With increased load, the load resistance is less and the current increases. In a three-phase induction motor, the rotating magnetic field of the stator passing through the rotor conductors induces a current in the rotor conductors.
What happens when motor load increases?
As the load rises the torque applied to the motor slows it down and ‘slip’ increases. The stator magnetic field cuts the rotor conductors more often. More force is generated on the rotor and the rotor torque increases.
Why no load current of induction motor is high?
In an induction motor, there is an air gap between the stator and the rotor. The air gap length increases the reluctance of the magnetic circuit. To produce the rated flux in the motor, the motor with larger air gap length draws more magnetizing current. … The motor takes about 1/3 rd of its FLC at no load operation.
Why does the power factor of an induction motor increases with the load?
The input power factor of the induction increases when the mechanical load increases because in general, the higher the resistance (a load), the higher the power factor. A higher power factor means that there is a tapping of electrical energy in terms of active power.
When the load of a three phase induction motor increases its slip?
Slip increases with increasing load – providing a greater torque. It is common to express the slip as the ratio between the shaft rotation speed and the synchronous magnetic field speed. When the rotor is not turning the slip is 100 %.
Why does a motor draw more current under load?
When the mechanical load requires more torque, this slows the motor shaft, since the motor RPM deviates farther from synchronous RPM, less back EMF is generated which causes more current to be drawn from the source, this extra current in turn generates additional torque on the motor shaft.
What is load on a motor?
Part-load is a term used to describe the actual load served by the motor as compared to the rated full-load capability of the motor. Motor part-loads may be estimated through using input power, amperage, or speed measurements.
Why is DC motor current so high?
The starting current is high as there is no back EMF or counter EMF present in the armature circuit because atstarting counter EMF is zero. … It’s armature has very less resistance due to this it need more current at starting time. Hence DC starters are used to limit the starting current ofmotor.
What is the no load current of induction motor?
The I2R losses on the primary side is neglected as they vary with the square of the current as we know that the no load current is 20-30% of the full load current, 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.
What is full load current of motor?
A full load current is the largest current that a motor or other device is designed to carry under particular conditions. … A full load current is the largest current that a motor or other device is designed to carry under particular conditions.
What is the power factor of induction motor?
The power factor of induction motors varies with load, typically from around 0.85 or 0.90 at full load to as low as about 0.20 at no-load. At no load, an induction motor draws a large magnetizing current and a small active component to meet the no-load losses.
Does motor power factor change with load?
Conclusions. The power factor of induction motors is one of the significant elements that must be maintained toward unity. The power factor is variable while the motor load changes from no-load to full/over-load.
How power factor is improved?
The simplest way to improve power factor is to add PF correction capacitors to the electrical system. PF correction capacitors act as reactive current generators. They help offset the non-working power used by inductive loads, thereby improving the power factor.
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 normal slip of an induction motor?
Because of this speed difference, the motor rotates at a speed slightly slower than the synchronous speed. Slip is normally expressed in percentage. Slip of a power induction motor is 2 to 3% when the motor is operated under the rated load.
What is synchronous speed?
Synchronous speed is a significant parameter for the rotating magnetic field-type AC motor. It is determined by the frequency and the number of magnetic poles. Synchronous speed No = [rps, revolutions per second] f = Frequency [Hz]