8.2 Three motors rated 6.9 ky are connected to the same bus. The motors are: No. 1: 5,000-hp, 0.8-p.f. synchronous motor, X" 17% No. 2: 3,000-hp, 1.0-p.f. synchronous motor, X" = 15% No. 3: 3,500-hp, induction motor, X" 20% Express the subtransient reactances of these motors in per unit on a base of 10,000 kva, 6.6 kv.

8.2 Three motors rated 6.9 ky are connected to the same bus. The motors are: No. 1: 5,000-hp, 0.8-p.f. synchronous motor, X" 17% No. 2: 3,000-hp, 1.0-p.f. synchronous motor, X" = 15% No. 3: 3,500-hp, induction motor, X" 20% Express the subtransient reactances of these motors in per unit on a base of 10,000 kva, 6.6 kv.

Delmar's Standard Textbook Of Electricity

7th Edition

ISBN:9781337900348

Author:Stephen L. Herman

Publisher:Stephen L. Herman

Chapter34: Motor Installation

Section: Chapter Questions

Problem 7RQ: A 100-HP three-phase squirrel-cage induction motor is connected to 480 volts. The conductors...

See similar textbooks

Similar questions

Q7: Which of the following is a correct combination of load and MCB rating? Five numbers of ordinary sockets of 13A, grouped in parallel: [6A, SP MCB] Nine numbers of light/fan grouped in parallel: [20A, SP, MCB] A 2-kW air conditioner: [20A, SP, MCB] A three phase motor of 4 KW: [20A, SP MCB]
A star-connected, 3-phase, 10 MVA, 6.6 kV alternator is protected by differential current protection scheme using 1000/5 amperes current transformers. The star point of the alternator is earthed through a resistance of 7.5 ohm. If the minimum operating current for the relay is 0.5 A, calculate the following parameters such that the each phase of the stator winding which is unprotected against earth-fault when machine is operating at normal voltage. (i) Per phase voltage (in Volts) (ii) Minimum fault current (in Amp) to operate the relay (iii) Unprotected part of alternator winding (in percent) (iv)The emf induced in the unprotected part of the alternator winding
A 350-HP squirrel-cage induction motor is connected to a 480-volts three-phase feeder. The nameplate lists the following: HP 350, Service factor 1.10, Full-load amps 408, NEMA Code B. The conductors are to be copper with THWN insulation, and 600:5 current transformers are used to reduce the current supplied to the overload heaters. The motor circuit is protected with dual-element time delay fuses. Determine the conductor size, overload heater size using the chart shown in Figure 34-7, the NEMA and IEC starter sizes, and the fuse size for this installation.
Due to the advantages of synchronous motor, analyze the application of the synchronous motor for driving the load. (Draw the related diagram for the analysis).
A 50-horsepower, 460V, 60Hz, 3-phase induction motor has a Nameplate Rating of 60 amperes. The nameplate also shows a temperature rise of 30°C. Conduit Size using EMT.
Two shunt generators are operating in parallel and taking equal shares of a 2400 A, 230 V bus load. The ratings of the generator are as follows: Generator 1: %VR is 3%, rated power is 500 kW, rated voltage 250 V. Generator 2: %VRis 4%, rated power 600 kW and rated voltage 250 V. If an additional 600 A load is connected to the bus, determine the current delivered by each generator at this condition
A 3-phase, 20 MVA, 1IkV, star-connected generator is protected by the current balancing system of protection. If the ratio of the current transformer is 1,200/5, the minimum operating current of the relay is 0.75 ampere and the neutral point earthing resistance is 6 ohms, calculate, the percentage of each phase of the stator winding which is unprotected against earth faults when the machine is operating at normal voltage. Show quantitatively. the effect of varying neutral earthing resistance [say R = 3 ohm and 12 ohm].
The synchronous generator connected to the endless busbar is idle and synchronous.rotates at speed. If the voltage applied to the excitation winding is increased, how does the active and reactive power given by the synchronous generator to the network change? Please explain without numbers.
A 60 MVA, 3 phase, 11 kV synchronous generator is protected by the Merz-Price protection using 1000/ 5 ratio CT's. It is provided with restricted earth fault protection with the earthing resistance of 9.5Ω.Calculate the percentage of winding unprotected in each phase against earth faults if the minimum operating current of the relay is 0.5 A.
The following data are obtained for 7.5 hp, 28A, 4-pole, 208V, 60Hz, Y-connected stator squirrel cage three-phase induction motor. DC Test: Voc = 13.6V , Ioc= 28A No-Load Test: Vt= 208V , IA= 8.12A , Pout= 420W Locked-Rolot Test: Vt=25V , IA= 28A , Pin = 920W Calculate the per-phase equivalent circuit parumeters of this motor referred to the stator side. ?????
A 50 MVA, 3 phase, 33 kV synchronous generator is protected by the Merz-Price protection using 1000/5 CT's. It is provided with restricted earth fault protection with the earthing resistance of 7.5 ohm. Calculate the percentage of winding unprotected in each phase against earth faults if the minimum operating current of the relay is 0.5 A.
7. If a 575-volt three-phase motor originally connected in 3-parallel △ is reconnected in 5-parallel Y, thenew voltage isA. 501 volts.B. 794 volts.C. 598 volts.D. 747 volts.