4-60
The motor overload protection function estimates the motor overload level based on the output current, output
frequency, motor characteristics and time. The motor overload trip time depends on the motor rated current when
the output frequency is greater than 60Hz.
On inverter power-up the motor overload protection internal thermal accumulation register is automatically reset.
To use the built-in motor overload protection function parameter 02-01 (motor rated current) has to match the
motor rated current on the motor nameplate.
Turn off the motor overload protection when using two or more motors connected to the inverter (set 08-05 =
xxx0b), and provide external overload protection for each motor (e.g. thermal overload switch).
With cold start enabled (08-05 = xx0xb), motor overload protection occurs in 5 and a half minutes when operating
the motor at 150% of the motor rated current at an output frequency greater than 60Hz.
With hot start enabled (08-05 = xx1xb), motor overload protection occurs in 3 and a half minutes when operating
the motor at 150% of the motor rated current at an output frequency greater than 60Hz.
Example: Motor overload protection standard curve.
Cold Start
Low Speed
(<60 Hz)
Hot Start
High Speed
(>60 Hz)
100% 150% 200%
Motor Load Current (%)
(02-01 = 100%)
5.5
3.5
Overload Protect Time (min)
3.0
1.0
Motor overload protection curve (example: standard motor)
When using force cooled motors (Special inverter motor), thermal characteristics are independent of the motor
speed, set 08-05 = x1xxb.
When 08-05 = x1xxb, overload protection function is based on motor rated current for output frequencies between
6 and 60Hz. If the output frequency is lower than 1Hz, the overload protection function uses 83% of the motor
rated current to determine an overload condition.
When 08-05 = x0xxb, overload protection function is based on 70% of the motor rated current for an output
frequency of 20Hz. If the output frequency is lower than 1Hz, the overload protection function uses 40% of the
motor rated current to determine an overload condition.
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