Omron OMNUC W Series User Manual page 116

Standard Models and Specifications
3,000-r/min Flat-style Servomotors (400 V AC)
The following graphs show the characteristics with a 3-m standard cable and 400-V AC input.
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.
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Chapter 2