Interpoles, Electrical Engineering

These are small poles fixed to the yoke and spaced in b/w the main poles. They are wound with comparatively few heavy gauge Cu wire turns and are connected in series with the armature so that they carry full armature current. Their polarity, in the case of a generator, is the same as that of the main pole ahead in the direction of rotation.


The function of interpoles is follows :


     (i) As their polarity is the same as that of the main pole ahead, they induce an e.m.f. in the coil (under commutation) which helps the reversalof current. The e.m.f. induced by the compoles is known as commutating or reversing e.m.f. The commutating e.m.f. neutralizes the reactance e.m.f. therby making commutating sparkles. With interpoles, sparkles commutation can be obtained up to 20 to 30% overload with fixed brush position. In fact, interpoles raise sparking limit of a machine to almost the same value as heating limit. Hence, for a given output, an interpole machine can be made smaller and, therefore, cheaper than a non - interpolar machine.


       As interpoles carry armature current their commutating e.m.f. is proportional to the armature current. This ensures automatic neutralization of reactance voltage which is also due to armature current. Connections for a shunt generator with interpoles.


(ii) Another function of the inerpoles is to neutralize the cross - magnetizing sffect of armature reaction. Hence, brushes are not to be shifted from the original position. As before, represent the m.m.f. due to main poles. OA represent the cross - magnetizing m.m.f. due to armature. BC which represent m.m.f. due to interpoles, is obviously in opposition to Oa, hence they cancelled out each other. This cancellation cross - magnetizing is automatic and for all loads because both are produced by the same armature current.


  The distinction b/w the interpoles and compensating windings should be clealy understood. Both are connected in series and their m.m.fs. are such as to neutralize armature reaction. But compoles additionally supply m.m.f. for counteracting the reaction voltage induced in the coil undergoing commutation. Moreover, the action of the compoles is localized, they have negligible effect on the armature reaction occurring on the reminder of the armature periphery.

Posted Date: 7/23/2012 1:51:45 AM | Location : United States

Related Discussions:- Interpoles, Assignment Help, Ask Question on Interpoles, Get Answer, Expert's Help, Interpoles Discussions

Write discussion on Interpoles
Your posts are moderated
Related Questions
The subject of electrical measurements is such a large one that entire books have been written on the topic. Only a few basic principles will be introduced here. Practical measurem

Q. Use necessary circuit and waveforms to explain the working of a Bootstrap sweep generator The bootstrap circuit illustrated in figure given below is a commonly used method f

Problem : a) What is an "Embedded System"? Discuss the characteristics of Embedded Systems. b) Describe three downfalls of "Embedded Systems". c) Explain the difference b

What is the difference between the unit step function u(n+4) and the time-scaled function u(2n+8)

Show how a typical DMA controller can be interfaced to an 8086/8085 based maximum mode system. For 8088 in maximum mode: The RQ/GT1 and RQ/GT0 pins are utilized to issue DMA

Classification of measures: measures or metrics can be classified under the following headings: 1 finance: income shareholder value added value rates of return costs. 2 outp

What is coupling? Explain the types of coupling

what is the use of capacitors in amplifiers

Q. Explain working of three-phase transformers? Transformation in three-phase systems can be accomplished in either of two ways: (1) connecting three identical single-phase tra

short note on armature reaction