Why are pole shoes used in DC machines?

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Why are pole shoes used in DC machines?

Pole shoe enlarges the area of armature core to come across the flux, which is necessary to produce larger induced emf. The functions of the pole shoe are: Support the field coils. Spread out flux for better uniformity.

What is the function of pole in DC motor?

Poles produce the magnetic flux when the field winding is excited. The magnetic poles of DC motor are fitted onto the inner wall of the yoke. The construction of pole is done using the lamination of particular shape to reduce the power loss due to eddy current.

What is a pole in a DC machine?

The magnetic poles of DC motor are structures fitted onto the inner wall of the yoke with screws. The construction of magnetic poles basically comprises of two parts. Namely, the pole core and the pole shoe stacked together under hydraulic pressure and then attached to the yoke.

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What is pole shoes?

Definition of pole shoe : an iron or steel plate sometimes attached to a field-magnet pole to support the field coil.

What is pole core and pole shoe?

Pole Core and Pole Shoe: The purpose of the pole core is to provide flux and to support the field windings, whereas the pole shoe is stretched so as to provide uniform air gap along the armature core and also to provide uniform flux distribution in the air gap.

What is a pole shoe?

What is the function of pole?

In complex analysis (a branch of mathematics), a pole is a certain type of singularity of a function, nearby which the function behaves relatively regularly, in contrast to essential singularities, such as 0 for the logarithm function, and branch points, such as 0 for the complex square root function.

What is the purpose of yoke in DC machine?

Yoke or the outer frame of DC generator serves two purposes, It holds the magnetic pole cores of the generator and acts as cover of the generator. It carries the magnetic field flux.In small generator, yoke are made of cast iron.

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Why is the pole shoe in a DC machine larger than its pole body?

9 Why is the pole shoe section of a dc machine made larger than its body? Ans: The pole shoe acts as a support to the field coils and spreads out the flux over the armature periphery more uniformly and due to larger x-section area reduces the reluctance of the magnetic path. Q.

What is pole shoe?

What is pole core?

Pole Cores and Pole Shoes : The core material where field winding is placed is known as pole core. Most machines use laminated steel material made up of pole cores. It holds the field winding and helps to establishes the magnetic poles. It provides a low reluctance path for magnetic flux generated by the field winding.

What is the purpose of pole and yoke?

What is the function of pole core and pole shoe in DC machine?

In DC machine, one is pole core and second is pole shoe. Pole core basically carries a field winding which is necessary to produce the flux. It directs the flux produced through air gap to armature core, to the next pole. Pole shoe enlarges the area of armature core to come across the flux, which is necessary to produce larger induced e.m.f.

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What is the function of the polarity shoe in DC machine?

Pole shoe in the DC machine is an extensive part as well as to enlarge the region of the pole. Because of this region, flux can be spread out within the air-gap as well as extra flux can be passed through the air space toward armature.

What is the function of pole shoe in windings?

(i) Pole shoes support the pole windings not to fall off their positions. (ii) it also facilitates the provision of an appropriate air gap over armature core so that appropriate flux density and flux wave shape can be obtained. The pole shoe extends outside the pole core giving large cross section, which serves two purpose:

What is a magnetic pole shoe?

Pole shoes are the part of magnetic poles nearest to the armature core: (i) Pole shoes support the pole windings not to fall off their positions.

Why are pole shoes used in dc machines?

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Why are pole shoes used in dc machines?

Pole shoe enlarges the area of armature core to come across the flux, which is necessary to produce larger induced emf. The functions of the pole shoe are: Support the field coils. Spread out flux for better uniformity.

What is the pole in DC machine?

The pole of the DC machine is an electromagnet and the field winding is winding among pole. Whenever field winding is energized then the pole gives magnetic flux. The materials used for this are cast steel, cast iron otherwise pole core.

What causes the reduction in flux or pole in a DC current machine?

Armature reaction weakens the main flux. In case of a dc generator, weakening of the main flux reduces the generated voltage. Armature reaction distorts the main flux, hence the position of M.N.A.

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What happens if motor back EMF is 0?

As the back emf vanishes zero, the whole supply voltage appears across armature and heavy current flows. If supplying unit didn’t trip down by this time, excess current in armature may heat up the armature and it may cause burning of armature winding.

Why armature MMF is triangular?

You must be talking about the DC motor. First of all i want ot correct you that the armature MMF is not excatly traingular but some sort of trapazoidal. This is bacause it is AC what is needed at the armature to rotate and due to saturation of the iron core it cannot reach its peak. Hence it looks like trapazoidal.

Why pole shoe is laminated?

Usually, the pole core and shoes are made of thin cast steel or wrought iron laminations which are riveted together under hydraulic pressure. The poles are laminated to reduce the Eddy Current loss.

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What is yoke in dc machine?

Yoke: The outer frame of a dc machine is called as yoke. It is made up of cast iron or steel. It not only provides mechanical strength to the whole assembly but also carries the magnetic flux produced by the field winding. The armature is built up of thin laminated circular steel disks for reducing eddy current losses.

In which DC motor flux per pole decreases with increase in armature current?

Flux per pole reduce in DC machines due to armature reaction effect. Armature Reaction: This is the effect of flux produced by armature winding on the main field flux. The armature winding carries considerable amount of current on load.

What is the difference between emf and back emf?

If an open coil is subjected to a variable magnetic field, at the ends of the coil a potential difference is induced which is called induced emf. If a coil is connected to an emf source and switched on, the rising current will produced an variable magnetic field which in turn produces an emf. It is called back emf.

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Is back emf AC or DC?

Back EMF can have either a sinusoidal (AC) or a trapezoidal (DC) waveform. The shape of the back EMF is important, as it determines the type of drive current and commutation method that should be used for the motor. Circuit diagram and example taken from New South Wales, Department of Education and Training, 2007.