EQ7 Series Instruction Manual - TECO-Westinghouse Motor Company

(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).
• Leakage current
A high frequency current component generated by insulated gate bipolar transistors (IGBTs) switching on/off inside the
inverter becomes leakage current through stray capacitance of inverter input and output wires or a motor. If any of the
problems listed below occurs, take an appropriate measure against them.
Problem
An earth leakage circuit
breaker* that is
connected to the input
(primary) side has
tripped.
*With overcurrent
protection
An external thermal relay
was activated.
Measures
1) Decrease the carrier frequency.
2) Make the wires between the inverter and motor shorter.
3) Use an earth leakage circuit breaker with lower sensitivity than the one currently
used.
4) Use an earth leakage circuit breaker that features measures against the high
frequency current component.
1) Decrease the carrier frequency.
2) Increase the current setting of the thermal relay.
3) Use the electronic thermal overload protection built in the inverter, instead of the
external thermal relay.
• Selecting inverter capacity
(1) To drive a general-purpose motor, select an inverter according to the nominal applied motor rating listed in the
standard specifications table. When high starting torque is required or quick acceleration or deceleration is
required, select an inverter with one rank higher capacity than the standard.
(2) Special motors may have larger rated current than general-purpose ones. In such a case, select an inverter that
meets the following condition.
Inverter rated current > Motor rated current
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