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What is the difference between a DC motor and a generator in terms of EMF?
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.
What does LRA mean in electrical terms?
Locked rotor amperage is the amperage the motor draws when the voltage is first applied to the motor and the rotor has not started to turn. This amperage is usually up to 300% of the motors running amperage. Once the rotor starts to turn the motor generates a back EMF (electro motive force) that opposes the high inrush current. This back EMF drives the amperage down until the motor gets up to its rated speed at which time the motor amperage will be at its run amperage.
Why motor burn at single phasing?
A 3-phase motor will not run on single-phase power or if one of the three phases is disconnected. If the motor is not running, there is no back-EMF generated in the coils, and they draw excessive current, thus overheating.
Why Back EMF occur in only dc motor?
It doesn't. It exists in all electrical machines, d.c. or a.c., motor, generator, or transformer.
Why can we start a shunt motor under no load but why can't a series motor?
The torque on a series motor is determined by the square of the armature current and, so, is very large -much larger than that of a shunt motor. Consequently, on starting, with no back-emf being generated, the torque on a series motor can be dangerously high if the machine has no mechanical load.
What is Back emf of DC motor?
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
What is the difference between a DC motor and a generator in terms of EMF?
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.
What is emf induced in a motor's coil that tends to reduce the current in the coil of the motor?
BACK emf induced in a motor's coil that tends to reduce the current in the coil of the motor. The answer should be 'back'.
What does LRA mean in electrical terms?
Locked rotor amperage is the amperage the motor draws when the voltage is first applied to the motor and the rotor has not started to turn. This amperage is usually up to 300% of the motors running amperage. Once the rotor starts to turn the motor generates a back EMF (electro motive force) that opposes the high inrush current. This back EMF drives the amperage down until the motor gets up to its rated speed at which time the motor amperage will be at its run amperage.
What causes the current to decrease as an induction motor accelerates?
The current in an induction motor decreases as it accelerates due to reduced rotor impedance and increased back EMF. As the motor speeds up, the rotor reacts with the rotating magnetic field produced by the stator, causing a decrease in the current needed to maintain acceleration. This decrease in current helps to improve the motor's efficiency and reduce energy consumption.
What is the emf equation of induction motor and prove it?
f=4.44fqm
Why motor burn at single phasing?
A 3-phase motor will not run on single-phase power or if one of the three phases is disconnected. If the motor is not running, there is no back-EMF generated in the coils, and they draw excessive current, thus overheating.
What is the significance of emf?
According to motor eq. Eb=v-Ia.Ra.And the speed of motor is directly proportional to back EMF.At starting of motor speed is 0,so that Eb is also 0.As the speed increases ,Eb also increases,so that armature current decreases.As the Eb decreases ,so that Ia increases.In this way the back EMF makes the motor self regulating to take armature current as per requriment of motor.Because of this reason EMF also called governor principle of DC motor.This is most important significance of Back EMF. The back EMF is Explaned with lenses Law
Why will a motor meant to operate on 60Hz burn when operated on 50Hz power supply?
it will burn because there is not as much EMF generated ...there fore the current will be higher through the windings generating more heat. EMF is like a "kickback" voltage from the motor and this repels current from the source ....the higher the frequency the more kickback voltage and less current.....this also happens when the motor is loaded and wants to slowdown there is less emf generated and therefore more current flows through the windings.
Why would a dc motor show high amps no voltage and struggle to turn?
The current flowing in a dc motor is determined by (Applied voltage-Motor EMF) divided by armature resistance. The motor emf is a function of the field excitation of the motor and the speed at which the motor turns. When the motor starts, there can be no EMF because motor speed is 0 rpm. Therefore the motor will draw more current. But as the motor begins to speed up, if it has field excitation, it has to build up EMF and the current will drop. So : If the motor shows high amps and no voltage and struggles to turn the possible reasons are: 1. The motor has no excitation - The permanent magnets are weak or the field winding is faulty or the field is not being supplied. 2. The armature winding is faulty - it has shorted windings. This assumes your supply is healthy of course.
The back emf indcuced in the armature is AC or DC?
only in dc motor...
Why is a starting current in a DC motor very high?
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.
