Bosch DOK-MOTOR-MCL Series, Project Planning Manual

Page: 107 / 196

P
V
Total loss in W
P
VI
Short-circuit loss in W
I Current in motor cable in A
R
12
Electrical resistance of the motor at 20°C in Ohm (see Chapter
4 ”Technical data)
f
T
Factor temperature-related resistance raise
ΔT Temperature increase in K
α
20
Temperature coefficient of cupper in 1/K
Fig. 9-7: Power loss of synchronous linear motors
When you determine the power loss according to Fig. 9-7 you
must take the temperature-related rise of the electrical resistance
into account. At a temperature rise of 100 K (from 20 °C up to 120
°C), for example, the electrical resistance goes up by the factor f
T
= 1.39.
Thermal time constant The temperature variation vs. the time is determined by the produced power
loss and the heat-dissipation and –storage capability of the motor. The heat-
dissipation and –storage capability of an electrical machine is (combined in
one variable) specified as the thermal time constant.
The following figure (Fig.
9-8 ) shows a typical heating and cooling process of
an electrical machine. The thermal time constant is the period within which
63% of the final over temperature is reached.
Together with the duty cycle, the correlation to Fig.
9-9 and Fig. 9-11 are
used to define the operating modes, e.g. acc. to DIN EN 60034-1.
DOK-MOTOR*-MCL********-PR05-EN-P Bosch Rexroth AG 105/193
Rexroth IndraDyn L Ironless Linear Motors MCL
Application and construction instructions