Instruction manual

40
INSTALLATION AND WIRING
 Countermeasures
• Use the electronic thermal relay function of the inverter.
• Decrease the carrier frequency. Note that motor noise increases. Selection of Soft-
PWM will make it unoffending.
To ensure that the motor is protected not to be influenced by line-to-line leakage
currents, we recommend the protection method which uses a temperature sensor
to directly detect motor temperature.
2.3.4 Inverter-driven 575V class motor
In the PWM type inverter, a surge voltage attributable to wiring constants is generated at
the motor terminals. Especially for a 575V class motor, the surge voltage may
deteriorate the insulation.
Surge voltage at a motor terminal by motor wiring length (reference)
When the 575V class motor is driven by the inverter, consider the following measures:
 Measures
(1) Inverter duty motor
Select an inverter duty motor. Many motor manufacturers sell motors with insulation
systems designed to withstand the stress imposed by PWM inverters.
(2) AC reactor
For added protection, install an AC reactor on the inverter output.
100%
0
200
150
Voltage at a motor terminal (%)
10 20 30 40 50 60 70 80 90 100
Motor wiring length (m)
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