Week 4 Session 5

Power converters in an Electric vehicle:

Power Converters:

Power convertion is process of converting electrical energy from one form to another. A power converter can convert AC into DC and it can be converted to any form,change the voltage or frequency of current or do some combination of these.

The power converter can be as simkple as a transformer or it can be complex as resonant converter.It is used to convert one ferquency of AC into another.

Power converter are classified based on the type of power conversion.There are four type:

• AC to AC converter.
• AC to DC converter.
• DC to DC converter.
• DC to AC converter.

1) DC to DC converter:

Converts an unregulated DC input to a regulated DC output.

• Non-isolated converters: Buck,Boost,BuckBoost.
• Isolated converters: Fly back,Forward Half bridge,Forward full bridge.
• Resonant converter: Different family of DC-DC converter used for high power conversion.

The converters that convert the dc signal of fixed frequency present at the input into a variable dc signal at the output are also known as choppers. Here the achieved output dc voltage may have different amplitude than the source voltage. Generally, power transistors, MOSFETs, and thyristors are the semiconductor devices used for their fabrication. The output is controlled by a low power signal that controls these semiconductor devices from a control unit.

2) DC to AC Converters

The devices that are designed to convert the dc signal into ac signal are known as inverters. The applied input is a fixed dc voltage that can be obtained from batteries but the output obtained is variable ac voltage. The voltage and frequency of the signal obtained are of variable nature. Here the semiconductor device i.e., the thyristors is turned off by using either line, load, or forced commutation.

Thus, it can be said that by the use of inverters, a fixed dc voltage is changed into an ac voltage of variable frequency. Generally, the semiconductor devices used for its fabrication are power transistors, MOSFETs, IGBT, GTO.

3) AC to DC Converters

A type of converter that changes input AC signal into a DC is known as AC to DC converter. We have already learned in basic electronics that the devices that convert the AC signal into DC signal are known as rectifiers.

4) AC to AC Converters

An ac to ac converter is designed to change the ac signal of fixed frequency into a variable ac output voltage.

Application in EV:

In electrical vehical application like

• Motor
• sensors
• converter/controllers
• auxillary load(1.Light,2. Horn, 3.whipers 4.Air conditioner,5.Power breaking,6.Power steering,7.Heater and etc..,)
• Battery

Battery:

In battery an AC supply is by the plug charger or charging station. it is stored in battery as DC supply, before that we want to convert AC to DC (rectifiers). are used to convert to DC and then stored in battery .

Sensors:

In sensor we sense the signals if the given input is corrected and allow the signal to output . EV makers rely on displacement or LVDT (linear variable differential transformer) sensors to measure pouch and prismatic cell swelling during battery validation testing. Because batteries bulge and expand over time, this testing helps determine durability of each cell and the appropriate type and size of battery housing. Our sensors offer high accuracy and resolution over wide temperature range, low drift over time and are suitable for use in harsh fluids and hostile environments. Hermetic options are available.

Converter/Controllers :

Controller are used to control the speed or torque of the motor. while Ac is given as input convert to DC and then we use DC -DC converter used for unregulatted DC to regulated DC is the input to the motor. maximum we use Induction motor in EV.

Motor:

The motor drive and control system is the core of electric vehicle. Induction motor which has advantages of simple structures, low prices, easy maintenances, broader constant power operation scope and so on has a broadest application in electric vehicle fields.It is the heart of the EV it help to acess the action of wheels.

Auxillary load:

The auxiliary power supply (static inverter) converts the power for interior light, displays, air conditioning, etc. Even though there is a propulsion inverter, the static inverter is installed in order to supply power that has low voltage and constant frequency.