3-14
D Installing a Magnetic Contactor
If the power supply for the main circuit is to be shut off because of the sequence, a mag-
netic 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. Frequently opening and closing the magnetic contactor, however,
may cause the Inverter to break down. In order not to shorten the service life of the
Inverter’s internal relays and electrolytic capacitors, it is recommended that the mag-
netic contactor is used in this way no more than once every 30 minutes.
•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
(R, S, T) 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 sup-
press 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, regenera-
tive energy will be fed back.
If the regenerative energy exceeds the Inverter capacity, overvoltage will be detected in
the main circuit. In such a case, use a Braking Resistor or Braking Resistor Unit.
Note Be sure to create a sequence that will turn OFF the Inverter power supply when
resistor overheating occurs. When using a Braking Resistor, be sure to install a
Design Chapter 3
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