What are the Advantages and Disadvantages of Stepper motors?

Advantages and Disadvantages of Stepper motors-

Advantages:

• Low cost for control achieved
• High torque at startup and low speeds
• Ruggedness
• Simplicity of construction
• Can operate in an open loop control system
• Low maintenance
• Less likely to stall or slip
• Will work in any environment
• Can be used in robotics in a wide scale.

Disadvantages:

• Require a dedicated control circuit
• Use more current than D.C. motors
• Torque reduces at higher speeds
• Resonances can occur if not properly controlled
• Not easy to operate at extremely high speeds.

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What is stepper motor? What types of stepper motor are there? Where stepper motors are used?

Stepper Motor: 

A stepper motor (or step motor) is a brushless DC electric motor that divides a full rotation into a number of equal steps. The motor's position can then be commanded to move and hold at one of these steps without any feedback sensor (an open-loop controller), as long as the motor is carefully sized to the application.

Stepper motor with cable

Types of Stepper Motor: 

There are four main types of stepper motors:

1. Permanent magnet stepper (can be subdivided into 'tin-can' and 'hybrid', tin-can being a cheaper product, and hybrid with higher quality bearings, smaller step angle, higher power density)
2. Hybrid synchronous stepper
3. Variable reluctance stepper
4. Lavet type stepping motor

Figure: Animation of a simplified stepper motor (unipolar).

Uses of Stepper Motor: 

• Stepper motors are used for operation control in computer peripherals, textile industry, IC fabrications and robotics etc. 
• Computer-controlled stepper motors are one of the most versatile forms of positioning systems. They are typically digitally controlled as part of an open loop system, and are simpler and more rugged than closed loop servo systems.
• Applications requiring incremental motion are typewriters, line printers, tape drives, floppy disk drives, numerically-controlled machine tools, process control systems and X-Y  plotters. Usually, position information can be obtained simply by keeping count of the pulses sent to the motor, thereby eliminating the need for expensive position sensors and feedback controls. 
• It includes commercial, military and medical applications where these motors perform such functions as mixing, cutting, striking, metering, blending and purging. 
• They also take part in the manufacture of packed food stuffs, commercial endproducts and even the production of science fiction movies. 
• Industrial applications are in high speed pick and place equipment and multi-axis machine CNC machines often directly driving lead screws or ball screws. 
• In the field of lasers and optics they are frequently used in precision positioning equipment such as linear actuators, linear stages, rotation stages, goniometers, and mirror mounts. 
• Other uses are in packaging machinery, and positioning of valve pilot stages for fluid control systems. 

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What is 2 phase motor?

A two phase motor is a motor with the starting winding and the running winding have a phase split. e.g; ac servo motor. Where the auxiliary winding and the control winding have a phase split of 90 degree.

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What is the difference between a four point starter and three point starter?

The shunt connection in four point starter is provided separately form the line where as in three point starter it is connected with line which is the drawback in three point starter.

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What are the Benefits of improved PF of a motor?

Benefits of improved PF:
• Reduced kVA
• Reduced losses
• Improved voltage regulation
• Increased efficiency of plant electrical system. 

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