For many years, no-load losses of three-phase induction motor have been regarded as stator copper loss, iron loss, the friction and windage losses, and the stray loss. Due to the no-load slip rate is very small, the rotor current is often assumed to be zero, ignoring the rotor aluminum loss.
What is no load test of induction motor?
The no-load test of an induction motor is similar to the open-circuit test of a transformer. The motor is not connected from its load, and the rated voltage at the rated frequency is applied to the stator to run the motor without a load. The 2-wattmeter method measures the input power of the system.
What happened when induction motor run on no load?
As the motor is running at no load, the total input power is equal to the constant iron loss, friction, and windage losses of the motor. Since the power factor of the induction motor under no-load condition is generally less than 0.5, thus the Wattmeter reading of one of the Wattmeter will show a negative reading.
What is the purpose of no load test?
The open-circuit test, or no-load test, is one of the methods used in electrical engineering to determine the no-load impedance in the excitation branch of a transformer. The no load is represented by the open circuit, which is represented on the right side of the figure as the “hole” or incomplete part of the circuit.
How do you calculate no load loss of a motor?
When motor runs for some times and bearings get lubricated fully, at that time readings of applied voltage, input current and input power are taken. To calculate the rotational loss, subtract the stator I2R losses from the input power.
What are the different losses that are present in an induction machine?
The following are the losses in an induction motor:
- Core loss in the stator and the rotor.
- Stator and rotor copper losses.
- Friction and windage loss.
Which loss in the motor is significant in no load test Why?
Since the motor is not supplying any load, the no-load current is small and stator copper losses are negligible. The input power, W o equals mechanical and core losses. To be more accurate the stator copper loss at no-load current should be deducted from the input when calculating the above losses.
What is no load current?
The no-load current is the current required just to turn the motor shaft with nothing connected. It is the current required to overcome the bearing and brush friction plus the aerodynamic drag caused by the rotor moving in the air and moving air through the motor for cooling purposes.
What is no load torque?
The torque-speed curve begins at the crossing of the Y axis, where torque is maximum and speed is zero. This is the stall torque—the maximum torque when the motor is running at nominal voltage. … This point is known as the no-load speed—the speed when running at nominal voltage and zero load.
What is the purpose of no load and blocked rotor test?
1. To obtain the variation of no load power and current and blocked rotor power and current with changes in the applied voltage to the stator. 2. To determine the equivalent circuit parameters of an induction motor.
What is no load test of 3 phase induction motor?
The no load test of 3 phase induction motor is performed on induction motor when it is running without load. This test tells us the magnitude of constant losses occurring in the motor.
What is the range of slip of induction motor for no load?
Q1 A 3-phase, 6-pole, 50 Hz induction motor has a slip of 1% at no-load and 3% at full-load.
What is slip formula?
Slip speed is the speed difference between the Synchronous speed and Rotor speed. Slip speed = Synchronous speed – Rotor speed = Ns -N. Slip, s = (Ns – N) / Ns.
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.
What is load test of induction motor?
The load test on induction motor is performed to compute its complete performance i.e. torque, slip, efficiency, power factor etc.
What is the efficiency of induction motor?
Ideally, there’s some slippage of the rotor relative to the frequency; typically, this is about 5%. As such, these motors are considered asynchronous motors. Efficiency of three-phase induction motors can vary from 85% to 96%.