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Abb AC Servo motors
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Speed – torque curves how to read motor performance curves
We have provided the following curves in order to simplify the process of selecting both a motor and control for a specific
application. The following paragraphs explain how the information in these curves should be interpreted.
In constant speed applications, motors are defined in terms of horsepower or kilowatts (which is torque at a base speed).
Servo motors normally operate over a wide speed range. The curves show continuous torque (defined as torque which will not
overheat the motor), and peak torque (defined as intermittent acceleration torque).
It is also necessary to know the current and voltage required for the motor to operate. The curves have a scale that shows
current required for any torque, and voltage required for any speed.
As an example, an application requires a continuous torque of 25 lb-in (2.8 Nm) at a speed of 1000 RPM. The peak torque
required for acceleration is 80 lb-in (9 Nm).
This curve shows that the motor will work in this application. The bus voltage required is 160Vdc. The continuous and peak
currents required is 3.5 and 12 amps.
SPEED (rpm) x 1000
CURRENT (Amps)
TORQUE (lb-in.)
160 VDC BUS
320 VDC BUS
TORQUE (Nm)
1
2
3
4
5
0
2
4
6
8
10
12
14
16
18
20
22
24
0
0
20
40
60
80
100
120
140
160
180
200
0
5
10
15
20
25
Peak motor
current
Peak current required
for the application
Continuous current
required for the
application
Required speed for the
application
Continuous torque for the
application
Peak torque for the
application
Intermittent operation area
Continuous operation area
Abb AC Servo motors