Electric Motor Control
10th Edition
ISBN: 9781133702818
Author: Herman
Publisher: CENGAGE L
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Textbook Question
Chapter 42, Problem 6SQ
What influence do both of the polarized field frequency relay (PFR) coils exert on the normally closed contact?
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Q2/ Design a 4-pole wave winding for an armature with 21 slots. Assume single turn coils and
two conductors per slot.
(35 mark)
What is the difference between a fuse and a relay ?
What is the difference between an overcurrent relay and current differential relay ?
Which of the statement is true?
A Normally closed (NC) relay contact is open when the relay coil is de – energized. It opens when the coil
energizes, but returns to closed position when the coil de – energizes.
O b. When a relay contact is normally open (NO), there is an open contact when the relay is energized.
O c. A NO relay contact is open when the relay coil is de – energized. It closes when the coil energizes but
returns to open position when the coil de – energizes.
d.
When a relay contact is Normally Closed (NC), there is a closed contact when the relay is energized.
Chapter 42 Solutions
Electric Motor Control
Ch. 42 - What are the two basic methods of automatically...Ch. 42 - What is an out-of-step relay?Ch. 42 - Why is an out-of-step relay used on automatic...Ch. 42 - Under what conditions will the out-of-step relay...Ch. 42 - What is the last control contact that closes on a...Ch. 42 - What influence do both of the polarized field...Ch. 42 - Prob. 7SQCh. 42 - Approximately how much time (in terms of...Ch. 42 - How does the AC coil of the PFR receive the...Ch. 42 - Why is a control relay (CR1) used in Figure 426?...
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- The preferred method for applying the field excitation voltage uses a field relay which operates on the principle of A. speed application. B. time application.C. angle application. D. thermal application.arrow_forwardHow does the AC coil of the PFR receive the induced field current without receiving the full field current strength?arrow_forwardWhat is the commutator pitch of a 4-pole, duplex wave-wound armature having 120 commutator bars?arrow_forward
- Explain the following armature winding terminologies (i)commutator Pitch (ii)Coil Side (iii)Pole Pitcharrow_forwardB: Relay is consist two circuits, what they are? And determine whether the next relay is normally open or normally closed. 3arrow_forwardAssume that HOA SW 120 has been set in the AUTO position. List four ways by which coil CR-8 could be energized.arrow_forward
- What is the difference between a balanced voltage relay and a Translay relay ?arrow_forwardA four-pole lap-wound DC machine armature has 54 slots with single-turn coils. How many armature conductors are required if there are two coil sides per slot?arrow_forwardDeterming the front pitch, back pitch, and average pitch of the armature winding. 12 poles 100 slots 2 conductors/slot 100 commutator segment progressive, simplexarrow_forward
- A 4-pole wave-wound motor armature has 880 conductors and delivers 120 A. The brushes have been displaced through 3 angular degrees from the geometrical axis. Calculate (a) demagnetising amp-turns/pole (b) cross- magnetising amp-turns/pole (c) the additional field current for neutralizing the demagnetisation of the field winding has 1100 turns/pole.arrow_forward1) Calculate the coil pitches and indicate the slots into which the first coil should be place for the following armature windings a. 36 slots , 4 poles b. 57 slots , 4 poles c. 76 slots , six poles d. 132 slots , eight poles e. 270 slots , 10 polesarrow_forwardwrite a technical report about the following relays: 1/ Frequency relays 2/ reverse power relay 3/ negative sequence relayarrow_forward
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