Data Sheet for Product

Motor Performance on PWM/IGBT AC Drives Technical Bulletin – TB255
Document Number 155-743
August 29, 2018
Information in this publication is based on current specifications. The company reserves the right to make changes in specifications and models as
design improvements are introduced. Product or company names mentioned herein may be the trademarks of their respective owners.
© 2018 Siemens Industry, Inc.
Siemens Industry, Inc.
Building Technologies Division
1000 Deerfield Parkway
Buffalo Grove, IL 60089
+ 1 847-215-1000
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Document No. 155-743
Printed in the USA
Page 4
Retrofit
Considerations
• Installation location
Select a location for the VFD that will minimize the motor cable length. The
appropriate distance is best determined by the ability of the motor to operate on IGBT
drives, as determined by the motor manufacturer. If motor specifications are
unavailable, generally be conservative and stay within 25 feet on 460 Vac systems
and 150 feet on 230 Vac systems. For 575 Vac systems, always use inverter-rated
motors and/or output filtering.
• Output filtering
Use appropriate output filtering in all cases where the motor distance is greater than
listed above.
• Age of motor
The older the existing motor and the harsher its environment, the less ability it has to
withstand the new stresses of an IGBT waveform output. This, combined with the
systems ability to withstand down time, should be considered when deciding if the
motor should be replaced when the drive is installed.
• Motor horsepower
The smaller the motor horsepower, the greater the chance that it is not perfectly
wound; there is little or no slot plate insulation material and varnish is of lower quality.
Because of this, and the fact that upgrading is relatively inexpensive, low horsepower
motors should be closely examined for replacement when installing IGBT drives.
Summary
Today’s drives provide tremendous energy savings and control benefits, but their effects
on motor performance should be considered strongly in selecting the right product for
reliable operation. By doing an appropriate cost, benefit, and risk analysis, appropriate
decisions can be made upfront to ensure expected performance. Summarizing the
parameters to consider:
• Motor specification: Type, voltage, rated speed, operating speed, horsepower,
stated specification.
• Installation considerations: Wire length, voltage, environment, ability to withstand
down time, requirement for low motor noise.
• Use appropriate field devices as required: Line reactors, dV/dT filters and others.