Description : A 1:5 step-up transformer has 120V across the primary and 600 ohms resistance across the secondary. Assuming 100% efficiency, the primary current equals (A) 0.2 Amp. (B) 5 Amps. (C) 10 Amps. (D) 20 Amps.
Last Answer : I1= V1 /R1 = 120/600 = 0.2 (η = 100%, losses are zero ∴V1 = VR = I1R1)
Description : What are the necessary tests to determine the efficiency, voltage regulation, and temperature rise of winding & insulation of transformer?
Last Answer : 1.Direct loading test 2.Open circuit test 3. Short circuit test 4. Sumpner's or back to back test
Description : Define the percentage voltage regulation and efficiency of a power transformer.
Last Answer : Voltage regulation is the difference between no load voltage and full load voltage by no load voltage. Voltage regulation = No load voltage - Full load voltage / No load voltage. Voltage regulation is mentioned ... . % Efficiency = Output in watts * 100 / Output in watts + losses.
Description : In order to take a current reading with a 'clamp-on' ammeter, the instrument's jaws _________________. A. should remain open B. cannot touch the adjacent conductor C. must be fully closed D. will act as a transformer primary
Last Answer : Answer: C
Description : The harmonic currents in a power transformer does not cause increase in: a) Secondary voltage b) Core loss c) Copper loss d) Magnetic interference with protective relays
Last Answer : Ans: A
Description : Define: (i) Efficiency (ii) Voltage regulation of transformer.
Last Answer : i) Efficiency : It is the ratio of output power to the input power of the transformer.It is denoted by η. ii) Voltage Regulation of transformer: The ratio of the change in Secondary Terminal ... So where, VNL = No Load Secondary voltage VFL = Full load secondary voltage
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 : Which of the following statements identifies the difference between the primary windings and the secondary windings of a 2:1 stepdown transformer? A. The secondary windings have twice as much resistance ... primary windings. D. The secondary windings have half as many turns as the primary windings.
Last Answer : Answer: D
Description : A load with an impedance of 440 ohms is connected across the secondary of the transformer illustrated. If the input voltage is 110 VAC and the step-up ratio is 10 to 1, what will be the primary current? EL-0055 A. 2.5 amps B. 25 amps C. 250 amps D. current cannot be determined with information given
Last Answer : Answer: B
Description : A load is connected to the secondary of the transformer illustrated and the current through the load is 10 amps. If the step-up ratio is 10 to 1 and the input voltage is 110 VAC, what will be the current flow through the primary? EL-0055 A. 1 amp B. 10 amps C. 100 amps D. 1000 amps
Description : Which of the following statements is true concerning stepdown transformer operation? A. The inductance on the primary side is the same as the inductance on the secondary side. B. The voltage to the primary ... . D. The voltage to the primary side is greater than the voltage from the secondary side.
Description : When a low input voltage is imparted to a device which then delivers a high output voltage, the device is known as a _____________. A. primary transformer B. secondary transformer C. stepdown transformer D. stepup transformer
Description : Relative to the secondary winding of a step-up transformer, the primary winding will have _____________. A. more turns B. fewer turns C. half as many turns D. twice as many turns
Description : When a transformer is used to step down voltage, the low voltage winding is _____________. A. part of the core B. the primary coil C. not insulated D. the secondary coil
Description : If a transformer is connected to a DC source, the transformer will overload at the ____________. A. contacts B. primary coil C. secondary coil D. core
Description : Increasing the load to the secondary windings of a transformer will cause a/an ____________. A. decrease in the primary voltage B. increase in the primary voltage C. decrease in the primary current D. increase in the primary current
Description : If we give 2334 A, 540V on Primary side of 1.125 MVA step up transformer, then what will be the Secondary Current, If Secondary Voltage=11 KV?
Last Answer : A. As we know the Voltage & current relation for transformer-V1/V2 = I2/I1 We Know, VI= 540 V; V2=11KV or 11000 V; I1= 2334 Amps. By putting these value on Relation540/11000= I2/2334 So,I2 = 114.5 Amps
Description : What current flows in the transformer primary when its secondary is open?
Last Answer : A. When the secondary is open, there is no current in the secondary of the transformer. The primary takes a small current I0) from the source called no-load current which has a magnetizing ... ) producing the magnetic flux and a working component (I0 cosθ0) supplying real power for iron losses.
Description : In a Tap changing transformer on which side is the tap connected, primary side or secondary side?
Last Answer : A. Tapings are always connected to high voltage winding side, because of low current. If we connect tapings to low voltage side, sparks will produce while tap changing operation due to high current.
Last Answer : As we know the Voltage & current relation for transformer-V1/V2 = I2/I1 We Know, VI= 540 V; V2=11KV or 11000 V; I1= 2334 Amps. By putting these value on Relation540/11000= I2/2334 So,I2 = 114.5 Amps
Description : In a three phase transformer, if the primary side is connected in star and secondary side is connected in delta, what is the angle difference between phase voltage in the two cases. (A) delta side lags by -30°. (B) star side lags by -30°. (C) delta side leads by 30°. (D) star side leads by -30°.
Last Answer : Ans: C This is vector group and has +30° displacement. Therefore, delta side leads by +30°.
