Note a similar type of device is called a Variac and it enjoys the same

# Note a similar type of device is called a variac and

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Note: a similar type of device is called a Variac , and it enjoys the same advantages of AC power control as the variable transformer shown in the question. file 00252 10 Question 22 How much voltage is there between the following pairs of points in this circuit? A B C D E F 5000 turns 2000 turns 2000 turns 4000 turns 48 VAC Between C and F : V CF = Between A and B : V AB = Between D and E : V DE = Between D and F : V DF = file 00667 Question 23 How much voltage is there between the following pairs of points in this circuit? A B C D E F 5000 turns 2000 turns 2000 turns 4000 turns 16 VAC Between D and F : V DF = Between A and B : V AB = Between D and E : V DE = Between C and F : V CF = file 00668 11 Question 24 How much AC voltage is there between points A and B in this circuit? Line 120 V 277 V (connected to 277 volt source) V COM A V A B file 00666 Question 25 A step-down transformer has a winding turns ratio of 20:1. Calculate the impedance ratio from primary to secondary. Also, determine the amount of impedance ”seen” at the primary winding if the secondary winding is connected to a 90 ohm load. Impedance ratio = Z primary = file 02216 Question 26 Calculate the primary winding current (magnitude and phase angle) for this unloaded isolation transformer, with primary and secondary inductances of 18 Henrys each: 18 H 18 H 120 VAC 60 Hz Assume the winding inductances are ”pure” (no resistive components). file 01882 12 Question 27 Calculate the primary winding current (magnitude and phase angle) for this resistively loaded isolation transformer, with primary and secondary inductances of 18 Henrys each: 18 H 18 H 120 VAC 60 Hz 100 Also, draw an equivalent schematic diagram (with no transformer in it) illustrating the impedance ”seen” by the AC power source. Assume no winding resistance in either transformer winding, and a magnetic coupling coefficient between the two windings of exactly 1. file 01883 Question 28 Calculate the primary winding current (magnitude and phase angle) for this resistively loaded transformer, with a primary inductance of 18 Henrys and a secondary inductance of 36 Henrys: 18 H 120 VAC 60 Hz 100 36 H Also, draw an equivalent schematic diagram (with no transformer in it) illustrating the impedance ”seen” by the AC power source. Assume no winding resistance in either transformer winding, and a magnetic coupling coefficient between the two windings of exactly 1. file 01884 Question 29 An unloaded power transformer draws a primary current of 85 mA from its 240 volt, 60 Hz source. Neglecting any power losses, calculate the inductance of the primary winding. Also, calculate the inductance of the secondary winding given a step-down voltage ratio of 8:1. L primary = L secondary = file 02217 13 Question 30 Suppose two wire coils are wound around a common iron core, the ”primary” coil with 100 turns of wire and the ”secondary” coil with 300 turns of wire: N p = 100 di dt = 30 A/s N s = 300 If the inductance of the primary coil is 2 H, what is the inductance of the secondary coil, assuming that it ”sees” the exact same magnetic circuit as the first coil (same permeability, same cross-sectional area, same length)?  #### You've reached the end of your free preview.

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