The temperature of the hottest point of the winding must be kept below the class limit and the total temperature is the sum of the ambient temperature with the temperature rise “Dt” plus the difference between the mean winding temperature and the hot. The electric motor standards marathon b206 belt drive define the maximum temperature rise “Dt”, so that the temperature of the hottest spot will be limited, based on the following considerations:
– The ambient temperature should be at most 40ºC per standard, because above that the working conditions are considered special;
– The difference between the average temperature and the hottest point will not change much from motor to motor and its value is fixed in norm, and is in practice is 5ºC for classes A and E, 10ºC for classes B and F and 15ºC for class H.
Engine standards set a maximum for ambient temperature and assign a maximum temperature rise for each insulation class, and the temperature of the hottest point of the engine is indirectly limited.