Shenzhen Hpmont Technology Co., Ltd Chapter 4 Electrical Installation
HD30 Series Inverters User Manual ―37―
When using more than one inverter, be careful not to loop the earth wire as shown in Figure 4-28.
Figure 4-28 Prohibited earthing method
4.5.5 EMI Filter
The EMI filter should be used in the equipment that may generate strong EMI or the equipment
that is sensitive to the external EMI. The EMI filter should be a dual-way low pass filter through
which lower frequency current can flow while higher frequency current can hardly flow.
Function of EMI filter
1
．
The EMI filter ensures the equipment not only can satisfy the conducting emission and
conducting sensitivity in EMC standard but also can suppress the radiation of the equipment.
2
．
It can prevent the EMI generated by equipment from entering the power cable and the EMI
generated by power cable from entering equipment.
Common mistakes in using EMI filter
1
．
Too long the power cable is between the EMI filter and the inverter
The filter inside the cabinet should be located near to the input power source. The length of the
power cables should be as short as possible.
2
．
Too close the input and output cables of the EMI filter
The distance between input and output cables of the filter should be as far apart as possible.
Otherwise the high-frequency noise may be coupled between the cables and bypass the filter.
Thus, the filter will become ineffective.
3
．
Bad earthing of the EMI filter
The EMI filter’s enclosure must be earthed properly to the metal case of the inverter. In order to
achieve better earthing effect, make use of a special earthing terminal on the filter’s enclosure. If
you use one cable to connect the filter to the case, the earthing is useless for high frequency
interference. When the frequency is high, so is the impedance of cable, hence there is little
bypass effect.
The correct installation: The filter should be mounted on the enclosure of equipment. Ensure to
clear away the insulation paint between the filter case and the enclosure for good earthing
contact.
Prohibited earthing method
PE
PEPE PE
HD30 HD30 HD30 HD30
4
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