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Stray losses are the only one which can improve efficiency without affecting size of the induction motor. This can be reduced by reducing harmonies in the machine, which can be controlled by selecting slot combination, winding layout, size of air gap, saturation, concentricity of air gap etc.
How can efficiency of induction motor be improved?
A common way to improve efficiency is by using a variable speed drive system in an induction motor; adding an inverter to change the motor speed can achieve the purpose of energy saving.
What is the efficiency of induction motor?
Efficiency of three-phase induction motors can vary from 85% to 96%. See the chart below for torque vs. slip. Induction motors of 50-100 HP for industrial applications vary in weight from 700 to almost 1,000 lbs.
What is the condition for maximum efficiency for induction motor?
Efficiency of an induction motor is maximum when the copper loss is equal to the fixed loss which comprise mainly of core loss. Voltage reduction is to maintain a better balance between the load dependent losses (i.e. stator and rotor losses) and the load independent losses (core losses).
What factors affect motor efficiency?
Motor performance depends on three elements such as voltage across terminals, resistance across terminals, and magnetic force.
What is efficiency of the motor?
For an electric motor, efficiency is the ratio of mechanical power delivered by the motor (output) to the electrical power supplied to the motor (input). Thus, a motor that is 85 percent efficient converts 85 percent of the electrical energy input into mechanical energy.
How can we increase motor power?
There are, however, ways to increase the power factor, which are: Purchase motors with an inherently high power factor. Do not select over-sized motors (the power factor decreases with reduced motor load) Install power factor correction capacitors (Motor running capacitors*) in parallel with motor windings.
Which motor has maximum efficiency?
Most electric motors are designed to run at 50% to 100% of rated load. Maximum efficiency is usually near 75% of rated load. Thus, a 10-horsepower (hp) motor has an acceptable load range of 5 to 10 hp; peak efficiency is at 7.5 hp. A motor’s efficiency tends to decrease dramatically below about 50% load.
Which induction motor has lowest efficiency?
Mechanical losses occur at the bearing and brush friction loss occurs in wound rotor induction motor. These losses are zero at start and with increase in speed these losses increases. In three phase induction motor the speed usually remains constant. Hence these losses almost remains constant.
Why does Tesla use an AC induction motor?
So, why does Tesla use 3-phase AC induction motors instead of DC motors? Tesla uses AC induction motors because it has more torque even at high speed, simple design, cost-effective, do not need rare earth minerals rich permanent magnet, high reliability, and easier regenerative braking system design.
What is the efficiency of synchronous motor?
Leading power factor synchronous motors have efficiencies approximately 0.5 to 1.0% lower.
What happens if fifth harmonic is given to induction motor?
It will rotates in normal operation. Either short circuit or open circuit occurs. The sinusoidal components having frequency five times of fundamental are known as fifth harmonics. Hence induction motor will rotates in reverse direction because of reverse phase sequence of fifth harmonics.
What is slip in induction motor?
“Slip” in an AC induction motor is defined as: As the speed of the rotor drops below the stator speed, or synchronous speed, the rotation rate of the magnetic field in the rotor increases, inducing more current in the rotor’s windings and creating more torque. Slip is required to produce torque.
How does current affect efficiency?
All cell losses increase with increasing current, so voltage efficiency decreases with increasing current density.
What is the formula for efficiency?
Efficiency is often measured as the ratio of useful output to total input, which can be expressed with the mathematical formula r=P/C, where P is the amount of useful output (“product”) produced per the amount C (“cost”) of resources consumed.
Why does motor efficiency increase with load?
Losses due to friction are essentially constant with respect to load so at low loads, the majority of your input power may be used to overcome friction. As the load increases, friction plays a smaller and smaller role in the overall efficiency.
What is motor efficiency formula?
The SI unit is Watts (W), or J/s. Typical Motor Efficiency Values: Efficiency is simply output (useful) power divided by input power, with the difference being losses due to imperfections in design and other inevitabilities. load = Output power as a percentage of rated power, and Pi = input power in kW.
How is motor efficiency calculated?
To calculate a motor’s efficiency, you must measure its mechanical output power and divide it by the electrical input power. Measuring mechanical output power is fairly easy: You can use a torque meter to find the mechanical power based on the motor’s speed and load.
How is motor power calculated?
By taking the voltage and multiplying it by the associated current, the power can be determined. A watt (W) is a unit of power defined as one Joule per second. For a DC source the calculation is simply the voltage times the current: W = V x A.
How can we increase the power of DC motor?
Clearly, the power of a DC motor depends on the torque of the coil. Since torque depends on the current and the area of the coil. Also, the magnetic field can be increased by adding a soft iron core. Hence the correct option is D.
How do you increase the power of an AC motor?
There are three ways to improve the starting torque of Single phase induction Motor Internal Rotor Resistance. The across the line starting torque at low speed can be increased by increasing the rotor resistance. External Rotor Resistance. Variable Voltage/Frequency.
How do you make an electric motor faster?
One easy way to make the motor run faster is to add another magnet. Hold a magnet over the top of the motor while it is running. As you move the magnet closer to the spinning coil, one of two things will happen. Either the motor will stop, or it will run faster.
