Electrical Power and Machines - Dr.Eng. Mohamed I. Abdo

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What did Russian engineer Yablochkov invent in 1876?

Lighting system based on a set of induction coils

In what transformer form are windings wrapped around the center leg of a laminated core?

Core form

What type of transformer is used to step the voltage up to the transmission level?

Unit transformer

What is the purpose of wrapping windings on top of each other in transformers?

To decrease flux leakage and increase efficiency Signup and view all the answers

At what voltage levels are power transformers used in power distribution systems referred to as substation transformers?

2.3 ... 34.5 kV Signup and view all the answers

What is the term for a transformer used at a substation to step the voltage down to the distribution level?

Substation transformer Signup and view all the answers

Who developed the first electrical power distribution system in the 1880s?

Edison Signup and view all the answers

Why was high current needed in the early electrical power distribution system?

Low voltages were used, so high currents were needed for power delivery. Signup and view all the answers

What was the major issue with the first electrical power distribution system designed by Edison?

Significant energy losses Signup and view all the answers

Who proposed the second generation of power distribution systems?

Tesla Signup and view all the answers

Why did Tesla suggest stepping up the voltage for power transmission?

To reduce losses by decreasing the current transmitted. Signup and view all the answers

How did Tesla's approach of increasing voltage for transmission reduce losses?

Decreasing the current transmitted Signup and view all the answers

What is a transformer?

A device that converts one AC voltage to another AC voltage at the same frequency. Signup and view all the answers

Who is credited with the invention of the transformer?

Faraday Signup and view all the answers

What is the purpose of the primary winding in a transformer?

Connected to a source of AC power. Signup and view all the answers

What is the purpose of the secondary winding in a transformer?

Connected to the loads. Signup and view all the answers

How are the coils in a transformer usually connected?

They are usually not connected electrically together. Signup and view all the answers

What is the common feature of the windings in a transformer?

Common ferromagnetic core. Signup and view all the answers

What is the relationship between the primary winding and secondary winding turns in a lossless transformer?

Np/Ns = a Signup and view all the answers

In phasor notation, what is the relationship between the primary voltage Vp and the secondary voltage Vs in an ideal transformer?

Vs = aVp Signup and view all the answers

What is the relationship between the primary current Ip and the secondary current Is in an ideal transformer?

Is = Ip/a Signup and view all the answers

What does an ideal transformer change in terms of voltages and currents?

Magnitudes but not their angles. Signup and view all the answers

What is another term for a transformer that converts the distribution voltage down to the final level?

Distribution transformer Signup and view all the answers

Apart from power transformers, what other types of transformers are used?

Other types of transformers Signup and view all the answers

What is the significance of the dot marking on one winding's terminal in a transformer?

Determining the polarity of voltages and currents Signup and view all the answers

In an ideal transformer, if the primary current flows into the dotted end of the primary winding, which direction will the secondary current flow?

Out of the dotted end of the secondary winding Signup and view all the answers

What is the formula to calculate the power supplied to an ideal transformer by the primary circuit?

$Pin = Vp imes Ip imes cos(\theta_p)$ Signup and view all the answers

How is the power supplied to the output circuits of an ideal transformer calculated?

$Pout = Vs imes Is imes cos(\theta_s)$ Signup and view all the answers

What is the relationship between the angles $\theta_p$ and $\theta_s$ in an ideal transformer?

$\theta_p = \theta_s$ Signup and view all the answers

What does an ideal transformer not affect in terms of the angles between voltages and currents?

Angles between voltages and currents Signup and view all the answers