Appendix
12.2.1Using the Inverter for an Existing Standard Motor
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12.2 Motor Application Precautions
12.2.1 Using the Inverter for an Existing Standard Motor
When a standard motor is operated with the Inverter, power loss is slightly higher than when operated with
a commercial power supply. In addition, cooling effects also diminish in the low-speed range, resulting in
an increase in the motor temperature. Therefore, the motor torque should be reduced in the low-speed range.
The following graph shows the allowable load characteristics of a standard motor.
If 100% torque is continuously required in the low-speed range, use a special motor or vector-exclusive mo-
tor for use with inverters.
Frequency (Hz)
60203
0
100
82
70
60
50
Torque
(%)
Continuous
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60% ED (or 40 minutes)
40% ED (or 20 minutes)
25% ED (or 15 minutes)
If the input voltage is high (440 V or higher) or the wiring distance is long, the motor insulation voltage must
be considered. Contact your Yaskawa representative for details.
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High-speed Operation
When using the motor at a high speed (60 Hz or more), problems may arise in dynamic balance and bearing
durability. Contact your Yaskawa representative for details.
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Torque Characteristics
The motor may require more acceleration torque when the motor is operated with the Inverter than when op-
erated with a commercial power supply. Check the load torque characteristics of the machine to be used with
the motor to set a proper V/f pattern.
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Vibration
The Inverter uses a high carrier PWM to reduce motor vibration. When the motor is operated with the Invert-
er, motor vibration is almost the same as when operated with a commercial power supply.
Motor vibration may, however, become greater in the following cases.
Resonance with the Natural Frequency of the Mechanical System
Takespecialcarewhena machinethathasbeen operatedata constantspeedis tobeoperatedinvariablespeed
mode.
If resonance occurs, install vibration-proof rubber on the motor base or use the frequency jump function to
skip any frequency resonating the machine.
Imbalanced Rotor
Take special care when the motor is operated at a higher speed (60 Hz or more).
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Noise
Noise is almost the same as when the motor is operated with a commercial power supply. Motor noise, how-
ever, becomes louder when the motor is operated at a speed higher than the rated speed (60 Hz).
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