Description : Mention the important parts of a power transformer and their purposes.
Last Answer : Conservator: This allows for shrinkage and swelling of transformer oil. When the oil is heated up it swells and rises to the conservator. When cools down it goes back to main tank. Conservator reduces sludge ... put. There are two types of tap changer. Online tap changer and off line tap changer.
Description : In the inverting configuration, what is the voltage (for all practical purposes) at the inverting input to the operational amplifier if the input signal is a 1-volt, peak-to-peak sine wave?
Last Answer : 0 volts.
Description : For what purposes is the SNAP II system designed?
Last Answer : To support shipboard and intermediate level maintenance, supply, financial, and administrative functions.
Description : Digital computers are generally used for what purposes?
Last Answer : Business and scientific data processing
Description : For what purposes transformer ratio meter can be used?
Last Answer : Transformer ratio meter can be used for, a. To find the ratio of a transformer. b. To find the phase angle deviation of primary and secondary voltage of transformer. c. To find the magnitude of magnetizing currents.
Description : What are the purposes or advantages of transformer?
Last Answer : Purposes a. Electrical energy may be transmitted economically over long distance by stepping up of voltages to reduce the line losses. b. To distribute the low voltages at consumer side by stepping down ... There by efficiency is high and about 95 to 98%. b. Practically maintenance is very less.
Description : Name the three power losses in a transformer
Last Answer : Copper-loss, eddy-current loss, and hysteresis loss
Description : The leads to the primary and the high-voltage secondary windings of a power transformer usually are of what color?
Last Answer : Primary leads-black; secondary leads red.
Description : What are the four basic sections of a power supply?
Last Answer : Transformer, rectifier, filter, regulator.
Description : If a power supply produces 20 volts with no load and 15 volts under full load, what is the percent of regulation?
Last Answer : 33.33%
Description : What is the commonly used figure of merit for a power supply?
Last Answer : Percent of regulator.
Description : What are the four basic sections to a power supply?
Description : What problem is caused by overcoupling in a transformer?
Last Answer : Low gain at the center frequency.
Description : What problem is caused in an rf amplifier by a loosely coupled transformer?
Last Answer : A too-narrow bandpass.
Description : Does 1:5 indicate a step-up or step-down transformer?
Last Answer : Step up.
Description : What effect does flux leakage in a transformer have on the coefficient of coupling (K) in the transformer?
Last Answer : it causes K to be less than unity (I).
Description : What causes a voltage to be developed across the secondary winding of a transformer?
Last Answer : The magnetic lines generated by the current in the primary cut
Description : What is meant by "exciting current" in a transformer?
Last Answer : Exciting current is the current that flows in the primary of a transformer with the secondary open (no load attached).
Last Answer : Step up
Description : What is meant is "transformer action"?
Last Answer : The transfer of energy from one circuit to another circuit by electromagnetic induction.
Description : What is the main reason for grounding the return side of the transformer to the chassis?
Last Answer : To eliminate shock hazard.
Description : In addition to stepping up or stepping down the input line voltage, what additional purpose does the transformer serve?
Last Answer : . It isolates the chassis from the power line.
Last Answer : Reduce the cost of manufacturing equipment.
Description : For what is the center tap on a transformer used?
Last Answer : Provides capability of developing two high-voltage outputs
Description : For what are the low voltage windings in a transformer used?
Last Answer : Filament voltage to the electron tubes.
Description : How does the supply voltage affect the accuracy of Wheatstone bridge measurements?
Last Answer : As the supply voltage increases, bridge components may heat up and become less accurate.
Description : . After rewinding a tape onto its supply reel, you examine the tape pack and notice pile-ups of tape resembling the example in figure 2-2. What causes this condition?
Last Answer : The tape is stopped too quickly when winding or rewinding.
Description : What term applies to the use of two or more generators to supply a common load?
Last Answer : Parallel operation.
Description : If the load requirement consists of both positive and negative voltages, what technique is used in the voltage divider to supply the loads from a single voltage source?
Last Answer : The ground (reference point) is placed in the proper point in the voltage divider so that positive and negative voltages are supplied
Description : What is a disadvantage of a direct-current system with respect to supply voltage?
Last Answer : the dc voltage must be generated at the level required by the load.
Description : In conversion of 3-phase to 2-phase supply with T connection, the transformation ratio of the teaser will be__ times to that of main transformer: a) 1.732 b) 1.15 c) 0.866 d) Unity
Last Answer : Ans: C
Description : The rating of the Transformer __ when the supply frequency is increased: a) Remains unchanged b) Increases c) Decreases d) None of the above
Last Answer : Ans: B
Description : The most common source of excitation for synchronous motors is a/an ______________. A. stepup transformer B. half-wave rectifier C. DC supply D. AC supply
Last Answer : Answer: C
Description : What happen when Transformer is given DC supply ?