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 : A shore power circuit breaker should be closed only _____________. A. when the ship's generators have been directly paralleled to those on shore B. in a shipyard C. if a quick disconnect coupling is used D. when the ship's generators have been removed from the bus
Description : The transistors in the illustrated circuit are connected using what type of coupling? EL-0049 A. RC coupling B. transformer coupling C. LC coupling D. direct coupling
Description : The transistors in the illustrated circuit are connected using what type of coupling? EL-0048 A. RC coupling B. transformer coupling C. LC coupling D. direct coupling
Last Answer : Answer: A
Description : The transistors in the illustrated circuit are connected using what type of coupling? EL-0051 A. RC coupling B. transformer coupling C. impedance coupling D. direct coupling
Description : The transistors in the illustrated circuit are connected using what type of coupling? EL-0050 A. RC coupling B. transformer coupling C. Impedance coupling D. direct coupling
Description : A transformer has negative voltage regulation when its load power factor is- (a) Zero (b) Unity (c) Leading (d) Lagging
Last Answer : Ans: C
Description : What is Meant by Regulation in a Transformer?
Last Answer : ANSWER: Voltage regulation in transformers is the difference between the no load voltage and the full load voltage. This is usually expressed in terms of percentage. For example: A transformer delivers 100 ... from 2% to 4%, depending on the size and the application for which they are used
Description : What is meant by regulation in a transformer?
Last Answer : A. Voltage regulation in transformers is the difference between the no load voltage and the full load voltage. This is usually expressed in terms of percentage. Example: A Transformer delivers 100 ... The regulation capacity varies depending on the size and the application for which they are used.
Last Answer : Voltage regulation in transformers is the difference between the no load voltage and the full load voltage. This is usually expressed in terms of percentage. For example: A transformer delivers 100 volts ... voltage drop in transformer/ no load voltage of transformer V2>E2 for leading p.f load V2
Description : A two-winding single phase transformer has a voltage regulation of 4.5% at full-load and unity power-factor. At full-load and 0.80 power-factor lagging load the voltage regulation will be (A) 4.5%. (B) less than 4.5%. (C) more than 4.5%. (D) 4.5% or more than 4.5%.
Last Answer : (C) more than 4.5%.
Description : In a transformer the voltage regulation will be zero when it operates at (A) unity p.f. (B) leading p.f. (C) lagging p.f. (D) zero p.f. leading.
Last Answer : (B) leading p.f.
Description : Define all day efficiency of a transformer?
Last Answer : A:It is computed on the basis of energy consumed during a certain period, usually a day of 24 hrs. All day efficiency=output in kWh/input in kWh for 24 hrs.
Description : 48.During light loads, the transformer efficiency is low because A. Secondary output is low B. Transformer losses are high C. Fixed loss is high in proportion to the output D. Cu loss is small
Last Answer : C. Fixed loss is high in proportion to the output
Description : __ is defined as th ned as the use of c e use of commercial ma cial marketing concep ng concepts and t ts and tools in ools in programs designed to influence individual's behavior to ... of society. a. Unsought product b. Internal marketing Internal marketing c. Social marketing d. Product line
Last Answer : c. Social marketing
Description : Booster transformer should never: a) Have fuse in the HV winding b) Be left open circuited c) Be left closed circuited d) None of the above
Description : What is the output current of a 480 Volt primary 208 volt secondary - 3 phase transformer?
Last Answer : You need to mention the Load connected to find the current.
Description : The secondary coil of a transformer in which the voltage is stepped down are usually made of thicker wire than primary. Why?
Last Answer : The secondary coil is made of thicker wire to sustain larger electric current.
Description : What are primary and secondary coil in a transformer?
Last Answer : The coil which is connected to input source is called primary coil. The coil which is connected to the output source is called secondary coil.
Description : In transformer, alternating current is induced inA. primary coil B. secondary coil C. iron core D. resistor
Last Answer : primary coil
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 : A transformer steps down 220V to 40 volts. If the secondary turns are 40 then primary turns will be: a. 20 b. 40 c. 120 d. 220
Last Answer : d. 220V
Description : Turn ratio of a transformer is 5. If 220 V AC is applied to its primary coil, voltage in the secondary coil will be: a. 44V b. 4.4 V c. 220V d. 1100V
Last Answer : c. 220V
Description : In a tap changing transformer, the tappings are provided on (a) primary winding (b) secondary winding (c) high voltage winding (d) any of the above
Last Answer : (b) secondary winding
Description : 66 While conducting short-circuit test on a transformer the following side is short circuited A. High voltage side B. low voltage side C. primary side D. secondary side
Last Answer : B. Low voltage side
Description : 59.An ideal transformer has infinite values of primary and secondary inductances. The statement is A. True B. False
Last Answer : B. False
Description : 57 In a transformer the resistance between its primary and secondary is A. Zero B. 1Ω C. 1000 Ω D. Infinite
Last Answer : D. Infinite
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 : 50 The equivalent resistance of the primary of the transformer having K = 5, R1 = 0.1 ohm when referred to secondary becomes .....ohm A. 0.5 B. 0.02 C. 0.004 D. 2.5
Last Answer : A. 0.5