AC Motor Drives

AC motor drives interface controllers to AC motors. They match the control signals (voltage and power levels) as well as the signal type (analog or digital). They also provide power conversion, amplification, and the sequencing of waveform signals. AC motor drives are used with many types of AC motors. Induction motors induce current into the rotor windings without any physical connection to the stator windings. They are suitable for many different environments and are capable of providing considerable power as well as variable speed control. Synchronous motors are no-slip devices that operate at constant speed up to full load. Subcategories include reluctance motors and permanent magnet devices such as AC servomotors. Many AC servomotors use brushless commutation with feedback provided by Hall effect sensors. Pole changing motors use pole number control, a method for changing the number of poles on the primary winding. Vector drive motors provide independent control of both the voltage and frequency, resulting in low-speed torque outputs that approach those of DC motors. In some designs, encoders or resolvers are used to provide feedback about position and speed. Linear motors generate force in only the direction of travel. Common technologies include moving coil, moving magnet, and switched reluctance designs.

Selecting AC motor drives requires an analysis of application categories. Multi-axis controllers are used to control and monitor multiple, independent axes of motion. Motor speed controllers are application-specific and used to control machines such as conveyors. Robotic motion controllers use digital motion control hardware and software for the coordinated multi-axis control of industrial robots and robotic systems. Servo amplifiers are electronic modules that convert low level analog command signals to high power voltages and currents. Inverter drives convert AC power inputs to DC outputs. High frequency drives supply power to AC motors at frequencies that are considerably higher than those used in standard-power applications. Regenerative drives support motor braking. Variable speed drives support speed control and adjustment. AC motor drives that use microcontrollers, silicon controlled rectifiers (SCR), digital signal processors (DSP), and pulse width modulation (PWM) are also available. 

AC motor drives differ in terms of electrical ratings, operating parameters, configurations, and features. Electrical ratings include maximum output voltage, rated power, continuous output current, peak output current, AC supply voltage, and DC supply voltage. AC motor drives use either single-phase or three-phase inputs at 50, 60, or 400 Hz. Operating parameters include specifications for setup and control. Some AC motor drives have manual controls such as knobs, DIP switches, jumpers or potentiometers. Others include a joystick, digital control panel, computer interface, or slots for PCMCIA cards. Control programs can be stored on removeable, nonvolatile storage media. Hand held devices are designed to be programmed remotely. Wireless and web-enabled controls are also available. Configurations for AC motor drives include several mounting styles. Most devices mount on a chassis, DIN rail, panel, rack, wall, or printed circuit board (PCB). Standalone devices and integrated circuit (IC) chips that mount on PCBs are also available. Features for AC motor drives include soft starting; dynamic, injection, or regenerative braking; brake outputs or auxiliary inputs/outputs (I/O); auto-tuning, self-diagnostics, and status monitoring; and alarms for conditions such as overvoltage. 

Computer-based AC motor drives use many different types of buses and communication standards. Bus types include advanced technology attachment (ATA), peripheral component interconnect (PCI), integrated drive electronics (IDE), industry standard architecture (ISA), general-purpose interface bus (GPIB), universal serial bus (USB), and VersaModule Eurocard bus (VMEbus). Communications standards include ARCNET, AS-i, Beckhoff I/O, CANbus, CANopen, DeviceNet, Ethernet, small computer systems interface (SCSI), and smart distributed system (SDS). Many serial and parallel interfaces are also available.

• Application Example: Increased Reliability in the Paper Industry (.pdf)
  Nowadays, the paper and pulp industry is interlinking intelligent hi-tech machines to highly efficient production lines. Higher power DC and AC motor drives perform the automation tasks. Every kind of...
  (read more)
• Motors and Drives: A Practical Technology Guide
  To some, motor speed control is somewhat of a mystical science, a science that causes motors and machines to sometimes operate in unexpected ways. Over 30 years ago, AC drives were considered "new...
  (read more)
• AN1162 - Sensorless Field Oriented Control (FOC) of an AC Induction Motor (ACIM)
  AN1162 Sensorless Field Oriented Control (FOC) of an AC Induction Motor (ACIM) operate at a speed that is roughly proportional to the Author: Mihai Cheles input frequency. As you decrease the...
  (read more)

Pages: 1 - 3 of 336

Part Numbers for AC Motor Drives