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Earthing (Grounding) Precautions - Mitsubishi Electric FR-XC-18.5K-PWM Instruction Manual

Fr-xc series multifunction regeneration converter
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Earthing (Grounding) precautions

2.9
Earthing (Grounding) precautions
• Always earth (ground) the multifunction regeneration converter and the dedicated reactor FR-XCL or FR-XCB.
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 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 touching it.
To avoid the influence of external noises, the earthing (grounding) is important to EMI-sensitive equipment that handle low-
level signals or operate very fast such as audio equipment, sensors, computers.
Earthing (grounding) system to be established
As described previously, the purpose of earthing (grounding) is roughly classified into the electrical shock prevention and the
prevention of malfunction due to the influence of electromagnetic noise. These two purposes should be clearly distinguished.
Leakage currents containing many high frequency components flow into the earthing (grounding) cables of the converter.
When any other devices (EMI-sensitive devices) are earthed (grounded) nearby, the appropriate earth (ground) system must
be established as follows to prevent malfunction of such EMI-sensitive devices due to the leakage current from the converter,
inverter, or reactor.
• Make the separate earth (ground) connection (I) for the converter, inverter, and reactor away from other EMI-sensitive
devices wherever possible.
Establishing adequate common (single-point) earth (ground) system (II) shown in the following figure is allowed only in
cases where the separate earth (ground) system (I) is not feasible. Do not make inadequate common (single-point) earth
(ground) connection (III).
In a high building, it may be effective to use its iron structure frames as earthing (grounding) electrode for EMI prevention in
order to separate from the earth (ground) system for electric shock prevention.
• 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 the thickest possible earthing (grounding) cable. The size of the earthing (grounding) cable should be the same or
larger than the one indicated in the table on
• The earthing (grounding) point should be as close as possible to the converter, and the earth (ground) cable length should
be as short as possible.
• Run the earthing (grounding) cable as far away as possible from the I/O wiring of the EMI-sensitive devices, and run them
in parallel in the minimum distance.
High frequency
EMI-sensitive
products
devices
(converter, etc.)
(I) Separate earthing (grounding): Good
Earthing (grounding) of the FR-XCL reactor
• The FR-XCL reactor is usually earthed (grounded) by being mounted securely on a panel of the enclosure. If it is not well
earthed (grounded) by being mounted on a panel of the enclosure, remove varnish from a mounting hole and make an
earthing (grounding) connection from the hole.
(For the location of the mounting hole whose varnish should be removed, refer to the outline dimensions on
• For earthing (grounding) of the reactor, use the same gauge earthing (grounding) cable as that for the converter (refer to
page
43).
66
INSTALLATION AND WIRING
page
43.
EMI-sensitive
High frequency
products
devices
(converter, etc.)
(II) Common (single-point)
earthing (grounding): OK
High frequency
EMI-sensitive
products
devices
(converter, etc.)
(III) Inadequate common (single-point)
earthing (grounding): Bad
page
165.)

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