3. It is recommended that the output power cables of the AC drive use shielded cables
or the power cables be shielded by steel pipes and that the shielding layer be
grounded reliably. It is also recommended that the lead cables of the equipment
suffering interference use twisted-pair shielded control cables, and the shielding layer
be grounded reliably.
4. When the length of motor cable is longer than 100 m, an output filter or a reactor
needs to be installed.
7.3.3 How to Handle Interference of Surrounding Equipment on the AC drive
The electromagnetic interference on the AC drive is generated because plenty of relays,
contactors and electromagnetic brakes are installed near the AC drive. When the AC drive
has error action due to the interference, the following measures can be taken:
1. Install a surge suppressor on the devices generating interference.
2. Install a filter at the input side of the AC drive. For the specific operations, see Section
7.3.6.
3. Use shielded cables as the control signal cable of the AC drive and lead cables of the
detection line and ensure that the shielding layer is grounded reliably.
7.3.4 How to Handle Interference of the AC Drive on Surrounding Equipment
The interference includes two types, radiation interference and conduction interference.
The two types of interference cause the surrounding electric equipment to suffer
electromagnetic or electrostatic induction, resulting in error actions of the surrounding
equipment. Handle different interference according to the following methods:
1. Signals of the measuring meters, receivers and sensors are generally weak. If placed
nearby the AC drive or together with the AC drive in the same control cabinet, these
instruments are easy to suffer interference and perform error actions. Handle such
situation as follows:
z Put these instruments in places far away from the interference source.
z Do not arrange the signal cables with the power cables in parallel and never bind
them together.
z Use shielded cables as the signal cables and power cables and ground the
shielding layer well.
z Install a ferrite magnetic ring (with suppressing frequency of 30 to 1,000 MHz) at
the output side of the AC drive and wind it 2 to 3 coils.
z Install an EMC output filter in more severe conditions.
2. When the equipment suffering interference and the AC drive use the same power
supply, it may cause conduction interference. If the above handling cannot eliminate
the interference, install an EMC filter between the AC drive and the power supply (for
the model selection operation, see Section 7.3.6).
3. Grounding the surrounding equipment separately can avoid the interference caused
by the leakage current of the AC drive’s grounding cable when common grounding
mode is adopted.
7.3.5 Leakage Current and Handling
There are two forms of leakage current when the AC drive is used. One is leakage current
to ground, and the other is leakage current between cables.
Factors Influencing the Leakage Current to Ground and Solutions
z There are distributed capacitance between lead cables and the ground. The larger
the distributed capacitance is, the larger the leakage current is. The distributed
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