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Aramco Standard Electrical and Instrument Question and answers
1. What the accessories of transformers?
Ans: Fans, Radiators, Oil Pumps, Pressure Relief device, Oil Level gauge, Temperature Gauges, Tap Charger, Bushings, Current Transformers, Voltage Transformers, Surge arrestors, Surge Capacitors, Dust filter bar, Post insulators.
2. Why the oil samples test shall be taken from the transformer?
Ans: To check the conductivity, analyses and characteristics of the oil.
3. What the factory tests shall be performed on the transformers?
Ans: 1. Ratio tests at the rated voltage connection and at all tap connections.
2. Polarity and phase relation tests on the rated voltage connection.
3. Applied potential tests.
4. No load and excitation current at rated voltage connection.
5. Impedance tests.
4. What are the transformers ratings?
Ans: 1. Primary and secondary KVA.
2. Voltage.
3. Taps.
4. Primary and secondary continuous current
5. Basic impulse level for equipment over 600 V
6. Impedance.
7. Insulation class and temperature rise.
8. Sound level.
5. What is the standard secondary rating of the CT?
Ans: 5 Amperes.
6. What is the symmetrical interrupting current rating fuse on the HV –side of transformers?
Ans: The symmetrical interrupting current rating of a fuse shall not be less than max symmetrical sub transient fault current.
7. Find out the full load current of a Single Phase motor 220 volt 600 watts?
Ans: I = P/V = 600/220= 2.727 Ans.
8. What are the main protections is required for a motor?
Ans: Over Current (Inst.), Thermal Over Load, Stalling Relay (Armature Jam), Earth Fault, Negative Sequence, Temperature.
9. Why do you use a thermal relay in a starter?
Ans: When winding temperature high then thermal relay active.
10. How do you check whether the winding of a motor is good or bad?
Ans: WR (Winding Resistance), IR (Insulation Resistance).
11. Why should ground all electrical equipment?
Ans: To prevent the earth fault.
12. What are the two method of winding connection in 3-Phase motors?
Ans: Star Winding & Delta Winding.
13. What is the liquid in the battery called?
Ans: Lead Acid (H2S04) & Alkaline.
14. What is the paint name which is the used in grounding cable?
Ans: Vetomens Paints.
15. What is the RPM of a 2 pole 60 HZ motor?
Ans: N = 120f/P = 120 x 60/2 = 3600 RPM
16. If the IR value of the motor winding is very low what would you do to improve it?
Ans: Motor need over hauling.
17. What is the name of the test equipment used to measure the following?
Ans: Current: Ammeter
Voltage: Voltmeter
Resistance: Ohm
Insulation Resistance: Megger
18. What is the different between primary and secondary cell?
Ans: Primary Cell is Anode (+) Secondary cell cathode (-)
19. If the current is 15A what will be the size of the cable?
Ans: 6 mm2 or 10 mm2
20. What is the max speed obtained by 3 phase induction motor with normal state supply?
Ans:
21. How to find the motor speed and write equation?
Ans:
22. Transformers Transformation Ration?
Ans:
23. What is the PI and how can found the PI value?
Ans: PI = Polarity Index
PI = Current Value ten minute / Current Value one minute
24. Which kind of motor it’s required to check the PI value?
Ans: It’s required more than 100 KW motor.
25. What is the breather, Details about the Silica Get?
Ans: It is a small container, contains silica gel and oil. It absorbs the moisture from the atmospheric air and allows the fresh air to the conservator.
Please read also: QC Notes Lecture_8_Aramco Standard Electrical and Instrument Question Answers Part_5
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Thanks in advancd n will be waiting for your article .
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