2009년 10월 1일 목요일
전기자동차의 기본적인 원리(CONTROLLER에 관해,DC/AC)
An Electric Car Example
The electric car that we will use for this discussion is shown here:
A typical electric car, this one has some particularly snazzy decals. This vehicle is owned by Jon Mauney.
This electric vehicle began its life as a normal, gasoline-powered 1994 Geo Prism. Here are the modifications that turned it into an electric car:
•The gasoline engine, along with the muffler, catalytic converter, tailpipe and gas tank, were all removed.
•The clutch assembly was removed. The existing manual transmission was left in place, and it was pinned in second gear.
•A new AC electric motor was bolted to the transmission with an adapter plate.
•An electric controller was added to control the AC motor.
The 50-kW controller takes in 300 volts DC and produces
240 volts AC, three-phase. The box that says "U.S. Electricar" is the controller.
•A battery tray was installed in the floor of the car.
•Fifty 12-volt lead-acid batteries were placed in the battery tray (two sets of 25 to create 300 volts DC).
•Electric motors were added to power things that used to get their power from the engine: the water pump, power steering pump, air conditioner.
•A vacuum pump was added for the power brakes (which used engine vacuum when the car had an engine).
The vacuum pump is left of center.
•The shifter for the manual transmission was replaced with a switch, disguised as an automatic transmission shifter, to control forward and reverse.
An automatic transmission shifter is used to select forward
and reverse. It contains a small switch, which sends a signal to the controller.
•A small electric water heater was added to provide heat.
The water heater
•A charger was added so that the batteries could be recharged. This particular car actually has two charging systems -- one from a normal 120-volt or 240-volt wall outlet, and the other from a magna-charge inductive charging paddle.
The 120/240-volt charging system
The Magna-Charge inductive paddle charging system
•The gas gauge was replaced with a volt meter.
The "gas gauge" in an electric car is either a simple volt meter or a more sophisticated computer that tracks the flow of amps to and from the battery pack.
Everything else about the car is stock. When you get in to drive the car, you put the key in the ignition and turn it to the "on" position to turn the car on. You shift into "Drive" with the shifter, push on the accelerator pedal and go. It performs like a normal gasoline car. Here are some interesting statistics:
•The range of this car is about 50 miles (80 km).
•The 0-to-60 mph time is about 15 seconds.
•It takes about 12 kilowatt-hours of electricity to charge the car after a 50-mile trip.
•The batteries weigh about 1,100 pounds (500 kg).
•The batteries last three to four years.
To compare the cost per mile of gasoline cars to this electric car, here's an example. Electricity in North Carolina is about 8 cents per kilowatt-hour right now (4 cents if you use time-of-use billing and recharge at night). That means that for a full recharge, it costs $1 (or 50 cents with time-of-use billing). The cost per mile is therefore 2 cents per mile, or 1 cent with time-of-use. If gasoline costs $1.20 per gallon and a car gets 30 miles to the gallon, then the cost per mile is 4 cents per mile for gasoline.
Clearly, the "fuel" for electric vehicles costs a lot less per mile than it does for gasoline vehicles. And for many, the 50-mile range is not a limitation -- the average person living in a city or suburb seldom drives more than 30 or 40 miles per day.
To be completely fair, however, we should also include the cost of battery replacement. Batteries are the weak link in electric cars at the moment. Battery replacement for this car runs about $2,000. The batteries will last 20,000 miles or so, for about 10 cents per mile. You can see why there is so much excitement around fuel cells right now -- fuel cells solve the battery problem (more details on fuel cells later in the article).