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MW99UE01-2104
Torque Motor Installation Manual
3.2 Thermal calculation
3.2.1 Heat loss
When the motor converts electric energy into kinetic energy, copper loss, iron loss and mechanical loss
are inevitable. Copper loss is the loss generated by the resistance when the current flows through the
stator coil of the motor. Iron loss, which can be classified into hysteresis loss and eddy current loss, is
generated by the conversion of the magnetic field between stator iron core and rotor magnet. As for
mechanical loss, it is generally much less than copper loss and iron loss; therefore, it can be ignored.
Copper loss under continuous torque is calculated as below.
��
=copper loss at coil temperature ��
��
��
= line-to-line resistance at coil temperature 25℃ [Ω]
25
��
=continuous current at coil temperature ��
��
��
= coil temperature [℃] (120℃
��
Iron loss is mainly caused by the change of magnetic flux during the commutation process and is
influenced by the frequency a lot. Since rotational speed is directly proportional to frequency, iron loss will
be larger at high speed. However, rotational speed for HIWIN torque motor is low, so iron loss is relatively
less than copper loss. Rotational speed value indicated by HIWIN drawing and specification is the
maximum peak speed that the motor can reach. Under the continuous operation of high speed, iron loss
must calculate extra heat given to rotor. At this time, motor loss increases rapidly. To avoid overheating,
users need to appropriately adjust operating conditions or apply heat dissipation on rotor.
Iron loss is mainly generated by eddy current and frequency. The faster the speed is, the more the iron
loss will be.
��
= iron loss [��]
����
�� = frequency [����]
Definition of frequency：
�� = rotational speed [������]
�� = Number of poles pair
Heat loss mainly transmits the loss of coil and iron core to motor outer casing via heat conduction. Take
natural air cooling for example. Lost heat source will be transmitted from the surface of outer casing
contacted by the air to external environment via heat convection, and from the customer's installation
surface via heat radiation and heat conduction. As for water cooling, lost heat source will be transmitted
from center of heat source to cooling water via heat conduction. Since the heat-conduction coefficient of
cooling water is much higher than that of air, the effect that heat source transmits to the air via convection
3-6
3
{ 1 + [ 0.00393 ( ��
��
=
��
��
25
2
[��]
��
[��
]
��
������
for TMRW series,
130℃
��
∝ ��
����
�� ⋅ ��
�� =
60
2
− 25 )]} ��
��
��
for TM-2/IM-2 series
2
Configuration
)
HIWIN MIKROSYSTEM Corp.
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