What is the need for starter in a DC motor?

The resistance should gradually cut in steps as the motor gains speed and develop back emf. In other words, the starter offers resistance to armature current during starting of dc motor only. Under normal working condition of dc motor , the starter is electrically out of armature circuit of the motor.

Also, why starter is used to start a motor?

The starter protects the armature of dc motor from getting damaged. As the speed of armature/motor build up, armature induced emf also starts building thus reducing the role resistance offered by the starter, hence requiring it to gradually reduce as the motor picks up full speed.

What is the use of 4 Point starter?

Working Principle of Four Point Starter. The 4 point starter like in the case of a 3 point starter also acts as a protective device that helps in safeguarding the armature of the shunt or compound excited DC motor against the high starting current produced in the absence of back emf at starting.

How do you reverse the direction of rotation of a DC motor?

To reverse the motor, you need to change the polarity of the supply voltage to either the field winding or the armature winding, but not both. Generally it is better to reverse the field voltage because the field current is less than the armature current, so your reversing switchgear is more lightweight.

Why do we need a starter to start a DC motor?

In other words, the starter offers resistance to armature current during starting of dc motor only. As the speed of armature/motor build up, armature induced emf also starts building thus reducing the role resistance offered by the starter, hence requiring it to gradually reduce as the motor picks up full speed.

Why do we need a starter?

In dc motors the armature is generally designed to have the least resistance possible. So when starting a dc motor starter is connectedsuch that it limits the current value by being in series with armature and later seperates from the circuit. But by then back emf develops in the armature.

What is the use of 3 point starter?

A 3 point starter in simple words is a device that helps in the starting and running of a shunt wound DC motor or compound wound DC motor. The back emf, develops as the motor armature starts to rotate in presence of the magnetic field, by generating action and counters the supply voltage.

What is the back EMF?

Counter-electromotive force (abbreviated counter EMF or simply CEMF), also known as back electromotive force (or back EMF), is the electromotive force or “voltage” that opposes the change in current which induced it.

Why starter is required for starting an induction motor?

the starter offers resistance to armature current during starting of dc motor only. As the speed of armature/motor build up, armature induced emf also starts building thus reducing the role resistance offered by the starter, hence requiring it to gradually reduce as the motor picks up full speed.

What are the applications of dc series motor?

Its high starting torque makes it particularly suitable for a wide range of traction applications. Industrial uses are hoists, cranes, trolly cars, conveyors, elevators, air compressors, vacuum cleaners, sewing machines etc.

What is the function of the starter motor?

The function of the starter motor is to start up the combustion engine. When the starter switch is turned on, the starter relay turns on the electric motor. This motor drives the starter gear ring via the pinion gear.The rotating movement of the starter motor is created through the interaction of two magnetic fields.

How do you reverse the direction of rotation of a DC shunt motor?

The direction of rotation of a DC shunt motor can be reversed by changing the polarity of either the armature coil or the field coil. You can reverse the direction by simply reversing the armature leads. The same can be done with a shunt motor and a compound motor.

Why is the current drawn by a DC motor so high at starting?

The starting current is high as there is no back EMF or counter EMF present in the armature circuit because at starting 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 of motor.

Why starter is used in tube light?

Fluorescent tubes/lamps are filled with mercury vapor. They use electric charge to excite mercury atoms in order to produce ultra violet light. A glow starter or commonly known as starter is used in the tube light circuit to provide an initial current to filaments of the tube light.

How does a DC motor start?

Starting of DC Motors. At the moment a DC motor is started the armature is stationary and there is no counter EMF being generated. The only component to limit starting current is the armature resistance, which, in most DC motors is a very low value (approximately one ohm or less), as shown in Equation (6-9).

What is the necessity of starters?

Necessity of Starter – If an AC motor is stated an full voltage it will draw from two to six times its normal running current. Because the motor is constructed to withstand the shock of starting no harm will be caused by this excessive flow of current.

Can a dc series motor be operated on AC supply?

When A.C. supply is given to a D.C. motor: 1)In case of Series connection of armature winding and field winding , it may run. 2)But, In case of parallel connection , it won’t rotate at all and will start humming and will create vibrations, as a torque produced by positive and negative cycle will cancel out each other.

What is DC motor starter?

So, a DC motor is started by using a starter. There are various types of dc motor starters, such as 3 point starter, 4 point starter, no-load release coil starter, thyristor controller starter etc. The basic concept behind every DC motor starter is adding external resistance to the armature winding during starting.

What is the meaning of starter motor?

A starter (also self-starter, self, cranking motor, or starter motor) is a device used to rotate (crank) an internal-combustion engine so as to initiate the engine’s operation under its own power. Starters can be electric, pneumatic, or hydraulic.

What is a soft start?

A soft starter is a solid-state device that protects AC electric motors from damage caused by sudden influxes of power by limiting the large initial inrush of current associated with motor startup. They provide a gentle ramp up to full speed and are used only at startup (and stop, if equipped).

What is the effect of back EMF in DC motor?

When the armature of a d.c. motor rotates under the influence of the driving torque, the armature conductors move through the magnetic field and hence e.m.f. is induced in them as in a generator. The induced e.m.f. acts in opposite direction to the applied voltage V (Lenz’s law) and in known as back or counter e.m.f.

Why a dc series motor has a high starting torque?

For any dc motor,torque is directly proportional to the flux and armature current. Hence torque is directly proportional to the square of armature current. So as current during starting is 1.5 times the rated so starting torque is higher for series motor.

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