EEE
UNIT 6Energy Storage Devices and Electric DrivesQ1) Explain working of batteries like Lithium- Iron Phosphate (LFP)A1) Lithium iron phosphate has a cathode of iron phosphate and an anode of graphite. It has a specific energy of 90/120 watt-hours per kilogram and a nominal voltage of 3.20V or 3.30V. The charge rate of lithium iron phosphate is 1C and the discharge rate of 1-25C.
lithium iron phosphate battery cells.Lithium-ion has a higher energy density at 150/200 Wh/kg versus lithium iron phosphate at 90/120 Wh/kg. Lithium iron phosphate batteries have voltage discharges that are excellent when at higher temperatures. The discharge rate does not significantly degrade the lithium iron phosphate battery as the capacity is reduced.These batteries can handle high temperatures with minimal degradation. They have a long life for applications that have embedded systems or need to run for long lengths of time before needing to be charged.Both lithium iron phosphate and lithium ion have good long-term storage benefits. Lithium iron phosphate can be stored longer as it has a 350-day shelf life. For lithium-ion, the shelf life is roughly around 300 days.Manufacturers across industries turn to lithium iron phosphate for applications where safety is a factor. Lithium iron phosphate has excellent thermal and chemical stability. This battery stays cool in higher temperatures. It is also incombustible when it is mishandled during rapid charges and discharges or when there are short circuit issues. Lithium iron phosphate does not normally experience thermal runaway, as the phosphate cathode will not burn or explode during overcharging or overheating as the battery remains cool. Q2) Write a short note on Lithium Nickel-Manganese-Cobalt (NMC)A2) Lithium nickel manganese cobalt oxide (NMC) is a class of electrode material that may be used in the fabrication of lithium-ion batteries. Lithium-ion batteries consist of anode, cathode, and electrolyte with a charge-discharge cycle. These materials enable the formation of greener and sustainable batteries for electrical energy storage.NMC is a novel lithium insertion electrode material for advanced lithium-ion batteries.Mn doping significantly increases the thermal stability besides increasing the electrochemical charge-discharge behaviour.NMC powder has a layered structure and can be used as an active cathode material. Further it is used in combination with single electrolyte interphase (SEI) for the fabrication of lithium-ion batteries. Q3) Write a short note on Lithium- Manganese Oxide (LMO)A3) Lithium–manganese dioxide cell systems have slowly gained wider application in small appliances, especially automatic cameras. Batteries of this kind have an operating voltage of 2.8–3.2 volts and offer high energy density and relatively low cost for the capability of the cells.Lithium Manganese Oxide (LiMn2O4) is a cathode material with a spinel structure, which allows the material to be discharged at high rates.LMO-based batteries are most suited for use in high rate applications. Q4) Briefly explain supercapacitor and hydrogen fuel cell in EVsA4) Supercapacitors are electric storage devices which can be recharged very quickly and release a large amount of power. They are used as ancillary devices to store energy from braking and to provide the necessary boost during quick accelerations, ultimately increasing the efficiency of the vehicle.Supercapacitor are sometimes called an ultracapacitor– like a battery which has the means to store and release electricity. But rather than storing energy in the form of chemicals, supercapacitors store electricity in a static state, making them better at rapidly charging and discharging energy.A supercapacitor is simply a larger capacitor with bigger electrode plates and less distance between them, allowing for a greater charge to be stored in the form of electrical potential energy. A supercapacitor uses porous electrode plates that are soaked in an electrolyte and separated by a very thin separator material. When a charge is passed through the electrodes, the atoms in them become polarised - giving the electrodes a positive or negative charge.These then attract electrons of the opposite polarity in the electrolyte, and thus create a double electric layer, meaning supercapacitors store a lot more power than their regular capacitor counterparts.AdvantagesSupercapacitors already exist in cars with regenerative braking systems. They have greater power density than chemical reaction-based batteries, which allows them to rapidly store and discharge electricity, handy for collecting energy generated under braking then quickly releasing it upon acceleration.Hydrogen fuelFuel cell vehicles use hydrogen gas to power an electric motor. Fuel cell cars and trucks combine hydrogen and oxygen to produce electricity, which runs a motor. Since they are powered entirely by electricity, fuel cell vehicles are considered electric vehicles (“EVs).Converting hydrogen gas into electricity produces only water and heat as a by-product, meaning fuel cell vehicles don’t create tailpipe pollution when they’re driven. Q5) What is Vehicle Battery Management SystemA5) The battery management systems performance relies on the communication between each system. It should be fast, and every subsystem should operate accurately because all information generated are so sensitive and with a small error, there could be a large damage. A functionality of a sample battery management system has shown below.
