Interpoles, Electrical Engineering

Assignment Help:

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.

Interpoles

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.


Related Discussions:- Interpoles

Frequency stability of quartz crystals, Q. Frequency stability of quartz cr...

Q. Frequency stability of quartz crystals ? The amount of frequency deviation from the ambient temperature frequency over the operating temperature range. This deviation is ass

What is ringer circuit in telephone hand set, Q. What is Ringer Circuit in ...

Q. What is Ringer Circuit in telephone hand set? Purpose of the ringer is to alert destination party of incoming calls. Audible tone from the ringer should be load enough to be

Calculating the damping ratio of the system, Consider the following mechani...

Consider the following mechanical system: a) Write a differential equation that describes the motion for this system. b) Take the Laplace transform of this equation and

Define time constant, Time constant Time constant, defines as time for ...

Time constant Time constant, defines as time for current achieve maximum (IM) if this maintain the early promotion rate current.

What do you mean by companding, Q. What do you mean by Companding? In o...

Q. What do you mean by Companding? In order to lower the crest factor of a waveform, so as to produce better performance, a process known as companding is used. It works like a

find the value of the slip and air gap power, The Thevenin equivalent circ...

The Thevenin equivalent circuit at the terminals of R2 / S for a 60 hz, 6 pole induction motor is shown below. a) Find the value of the slip for maximum torque and the maximum t

Electrical starter motor, ELECTRICAL STARTER MOTOR This usually consist...

ELECTRICAL STARTER MOTOR This usually consists of a heavy duty, compound wound, DC motor, which draws its electrical supply from an external source. The motor works in conjunc

Determine the current for given capacitance values, Q. Consider the circuit...

Q. Consider the circuit of Figure. Determine and sketch i L (t) and v C (t) for capacitance values of (a) 1/6 F, (b) 1/8 F, and (c) 1 / 26 F. Note that the capacitance values ar

Write Your Message!

Captcha
Free Assignment Quote

Assured A++ Grade

Get guaranteed satisfaction & time on delivery in every assignment order you paid with us! We ensure premium quality solution document along with free turntin report!

All rights reserved! Copyrights ©2019-2020 ExpertsMind IT Educational Pvt Ltd