How an Electric Car Works

Inside an Electric Car

A straightforward DC controller linked to the batteries and the DC electric motor. If the drivers pushes the accelerator pedal, the controller gives the entire 96 volts from the batteries to the electric motor. If the drivers take his/her foot off the accelerator, the controller provides zero volts to the motor/engine. For any environment in between, the controller “chops” the 96 volts thousands of times per second to generate an average voltage somewhere between 0 and 96 volts.

The heart of a power car is the blend of:

• The electric motor
• The motor’s controller
• The batteries

The controller takes power from the batteries and offers it to the motor. The accelerator pedal hooks to a set of potentiometers (variable resistors), and these potentiometers supply the signal that tells the controller how much power it is meant to provide. The controller can deliver zero power (when the automobile is stopped), full power (when the driver floors the accelerator pedal), or any power level among.

The controller normally dominates the scene when you open the hood, as you can plainly see here:

The 300-volt, 50-kilowatt controller because of this electric car is the box marked “U.S. Electricar.”

With this car, the controller consumes 300 volts DC from the battery power. It converts it into no more than 240 volts AC, three-phase, to send to the motor. It can this using large transistors that rapidly turn the batteries’ voltage on / off to make a sine wave.

If you push on the gas pedal, a cable from the pedal connects to both of these potentiometers:

The potentiometers hook to the gas pedal and send a sign to the controller.

The signal from the potentiometers tells the controller how much capacity to deliver to the electric car’s motor. You will discover two potentiometers for safety’s sake. The controller reads both potentiometers and makes certain that their signals are equal. If the signals don’t match, then the controller doesn’t work. This procedure protects against a condition where a potentiometer possibly fails in the full-on position.

Heavy cables (on the left) connect the controller to the battery pack. There is a very large on/off switch in the middle. The pack of small wires on the right transfers signals from thermometers placed between the batteries, as well as power for fans that keep the batteries cool and ventilated.

 

The heavy wires entering and leaving the controller

It easy to understand the controller’s job in a DC electric car. Let’s assume that the battery pack contains 12 12-volt batteries, wired in series to make 144 volts. The controller consumes 144 volts DC, and offers it to the motor in a handled way.

The simplest DC controller would be a huge on/off switch wired to the accelerator pedal. If you push the pedal, it could turn the activate, so when you take your foot from the pedal, it could transform it off. As the driver, you’ll have to push and release the accelerator to pulse the motor on / off to maintain confirmed speed.

Obviously, that type of on/off approach works but it might be a pain to operate a vehicle, therefore the controller does the pulsing for you. The controller reads the setting of the accelerator pedal from the potentiometers and regulates the energy accordingly. Suppose which you have the accelerator pushed halfway down. The controller reads that setting from the potentiometer and rapidly switches the energy to the motor on / off such that it is on half enough time and off half enough time. When you have the accelerator pedal twenty five percent of just how down, the controller pulses the energy so that it is on twenty five percent of that time period and off 75 percent of that time period.

Most controllers pulse the energy more than 15,000 times per second, in order to keep the pulsation outside the range of human hearing. The pulsed current helps the motor housing to pulsate at that frequency, so by vibrating at more than 15,000 cycles per second, the controller and motor are silent to human ears.

 

An AC controller hooks to an AC motor. The controller takes in 300 volts DC and produces 240 volts AC(3-phase) using six sets of power transistors. To understand how the Power Grid Works refer to 3-phase power working mechanism. The controller furthermore offers a charging system for the batteries, and a DC-to-DC converter to recharge the 12-volt accessory battery.

Its functionality is a little more complicated in an AC controller, but it is the same idea. The controller creates three pseudo-sine waves. It does this by DC voltage imput from the batteries and pulsing it on and off. An AC controller requires to reverse the polarity of the voltage 60 times a second. Therefore, six sets of transistors are required in an AC controller, while you need only one set in a DC controller. In the AC controller, for each phase you need one set of transistors to pulse the voltage and another set to reverse the polarity. While for three phase you replicate that three times — six total sets of transistors.

Most DC controllers come from the electric forklift industry which are used in electric cars. The Hughes AC controller visble in the photo is the same kind of AC controller used in the GM/Saturn EV-1 electric vehicle. It can deliver upto 50,000 watts to the motor.

Images Source: howstuffworks?