The battery management system is a combination of hardware component and a software. State of charge (SOC) determination, state of health determination, cell balancing control, fault detection and communication with the user interface is done by using the software. All the functions are mathematically calculated along to the fed equations. Software is programmed to a microcontroller when the system is implementing. In the hardware system, typically there are safety circuits, sensor system, Controlling circuits and communication circuits The battery management system hardware consists of three kind of topologies presently used. They are categories as centralized, distributed and modular structureIn centralizes static battery balancing system method voltage and the temperature of cells are measured also the current through the battery stack also measured by using Hall Effect current sensors. Sensing and balancing modules (SBM) are installed in each individual cell or in each cell pack. A master controller controls sensing and balancing modules. Higher voltage cells are reduced to match with the lowest voltage cells. But most of centralized static architectures uses passive cell balancing methods
Q6) What are Electric DrivesA6) The systems which control the motion of the electrical machines, are known as electrical drives. A typical drive system is assembled with electric motor and a sophisticated control system that controls the rotation of the motor shaft.This control can be with the help of software, hence controlling becomes more and more accurate and this concept of drive also provides the ease of use.The load in the figure represents various types of equipment’s which consists of electric motor like fans, pumps, washing machines etc.
Factors used for selection of the electric motor in EVs BLDC hub motor drive for EVsCreation: Not all EVs are created equal. There are three types hybrid electric (HEV), plug-in hybrid (PHEV) and battery electric (BEV). HEVs have a gas-powered internal combustion engine along with an electric motor but do not plug in for charging. A PHEV has two ranges: electric and gasoline. Once the electric charge runs out,the vehicle switches energy sources. On an average, they can travel between 10 and 50 miles on electricity before being plugged in, while their gas tanks extend total range to between 300 and 600 miles. Lastly, BEVs run exclusively on electricity from the grid and do not produce any exhaust from the burning of fuel.2. Cost : Through federal and state tax incentives, along with time-of-use rates provided by the electric co-op to save money on charging the EV’s battery overnight not having to even get oil changes again, hence a variety of savings. The co-op even provides rebates for installing a charger at home. 3. Ranges: Range anxiety is real, but with BEVs now typically equipped with ranges of more than 100 miles. Future models are even promising ranges of around 300 miles.4. Public charging stations Accessibility: There are three types of charging stations with varying charging times. Level 1s, on average, fully charge in about eight hours; Level 2s take anywhere from two- to-six hours; and DC fast chargers can fully charge an EV in about 30 minutes. 5. EV ‘fuel’: Electric motors are already 80 to 95 percent efficient, so they use significantly less energy than vehicles with a traditional drive train. But the fuel used in those EVs is being generated by a growing number of renewable energy resources. Q7) Elaborate the characteristics of brushless DC motorsA7) The main feature of brushless DC motors is that they are Maintenance-free. There are several differences from DC motors. One of these differences is their small size. A high-performance brushless DC motor accommodates high-performance magnets in a space smaller than that for the rotor of conventional DC motors. A higher magnetic flux density provides higher motor efficiency and suppresses heat generation. Since the coil of a brushless motor is positioned on the stator side, the motor's heat radiation performance is enhanced. The advantage of brushless motors is their high degree of freedom of design. Q8) Write a short note on speed control of BLDC motorA8) Speed control of BLDC motor is essential for making the motor work at desired rate. Speed of a brushless dc motor can be controlled by controlling the input dc voltage / current. The higher the voltage more is the speed.Many different control algorithms have been used to provide control of BLDC motors. The motor voltage is controlled using a power transistor operating as a linear voltage regulator. This is not practical when driving higher-power motors. High-power motors must use PWM control and require a microcontroller to provide starting and control functions.
