February 20, 2017

What are the Characteristics, Power Ranges and Applications of different types of AC & DC Motors?

Characteristics, Power Range and Applications of some AC & DC Motors:

Motor Types
Power Range
DC Motors
DC shunt motor
Constant flux constant speed motor creates moderate torque at start.

Up to 200 hp
Machine tools like lathes, milling machines, grinding machines, centrifugal and reciprocating pumps, blowers, and fans.
DC series motor
Creates dangerously high torques at low speeds and should be always connected to the load; speed can be varied.
Up to 200 hp
Preferred for traction-type loads; employed in electric locomotives, conveyors, cranes, elevators, trolleys.
Permanent magnet
DC motor
Higher efficiency, smaller size and simpler architecture; magnets can become demagnetized due to excessive use and overheating; produces lower torque.
Up to 10 hp
Power windows in automobiles, computer peripherals.
Separately excited
Can be controlled either by varying the voltage applied to the field winding or by varying the voltage applied to the armature; can produce high torques.
Up to 100 hp
Traction applications, to control the speed and torque of the motor by changing both armature voltage and stator current.
AC Motors
Three-phase induction motor (Squirrel cage rotor)
Moderate starting torque. Simple robust and maintenance free construction. Speed control by addition of rotor resistance is not possible.
1–5000 hp
Lathe machines, water pumps, grinders, printing machines, large refrigeration and air-conditioning units, small compressors.
Three-phase induction motor (Slip ring rotor)
Very high starting torque. Speed control by rotor resistance possible. High cost. Complicated construction which requires maintenance due to use of slip rings and brush.
1–5000 hp
Cranes, hoists, elevators, large compressors, industrial fans and blowers.
Three-phase synchronous motor
Constant speed irrespective of load, need of a starting device, need for two different excitation sources, variable frequency drives required for speed control.
Up to 50,000 hp
Motor generator sets, timing devices, centrifugal pumps, textile mills, cement mills, rolling mills.
Special Types of Motors
induction motor
Simple and rugged construction.
Up to 5 hp
Fans, water pumps, and refrigerators.
Stepper motor
Smooth rotation, linear relation between electrical input and step rotation.
Used for precise position control in printers, floppy disk drives, robotics, process control, machine tools.
Brushless DC motor
No maintenance required, long life, high reliability and efficiency, low inertia and friction, low starting torque and high costs, ability to run at speeds as high as 50,000 rpm.
Up to 300 hp
Video recorders, computer peripherals, biomedical instruments, commercial ovens, film processing equipment, printing technology, and material handling equipment.
Universal motor
High-power-to-weight ratio, can produce high starting torque, can operate at very high speeds, suits wide variety of applications demanding different torques, shorter lifespan.
Used exclusively
in fractional
Small appliances like mixers, blenders, drills, saws, vacuum cleaners, sewing machines.


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