Chapter 6 Troubleshooting
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Ch
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ter 6
4)When the length of motor cable is longer than 30 meters, it needs to install output filter or
reactor.
6-3-3.
Remedies for the interferences from the surrounding
electromagnetic equipments to the inverter
Generally the electromagnetic interference on the inverter is generated by plenty of relays,
contactors and electromagnetic brakes installed near the inverter. When the inverter has error action
due to the interferences, the following measures is recommended:
1) Install surge suppressor on the devices generating interference;
2) Install filter at the input end of the inverter, please refer to Section 6.3.6 for the specific
operations.
3) The lead cables of the control signal cable of the inverter and the detection line shall use the
shielded cable and the shielding layer shall be grounded reliably.
6-3-4.
Remedies for the interferences from the inverter to the
surrounding electromagnetic equipments
These noise interferences are classified into two types: One is the radiation interference of the
inverter, and the other is the conduction interference of the inverter. These two types of
interferences cause that the surrounding electric equipments suffer from the affect of
electromagnetic or electrostatic induction. Further, the surrounding equipment produces error
action. For different interferences, please refer to the following remedies:
1) Generally the meters, receivers and sensors for measuring and testing have more weak
signals. If they are placed nearby the inverter or together with the inverter in the same control
cabinet, they easily suffer from interference and thus generate error actions. It is recommended to
handle with the following methods: Away from the interference source as far as possible; do not
arrange the signal cables with the power cables in parallel and never bind them together; both the
signal cables and power cables shall use shielded cables and shall be well grounded; 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 turns; install EMC output filter in more severe conditions.
2) When the interfered equipment 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 6.3.6 for the selection operation);
3) The surrounding equipment shall be separately grounded, which can avoid the interference
caused by the leakage current of the inverter's grounding wire when common grounding mode is
adopted.
6-3-5.
Remedies for leakage current
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 of affecting leakage current to the earth and its solutions:
There are the distributed capacitance between the lead cables and the earth. The larger the
distributed capacitance, the larger the leakage current; the distributed capacitance can be reduced
by effectively reducing the distance between the inverter and the motor. The higher the carrier
frequency, the larger the leakage current. The leakage current can be reduced by reducing the
carrier frequency. However, the carrier frequency reduced may result in the increase of motor
noise.Please note that additional installation of reactor is also an effective method to solve leakage
current problem.The leakage current may increase with the increase of circuit current. Therefore,
when the motor power is higher, the corresponding leakage current will be higher too.
2) Factors of producing leakage current between the cables and its solutions:
There is the distributed capacitance between the output cables of the inverter. If the current
passing lines has higher harmonic, it may cause resonance and thus result in leakage current. If the
thermal relay is used, it may generate error action.The solution is to reduce the carrier frequency or
install output reactor. It is recommended that the thermal relay shall not be installed in the front of
the motor when using the inverter, and that electronic over current protection function of the
