Yaskawa VS-626 MC5 - Manual (Page 273)

Appendix
12.2.1 Using 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 for use with inverters.
Frequency (Hz)
60 20 3
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.
J 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.
J 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.
J 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
Take special care when a machine that has been operated at a constant speed is to be operated in variable speed
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).
J 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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