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Monday, 19 December 2011

How to Select a Suitable Motor

Before Starting VFD take the following precautions


When using the AC Motor Drive to operate a standard 3-phase induction motor, take the following precautions:
  • The energy loss is greater than for an inverter duty motor.
  • Avoid running motor at low speed for a long time. Under this condition, the motor temperature may rise above the motor rating due to limited airflow produced by themotor’s fan. Consider external forced motor cooling.
  • When the standard motor operates at low speed for long time, the output load must be decreased.

 The load tolerance of a standard motor is as follows:



  •  Pole-changing (Dahlander) motor:
The rated current is differs from that of a standard motor. Please check before operation and select the capacity of the AC motor drive carefully. When changing the pole number the motor needs to be stopped first. If over current occurs during operation or regenerative voltage is too high, please let the motor free run to stop (coast).
  • Submersible motor:
The rated current is higher than that of a standard motor. Please check before operation
and choose the capacity of the AC motor drive carefully. With long motor cable between
AC motor drive and motor, available motor torque is reduced.
  • Explosion-proof (Ex) motor:
Needs to be installed in a safe place and the wiring should comply with the (Ex)
requirements. Delta AC Motor Drives are not suitable for (Ex) areas with special
precautions.
  • Gear reduction motor:
The lubricating method of reduction gearbox and speed range for continuous operation
will be different and depending on brand. The lubricating function for operating long time
at low speed and for high-speed operation needs to be considered carefully.
  • Synchronous motor:
The rated current and starting current are higher than for standard motors. Please check before operation and choose the capacity of the AC motor drive carefully. When the AC motor drive operates more than one motor, please pay attention to starting and changing the motor.
  • Power Transmission Mechanism
Pay attention to reduced lubrication when operating gear reduction motors, gearboxes, belts and chains, etc. over longer periods at low speeds. At high speeds of 50/60Hz and above, lifetime reducing noises and vibrations may occur.

  • Motor torque
The torque characteristics of a motor operated by an AC motor drive and commercial mains power are different.

Source: Delta VFD B Series manual.

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