WEEK 10 Single and Three Phase AC Electricity

WEEK 10: Single and Three Phase AC Electricity Generation

Induction • Which hand is used? • What happens when: • The conductor is moved in the opposite direction? • The conductor stops moving? • The conductor is moved slowly? • Quickly?

• Conductor position in rotation vs voltage/current output

• Does it matter if the conductor is moved or the magnet is moved?

Alternating Current Generation • A simple generator consists of a loop of wire in a magnetic field • The ends of the loop are connected to brushes • Brushes and slip rings facilitate an electrical connection and current flow even though some components (brushes) must be stationary and the loop of wire (armature) must turn • The loop is rotated through the magnetic field Image Courtesy of US DOE Fundamentals Handbook

Graphing Output • What was on the ‘x’ axis of our graph? ‘Y’ axis? • What would happen if the x axis was time?

Sine Wave Output • The electricity generated by the simple generator is in the form of a sine wave • This output is alternating current (AC) Image Courtesy of US DOE Fundamentals Handbook

• How many windings in: • Rotor? • Stator?

AC Generation • What does the output current and voltage depend upon? • ___________________ • What does the strength of an electromagnet depend upon? • Could an electromagnet be used • To what advantage? • DC or AC to the rotor?

• Degrees or time on X-axis…? • What changes if the x axis is seconds?

Hertz: • SI unit of frequency • Equal to one cycle per second • Household frequency in North America is 60 Hz • What effect does changing the rotor speed have on generator function?

• • WRT rotational speed, single and 3 phase behave the same Effect on output (current, voltage)? • • If RPM is increased then current and voltage output _________ Effect on frequency (Hertz)? • Frequency alone: If RPM is increased then the frequency __________

Original Double the number of stationary conductors will double the induced voltage / current Double the rotational speed (RPM or frequency) will double the induced voltage / current and doubles the frequency output *** Ideal – not ‘real’

Three Phase Electricity • • Rotor Stator How many windings? Where?

Three Phase Electricity

Rotational Speed… • Effect on voltage and current output • Effect on frequency