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Electric car or vehicle component and function depend on the car type. There are at least four types of electric cars currently sold commercially and operates in the world. This article will discuss various common main electric car components or parts or elements and their function such as traction batteries, inverters (DC-DC converters), traction motors, on-board chargers and controllers. The different types of electric car components determines how the car works. Electric cars (vehicles) components and functions can be explained by means of picture below.
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When the car pedal is pressed, then:
Note: The working principle above is for battery electric vehicle (BEV) type.
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The basic main elements of electric cars installed in almost all types of electric cars are as follows:
The function of the battery in an electric car is as an electrical energy storage system in the form of direct-current electricity (DC). If it gets a signal from the controller, the battery will flow DC electrical energy to the inverter to then be used to drive the motor. The type of battery used is a rechargeable battery that is arranged in such a way as to form what is called a traction battery pack.
There are various types of electric car batteries. The most widely used is the type of lithium-ion batteries. Please read the article “Electric Car Batteries and Their Characteristics” to get a little idea about batteries for electric cars.
The inverter functions to change the direct current (DC) on the battery into an alternating current (AC) and then this alternating current is used by an electric motor. In addition, the inverter on an electric car also has a function to change the AC current when regenerative braking to DC current and then used to recharge the battery. The type of inverter used in some electric car models is the bi-directional inverter category.
The main function of the controller is as a regulator of electrical energy from batteries and inverters that will be distributed to electric motors. While the controller itself gets the main input from the car pedal (which is set by the driver). This pedal setting will determine the frequency variation or voltage variation that will enter the motor, and at the same time determine the car’s speed.
In brief, this unit manages the flow of electrical energy delivered by the traction battery, controlling the speed of the electric traction motor and the torque it produces. This component will determine how electric car work.
Because the controller provides electrical power from the traction battery, the electric traction motors will work turning the transmission and wheels. Some hybrid electric cars use a type of generator-motor that performs the functions of propulsion and regeneration. In general, the type of electric motor used is the BLDC (brushless DC) motor
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Charger (E) is a battery charging device. Chargers get electricity from outside sources, such as the utility grid or solar power plants. AC electricity is converted into DC electricity and then stored in the battery. There are 2 types of electric car chargers:
Transmission (F): The transmission transfers mechanical power from the electric traction motor to drive the wheels.
DC/DC Converter (G): This one of electric car parts that to converts higher-voltage DC power from the traction battery pack to the lower-voltage DC power needed to run vehicle accessories and recharge the auxiliary battery.
Battery (H): In an electric drive vehicle, the auxiliary battery provides electricity to power vehicle accessories.
Thermal System – Cooling (I): This system maintains a proper operating temperature range of the engine, electric motor, power electronics, and other components.
Charge Port (J): The charge port allows the vehicle to connect to an external power supply in order to charge the traction battery pack.
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An electric drive (often referred to as an electric controller) is a device used to control the output of a motor used, for example, to produce linear motion in an electric actuator. In our article on electric motors we referred to the feedback mechanism from a servo motor, shown schematically below.
The drive will accurately control the motor output and the motor response against a controlling input (nset in the schematic above).
Electric drives require a three-phase AC supply. The incoming fixed frequency AC supply is rectified to provide a DC signal; this is then smoothed and circuitry provides a decoupling of the input and output stages as shown below.
The output stage uses software controlled Insulated Gate Bi-junction Transistors (IGBT’s) to switch and provide a variable frequency three phase AC supply to the motor. To understand the output stage in more detail, we can refer to the following equivalent circuit.
In the circuit, the IGBT’s are represented by the switches 1 to 6; a centre tap of each column of switches is connected to an individual phase of the motor windings. In the diagram switches 5 and 4 are closed which passes current through the W and V phases. In the next mode of operation, switches 5 and 4 may open and 3 and 2 close; this will pass current through the V and U phases. The software controls the successive opening and closing of the switches and the duration of each step; this creates a pulse width modulation.
The varying pulse width effectively simulates an AC waveform as seen by the load of the motor windings; for example, at A in the diagram above, a pulse width of ‘0’ will result in zero voltage across the windings, where as at B, the maximum voltage will be applied.
The drive must be capable of supplying and controlling the motor which, in turn, will be matched to the requirements of an application.
The motor voltage, power rating and full-load current will all need to be matched; any over-load requirements will need to be considered, for example if higher torque is required for start-up.
The feedback mechanism and any input/output (I/O) requirements should be accommodated.
Communication protocols– for example CANOpen, Profibus, etc, and the operating temperature should be considered and, hence, the need for any ventilation or forced cooling.
Drives will need to control either DC or AC motors, the latter single- or three-phase. Different variants will be required, dependent on the parameters mentioned above – for example, voltage.
Drives can also be classified into single-, group- and multi-motor drives. Single are the most basic and are often used in domestic appliances; group lend themselves to use in more complex systems and multi are used in heavy, or multiple motor applications.
Cabling will be required for power and control signals to the motor, along with suitable supply for operation of the drive itself.
It is good practice to have input fuses for protection; if EMI is a potential problem, then filters can be built into the circuitry. A cooling fan, with suitable ventilation, will be required if high operating temperatures are encountered.
Depending on application requirements a dynamic brake is available.
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