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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What is the purpose of starting resistors? They are the Gramme-ring and the drum-wound types. The device to be driven by the motor.

LOAD on a motor is the physical intetpole to be moved by the motor. The following information provides a summary of the main subjects for review. When its speed is reduced by a load, the series motor develops greater torque. When the armature current is reversed, windngs current through the interpole is also reversed.

It maintains a constant speed under varying loads. There are no differences. Nearly all DC motors have drum-wound armatures.

By winding the armature in a way that places the entire coil where it is exposed to maximum flux. It must have a load connected to avoid damage from excess speed.

Like poles of the armature and field then repel each other, causing armature rotation to continue. The proper division of surge current can be obtained by inserting, in series with the interpole shunt, a conductor wound around an iron core to form an inductance just equal to that of the interpole coils.


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.

The inductance of the coil tends to retard the reversal of the coil current by generating a prolonging voltage. If the ordinary resistance diverter were used, a sudden surge of current caused by a sharp increase in load would not divide between the interpole path and the diverter path in inverse proportion to their respective resistances; but, because of windinhs high reactance of the interpole path, a disproportionately large portion of the surge current would flow through the diverter.

Direction of armature current, and direction of magnetic flux in field. 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 windijgs distorting ampere-turns of the armature.

All trademarks, copyrights, patents, and other rights of ownership to images and text used on the RF Cafe intetpole are hereby acknowledged. Increasing the armature circuit resistance decreases motor speed.

These interpoles, being midway between main poles, are just opposite the armature poles shown in Fig. To limit armature current until counter EMF builds up. The DC motor is reversed by reversing the direction of the current in the armature. Therefore, the interpole still has the proper polarity to provide automatic commutation. 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.


Direction of conductor movement rotationdirection of flux, and the direction of current flow.


Unloaded operation of large machines is dangerous. The brushes are located on the no-load neutral plane. The speed and torque characteristics are a combination of the desirable characteristics of both series and shunt motors. In interole generator the interpoles must be of the same polarity as the main poles which they precede in the direction of rotation. Its speed varies widely between full-load and no-load.


The automatic devices are usually just interople controlled by motor speed sensors. Electrical Engineering is a free introductory textbook to the basics of electrical engineering. Kimberly To avoid the commutation difficulty actually encountered in old-style generators, narrow poles called interpoles or commutating poles are used, as indicated in Fig.

Automatic starters are not covered in detail in this module.

This causes the neutral plane to be shifted in the direction opposite to that of armature rotation.