Issue:
Definition of motor power, motor thermal state and drive thermal state on the ATV61/ATV71.

Product Line:
ATV61 and ATV71

Environment:
All

Cause:
Description of motor power, motor thermal state, and drive thermal state

Resolution:
Drive Thermal state (THD)
The drive thermal state is given by the parameter THD.
When THD is at 118% it means 100ﾰC on the heatsink.
Here are some values regarding the THD level and the temperature.
THD => Temperature
0 % => -20ﾰC
10 % => 0ﾰC
50 % => 40ﾰC
90 % => 80ﾰC
118 % => 100ﾰC
Take care because the law is not linear. Motor thermal state (THR)
The motor thermal stage is expressed as Iﾲt.
The thermal motor takes into account the copper and iron constants as well as the type of motor ventilation.
The motor thermal state is calculated with the square of the ratio of RMS-measured current over the ITH value.
So the value THR does not correspond really to a temperature, but a percent of ITH current.
For example:
We could approach the THR value with the iﾲt curve.
(Note: this calculation is just to give an idea because it does not take into account the copper and iron
constants, the drive frequency, type of motor ventilation, and operating time ?)
The actual drive current is 1,1A and the ITH was set to 2,2A.
In/ITH = 0,5
With Iﾲt curve we calculate around 25%.
After a test on a product I read THR = 22%
The actual drive current is 1,1A and the ITH was set to 2,7A.
In/ITH = 0,40
With Iﾲt curve we calculate around 16%.
After a test on a product I read THR = 15%
The actual drive current is 1,1A and the ITH was set to 1,5A.
In/ITH = 0,73
With Iﾲt curve we calculate around 53%.
After a test on a product I read THR = 48%

Motor Power (OPR)
The Motor power (OPR) is a % of the rated power.
The value is given in %, and 100% corresponds to the motor power entered by the user with the nameplate data (NPR parameter).

Released for: Schneider Electric Egypt and North East Africa