
Electronic RCD
Electromagnetic RCD
Low cost, high sensitivity, small size,
vulnerable to voltage fluctuation of the
grid and ambient temperature, weak
anti-interference capacity
Require the zero sequence current transformer to be
quite sensitive, precise and stable, made from
permalloy material with high permeability,
complicated process and high cost, immune to
voltage fluctuation of the grid and ambient temp.,
strong anti-interference capacity
Solution to mal-operation of RCD (on the part of inverter)
a)
Try to disassemble the jumper cap in “EMC/J10” (refer to chapter 2.1.1 for the position of J10
jumper)
b) Try to decrease the carrier frequency to 1.5kHz (P00.14=1.5);
c)
Try to change the modulation mode to “3-phase modulation and two-phase modulation”
(P8.40=00)
Solution to mal-operation of RCD (on the part of system distribution)
a) Check and confirm the power cable is not immersed in water
b) Check and confirm the cable is not broken or switched over;
c) Check and confirm if secondary grounding occurred to the null line;
d) Check and confirm if power cable terminal is in the air switch or the contactor is poorly contacted
(loose screws);
e) Check the single-phase electric equipment and confirm if the ground line is misused as null line;
f) Inverter power cable and motor cable should not be shielded ones.
Leakage protection of motor autotuning
During motor autotuning, the measurement on differing motor parameters is conducted step by step,
in which the first two steps is to measure the resistance of motor stator/rotor while the inverter will
output square wave to motor stator winding at 4kHz (default carrier frequency), as leakage current
generated by 4kHz carrier frequency against distributed capacitance between motor rotor and stator
during charging/discharging is quite obvious, which may cause mal-operation of RCD. If such
problem occurred, bypass RCD first and restore after parameter autotuning is completed.
B.5 Problem of charged device shell
The problem mainly lies in that the device shell carries detectable voltage which gives anyone who
touches it a feeling of electrical shock, however, when the inverter is powered up without running, the
shell will be uncharged (or the voltage it carries is far lower than human body safety voltage).
