Motor Application Precautions; Use With Existing Standard Motors - YASKAWA GA700 Technical Manual

2.25

Motor Application Precautions

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Use with Existing Standard Motors

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Low Speed Range
When a drive is used to operate a standard motor, power loss will increase compared to cases when the motor is
operated using a commercial power supply. In the low speed range, the self-cooling capability of such a motor
decreases with the speed, so the temperature of the motor will tend to rise quickly. Therefore, reduce the load
torque of the motor in the low speed range. The following figure shows the allowable load characteristics for a
Yaskawa standard motor. Use a motor designed specifically for operation with a drive when 100% continuous
torque is needed at low speeds.
A - 25% ED (or 15 min.)
B - 40% ED (or 20 min.)
Figure 2.72 Allowable Load Characteristics for a Yaskawa Standard Motors
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Insulation Withstand Voltage
Consider motor voltage tolerance levels and motor insulation in applications with an input voltage of over 440 V
or particularly long wiring distances. Use an insulated drive motor.
NOTICE: Use a motor that provides insulation suitable for PWM drives. Failure to comply may cause a short circuit or ground
fault due to insulation deterioration.
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High-Speed Operation
Problems may occur with the motor bearing durability and dynamic balance of the machine when operating a
motor beyond its rated speed. Contact the motor or machine manufacturer.
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Torque Characteristics
Torque characteristics differ compared to operating the motor directly from line power. The user should have a
full understanding of the load torque characteristics for the application.
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Vibration
Vibrations could occur in the following situations.
• Resonance with the natural frequency of machinery
Take particular caution when adding a variable speed drive to an application running a motor from line power at
a constant speed. If resonance occurs, install shock-absorbing rubber around the base of the motor and enable
the Jump frequency control.
• Unbalance of the revolving member itself
Take particular caution when the speed of the motor is increased above the rated motor speed.
• Subsynchronous resonance
Subsynchronous resonance can occur with long motor shafts and in applications such as turbines, blowers, and
fans with high inertia loads.
Use Closed Loop Vector Control when these applications experience subsynchronous resonance problems.
YASKAWA ELECTRIC SIEP C710617 01B YASKAWA AC Drive GA700 Technical Manual

2.25 Motor Application Precautions

C - 60% ED (or 40 min.)
D - Continuous operation
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