Page 152 - Electromechanical Devices and Components Illustrated Sourcebook

114 Electromechanical Devices & Components Illustrated Sourcebook

Speed (Oscillator)
Speed (0 to 10 Volts)
Run
3 Single Step
2 4
CW/CCW
1 5 Between Poles
Rotor
6
6
Stepper
5 1 Controller
4 2
3
Stepper
Motor 120 VAC
Figure 6-33 Half-Step Position
Pole
Switches
DC Power
Supply
Figure 6-36 Stepper Motor Control

3
2 4
1 5 Multi Positional Servo Motors
Rotor
6 6 A servo motor is simply a DC motor with a positional feed-
back resolver attached to its shaft. These motors are the pre-
5 1
ferred choice for motion control applications that have high
4 2
3
or varying loads, such as machine tools and material-handling
systems. Figure 6-37 shows a commercial DC servo motor.
Note the resolver housing on the back side of the motor. The
Figure 6-34 Microstep Positioning housing contains a sensor that can feed speed and position
information back to the controller.
Figure 6-38 shows a block diagram of a typical servo
motor control system. The motor resolver feeds position and

Terminal Wires
Mounting Holes
Mounting Holes
Frame Bolts Frame Speed & Position
Frame Bolts Leads Box
Mount Flange Data Port
Alignment Boss
Alignment Boss Cooling Resolver
Fins
Mount Housing
Output Shaft
Flange

End Cap
Output Shaft
Figure 6-35 Commercial Stepper Motor Brushes
Figure 6-37 Commercial DC Servo Motor

Stepper motors require a special controller to operate. The
controller generally consists of a series of switches that turn
the poles on and off. These switches are usually in the form of
Variable DC
power transistors, which direct the output of a DC power sup- Power Supply
ply to the appropriate pole set. The switches are connected the
stepper controller, which provides speed, step and rotation
control. Figure 6-36 shows a block diagram of a typical step- Input From
per motor control system. It should also be noted that this System
arrangement is referred to as an open-loop system. In an open Controller
loop system the motor does not provide any feedback to the Servo Motor
controller. Figure 6-38 Closed-Loop Servo Motor Control System