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Electricity Power/Energy Basics:

In US household electricity is 120 volts AC

60 cycles (therefore most appliances and

electronic equipment require this type ofcurrent).

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Actual voltage with time in a 120 volt 60 cycle system

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Effective voltage of the AC power system is 0.707 times

the peak voltage. Peak voltage is about 170 volts. Thus

the 120 volts is really an effective voltage. Effective

voltage is sometimes known as the rms (root mean

square) voltage.

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Reasons for Alternating Current:

Electromechanical generators produce alternatingcurrent

Less energy loss in transmission lines if power (P) is

transmitted at higher voltages (V) and lower

current(I). Lower current yields less power loss (Pl).

P = I x V

Pl = I2 x R (R= resistance in transmission line).

Voltage can be altered by transformers only for AC.

For example to lower transmission voltages

(e.g.,345Kv) to 120 v for household use.

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The frequency of generation (60 cycles persec) is a function of the generator rotator

speed. Why 60 ? Why not 50 as in

Europe? Historians suggest that 60 was

selected so some clocks could besynchronized with this frequency ( 60

sec/min, 60 min/hr???).

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Simple inverter (top = mechanical switch,bottom = transistor switch)

Converting DC to AC

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Half-wave rectifier:

Converting AC to DC

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Full- wave rectifier:

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Using capacitors and inductors we can

level the voltage output of a rectifier:

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A capacitoropposes changes in voltage

An inductoropposes changes in current.

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The following circuit can be used to levelthe voltage output

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A typical capacitor input filter consists of a filter

capacitor C1, connected across the rectifier

output, a choke L in series and another filter

capacitor connected across the load.

The capacitor C1 offers low reactance to the ACcomponent of the rectifier output while it offers

infinite reactance to the DC component. As a

result the capacitor bypasses an appreciable

amount of the AC component while the DC

component continues its journey to the choke L.

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The choke L offers high reactance to the ACcomponent but it offers almost zero reactance to

the DC component. As a result the DC component

flows through the choke while the AC component

is blocked.

The capacitor C2 bypasses the AC component

which the choke had failed to block. As a resultonly the DC component appears across the load.

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Filtering the full-wave rectified signal using capacitors

(capacitor effect indicated by red lines) yields the

following output.

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Existing electrical power sources:

2 - 68 kW Caterpillar generators

1 - 30 kW Detroit generators

Output = 480 volts

480 volts used for saltwater pump and reverse

osmosis, Voltage stepped down to 120/240 for otheruses.

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For future comparison purposes average dieselfuel consumption per capita by generators:

0.028 gal/hr

(This translates to $0.20 $0.25/kW-hr)

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Average Generator Capacity Utilization over a Day

0

10

20

30

40

50

60

10:15 AM 4:15 PM 10:15 PM 4:15 AM 10:15 AM

PowerUse

d(kW)

0%

15%

29%

44%

59%

74%

88%

CapacityUtilized