EM15 User's Manual
6. EMC(Electromagnetic compatibility)
109
6.3.3 Handling method for the interferences of the surrounding equipment on the inverter
The electromagnetic interference on the inverter is generated because plenty of relays, contactors and
electromagnetic brakes are installed near the inverter. When the inverter has error action due to the interferences,
the following measures can be taken:
1)
Install surge suppressor on the devices generating interference;
2)
Install filter at the input end of the inverter.
3)
The lead cables of the control signal cable of the inverter and the detection line employ shielded cable and the
shielding layer shall be earthed reliably.
6.3.4 Handling method for the interferences of frequency inverter on the surrounding
equipment
These interferences include two types: one is radiation interference of the inverter, and the other is conduction
interference of the inverter. These two types of interferences cause the surrounding electric equipment to suffer
electromagnetic or electrostatic induction. The surrounding equipment hereby produces error action. For different
interferences, it can be handled by referring to the following methods:
1)
For the measuring meters, receivers and sensors, their signals are generally weak. If they are placed nearby the
inverter or together with the inverter in the same control cabinet, they are easy to suffer interference and thus
generate error actions. It is recommended to handle with the following methods: Put in places far away from
the interference source; do not arrange the signal cables with the power cables in parallel and never bind them
together; both the signal cables and power cables employ shielded cables and are well earthed; install ferrite
magnetic ring (with suppressing frequency of 30 to 1,000MHz) at the output side of the inverter and wind it 2
to 3 cycles; install EMC output filter in more severe conditions.
2)
When the equipment suffering interferences and the inverter use the same power supply, it may cause
conduction interference. If the above methods cannot remove the interference, it shall install EMC filter
between the inverter and the power supply (refer to Section 7.3.6 for the prototyping operation); the
surrounding equipment is separately earthed, which can avoid the interference caused by the leakage current of
the inverter’s earth wire when common earth mode is adopted.
3)
The surrounding equipment is separately earthed, which can avoid the interference caused by the leakage
current of the inverter’s earth wire when common earth mode is adopted.
6.3.5 Leakage current and handling
There are two forms of leakage current when using the inverter. One is leakage current to the earth, and the other
is leakage current between the cables.
1)
Factors influencing the leakage current to the earth and the solutions:
There are distributed capacitance between the lead cables and the earth. The larger the distributed capacitance is,
the larger the leakage current will be. The distributed capacitance can be reduced by effectively reducing the
distance between the inverter and the motor. The higher the carrier frequency is, the larger the leakage current will
be. The leakage current can be reduced by reducing the carrier frequency. However, reducing the carrier frequency
may result in addition of motor noise. Note that additional installation of reactor is also an effective method to
remove the leakage current.
The leakage current may increase following the addition of circuit current. Therefore, when the motor power is
high, the corresponding leakage current will be high too.
2)
Factors of producing leakage current between the cables and solutions:
There is distributed capacitance between the output cables of the inverter. If the current passing the lines has
higher harmonic, it may cause resonance and thus result in leakage current. If thermal relay is used, it may
