Technical data

Rexroth IndraDyn H Notes Regarding Application 9-7
DOK-MOTOR*-MBS-H******-PR02-EN-P
Thermal Behavior
The achievable rated torque of an IndraDyn H motor is mainly
determined by the power loss P
V
that is produced during the energy
conversion process. The power loss fully dissipates in form of heat. Due
to the limited permissible winding temperature it must not exceed a
specific value.
Note: The maximum winding temperature of IndraDyn H motors is
155°C. This corresponds to insulation class F.
The total losses of these kit motors are chiefly determined by the losses
in the stator.
T12
2
ViV
fRi
4
3
P P ⋅⋅⋅=≈
P
V
: Total loss in W
P
Vi
: Current heat dissipation in W
i: Current in motor cable (peak value) 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 rise
Fig. 9-1: Power loss of IndraDyn H motors
Note: 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 115 K (from
20°C up to 135°C), for example, the electrical resistance goes
up by the factor f
T
= 1.45.
The temperature variation vs. time is determined by the produced power
loss, the heat-dissipation and heat–storage capability of the motor. The
heat-dissipation and heat–storage capability of an electrical machine is
(combined in one variable) specified as the thermal time constant.
Note: With liquid cooling systems, the thermal time constant is
between 5...10 min. (depending on size).
The following 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. With liquid cooling, the
cooling time constant corresponds to the heating time constant. Thus,
the heating process and the cooling process can both be specified with
the specified thermal time constant (heating time constant) of the motor.
Power loss
Thermal time constant