NEC Table 430.52 gives four options for selecting the maximum size motor branch-circuit, short-circuit, and ground-fault protective devices. These options are listed in problems 8, 9, 10, and 11. For each option, determine the correct rating or setting for a 25-horsepower, 3-phase, 230-volt motor. The motor is marked “Design B.” 8.Non-time-delay fuses: 9..Dual-element, time-delay fuses: 10.Instantaneous-trip breakers: 11.Inverse time breakers:

NEC Table 430.52 gives four options for selecting the maximum size motor branch-circuit, short-circuit, and ground-fault protective devices. These options are listed in problems 8, 9, 10, and 11. For each option, determine the correct rating or setting for a 25-horsepower, 3-phase, 230-volt motor. The motor is marked “Design B.” 8.Non-time-delay fuses: 9..Dual-element, time-delay fuses: 10.Instantaneous-trip breakers: 11.Inverse time breakers:

Electricity for Refrigeration, Heating, and Air Conditioning (MindTap Course List)

10th Edition

ISBN:9781337399128

Author:Russell E. Smith

Publisher:Russell E. Smith

Chapter6: Reading Schematic Diagrams

Section: Chapter Questions

Problem 22RQ

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A 460VAC rated, 60 Hz, 125-Hp Three-phase induction type motor is to be connected for across-the-line starting. The nameplate indicates the motor’s maximum ampere rating, 160A. It has a NEMA code letter B. The ambient temp of the installation place is and TW copper will be used. Short-circuit protection device that will be used is Inverse Time Breaker. Calculate the Branch Circuit Protection.
A 460VAC rated, 60 Hz, 125-Hp Three-phase induction type motor is to be connected for across-the-line starting. The nameplate indicates the motor’s maximum ampere rating, 160A. It has a NEMA code letter B. The ambient temp of the installation place is and TW copper will be used. Short-circuit protection device that will be used is Inverse Time Breaker. Calculate the Conductor size.
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A 460VAC rated, 60 Hz, 125-Hp Three-phase induction type motor is to be connected for across-the-line starting. The nameplate indicates the motor’s maximum ampere rating, 160A. It has a NEMA code letter B. The ambient temp of the installation place is and TW copper will be used. Short-circuit protection device that will be used is Inverse Time Breaker. Calculate the Thermal Overload Protection.
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#21
6.a. Arcing in manual starters is eliminated by the use ofA. overload relays.B. nonconductive contacts.C. blowout coils.D. spring-loaded handles.6.b. Chattering of AC contactors is prevented byA. blowout coils.B. air gaps.C. secondary windings.D. shading poles.
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9.a. A servo system is oscillating at standstill. This is an indication thatA. the following error limit has been exceeded.B. a motor winding is open.C. the system gain is too high. 9.b. In a DC servo motor system, the tachometer feeds back a voltage that’s proportional to motor speed.Where does this voltage go to?A. The interpolator cardB. The driverC. The CPU in the main controller
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