Stepper motors are brushless, synchronous electric motors that convert digital pulses into mechanical rotation. Due to rugged construction, high reliability, high torque at low speeds, and their lower price, they are seen in both commercial and industrial applications.
The Fundamental Notion
Every revolution of a stepper motor is divided into a discrete amount of measures. Typically an individual turning is 200 measures or 1.8 degrees of rotation per step. Each step is the same size, and since a stepper motor can only just take one step at a time, the position of the motorcan be controlled without feedback. Clearly, as the pulsation frequency increases the discrete measure movement will change with the rate directly proportional to the pulsation frequency – into continuous rotation.
Types of Step Motors
You can find three basic types: variable reluctance, permanent magnet, and hybrid. Hybrid motors combine the finest characteristics of the other two kinds. They are built with a permanent magnet rotor and toothed stator poles. Standard hybrids have 200 rotor teeth and rotate at 1.8 degrees per step. Winding connection stepper motor windings may be connected in parallel or series. Sequence connection provides greater torque at low speeds. Concurrent connection lowers the inductance providing increased torque at speeds that are quicker. The main advantage of steppers over DC Motors (Gleichstrommotoren) or DC Gearmotors (Getriebemotoren) is that they are able to react much faster without increasing the current.
Driver Output Restricting
The available motor torque vs. speed depends on the driver output voltage. The drive should be current limited to the step motor evaluation, since the driver output signal can be rated as much as twenty times higher than the motor voltage.Summary controller, or the indexer, provides step and direction outputs to the driver. Most applications demand that the indexer also handles steps per space and second, acceleration, deceleration.The indexer is not incapable of receiving high level commands from a host and generating the crucial step and direction pulses to the driver. Communicating to the indexer is usually via a RS232 or RS485 interface. Nevertheless, it can also monitor input signals from Go, Jog, Home and Limit switches that are external.
Indexer Stand-Alone Operation
Independent of the host cans also operate. It can be initiated from auxiliary I/O. or remote operator HMI’s once a program is loaded into the controller
Closed loop applications that demand booth detection and exact motor position capacity will generally be pre-packaged with power supply, a driver and optional encoder.
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