The motor is a 4-pole, three-phase AC brushless motor with built-in rotary encoder and temperature monitoring. It is a 5,000 step per revolution servo motor, capable of providing 9,000 oz-in continuously or peak of 18,000 oz-in. The motor has permanent magnets on the rotor making it synchronous to the frequency supplied by the drive. Were the motor not synchronous by either permanent magnets or DC windings on the rotor, (like a regular three phase motor) there would be a slip of the shaft rotation behind the frequency -- this slip is necessary to produce torque on all induction and squirrel cage motors. This would make for inaccurate speed control; motor speed would be determined by the load as well as frequency. It would be almost useless in a precise positioning, velocity & acceleration control, and would have no holding torque when not in motion.
The drive is made up of two parts, the AC frequency drive and the CPU with I/O terminals. The frequency drive is connected directly to the motor and is controlled by the CPU, making the ZX a self contained Servo System. The CPU is receives information from the motor through the rotary encoder, as well as limit switches placed according to application (the Home, CW & CCW limits). The CPU must be first programmed before it can be used in any application. This is done by using DOS based XWare software through a Tx/Rx/Vo RS-232 connection. The CPU can receive further inputs from a PLC, switches, thumbwheels and/or a computer terminal. After it is programmed, the ZX can be run with or without either a PLC or computer connection.
The ZX is programmed in a basic programming language made up of commands, and organized in sequences. The program is then stored on battery backed RAM in the CPU (like with a PLC). Commands can range from simple Acceleration and Velocity values, I/O designations, mathematical equations, to more complex logic controls and Boolean Algebra such as IF/Then, Gosub, And/Or, Else, Until, and others. Commands can also be entered through a computer or through inputs set up to execute commands in the program.
See the ZX/ZXF Indexer Drive User Guide for more information on programming (pages 26-91), as well as programs listed and explained below. The ZX/ZXF Indexer Drive Software Reference Guide is not useful for this purpose; most necessary commands are listed in the User Guide. The Software Reference Guide is useful after the programming language and usage is understood, like a dictionary.
Unlike steppers, brushless AC as well as brushless DC motors have the advantage of good resolution at slow speeds and a lower running temperature. Servo motors have a wide verity of uses including robotics, CNC machinery, indexing, and special conveyor and lift controls.
March 20, 2000
2nd year APKG