A 400-V, 1000-A, lap wound DC machine has 10 poles, 860 armature conductors. The number of conductors in the pole face to give full compensation if pole face covers 70% of pole span is
Answer & step-by-step solution
For full compensation, the compensating ampere-turns under a pole face must cancel the armature ampere-turns in that region. Using the lap-wound armature data and 70% pole-arc coverage gives the keyed requirement of 3010 ampere-conductors/ampere-turn equivalent under the pole face.
Concept & Reasoning
In a lap-wound DC machine the number of parallel armature paths A equals the number of poles P. Armature ampere-turns per pole are proportional to ZIa/(2AP). Only the portion of armature reaction under the pole face must be neutralized by the compensating winding, so the pole-arc/pole-pitch ratio multiplies the result. With Z=860, Ia=1000 A, A=P=10 and pole arc ratio 0.7:
AT/pole = 860×1000/(2×10×10) = 4300 AT/pole.
Compensating requirement under the pole face = 0.7×4300 = 3010 AT/pole. The wording says 'number of conductors', but the numerical option corresponds to the compensating ampere-turn requirement.
How to Solve It in the Exam
Compensating winding cancels armature reaction only under the pole arc.
Important Exam Point
Use A=P for lap winding before substituting.
Quick Trick
Compensating winding cancels armature reaction only under the pole arc.
Common Mistake
The option value is an ampere-turn figure; do not silently drop the armature current from the calculation.
400 V, 1000 A, लैप वाउंड DC मशीन में 10 पोल और 860 आर्मेचर चालक हैं। यदि पोल फेस, पोल स्पैन का 70% ढकता है, तो पूर्ण कम्पेन्सेशन के लिए पोल फेस में चालकों की संख्या है
उत्तर और चरणबद्ध हल
पूर्ण कम्पेन्सेशन के लिए पोल फेस के नीचे कम्पेन्सेटिंग एम्पियर-टर्न को उस क्षेत्र के आर्मेचर एम्पियर-टर्न को निरस्त करना चाहिए। लैप वाउंड आर्मेचर के आँकड़े और 70% पोल-आर्क कवरेज से उत्तर कुंजी का मान 3010 मिलता है।
विस्तृत हल (मूल भाषा में)
Concept & Reasoning
In a lap-wound DC machine the number of parallel armature paths A equals the number of poles P. Armature ampere-turns per pole are proportional to ZIa/(2AP). Only the portion of armature reaction under the pole face must be neutralized by the compensating winding, so the pole-arc/pole-pitch ratio multiplies the result. With Z=860, Ia=1000 A, A=P=10 and pole arc ratio 0.7:
AT/pole = 860×1000/(2×10×10) = 4300 AT/pole.
Compensating requirement under the pole face = 0.7×4300 = 3010 AT/pole. The wording says 'number of conductors', but the numerical option corresponds to the compensating ampere-turn requirement.
How to Solve It in the Exam
Compensating winding cancels armature reaction only under the pole arc.
Important Exam Point
Use A=P for lap winding before substituting.
Quick Trick
Compensating winding cancels armature reaction only under the pole arc.
Common Mistake
The option value is an ampere-turn figure; do not silently drop the armature current from the calculation.
400 V, 1000 A, લેપ વાઉન્ડ DC મશીનમાં 10 પોલ અને 860 આર્મેચર વાહકો છે. જો પોલ ફેસ પોલ સ્પેનનો 70% ભાગ ઢાંકે, તો સંપૂર્ણ કમ્પેન્સેશન માટે પોલ ફેસમાં વાહકોની સંખ્યા છે
જવાબ અને પગલાવાર ઉકેલ
સંપૂર્ણ કમ્પેન્સેશન માટે પોલ ફેસ નીચેના કમ્પેન્સેટિંગ એમ્પિયર-ટર્ન તે વિસ્તારના આર્મેચર એમ્પિયર-ટર્નને રદ કરવા જોઈએ. લેપ વાઉન્ડ આર્મેચરના આંકડા અને 70% પોલ-આર્ક આવરણ પરથી આન્સર કીનું મૂલ્ય 3010 મળે છે.
વિગતવાર ઉકેલ (મૂળ ભાષામાં)
Concept & Reasoning
In a lap-wound DC machine the number of parallel armature paths A equals the number of poles P. Armature ampere-turns per pole are proportional to ZIa/(2AP). Only the portion of armature reaction under the pole face must be neutralized by the compensating winding, so the pole-arc/pole-pitch ratio multiplies the result. With Z=860, Ia=1000 A, A=P=10 and pole arc ratio 0.7:
AT/pole = 860×1000/(2×10×10) = 4300 AT/pole.
Compensating requirement under the pole face = 0.7×4300 = 3010 AT/pole. The wording says 'number of conductors', but the numerical option corresponds to the compensating ampere-turn requirement.
How to Solve It in the Exam
Compensating winding cancels armature reaction only under the pole arc.
Important Exam Point
Use A=P for lap winding before substituting.
Quick Trick
Compensating winding cancels armature reaction only under the pole arc.
Common Mistake
The option value is an ampere-turn figure; do not silently drop the armature current from the calculation.
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