Siemens MICROMASTER 420 - Manual (Page 137)

Issue 07/04 3 Functions
MICROMASTER 420 Operating Instructions
6SE6400-5AA00-0BP0 137
Temperature Classes
The permissible temperature rise of electrical machinery (motors) is limited due to
the thermal strength of the insulating materials.
Different maximum values are permissible depending on the material used. In
compliance with regulations for rotating electrical machinery, a differentiation is
made between several temperature Classes (refer to the motor rating plate) and
these are assigned to the highest permissible continuous temperature. An excerpt
from IEC 85 is shown in the "Thermal Classes" table.
Table 3-25 Thermal classes
Max.perm.temperature Thermal Class
Y
A
E
B
F 90 °C
105 °C
120 °C
130 °C
155 °C
H 180 °C
Excerpt from IEC 85
3.19.2 PTC temperature sensor
When the motor is operated below the
rated speed the cooling effect of the
shaft-mounted fan is reduced. As a
result, for most motors when continually
operated at lower frequencies, the
power has to be reduced. Under these
particular conditions, the motors are
only protected against overheating if
either the parameters of the motor
temperature model (refer to Section
3.19.1) were precisely determined or a
PTC temperature sensor is mounted to
the motor and connected to one of the
digital inputs of the MICROMASTER
420 (refer to Fig. 3-57).
Parameters P0701, P0702 or P0703 =
29 (external fault) should be set to
activate the shutdown (tripping) function
for a motor overtemperature condition.
If the resistance of the PTC temperature
sensor exceeds the shutdown (trip)
threshold (motor overtemperature
condition), then Fault F0085 is output
(external fault).
Fig. 3-57 PTC characteristic for
1LG / 1LA motors