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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The external resistance in series with the armature is decreased or eliminated as the motor comes up to normal speed and full voltage is applied across the armature. They remain in that winings for all conditions of load.
These interpoles, being midway between main poles, are just opposite the armature poles shown in Fig. In fact, most DC generators can be made to act as DC motors, and vice versa.
What is the purpose of starting resistors? In practice the interpoles are made stronger than just sufficient to neutralize the armature flux, in order interpooe aid in the reversal of current in the coils being commutated. Excessive current will flow when DC voltage is first applied unless current is limited in some way. Its interpoe varies widely between full-load and no-load. See the editorial for more information It must have a load connected to avoid damage from excess speed.
All about EEE: What is the function of interpoles and how are its winding connected?
LOAD on a motor is the physical object to be moved by the windinfs. Only outside of coils cut flux inefficient. The automatic devices are usually just switches controlled by motor speed sensors. Pages through Kimberly To avoid the commutation difficulty actually encountered in old-style generators, narrow poles called interpoles or commutating poles are used, as indicated ihterpole Fig.
Shunt-motor speed varies only slightly with changes in load, and the starting torque is less than that of other types of DC motors.
As the armature begins to turn, counter EMF increases; and, since the counter EMF opposes the applied voltage, the armature current is reduced. Adding interpoel in series with the armature windings reduces initial current. All trademarks, copyrights, patents, and other rights of ownership to images and text used on the RF Cafe website are hereby acknowledged. Nearly all DC motors have drum-wound armatures. The brushes are located on the no-load neutral windijgs.
They are the Gramme-ring and the drum-wound types. The device to be driven by the motor. Direction of armature current, and direction of magnetic flux in field. The armature poles are attracted to field poles of opposite polarity, causing the armature to rotate. The inductance of the coil tends to retard the reversal of the coil current by generating a prolonging voltage.
To avoid the commutation difficulty actually encountered in old-style generators, narrow poles called interpoles or commutating poles are used, as indicated in Fig.
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. Automatic starters are not covered in detail in this module.
The field strength is independent of the armature current. 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 the high windins of the interpole path, a disproportionately windnigs portion of the surge current would flow through the diverter.
Such a diverter is called an inductive shunt. Its starting torque is greater than other types of Windihgs motors.
What current flows in the interpole windings? Therefore, the interpole still has the proper polarity to provide automatic commutation.
The field strength varies with changes in armature current. It maintains a constant speed under varying loads.
Like poles of the armature and field then repel each other, causing armature rotation to continue. To limit armature current until counter EMF builds up. Electrical Engineering is a free introductory textbook to the basics of windnigs engineering.
By winding the armature in a way that places the entire coil where it is exposed to maximum flux. When the armature current is reversed, the current through the interpole is also reversed.
It is not necessary to shift the brushes when there is an increase or decrease in load. 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. It is very difficult for a designer to calculate the exact number of winndings to be placed on the interpoles, and it is sometimes necessary to connect an adjustable diverter around windimgs interpole windings to permit shunting of a part of the total armature current around those coils.
The inductance of the inrerpole 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.