The control algorithm must provide three things:PWM voltage to control the motor speed Mechanism to commutate the motor Method to estimate the rotor position using the back-EMF or Hall Sensors Pulse-width modulation is used to apply a variable voltage to the motor windings. The effective voltage is proportional to the PWM duty cycle. When properly commutated, the torque-speed characteristics of the BLDC motor are identical to a dc motor. The variable voltage can be used to control the speed of the motor and the available torque. Q9) Explain Three phase induction motor drive for EVsA9) The basic structure of the three-phase electric vehicle induction motor is shown in Fig (a). The electric vehicle motor is 3-phase, Y-connection type 220V 40kW induction motor and the battery voltage of the electric vehicle is 360~420V. The auxiliary battery voltage is 24V and it is supplied by the isolated DC/DC converter for the low-voltage power to start the electric vehicle.Once the electric vehicle is turned on, auxiliary power is on, the resistor R of the battery soft charge the capacitor C of the DC voltage to reduce the rush current. When the DC voltage Vdc increases to the pre-set value, the driving control circuit will output the control signal to turn the main relay for the completion of the IGBT driving power and all the power of the electric vehicle is finished now. Finally, drivers can drive the electric vehicle on the car control pedal. The magnetic torque that the three-phase induction motor generates is the direct proportion to the multiplication of the rotor flux and d axis stator current. The key to control the torque amount is to keep the rotor flux as a fixed value and control the current of d axis stator current. The rotor flux and d axis stator current can be controlled individually just as the DC brushed motor control. The basic structure of the field-oriented control in the vehicle induction motor driver is shown in Fig (b).
lithium iron phosphate battery cells.Lithium-ion has a higher energy density at 150/200 Wh/kg versus lithium iron phosphate at 90/120 Wh/kg. Lithium iron phosphate batteries have voltage discharges that are excellent when at higher temperatures. The discharge rate does not significantly degrade the lithium iron phosphate battery as the capacity is reduced.These batteries can handle high temperatures with minimal degradation. They have a long life for applications that have embedded systems or need to run for long lengths of time before needing to be charged.Both lithium iron phosphate and lithium ion have good long-term storage benefits. Lithium iron phosphate can be stored longer as it has a 350-day shelf life. For lithium-ion, the shelf life is roughly around 300 days.Manufacturers across industries turn to lithium iron phosphate for applications where safety is a factor. Lithium iron phosphate has excellent thermal and chemical stability. This battery stays cool in higher temperatures. It is also incombustible when it is mishandled during rapid charges and discharges or when there are short circuit issues. Lithium iron phosphate does not normally experience thermal runaway, as the phosphate cathode will not burn or explode during overcharging or overheating as the battery remains cool. Q2) Write a short note on Lithium Nickel-Manganese-Cobalt (NMC)A2) Lithium nickel manganese cobalt oxide (NMC) is a class of electrode material that may be used in the fabrication of lithium-ion batteries. Lithium-ion batteries consist of anode, cathode, and electrolyte with a charge-discharge cycle. These materials enable the formation of greener and sustainable batteries for electrical energy storage.NMC is a novel lithium insertion electrode material for advanced lithium-ion batteries.Mn doping significantly increases the thermal stability besides increasing the electrochemical charge-discharge behaviour.NMC powder has a layered structure and can be used as an active cathode material. Further it is used in combination with single electrolyte interphase (SEI) for the fabrication of lithium-ion batteries. Q3) Write a short note on Lithium- Manganese Oxide (LMO)A3) Lithium–manganese dioxide cell systems have slowly gained wider application in small appliances, especially automatic cameras. Batteries of this kind have an operating voltage of 2.8–3.2 volts and offer high energy density and relatively low cost for the capability of the cells.Lithium Manganese Oxide (LiMn2O4) is a cathode material with a spinel structure, which allows the