Mitsubishi -NAFR-F720-00167-NA, Instruction Manual

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23
Main circuit terminal specifications
2
W
IRING
(2) Notes on earthing (grounding)
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 which the
inverter is connected with the other equipment at an earthing (grounding) point.
The (lll) common earthing (grounding) as in the figure below, which inverter shares a common earthing
(grounding) cable with the other equipment, must be avoided.
A leakage current including many high frequency components flows in the earthing (grounding) 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 code (NEC section 250, IEC 536 class 1 and other applicable
standards).
A neutral-point earthed (grounded) power supply for 400V class inverter in compliance with EN standard must
be used.
(c) Use the thickest possible earthing (grounding) cable. The earthing (grounding) cable size should be no less
than the size indicated in the table on the previous page.
(d) The earthing (grounding) point should be as close as possible to the inverter, and the earthing (grounding)
wire length should be as short as possible.
(e) 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.
To be compliant with the EU Directive (Low Voltage Directive), refer to the Installation Guideline .
Inverter
Other
equipment
(I) Independent earthing (grounding).......Best
Inverter
Other
equipment
(II) Common earthing (grounding).......Good
Inverter
Other
equipment
(III) Common earthing (grounding) cable...Not allowed