3-13
Input power supply capacity [kVA] =
Motor output [kW]/(Motor efficiency x Inverter efficiency x Inverter input power factor)
Normal motor efficiency = 0.8, Normal inverter efficiency = 0.9,
Inverter input power factor = 0.65 to 0.9
Note The Inverter’s input power factor will vary with the impedance of the power supply
facilities. Use 0.9 when using an AC reactor and 0.65 when not using an AC reac-
tor.
For the input current, divide the input power supply capacity by the input voltage.
Assuming the Inverter’s resistance to overloads to be 150%, the calculated value can
be multiplied by 1.5.
Example for 3-phase 200 V: 1.5 x input power supply capacity/(p3 x 200 V)
Example for single-phase 200 V: 1.5 x input power supply capacity/200 V
H Wiring on the Input Side of Main Circuit
D Installing a Molded-case Circuit Breaker
Always connect the power input terminals (R/L1, S/L2, and T/L3) and power supply via a
molded case circuit breaker (MCCB) suitable to the Inverter.
•Install one MCCB for every Inverter used.
•Choose an appropriate MCCB capacity according to the Circuit breaker capacity col-
umn in the table on the previous page.
•For the MCCB’s time characteristics, be sure to consider the Inverter’s overload
protection (one minute at 150% of the rated output current).
•If the MCCB is to be used in common among multiple Inverters, or other devices, set up
a sequence such that the power supply will be turned off by a fault output.
D Installing a Ground Fault Interrupter
Inverter outputs use high-speed switching, so high-frequency leakage current is gener-
ated.
In general, a leakage current of approximately 100 mA will occur for each Inverter (when
the power cable is 1 m) and approximately 5 mA for each additional meter of power
cable.
Therefore, at the power supply input area, use a special-purpose breaker for Inverters,
which detects only the leakage current in the frequency range that is hazardous to hu-
mans and excludes high-frequency leakage current.
•For the special-purpose breaker for Inverters, choose a ground fault interrupter with a
sensitivity amperage of at least 10 mA per Inverter.
•When using a general leakage breaker, choose a ground fault interrupter with a sensi-
tivity amperage of 200 mA or more per Inverter and with an operating time of 0.1 s or
more.
Design Chapter 3
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