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EMC (Electromagnetic compatibility)
3) Control signal line and lead of detection circuit adopt shield cable, and keep reliable earthing.
7.3.4 Handling method of interference produced by peripheral equipment for frequency convertor: there
are two kinds of noise, namely radiated interference of frequency convertor and conducted
interference of frequency convertor. These two interference lead to electromagnetic or electrostatic
induction of peripheral electrical equipment, and then cause malfunction of equipment. Aiming at
different interference, below solutions can be referred:
1) The signal of instruments, receivers and sensor for measurement is generally weak. If they are
near to frequency convertor or in the same control cabinet, the frequency convertor is easily
interfered and malfunction produces. It's suggested to adopt below solutions: keep away from
interference source as far as possible; do not layout signal line and power line in parallel, or bundle
up them in parallel; signal line and power line adopt shield line, keep reliable earthing; install ferrite
core (range of blanketing frequency is 30 ～ 1000MHz) on output side of frequency convertor and
wind 2~3 turns in the same direction. For serious situation, EMC output filter can be installed;
2) If interfered equipments share the same power with frequency convertor, conducted interference
will produce. If interference can't be eliminated through above method, EMC filter shall be installed
between frequency convertor and power (refer to 7.3.6 for model selection operation);
3) Independent earthing of peripheral equipment can eliminate the interference produced by leak
current of ground lead of frequency convertor.
7.3.5 Leak current and handling: there are two kinds of forms of leak current when using frequency
convertor: leak current to ground, and leak current between lines.
1) Factors influencing leak current to ground and solutions:
There is distributed capacitance between wire and ground. The larger the distributed capacitance, the
larger the leak current will be, so reduce the distance between frequency convertor and motor to decrease
distributed capacitance. The larger the carrier frequency, the larger the leak current will be, so decrease
carrier frequency to reduce leak current. However, decreasing carrier frequency will lead to increasing
motor noise. Please note that installing reactor is an effective way to solve leak current.
Leak current increases with enlargement of loop current, so the larger the motor power, the larger
the corresponding leak current will be.
2) Factors influencing leak current between lines and solutions:
There is distributed capacitance between output wiring of frequency convertor. If the current
passing circuit contains higher harmonic, resonance may be caused to produce leak current. If using
thermal relay at this time, malfunction may occur.
The solution is to reduce carrier frequency or install output reactor. When using frequency convertor,
it's not suggested to install thermal relay between frequency convertor and motor, but use electric over-
current protection function of frequency convertor.
7.3.6 Precautions about installing EMC input filter on power input terminal:
1)
Caution: please strictly abide by rated value when using filter. As filter is I-class electric
appliance, metal shell of filter should contact well with metal of installing cabinet, and good electric
conduction continuity is required, otherwise there is risk of electric shock and EMC effect will be
seriously influenced;
2) According to EMC test, filter and PE terminal of frequency convertor should be connected on the
same ground, otherwise EMC effect will be seriously influenced;
3) The filter should be installed nearby power input terminal of frequency convertor as far as possible.
Specification of high-performance vector convertor
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