1-6
Chap. 1
BEFORE USING THE INVERTER
If no zero-phase current (earth leakage current) detective device such as a ground-fault relay is installed in the
upstream power supply line in order to avoid the entire power supply system's shutdown undesirable to factory
operation, install a residual-current-operated protective device (RCD)/earth leakage circuit breaker (ELCB)
individually to inverters to break the individual inverter power supply lines only.
Otherwise, a fire could occur.
(6) Magnetic contactor (MC) in the inverter input (primary) circuit
Avoid frequent ON/OFF operation of the magnetic contactor (MC) in the input circuit; otherwise, the inverter failure may
result. If frequent start/stop of the motor is required, use FWD/REV terminal signals or the
/ keys on the
inverter's keypad.
The frequency of the MC's ON/OFF should not be more than once per 30 minutes. To assure 10-year or longer service
life of the inverter, it should not be more than once per hour.
• From the system's safety point of view, it is recommended to employ such a sequence that shuts down the
magnetic contactor (MC) in the inverter input circuit with an alarm output signal ALM issued on inverter's
programmable output terminals. The sequence minimizes the secondary damage even if the inverter breaks.
When the sequence is employed, connecting the MC's primary power line to the inverter's auxiliary control
power input makes it possible to monitor the inverter's alarm status on the keypad.
• The breakdown of a braking unit or misconnection of an external braking resistor may trigger that of the
inverter's internal parts (e.g., charging resistor). To avoid such a breakdown linkage, introduce an MC an
three seconds after the MC is switched on.
For the braking transistor built-in type of inverters, assign a transistor error output signal DBAL on inverter's
programmable output terminals to switch off the MC in the input circuit.
(7) Magnetic contactor (MC) in the inverter output (secondary) circuit
If a magnetic contactor (MC) is inserted in the inverter's output (secondary) circuit for switching the motor to a
commercial power or for any other purposes, it should be switched on and off when both the inverter and motor are
completely stopped. This prevents the contact point from getting rough due to a switching arc of the MC. The MC should
not be equipped with any main circuit surge killer.
Applying a commercial power to the inverter's output circuit breaks the inverter. To avoid it, interlock the MC on the
motor's commercial power line with the one in the inverter output circuit so that they are not switched ON at the same
time.
(8) Surge absorber/surge killer
Do not install any surge absorber or surge killer in the inverter's output (secondary) lines.
Noise reduction
If noise generated from the inverter affects other devices, or that generated from peripheral equipment causes the inverter to
malfunction, follow the basic measures outlined below.
(1) If noise generated from the inverter affects the other devices through power wires or grounding wires:
- Isolate the grounding terminals of the inverter from those of the other devices.
- Connect a noise filter to the inverter power wires.
- Isolate the power system of the other devices from that of the inverter with an insulated transformer.
- Decrease the inverter's carrier frequency (F26).
(2) If induction or radio noise generated from the inverter affects other devices:
- Isolate the main circuit wires from the control circuit wires and other device wires.
- Put the main circuit wires through a metal conduit pipe, and connect the pipe to the ground near the inverter.
- Install the inverter into the metal panel and connect the whole panel to the ground.
- Connect a noise filter to the inverter's power wires.
- Decrease the inverter's carrier frequency (F26).
(3) When implementing measures against noise generated from peripheral equipment:
- For inverter's control signal wires, use twisted or shielded-twisted wires. When using shielded-twisted wires, connect
the shield of the shielded wires to the common terminals of the control circuit.
- Connect a surge absorber in parallel with magnetic contactor's coils or other solenoids (if any).
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