Mitsubishi Electric FR-D720-0.1K Instruction Manual page 27

Main circuit terminal specifications
(2) Earthing (Grounding) precautions
Always earth (ground) the motor and inverter.
1) 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 impossible to manufacture
an insulating material that can shut off a leakage current completely, and actually, a slight current flow into the case.
The purpose of earthing (grounding) the case of an electrical apparatus is to prevent operator from getting an electric
shock from this leakage current when touching it.
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.
2) Earthing (grounding) methods and earthing (grounding) work
As described previously, earthing (grounding) is roughly classified into an electrical shock prevention type and a noise-
affected malfunction prevention type. Therefore, these two types should be discriminated clearly, and the following
work must be done to prevent the leakage current having the inverter's high frequency components from entering the
malfunction prevention type earthing (grounding):
(a)If possible, use (l) independent earthing (grounding) in figure below for the inverter. If independent earthing
(grounding) is not available, use (ll) common earthing (grounding) in the figure below where the inverter is connected
with the other equipment at an earthing (grounding) point.
The (lll) common earthing (grounding) cable as in the figure below, which inverter shares a common earth (ground)
cable with the other equipment, must be avoided.
A leakage current including many high frequency components flows in the earth (ground) cables of the inverter and
inverter-driven motor. Therefore, use the independent earthing (grounding) and separate the earthing (grounding)
cable of the inverter from equipment sensitive to EMI.
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.
(b)This inverter must be earthed (grounded). Earthing (Grounding) must conform to the requirements of national and
local safety regulations and electrical codes. (NEC section 250, IEC 536 class 1 and other applicable standards).
Use an neutral-point earthed (grounded) power supply for 400V class inverter in compliance with EN standard.
(c)Use the thickest possible earth (ground) cable. The earth (ground) cable size should be no less than the size
indicated in the table on page 17.
(d)The earthing (grounding) point should be as close as possible to the inverter, and the earth (ground) cable length
should be as short as possible.
(e)Run the earth (ground) 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.
Inverter
(I)Independent earthing (grounding).......Best
POINT
To be compliant with the EU Directive (Low Voltage Directive),
18
Other
Inverter
equipment
(II)Common earthing (grounding).......Good
Other
equipment
(III)Common earthing (grounding) cable.......Not allowed
refer to the Instruction Manual (Basic).
Other
Inverter
equipment