equation of ac machine
The factors determining induced electromotive force (emf) in a DC machine include the strength of the magnetic field, the number of turns in the coil, the speed of rotation of the armature, and the angle of the coil relative to the magnetic field lines. The induced emf is directly proportional to the magnetic field strength, the number of turns in the coil, and the speed of rotation, while it is also affected by the angle of the coil in relation to the magnetic field. These factors collectively determine the magnitude of the induced emf in a DC machine.
In dc motor, the armature conductors are revolving in the magnetic field and emf is induced in the armature conductors. The direction of the induced emf is in opposite direction to the applied voltage as per Flemings left hand rule. So, the induced emf in motor is called as back emf or counter emf. Vydehi
A rotating d.c. motor generates a back-emf which opposes the supply voltage and reduces the current drawn by the motor. When the motor is stationary, it cannot generate this back emf and, so, the only opposition to current is the resistance of its windings which is relatively low. So, on startup, the current is large; as the machine starts to run, the resulting back emf, acts to reduce the current.
What motor is NOT suitable for use as a DC machine?
All types of generators induce EMF in sinusoidal wave form. (A.C.) In a D.C. generator the function of a commutator is to convert A.C. EMF into D.C. The commutator rectifies the output that is the alternating current so as to produce unidirectional alternating current (pulsating DC). This reverses the negative polarity current to a positive one so as the output is a pulsating DC.
The equation for the average over time T is integral 0 to T of I.dt
when the pole flux is zero there is no induced emf in the armature conductor of dc machine as a result of this there is no back emf for controlling action so speed become dangerously high or we can say it will be infinite.
During the operation of a DC motor, EMF is created across its terminals using an external source. Whereas, in a DC generator EMF is created across its terminal based on principle of dynamically induced EMF. So talking in terms of EMF, in DC motor EMF is consumed by the motor coil and utilized to rotate the axle. On the other hand, in DC generator EMF developed across coil is transfered to a load or a battery and consumed by them.
The factors determining induced electromotive force (emf) in a DC machine include the strength of the magnetic field, the number of turns in the coil, the speed of rotation of the armature, and the angle of the coil relative to the magnetic field lines. The induced emf is directly proportional to the magnetic field strength, the number of turns in the coil, and the speed of rotation, while it is also affected by the angle of the coil in relation to the magnetic field. These factors collectively determine the magnitude of the induced emf in a DC machine.
only in dc motor...
Electro Magnetic Field
In dc motor, the armature conductors are revolving in the magnetic field and emf is induced in the armature conductors. The direction of the induced emf is in opposite direction to the applied voltage as per Flemings left hand rule. So, the induced emf in motor is called as back emf or counter emf. Vydehi
The fluctuation of the AC which sets up an magnetic field and causes a reverse emf is lost with DC because there is no variation in the field.
increased Back emf
bad connection
It depends entirely on the design of the motor.
They are Same for dc motor