Figure —Armature reaction. Now you have two fields — the main field, view A, and the field around the armature coil, view B. View C of figure shows . These interpoles, being midway between main poles, are just opposite the The interpole windings are connected in series with the armature. Stator of a DC machine. ▫ Stator is the stationary part. ▫ Main poles as field winding. ▫ Further windings. ▫ Interpole. ▫ Compensation eliminate unwanted effects.

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Navy Electricity and Electronics Training Series (NEETS), Module 5, through – RF Cafe

Kimberly To avoid the commutation difficulty actually encountered in old-style generators, narrow poles called interpoles interrpole commutating poles are used, as indicated in Fig. Therefore, the interpole still has the proper polarity to provide automatic commutation.

The following information provides a summary of the main subjects for review. If both are reversed, rotation will continue intetpole the original direction. It maintains a constant speed under varying loads. What current flows in the interpole windings?

Unloaded operation of large machines is dangerous. It must have a load connected to avoid damage from excess speed. Its speed varies widely between full-load and no-load.

When the armature current is reversed, the current through the interpole is also reversed. It may then be removed after counter EMF has been built up. Widings are no differences. The armature poles are attracted to field poles of opposite polarity, causing the armature to rotate.



In fact, most DC generators can be made to act as DC motors, and vice versa. As the armature begins to interople, counter EMF increases; and, since the counter EMF opposes the applied voltage, the armature current is reduced. The inductance of the coil tends to retard the reversal of the coil current by generating a prolonging voltage and the interpoles must have sufficient additional strength to neutralize this inductive voltage.

The DC motor is reversed by reversing the direction of the current in the armature. When its speed is reduced by a load, the series motor develops greater torque. Increasing shunt-field circuit resistance increases motor speed.


The interpole windings are connected in series with the armature windings, and therefore their correction ampere-turns increase or decrease in the same proportion as do the distorting ampere-turns of the armature. They remain in that position for all conditions of load. It is very difficult for a designer to calculate the exact number of turns to be placed on the interpoles, and it is sometimes necessary to connect an adjustable diverter around the interpole windings to permit shunting of a part of the total armature current around those coils.

Like windngs of the armature and field then repel each other, causing armature rotation to continue. Direction of armature current, and direction of magnetic flux in field. The field strength is independent of the armature current.

Its starting torque is greater than other types of DC motors. To avoid the commutation difficulty actually encountered in old-style generators, narrow poles called interpoles or commutating poles are used, as indicated in Fig. Gramme-ring wound armatures are seldom used for this reason. Increasing the armature circuit resistance decreases motor speed. Such a diverter is called an inductive shunt. Motor will slow down.


Only outside of coils cut flux inefficient.

In a generator the interpoles must be of the same polarity as the main poles which they precede in the direction of rotation.

High torque turning force at low speed. If their polarities be made the same as those of the armature poles opposite to them, and if their strength be made equal to that of the armature poles, then the distortion of the main field at the commutating point, as in Fig. By winding the armature in a way wijdings places the entire coil where it is exposed to maximum flux.

Such an improper division would cause the interpole field to fail to rise in proportion to the armature current to be commutated, and would probably cause the commutator to flash over at the brushes. To limit armature current until counter EMF builds up.

Interpoles and compensating windings are intwrpole to reduce the effect of armature reaction on motor operation. Its primary purpose was to provide me with ready access to commonly needed formulas and reference material while performing my work as an RF system and circuit design engineer.

What is the purpose of starting resistors?