Mitsubishi Electric FR-D720-0.2K-G Instruction Manual page 28

(2) Earthing (Grounding) precautions
 Always earth (ground) the motor and drive unit.
1) Purpose of earthing (grounding)
Generally, an electrical apparatus has an earthing (grounding) 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 drive unit'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 drive unit. If independent earthing
(grounding) is not available, use (ll) common earthing (grounding) in the figure below where the drive unit is
connected with the other equipment at an earthing (grounding) point.
The (lll) common earthing (grounding) cable as in the figure below, which drive unit 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 drive
unit and drive unit-driven motor. Therefore, use the independent earthing (grounding) and separate the earthing
(grounding) cable of the drive unit 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 drive unit must be earthed (grounded). Earthing (Grounding) must conform to the requirements of national and
local safety regulations and electrical codes. (NEC section 250, IEC 61140 class 1 and other applicable standards).
Use an neutral-point earthed (grounded) power supply for 400V class drive unit in compliance with EN standard.
(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 page 16.
(d)The earthing (grounding) point should be as close as possible to the drive unit, and the earthing (grounding) cable
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.
Drive unit
(I)Independent earthing (grounding).......Best
POINT
To be compliant with the EU Directive (Low Voltage Directive),
(3) Total wiring length
Connect a PM motor within the total wiring length of 30m.
Use one PM motor for one drive unit. Multiple PM motors cannot be connected to a drive unit.
NOTE
 Especially for long-distance wiring, the drive unit may be affected by a charging current caused by the stray
capacitances of the wiring, leading to a malfunction of the overcurrent protective function or the stall prevention
function, or a malfunction or fault of the equipment connected on the drive unit's output side. If malfunction of stall
prevention function occurs, increase the stall level. (Refer to page 83 for Pr. 22 Stall prevention operation level and Pr. 156 Stall
prevention operation selection.)
Other
Drive unit
equipment
(II)Common earthing (grounding).......Good
Main circuit terminal specifications
Other
Drive unit
equipment
(III)Common earthing (grounding) cable.......Not allowed
refer to the Instruction Manual (Basic).
2
Other
equipment
17