material to be discharged at high rates.LMO-based batteries are most suited for use in high rate applications. Q4) Briefly explain supercapacitor and hydrogen fuel cell in EVsA4) Supercapacitors are electric storage devices which can be recharged very quickly and release a large amount of power. They are used as ancillary devices to store energy from braking and to provide the necessary boost during quick accelerations, ultimately increasing the efficiency of the vehicle.Supercapacitor are sometimes called an ultracapacitor– like a battery which has the means to store and release electricity. But rather than storing energy in the form of chemicals, supercapacitors store electricity in a static state, making them better at rapidly charging and discharging energy.A supercapacitor is simply a larger capacitor with bigger electrode plates and less distance between them, allowing for a greater charge to be stored in the form of electrical potential energy. A supercapacitor uses porous electrode plates that are soaked in an electrolyte and separated by a very thin separator material. When a charge is passed through the electrodes, the atoms in them become polarised - giving the electrodes a positive or negative charge.These then attract electrons of the opposite polarity in the electrolyte, and thus create a double electric layer, meaning supercapacitors store a lot more power than their regular capacitor counterparts.AdvantagesSupercapacitors already exist in cars with regenerative braking systems. They have greater power density than chemical reaction-based batteries, which allows them to rapidly store and discharge electricity, handy for collecting energy generated under braking then quickly releasing it upon acceleration.Hydrogen fuelFuel cell vehicles use hydrogen gas to power an electric motor. Fuel cell cars and trucks combine hydrogen and oxygen to produce electricity, which runs a motor. Since they are powered entirely by electricity, fuel cell vehicles are considered electric vehicles (“EVs).Converting hydrogen gas into electricity produces only water and heat as a by-product, meaning fuel cell vehicles don’t create tailpipe pollution when they’re driven. Q5) What is Vehicle Battery Management SystemA5) The battery management systems performance relies on the communication between each system. It should be fast, and every subsystem should operate accurately because all information generated are so sensitive and with a small error, there could be a large damage. A functionality of a sample battery management system has shown below.The battery management system is a combination of hardware component and a software. State of charge (SOC) determination, state of health determination, cell balancing control, fault detection and communication with the user interface is done by using the software. All the functions are mathematically calculated along to the fed equations. Software is programmed to a microcontroller when the system is implementing. In the hardware system, typically there are safety circuits, sensor system, Controlling circuits and communication circuits The battery management system hardware consists of three kind of topologies presently used. They are categories as centralized, distributed and modular structureIn centralizes static battery balancing system method voltage and the temperature of cells are measured also the current through the battery stack also measured by using Hall Effect current sensors. Sensing and balancing modules (SBM) are installed in each individual cell or in each cell pack. A master controller controls sensing and balancing modules. Higher voltage cells are reduced to match with the lowest voltage cells. But most of centralized static architectures uses passive cell balancing methods Q6) What are Electric DrivesA6) The systems which control the motion of the electrical machines, are known as electrical drives. A typical drive system is assembled with electric motor and a sophisticated control system that controls the rotation of the motor shaft.This control can be with the help of software, hence controlling becomes more and more accurate and this concept of drive also provides the ease of use.The load in the figure represents various types of equipment’s which consists of electric motor like fans, pumps, washing machines etc. Factors used for selection of the electric motor in EVs BLDC hub motor drive for EVs
The control algorithm must provide three things: 
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