Low-voltage motor of 600V or less 500V 1M (Ω) or more
12
6-3) Measuring Insulation Resistance
• When measuring the insulation resistance, disconnect the motor from the control panel. Check the motor separately.
Measure the insulation resistance before wiring. The insulation resistance (R) varies according to the motor output,
voltage, type of insulation, coil temperature, humidity, dirt, period of operation, test electrification time, etc. Usually, the
insulation resistance exceeds the values shown in Table 10.
Motor voltage Megohmmeter voltage Insulation resistance (R)
Table 10 Insulation Resistance
Referance : The following equations are shown in JEC-2100.
R≥
Rated Voltage (V)
Rated Output (kW)+1000
(M Ω)
R≥
Rated Voltage(V)+Speed(rpm)/3
Rated Output(kW)+2000
+0.5(M Ω)
A drop in insulation resistance may be attributed to poor insulation. In that case, do not turn on the power. Contact our
nearest agent, distributor, or sales office.
6-4) Protection Coordination
(1) Use a molded case circuit breaker for protection against short circuit.
(2) Use an overload protection device that protects the unit against a surge of electric current exceeding that shown on the
rating plate.
(3) For an explosion-proof type motor , use an overload protector that can protect the unit within the allowable binding
hour by means of the locked rotor current shown on the rating plate.
6-2) Connection with Power Source Cable
Connecting method is shown below.
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