Earthing (Grounding) Precautions - Mitsubishi Electric FR-CS84-012 Instruction Manual

Total wiring length (example of 400 V class inverter of the FR-CS84-120 or higher)
100 m or less
When driving a 400 V class motor by the inverter, surge voltages attributable to the wiring constants may occur at the motor
terminals, deteriorating the insulation of the motor. In this case, take one of the following measure.
• Use a "400 V class inverter-driven insulation-enhanced motor" and set
length.
Wiring length 50 m or Wiring length 50 to 100
shorter m
Any setting 8 (8 kHz) or lower
NOTE
• Especially for long-distance wiring, the inverter may be affected by a charging current caused by stray capacitances of the
wiring, leading to an activation of the overcurrent protection, malfunction of the fast-response current limit operation, or even
to an inverter failure. It may also cause a malfunction or fault of the equipment connected ON the inverter output side. If the
fast-response current limit function malfunctions, disable this function. (Refer to
page 119.)
• For the details of PWM frequency selection, refer to
• Refer to page 59
2.5.4

Earthing (grounding) precautions

Always earth (ground) the motor and inverter.
 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, this earthing (grounding) is important to audio equipment, sensors, computers and
other apparatuses that handle low-level signals or operate very fast.
 Earthing (grounding) methods and earthing (grounding) work
As described previously, earthing (grounding) is roughly classified into an electrical shock prevention type and a noise-
influenced malfunction prevention type. Therefore, these two types should be clearly distinguished, 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):
100 m + 50 m = 150 m
to drive a 400 V class motor by the inverter.
100 m
50 m
Pr.72 PWM frequency selection
Pr.156 Stall prevention operation selection
page 92.
according to the wiring
2. INSTALLATION AND WIRING
2.5 Main circuit terminals
1
2
3
5
5
6
on
7
8
9
10
33