Chapter 2
2-38
Standard Models and Specifications
●
Servomotor and Mechanical System Temperature Characteristics
• SMARTSTEP A-series Servomotors use rare earth magnets (neodymium-iron magnets). The tem-
perature coefficient for these magnets is approximately –0.13%/
°
C. As the temperature drops, the
Servomotor’s momentary maximum torque increases, and as the temperature rises the Servomo-
tor’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
particular, in systems which use reduction gear, the load torque at low temperatures may be nearly
twice the load torque at normal temperatures. Check with a current monitor to see whether over-
loading 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 tem-
peratures. Check to see whether there is optimal operation at low temperatures too.
2-4-3 Encoder Specifications
Item
Specification
Cylinder-style Servomotors
Flat-style Servomotors
Encoder method
Optical encoder (incremental)
Magnetic encoder
(incremental)
Number of output pulses
Phase A, B: 2,000 pulses/revolution
Phase Z: 1 pulse/revolution
Power supply voltage
5 V DC
±
5%
Power supply current
150 mA max.
Maximum rotation speed
4,500 r/min
Output signals
+A, –A, +B, –B, +S, –S
Output interface
Conforming to EIA RS-422A.
Output based on AM26LS31CN or equivalent.
Serial communications data
Phase Z, poll sensor, phases U, V, W
Serial communications method
Combined communications method using phases A, B, and S.
Summary of Contents for SMARTSTEP A Series
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