OPERATION AND MAINTENANCE MANUAL
ID MOTORS
PAGE: 18
CODE: CTT52 EDITION: 03 RELEASE: APRIL 2019
Subject to technical changes without prior notice
Insulation class
3.3.6
The insulation rating of an electrical machine is identified on the motor specifications plate by means of a letter in accordance with
the IEC/EN 60034-18 standard.
The following table summarises the maximum allowed temperature in the installation of a winding in accordance with its insulation
rating:
Class
Maximum temperature
A
105ºC
E
120ºC
B
130ºC
F
155ºC
H
180ºC
Table 9:
Insulation classes
Heating limits
3.3.7
The IEC60034-1 standard defines the maximum admissible heating (increase in temperature) for the windings as specified in the
following table:
Thermal Class
Coolant
temperature
Heating
(per element)
Operating
temperature
B (130ºC)
< 40ºC
< 80ºC
< 120ºC
F (155ºC)
< 40ºC
< 105ºC
< 145ºC
H (180ºC)
< 40ºC
< 125ºC
< 165ºC
Table 10:
Heating limits
Accordingly, the rated working conditions of the motor must be such that the operating temperature on the windings is always
below the temperature specified by the insulation class of the part materials. Therefore, the working thermal class of a motor can
correspond to the following:
a)
The same thermal insulation class
. This would be the case of a motor built with
Class F
insulation (155°C) with a
maximum working temperature of 140°C, corresponding to a
Class F
.
b)
A thermal class lower than the insulation class
. This would be the case of a motor built with
Class H
insulation
(180°C) with a maximum working temperature of 140°C, corresponding to a
Class F
.
