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Three-phase squirrel-cage induction motors are widely used as industrial drives because they are self-starting, reliable and economical. Although traditionally used in fixed-speed service, induction motors are increasingly being used with variable-frequency drives (VFD) in variable-speed service.
Why do we use induction motor instead of DC?
AC motors are generally considered to be more powerful than DC motors because they can generate higher torque by using a more powerful current. However, DC motors are typically more efficient and make better use of their input energy.
Why are induction motors the most common?
Induction machines are the most frequently-used type of motor used in residential, commercial, and industrial settings so far. This is because an induction motor always runs at a slower speed than synchronous speed. The speed of the rotating magnetic field in the stator is called synchronous speed.
Why induction motor are extensively used these days?
Some of the key points that why induction motor is widely used in industry? The induction motor is a singly excited motor whereas the synchronous motor is a doubly excited one. The induction motor is cheaper than a synchronous motor. Induction motor robust in construction and it can also work in any dusty environment.
What are the disadvantages of induction motor?
Disadvantages of induction motor: The power factor of the motor is very low during light load conditions. During light load conditions, it operates at a very low power factor. It has low efficiency. Single-phase induction motor is not self-starting.
What are the disadvantages of DC motor?
Disadvantages of DC motors High initial cost. Increased operation and maintenance cost due to the presence of commutator and brush gear. Cannot operate in explosive and hazard conditions due to sparking occur at brush (risk in commutation failure).
What three things are needed for an induction motor to work?
A 3-phase induction motor includes two essential components namely the stator & the rotor. In this motor, the stationary part is the stator whereas the rotating part is the rotor. In this motor, the load is connected to the shaft. Three-phase armature winding can be wound over the stator.
Are induction motors more powerful?
Although the power factor with a drive may not be as high as a motor-only induction machine, PMAC motors generally provide higher power density due to higher magnetic flux. Therefore, more torque can be produced in a given physical size, or equal torque produced in a smaller package.
What can I do with an induction motor?
Single-phase induction motors are used extensively for smaller loads, such as household appliances like fans. Although traditionally used in fixed-speed service, induction motors are increasingly being used with variable-frequency drives (VFD) in variable-speed service.
What is advantage and disadvantage of induction motor?
Induction motors always operate under lagging power factor and during light load conditions they operate at very worst power factor (0.2 to 0.4 lagging). Some of the disadvantages of poor power are increase in I2R losses in the system, reduction in the efficiency of the system.
What is the main disadvantage of 1ph induction motors?
1. The main disadvantage of an induction motor is, it draws a very high inrush current during its starting, for this reason, it makes a dip in voltage during starting which can affect other electrical loads connected to the same power source.
Are induction motors good?
Unlike synchronous motors, a 3 phase induction motor has a high starting torque, good speed regulation and reasonable overload capacity. An induction motor is a highly efficient machine with full load efficiency varying from 85 to 97 percent.
Which induction motor has maximum speed?
Synchronous and full load speed of amplitude current (AC) induction motors Speed (rpm) Number of Poles Frequency (Hz, cycles/sec) Synchronous Full Load 2 3600 2900 4 1800 1450.
What is the main disadvantage of synchronous motors?
Disadvantages or Demerits: Synchronous motors requires dc excitation which must be supplied from external sources. Synchronous motors are inherently not self starting motors and needs some arrangement for its starting and synchronizing. The cost per kW output is generally higher than that of induction motors.
What is the difference between normal motor and induction motor?
The stator winding of Induction Motor is energized from an AC source. Synchronous Motor always runs at synchronous speed, and the speed of the motor is independent of load, but an induction motor always runs less than the synchronous speed. If the load increased the speed of the induction motor decreases.
What are the advantages of DC motor?
Below are some of the most prominent advantages of DC motors: They are suitable for low-speed torque. They have adjustable speed. They offer a wide range of speed control both below and above the rated speed.
When would you use a DC motor?
DC motors are suitable for many applications – including conveyors, turntables and others for which adjustable speed and constant or low-speed torque are required. They also work well in dynamic braking and reversing applications, which are common in many industrial machines.
Why are DC motors so expensive?
The heavier rotor of the DC motor may require more expensive bearings. The rotor design is probably the most important factor in making the DC motor more expensive. If the DC motor stator has permanent magnets, that could make it more expensive or not depending on the magnet material.
How does an induction motor start?
When the supply is connected to the stator of a three-phase induction motor, a rotating magnetic field is produced, and the rotor begins rotating and the induction motor starts. At the time of starting, the motor slip is unity, and the starting current is very large.
What is the principle of induction motor?
Working Principle of Induction Motor The motor which works on the principle of electromagnetic induction is known as the induction motor. The electromagnetic induction is the phenomenon in which the electromotive force induces across the electrical conductor when it is placed in a rotating magnetic field.
Is 3 phase induction motor is self starting?
Three-phase induction motor is self-starting, because winding displacement is 120 degrees for each phase and supply also has 120 phase shift for 3-phase. It results in a unidirectional rotating magnetic field is developed in air gap which causes 3-phase induction motor to self-start.
