2-94
D
Servomotor and Mechanical System Temperature Characteristics
•
W-series AC Servomotors use rare earth magnets (neodymium-iron magnets). The temperature
coefficient for these magnets is approximately -0.13%/
°
C. As the temperature drops, the Servomo-
tor’s momentary maximum torque increases, and as the temperature rises the Servomotor’s
momentary maximum torque decreases. When the normal temperature of 20
°
C and --10
°
C are
compared, the momentary maximum torque increases by approximately 4%. Conversely, when the
magnet warms up to 80
°
C from the normal temperature of 20
°
C, the momentary maximum torque
decreases by approximately 8%.
•
Generally, in a mechanical system, when the temperature drops the friction torque increases and the
load torque becomes larger. For that reason, overloading may occur at low temperatures. In particu-
lar, in systems which use deceleration devices, the load torque at low temperatures may be nearly
twice the load torque at normal temperatures. Check with a current monitor to see whether overload-
ing is occurring at low temperatures, and how much the load torque is. Likewise, check to see
whether there abnormal Servomotor overheating or alarms are occurring at high temperatures.
•
An increase in load friction torque visibly increases load inertia. Therefore, even if the Servo Driver
parameters are adjusted at a normal temperature, there may not be optimal operation at low temper-
atures. Check to see whether there is optimal operation at low temperatures too.
Caution
Do not use 900-W, 2-kW, 4-kW, or 5.5-kW Servomotors within the shaded portions of the
following diagrams. If used in these regions, the Servomotor may heat, causing the encoder
to malfunction.
Effective torque (N.m)
Effective torque (N.m)
Effective torque (N.m)
Ambient temperature (
_
C)
Ambient temperature (
_
C)
Ambient temperature (
_
C)
R88M-W90010
j
(900 W)
R88M-W2K010
j
(2 kW)
R88M-W3K010
j
(3 kW)
Effective torque (N.m)
Effective torque (N.m)
Ambient temperature (
_
C)
Ambient temperature (
_
C)
R88M-W4K010
j
(4 kW)
R88M-W5K510
j
(5.5 kW)
Standard Models and Specifications
Chapter 2
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