Design
Chapter 3
D Installing a Ground Fault Interrupter
Inverter outputs use high-speed switching, so high-frequency leakage current is generated. 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 frequen-
cy range that is hazardous to humans and excludes high-frequency leakage current.
Countermeasures taken for the EMC tend to increase the leakage current, therefore careful attention
must be paid in selecting a breaker.
• For the special-purpose breaker for Inverters, choose a ground fault interrupter with a sensitivity am-
perage of at least10 mA per Inverter.
• When using a general leakage breaker, choose a ground fault interrupter with a sensitivity amperage
of 200 mA or more per Inverter and with an operating time of 0.1 s or more.
D Installing a Magnetic Contactor
This Inverter can be used without a magnetic contactor (MC) on the power supply side.
If the power supply for the main circuit is to be shut off because of the sequence, a magnetic contactor
can be used instead of a molded-case circuit breaker.
However, when a magnetic contactor is installed on the primary side of the main circuit to forcibly stop a
load, note that regenerative braking does not work and the load coasts to a stop.
• A load can be started and stopped by opening and closing the magnetic contactor on the primary side.
Note, however, that frequently opening and closing the magnetic contactor may cause the Inverter to
break down.
• When the Inverter is operated with a Digital Operator, automatic operation cannot be performed after
recovery from a power interruption.
D Connecting Input Power Supply to the Terminal Block
Because the phase sequence of input power supply is irrelevant to the phase sequence (L1, L2/N, L3) of
the terminal block, input power supply can be connected to any terminal on the terminal block.
D Installing an AC Reactor
It is recommended that an AC reactor be inserted in the input power supply side to suppress harmonics.
If the Inverter is connected to a large-capacity power transformer (600 kW or more) or the phase
advance capacitor is switched, an excessive peak current may flow through the input power circuit,
causing the converter unit to break down. To prevent this, install an optional AC reactor on the input side
of the Inverter. This also improves the power factor on the power supply side.
D Installing a Surge Absorber
Always use a surge absorber or diode for the inductive loads to be connected to the Inverter. These
inductive loads include magnetic contactors, electromagnetic relays, solenoid valves, solenoids, and
magnetic brakes.
D Wiring of Braking Resistor/Braking Resistor Unit
When using an Inverter for loads with a large inertia or for vertical axis loads, regenerative energy will be
fed back.
3-15
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