Unit 4

Question 1

Purpose of Dc motors starter

Answer 1

ToProtect from overloads and faults
Used for smoothing starting a motor. Variable resistance in series with armature
To increase the resistance incrementally
Thus restricting the armature current to a safe value
To disconnect motor in case of an overload
To disconnect the motor when the field current is reduced beyond limit

Question 2

Purpose of a no volt strip

Answer 2

To disconnect the motor if the supply voltage fails
Provided automatic tripping there’s a major voltage dip
Pretends the motor from restarting if the power supply is on
When the power supply is cut the coil demagnetises and the starter handle spring returns to off position

Question 3

How does half bridge rectifier work

Answer 3

Diode only conducts in one direction
Half of an ac wave being conducted to output

Question 4

How does half bridge rectifier work

Answer 4

Diode only conducts in one direction
Half of an ac wave being conducted to output

Question 5

How does load regulator work

Answer 5

Maintains contestant or little change in voltage regardless of the load on the output

Question 6

Applications of shunt motors

Answer 6

Very stable power output
So useful when consistent power is needed
Power tools fans

Question 7

Applications of series motors

Answer 7

At low or oV high torque
Useful if you need to start a motor at high torque

Question 8

How to change the speed of a series motor

Answer 8

Put motor and variable resistor in series
Increase R
I decreases
Speed decrease

Question 9

Speed control for shut motors

Answer 9

Variable resistor in series with motor(R increases so I decreases so speed decreases)
Variable resistor in parallel ( R increases so I increases and the speed will increases

Question 10

What are separately excited generators

Answer 10

Inductor that is separate to the circuit

Question 11

Difference between normal generators and separately excited generators

Answer 11

Separate have the inductor that is separate to the circuit
Better at dealing with varying field strengths
More expensive

Question 12

Simple phase advantage

Answer 12

Simple construction so cheaper
More efficient at low power

Question 13

Three phase

Answer 13

Constant power so no fluctuations
Multiple voltage stages available on 3 phase supplies
No fluctuating power so thinner cables can be used

Question 14

Single phase voltage

Answer 14

240

Question 15

Three phase voltage

Answer 15

415V

Question 16

3 phase phase difference

Answer 16

120 degrees

Question 17

A.A

Answer 17

A

Question 18

A.1

Answer 18

A

Question 19

A.0

Answer 19

0

Question 20

A.Abar

Answer 20

0

Question 21

A+A

Answer 21

A

Question 22

A+1

Answer 22

1

Question 23

A+0

Answer 23

A

Question 24

A+A

Answer 24

A

Question 25

How do diodes protect the circuit

Answer 25

Prevents current from being drawn on the wrong direction so the component won’t be damaged from the reverser current

Question 26

How do diodes protect the circuit

Answer 26

Prevents current from being drawn on the wrong direction so the component won’t be damaged from the reverser current

Question 27

Differences between inverting and non inverting

Answer 27

NIĄ: vin into non-inverting input
IA:Vin into inverting input
NIĄ: feedback loop into ground
IA: non-inverting lnput into ground
IA: input connected to output via the voltage divider
NIĄ input not connected to output

Question 28

Bistable meaning

Answer 28

The bistable or flip flop is a switching circuit with two outputs one which is high when the other is low and vice versa

Question 29

Bistable meaning

Answer 29

The bistable or flip flop is a switching circuit with two outputs one which is high when the other is low and vice versa

Question 30

Q bar

Answer 30

Complementary input

Question 31

Q

Answer 31

Primary input

Question 32

Ck

Answer 32

Clock input

Question 33

D

Answer 33

Primary input

Question 34

Inverting gain

Answer 34

-RF/Rin