What is no load EMF?
The no-load induced emf (open circuit voltage) or internal generated voltage is kept constant. The torque/power or coupling angle is the angle between the no load induced emf and the terminal voltage. This angle also corresponds to the angle between the field flux (rotor) and the armature generated rotating flux.
What is the power factor of a synchronous motor at no load?
unity power factor
If the field current is increased, the pf will become. leading and the current will increase.
Is there back EMF in synchronous motor?
In a synchronous machine, the back EMF (Eb) is set up in the armature by the rotor flux which opposes the applied voltage V. When back emf is equal to the applied voltage the synchronous motor is at unity power factor and the excitation is said to be 100\%.
What can be said about the generated EMF if there is no load?
At no load with no mechanical or other losses the magnetic field produced by stationary windings is equal and exactly opposite to the rotating magnetic field generated by rotor field winding.
Can a series motor be operated on no load?
Originally Answered: Why can’t DC series motor operate on no load condition? The flux produced by a DC series motor is proportional to the load current I. So at light loads flux is less and the speed will be tending to infinity i.e. very high. Hence a DC series motor should never be run on no load.
How speed of the DC shunt motor can be increased?
How speed of the DC shunt motor can be increased? Decreasing armature current will help in increasing speed for DC shunt motor. Since load current is addition of armature current and field current we’ll get less armature current for more field current.
When motor runs on no load then?
When the motor is connected across the supply mains without load, it draws small current from the supply mains. This current will flow through the series field and armature, the speed tends to increase so that back emf may approach the applied voltage in magnitude.
What is the power factor of synchronous motor?
The usual synchronous motor power factors are unity (1.0) or 0.8 leading. Values of 0.7 or 0.6 leading will give more leading correction to an otherwise lagging system.
When load on a synchronous motor is increased?
There is a limit to the mechanical load that can be applied to asynchronous motor. As the load is increased, the torque angle δ also increases until the condition arises when the rotor is pulled out of synchronism and the motor is stopped.
What is load angle in synchronous motor?
Load Angle in synchronous machine is defined as the angle between the filed mmf or flux and the resultant air gap mmf or flux. Load angle is also defined as the angle between the no load excitation voltage Ef and terminal voltage Vt.
What will happen if the back emf in the motor absent?
If back emf of a dc motor vanishes suddenly, motor circuit will try to retain back emf by drawing more current from supply. As the back emf vanishes zero, the whole supply voltage appears across armature and heavy current flows.
When a DC motor has no load what will happen to the back emf?
At no load condition,( i.e when there is no mechanical load connected to armature end) small torque is required to overcome the friction and windage losses. Since torque is directly proportional to armature current Ia ,therefore the armature current Ia is small so the back emf is nearly equal to the applied voltage.