Product User Manual
Operating Instructions, Version AE 12/2009, A5E01454341C
33
Theory
3
3.1 Introduction
The Harmony series drives provide variable speed operation by converting utility power at
fixed frequency and fixed voltage to variable frequency, variable voltage power. This
conversion is done electronically, without moving parts. Unlike older drive types, the
Harmony series does not force the user to accept unpleasant by-products of this conversion
process.
Specifically:
● The Perfect Harmony series drives do not inject significant harmonic distortion into the
plant’s distribution system. No power filters are required. No interference to sensitive
equipment or resonance problems with power factor capacitors will occur.
● The Perfect Harmony series drives present a high power factor to the utility, typically 94%
or better throughout the speed range. No power factor correction is required.
● The Perfect Harmony series drives do not require any derating of the motor due to output
harmonics. No additional motor heating is produced, versus operation directly from the
utility.
● The Perfect Harmony series drives, when set up properly, do not produce torque
pulsations, which can excite mechanical resonance.
● The Perfect Harmony series drives cause no noticeable increase in acoustic noise from
the motor, versus operation directly from the utility.
● The Perfect Harmony series drives cause no appreciable additional stress to the motor
insulation, versus operation directly from the utility.
● The Perfect Harmony series drives allow unrestricted use of rated motor torque
throughout the speed range, subject only to the thermal limitations of the motor.
● The Perfect Harmony series drives are virtually silent in operation, if liquid-cooled, so that
normal conversation is possible next to drives running at full power.
● The Perfect Harmony series drives are completely modular in construction, so that if
necessary, a defective module can be replaced in minutes. Sophisticated
microprocessor-based diagnostics pinpoint the location of any defects.
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