Main circuit terminals
Earthing (grounding) precautions
Always earth (ground) the motor and inverter.
Purpose of earthing (grounding)
Generally, an electrical apparatus has an earth (ground) terminal, which must be connected to the
ground before use.
An electrical circuit is usually insulated by an insulating material and encased. However, it is impos-
sible to manufacture an insulating material that can shut off a leakage current completely, and actu-
ally, a slight current flows into the case. The purpose of earthing (grounding) the case of an electrical
apparatus is to prevent operators from getting an electric shock from this leakage current when
To avoid the influence of external noises, this earthing (grounding) is important to audio equipment,
sensors, computers and other apparatuses that handle low-level signals or operate very fast.
Earthing (grounding) methods and earthing (grounding) work
As described previously, earthing (grounding) is roughly classified into an electrical shock prevention
type and a noise-influenced malfunction prevention type. Therefore, these two types should be clear-
ly distinguished, and the following work must be done to prevent the leakage current having the in-
verter's high frequency components from entering the malfunction prevention type earthing
● Whenever possible, use the independent earthing (grounding) for the inverter.
If independent earthing (grounding) (I) is not available, use (II) common earthing (grounding) in
the figure below where the inverter is connected with the other equipment at an earthing
(grounding) point. Do not use the other equipment's earthing (grounding) cable to earth (ground)
the inverter as shown in (III).
A leakage current containing many high frequency components flows into the earthing (ground-
ing) cables of the inverter and peripheral devices. Because of this, the inverter must be earthed
(grounded) separately from EMI-sensitive devices.
In a high building, it may be effective to use the EMI prevention type earthing (grounding)
connecting to an iron structure frame, and electric shock prevention type earthing (grounding)
with the independent earthing (grounding) together.
● This inverter must be earthed (grounded). Earthing (Grounding) must conform to the require-
ments of national and local safety regulations and electrical codes. (NEC section 250, IEC 536 class
1 and other applicable standards).
A neutral-point earthed (grounded) power supply for 400 V class inverter in compliance with EN
standard must be used.
● Use the thickest possible earthing (grounding) cable. The earthing (grounding) cable should be
the size indicated in the table on page 2-37.
● The earthing (grounding) point should be as close as possible to the inverter, and the earth
(ground) wire length should be as short as possible.
● Run the earthing (grounding) cable as far away as possible from the I/O wiring of equipment
sensitive to noises and run them in parallel in the minimum distance.
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Installation and wiring