terry can ride 30 miles in 2 hrs riding speed is reduced by 3 miles per hours how far can he ride in 1.7 hours

A car travels 90 meters north in 15 seconds. Then turns around and travels at 40 meters south in 5.0 seconds. what is the averag

Viefleur [7K]

Average velocity = (displacement) / (total time)

Displacement = distance and direction between
the starting point and the end point

The car travels 90 meters north, then 40 meters south.
So it ends up 50 meters north of where it began.

Displacement = 50 meters north
Total time = (15 + 5) = 20 seconds

Average velocity = (50 meters north) / (20 seconds)

= 2.5 m/s north

4 0

2 years ago

Determine the voltage ratings of the high-and-low voltage windings for this connection and the MVA rating of the autotransformer

SIZIF [17.4K]

Complete Question

The complete question is shown on the first uploaded image

Answer:

a

The High Voltage Rating for Auto - Transformer is 86kV

The Low Voltage Rating for Auto - Transformer is 78kV

The MVA rating is 268.75 $MVA$

b

The efficiency is 99.4%

Explanation:

From the question we are given are given that

The transformer has Mega Volt Amp rating of 25MVA

The frequency is 60-Hz

Voltage rating 8.0kV : 78kV

The short circuit test gives : 453kV,321A,77.5kW

The open circuit test gives : 8.0kV, 39.6A, 86.2kW

This can be represented on a diagram shown on the second uploaded image

From this diagram we can deduce that the The High Voltage Rating for Auto - Transformer is 86kV and the Low Voltage Rating for Auto - Transformer is 78kV

Now to obtain the current flowing through the 8kV coil in the Auto-transformer we have

$\frac{25 \ Mega \ Volt\ Ampere }{8\ Kilo Volt}$

The volt will cancel each other

$\frac{25*10^6}{8*10^3} = 3125\ A$

Now to obtain the required MVA rating we would multiply the value of Power obtained during the open circuit test by the value of the current calculated.we are making use of the power obtain during open circuit testing because the transformer at this point is not under any load.

$MVA \ rating = (86*10^3)(3125) =268.75$