Last Answer : When DC supply is given to the transformer primary winding no back emf is induced in the transformer. Importance of Back emf is that it limits the current drawn by the machine. In the absence ... in burning down of primary winding. So when dc supply is given to transformer primary windings will burn
Description : What is the supply rated o/p if two single phase transformer connect to give three phase o/p from a three phase I/p?
Last Answer : A. Each transformer is only capable of supplying 86.6%of its o/p rating
Description : What will happen if DC supply is given on the primary of a transformer?
Last Answer : A. Mainly transformer has high inductance and low resistance. In case of DC supply there is no inductance, only resistance will act in the electrical circuit. So, high electrical current will flow through primary side of the transformer. Due to this the coil and insulation will burn out.
Description : There Are A transformer And An Induction Machine. Those Two Have The Same Supply. For Which Device The Load Current Will Be Maximum? And Why?
Last Answer : The motor has max load current compare to that of trformer because the motor consumes real power.. and the trformer is only producing the working flux and its not consuming.. hence the load current in the trformer is because of core loss so it is minimum.
Last Answer : Mainly transformer has high inductance and low resistance. In case of DC supply there is no inductance, only resistance will act in the electrical circuit. So high electrical current will ... secondary emf induced in secondary winding so primary current may goes high and burn transformer winding.
Description : [53] The iron loss of the transformer is negligible during short circuit test because A. The entire input is just sufficient to meet Cu losses only B. Flux produced is a small fraction of the normal flux C. Iron core becomes fully saturated D. Supply frequency is held constant
Last Answer : B. Flux produced is a small fraction of the normal flux
Description : 52 A transformer has 1000 primary turns, connected to 250V ac supply. To get 400V secondary voltage the no of secondary turns should be A. 1600 B. 250 C. 400 D. 1250
Last Answer : A. 1600
Description : A 220/440 V, 50 Hz, 5 KVA, single phase transformer operates on 220V, 40Hz supply with secondary winding open circuited. Then (A) Both eddy current and hysteresis losses decreases. (B) Both ... same but hysteresis loss increases. (D) Eddy current loss increases but hysteresis loss remains the same.
Last Answer : (A) Both eddy current and hysteresis losses decreases.
Description : The primary winding of a 220/6 V, 50 Hz transformer is energised from 110 V, 60 Hz supply. The secondary output voltage will be (A) 3.6 V. (B) 2.5 V. (C) 3.0 V. (D) 6.0 V.
Last Answer : (C) 3.0 V.
Description : An AC supply of 230 V is applied to half wave rectifier circuit. A transformer turns ratio is 20 : 1. Find i) Output DC voltage (ii) Peak Inverse Voltage (PIV)
Last Answer : Solution:
Description : An AC supply of 230 V is applied to a half-wave rectifier circuit through a transformer having primary to secondary turn’s ratio 12:1. The peak inverse voltage is A) 8.62 V B) 12 V C) 19.17 V D) 27.11 V
Last Answer : An AC supply of 230 V is applied to a half-wave rectifier circuit through a transformer having primary to secondary turn’s ratio 12:1. The peak inverse voltage is A) 8.62 V B) 12 V C) 19.17 V D) 27.11 V
Description : A single phase transformer is designed to operate from 50 Hz, 1100 V supply and to have an output voltage of 240 V at no load. The core has mean area of 30 cm2 and the flux density has not to exceed 1.3T. The number of secondary turns will be (a) 1270 (b) 1017 (c) 768 (d) 277
Last Answer : E2=e2=4.44*flux*N2*f=240 V Flux=Flux density* Area Area=30 cm2 =30*10-4 m2 Flux= 1.3*30*10-4 Wb=39*10-4 Wb E=240= 4.44*39*10-4 *N2*50 N2=277.
Last Answer : The primary winding of a 220/6 V, 50 Hz transformer is energised from 110 V, 60 Hz supply. The secondary output voltage will be 3.0 V.
Description : What will happen if the primary of a transformer is connected to D.C. supply? (A) Transformer will operate with low efficiency (B) Transformer will operate with high efficiency (C) No effect (D) Transformer may start to smoke and burn
Last Answer : What will happen if the primary of a transformer is connected to D.C. supply? (A) Transformer will operate with low efficiency (B) Transformer will operate with high efficiency (C) No effect (D) Transformer may start to smoke and burn
Description : The inrush current of a transformer at no load is maximum if the supply voltage is switched on (1) at peak voltage value (2) at zero voltage value (3) at half voltage value (4) at 0.866 time voltage value
Last Answer : At 0.866 time voltage value
Description : The main application of delta/zig-zag connected 3-phase transformer is to supply (A) balanced loads (B) unbalanced loads (C) furnace loads (D) single-phase loads
Last Answer : The main application of delta/zig-zag connected 3-phase transformer is to supply unbalanced loads