Principles/Science Flashcards
What is the formula for XL? (Inductive reactance)
XL = 2π × F x L
What is the formula for XC? (inductive capacitance)
XC = 1 ÷ 2π×F×C
What is F in inductive reactance triangle? Measured in what?
Frequency. Measured in Hertz
What is L in inductive reactance triangle? Measured in what?
Inductance. Measured in Henry’s
What is C in inductive reactance triangle? Measured in what?
Capacitance. Measured in Farads
What is R in reactive inductance triangle? Measured in what?
Resistance. Measured in Ohms
What is Z in inductive reactance triangle? Measured in what?
Impedance. Measured in ohms
What is the formula for Z in inductive reactance triangle?
Z = ²ROOT R + (Xl - XC)²
What is the formula for power factor in inductive reactance triangle?
P.F = Adjacent ÷ hypotenuse or ²ROOT c²
What is the formula for phase angle?
Phase angle = cos-1(p.f)
What is the formula for current in reactive inductance triangle?
Current = V÷Z
What degree does current lead voltage by?
90⁰
What goes up, when frequency goes up?
Current
What goes down, when frequency goes up?
Reactance
What are the 2 types of 3-phase induction motors?
Wound rotor, squirrel cage
2 advantages of squirrel cage motor?
Easier to manufacture, cheaper
What are 2 advantages of wound rotors?
It can control the speed, it can control the loading of the rotor
What cuts off the conductors in the wind rotor?
A magnetic field
How is a second magnetic field produced?
Cutting the rotor bars, which creates an induced emf in the rotor, which creates an induced current
What can a universal motor do?
Can operate on either a single-phase AC or DC supply
What does a motor of 5kW + need?
Means of controlling initial start current
What must motors of 370w + need?
Overload protection
What are the 4 types of starters used on 3-phase induction motors?
Direct-on-line
Star-delta
Auto-transformer
Rotor resistance
