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General-purpose Motors and Inverter Motors
Induction motors are classified as general-purpose motors or Inverter
motors based on their cooling capabilities. The motor overload function
operates differently for these two motor types.
Example for 200 V-Class Motors
Cooling Effect Torque Characteristics Electronic Ther-
mal Overload
General-purpose Motor
Effective when
operated at 50/
60 Hz from com-
mercial power
supply.
Base Frequency 60 Hz
(V/f for 60-Hz, 220-V Input Voltage)
For low-speed operation, torque
must be limited in order to stop
motor temperature rise.
An error
(motor overload
protection) oc-
curs when contin-
uously operated
at 50/60 Hz or
less at 100%
load.
Inverter Motor
Effective even
when operated
at low speed
(approx. 6 Hz)
Base Frequency 60 Hz
(V/f for 60-Hz, 220-V Input Voltage)
Use an Inverter motor for continu-
ous operation at low speed.
Electronic ther-
mal overload pro-
tection is not
activated even for
continuous opera-
tion at 50/60 Hz
or less at 100%
load.
Torque
(%)
60 s
Short-term
Continuous
Rating
Operation Frequency (Hz)
Torque
(%)
60 s
Short-term
Continuous
Rating
Operation Frequency (Hz)
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