Principles/Science

Question 1

What is the formula for XL? (Inductive reactance)

Answer 1

XL = 2π × F x L

Question 2

What is the formula for XC? (inductive capacitance)

Answer 2

XC = 1 ÷ 2π×F×C

Question 3

What is F in inductive reactance triangle? Measured in what?

Answer 3

Frequency. Measured in Hertz

Question 4

What is L in inductive reactance triangle? Measured in what?

Answer 4

Inductance. Measured in Henry’s

Question 5

What is C in inductive reactance triangle? Measured in what?

Answer 5

Capacitance. Measured in Farads

Question 6

What is R in reactive inductance triangle? Measured in what?

Answer 6

Resistance. Measured in Ohms

Question 7

What is Z in inductive reactance triangle? Measured in what?

Answer 7

Impedance. Measured in ohms

Question 8

What is the formula for Z in inductive reactance triangle?

Answer 8

Z = ²ROOT R + (Xl - XC)²

Question 9

What is the formula for power factor in inductive reactance triangle?

Answer 9

P.F = Adjacent ÷ hypotenuse or ²ROOT c²

Question 10

What is the formula for phase angle?

Answer 10

Phase angle = cos-1(p.f)

Question 11

What is the formula for current in reactive inductance triangle?

Answer 11

Current = V÷Z

Question 12

What degree does current lead voltage by?

Answer 12

90⁰

Question 13

What goes up, when frequency goes up?

Answer 13

Current

Question 14

What goes down, when frequency goes up?

Answer 14

Reactance

Question 15

What are the 2 types of 3-phase induction motors?

Answer 15

Wound rotor, squirrel cage

Question 16

2 advantages of squirrel cage motor?

Answer 16

Easier to manufacture, cheaper

Question 17

What are 2 advantages of wound rotors?

Answer 17

It can control the speed, it can control the loading of the rotor

Question 18

What cuts off the conductors in the wind rotor?

Answer 18

A magnetic field

Question 19

How is a second magnetic field produced?

Answer 19

Cutting the rotor bars, which creates an induced emf in the rotor, which creates an induced current

Question 20

What can a universal motor do?

Answer 20

Can operate on either a single-phase AC or DC supply

Question 21

What does a motor of 5kW + need?

Answer 21

Means of controlling initial start current

Question 22

What must motors of 370w + need?

Answer 22

Overload protection

Question 23

What are the 4 types of starters used on 3-phase induction motors?

Answer 23

Direct-on-line
Star-delta
Auto-transformer
Rotor resistance