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Mitsubishi Electric FR-E720-0.1K(SC) Instruction Manual Page 29

Fr-e700 series.
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Main circuit terminal specifications
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) joint 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 cable with the other equipment, must be avoided.
A leakage current including many high frequency components flows in the earthing cables of the inverter and
inverter-driven motor. Therefore, use the independent earthing (grounding) and separated the earthing (grounding)
cable of the inverter from equipments 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)
(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 earthing cable. The earthing cable should be of not less than the size indicated in the table
on the previous page 18.
(d)The grounding point should be as near as possible to the inverter, and the ground wire length should be as short as
(e)Run the earthing 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.
(I)Independent earthing.......Best
To be compliant with the EU Directive (Low Voltage Directive),
(II)Common earthing.......Good
(III)Common earthing.......Not allowed
refer to the Instruction Manual (Basic).


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