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Line voltage drop [V] =
Use a larger diameter cable when the wiring distance is long or when it is desired to decrease the voltage drop (torque
reduction) in the low speed range.
NOTE
• Tighten the terminal screw to the specified torque.
A screw that has been tightened too loosely can cause a short circuit or malfunction.
A screw that has been tightened too tightly can cause a short circuit or malfunction due to the unit breakage.
• Use crimp terminals with insulation sleeves to wire the power supply and motor.
2.6.6
Earthing (grounding) precautions
• Always earth (ground) the converter unit.
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. Therefore, these two types should be clearly
distinguished, and the following work must be done to prevent the leakage current having the converter unit's high frequency
components from entering the malfunction prevention type earthing (grounding):
• Whenever possible, use the independent earthing (grounding) for the converter unit.
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).
As leakage currents containing many high frequency components flows into the earthing (grounding) cables of the
converter unit, the converter unit must also be earthed (grounded) separately from the EMI-sensitive equipment described
above.
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).
A neutral-point earthed (grounded) power supply must be used to be compliant with EN standard.
• Use the thickest possible earthing (grounding) cable. The earthing (grounding) cable should be the size indicated in the
table on
page
43.
• The earthing (grounding) point should be as close as possible to the converter unit, and the earth (ground) wire length
should be as short as possible.
44
2. INSTALLATION AND WIRING
2.6 Main circuit terminals (for 12-phase rectification)
× wire resistance [mΩ/m] × wiring distance [m] × current [A]
1000
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