Transformer MCQs Part 9
Contents
- 1 A core type transformer provides
- 2 Open-circuit test on transformer is carried out in order to determine
- 3 A low voltage electrical system employs a 100V to 40 step down transformer for safety. The equivalent resistance of electrical system is 10 ohms. Considering the transformer to be ideal and overall system as lossless, what is the current in primary coil
- 4 The maximum flux produced in core of transformer is
- 5 Transformer voltage equation is mathematically written in the form
A core type transformer provides
A core type transformer provides:
- Shorter magnetic path
- Longer magnetic path
- Lesser average length per turn
- None of these
Correct answer: 1. Shorter magnetic path
Open-circuit test on transformer is carried out in order to determine
Open-circuit test on transformer is carried out in order to determine:
- Iron losses
- Copper losses
- Friction losses
- Total losses
Correct answer: 1. Iron losses
A low voltage electrical system employs a 100V to 40 step down transformer for safety. The equivalent resistance of electrical system is 10 ohms. Considering the transformer to be ideal and overall system as lossless, what is the current in primary coil
A low voltage electrical system employs a 100V to 40 step down transformer for safety. The equivalent resistance of electrical system is 10 ohms. Considering the transformer to be ideal and overall system as lossless, what is the current in primary coil:
- 1.6 A
- 4 A
- 5 A
- 10 A
Correct answer: 1. 1.6 A
Explanation:
Secondary current (Is) = Vs/R = 40/10 = 4 A
Primary current (Ip) = (Vs * Is)/Vp = 1.6 A
The maximum flux produced in core of transformer is
The maximum flux produced in core of transformer is:
- Inversely proportional to primary voltage
- Inversely proportional to supply frequency
- Directly proportional to supply frequency
- None of these
Correct answer: 2. Inversely proportional to supply frequency
Explanation:
Transformer voltage equation is mathematically written in the form
Transformer voltage equation is mathematically written in the form:
V1 = 4.44 * N1 * Φmax * f
A 110/2300 V transformer takes no-load current of 5 Amps at a lagging power factor of 0.3. The core loss expressed in watts is:
- 120 W
- 150 W
- 165 W
- 200 W
Correct answer: 3. 165 W
Solution: Core loss, Wo = Vp Io cos Φo = 110 * 5 * 0.3 = 165 W
Or Alternatively:
Φmax = V1/(4.44 * N1 * f)
Where
V1 = Applied primary voltage
N1 = Number of primary turns
From equation one can understand that maximum flux produced in core is inversely proportional to supply frequency.