DC and AC Sources
Content
ANTONY TEMPLEMAN HND AIRCRAFT ENGINEERING ELECTRICAL FUNDAMENTALS 2011/2012
AC & DC SOURCES REPORT
Introduction Within this report we cover many aspects of the fundamentals of the portable power sources we use today in society. The information is to educate and help individuals understand how they are constructed and the way in which they operate. D/C and A/C Sources When talking about electrical fundamentals we must be aware of certain terms and understanding these terms will add to our explanations when asked to describe aspects about the subject. Within this report we are going to explore DC and AC sources, covering what they are and where they come from. First of all we must start with the abbreviations which are; • • DC - Stands for direct current, this always travels continuously in the same direction (Positive to Negative) AC – Stands for alternating current which means periodically over time it will reverse its direction
So to help explain this refer to the diagram, an AC current sine wave can be seen to have peaks and troughs whereas a DC current looks to be at a constant.
Current Current within a DC circuit can be said to be the rate in which the electricity flows, where the positively charged particles flow around the circuit from positive to negative terminals. The rate of flow or current is measured in "amperes" (A). Voltage Voltage is the difference in potiential energy or resistive load that is measured at any given point within the circuit, sometimes referred to as potiential difference (p.d.) and measured in "volts" (V)
Cell Construction Ayr college HND Electrical funamentals notes describes a "battery" as; " A battery is a voltage source in a single container made from one or two cells." Usually batteries are made up of cells, including electrodes and an electrolyte encased in a container, most containers are made from a material that is resistant to the electrolyte and mechanical shock as well as high temperatures. The case itself is vented to allow any detromental gases created to escape and evaporate in the air. When referring to a power source such as a battery we must be aware that it is made up of cells (although a single cell can also be a battery). When further broken down to its base contents it is made up of; 1)Electrodes - 2 Dissimular metal plates, one positively charged (Annode) the other negative (Cathode). 2)Electrolyte - The solution that acts upon the electrodes and allows the chemical reaction to take place 3)Container – The medium where the electrodes and electrolyte is housed.
Types of Cell Bearing this in mind we must be aware that there are two different types of cell: 1.Primary cell 2.Secondary cell The primary cell is the type where due to the chemical rection the negative electrode is damaged beyond repair resulting in a useless battery which cannot be recharged. However the secondary cell's electrodes can be returned to their origional state but reversing the current, therefor this means it can be recharged and used again.
Sizes There are many sizes of batteries available to us all providing different voltages and currents, the one which we choose to use is usually advised on the item we are using the power source in or within a user manual. The sizes are: -D cell -A23 Cell -C cell -AA Cell -AAA Cell -9-volt PP3 battery -Button Cells (CR2023 & LR44) -AAAA Cell
Batteries Connections When we have an appliance that requires a portable power source (i.e batteries) we require different sizes of batteries for different output voltages to ensure the appliance will work correctly. Sometimes we cannot use large batteries on small appliances otherwise we would compromise the size its casing so when this becomes a factor we use many small batteries aligning them in "series" (one after another in the circuit) so that the normal output has been added to so that it is sufficient enough so that applience will work. There are three ways in which we can connect batteries to attribute certain qualities we wish a circuit to have. 1.Series – Cells connected in series which provides a higher voltage with no change in current. 2.Parrallel – Cells connected in parrallel to provide an increase in current or the same current but for a longer duration with no increase in voltage. 3.Series-Parrallel – Cells connected in parrallel but in series also this provides increased current and voltage than a singular cell.
Alkaline Cell The alkaline battery is simular to most types out in the market today it is made up of electrodes, electrolyte and a container. The main differences are that the electrolyte used its of potassium hydroxide as opposed to the acidic electrolyte used by zinc-carbon batteries, which allows it to have a higher energy density and longer shelf life in comparison. The cathode is made of maganese dioxide, whereas the annode is created of a zinc powder which allows more surface area to allow an increase in the rate of reaction resulting in increased electron flow. To way in which this battery works is basic to every cell and battery the annode and cathode are made up of two dissimular metals (i.e zinc and copper), connected via a wire and then placed in an electrolyte within a container. A chemical reaction will take place in which the positively charged particles flow from one metal to the other negatively charged particles on the other peice of metal. It is this flow of current created from the moving of the particles and the burning of the negatively charged metal (Zinc) that creates our charge or electricity.
Lead Acid Cell The structure of the lead acid cell is simular to the others except usually larger and it containes a different electrolyte (dilute solution of sulphuric acid) and the negative electrode is comprised of a sponge lead and the positively charged electrode is comprised of lead peroxide. When the chemical reaction is taking place between the three chemicals it forms lead sulphate on the electrodes and the acid becomes water but by recharging the battery it reverses this change to the origional chemicals.
Nickel-Cadmium Cell Within the cell make-up, Annode is created from nickel hydroxide, Cathode of cadmium hydroxide and the, Electrolyte is an alkaline solution made up of potassiom hydroxide and distilled/de-ionised water. However the electrolyte is not playing an active part in the chemical reaction but is used to provide a path for the current flow instead. Whilst charging the cell an ion exchange takes place where oxygen is removed from the negative electrode and then is transferred to the positive electrode which means the electrolyte is acting as an ionised conductor resulting in the positive electrode being at a higher state of oxidisation. When the charging process is finished all the oxygen is driven out of the negative electrode leaving only metallic cadmium and the positive electrode consisting of oxidised nickel hyrdoxide. Toward the end of the charging process gassing begins to occur and as a result of electrolysis which reduces the water content, which means the water must be refilled periodically.
Types Of Cells Primary cells or non-rechargeable batteries • Alkaline battery • Aluminium battery • Atomic battery • Optoelectric nuclear battery • Nuclear micro-battery • Bunsen cell • Chromic acid cell • Clark cell • Daniell cell • Dry cell • Earth battery • Frog battery • Galvanic cell • Grove cell • Leclanché cell • Lemon battery • Lithium battery • Lithium air battery • Mercury battery • Molten salt battery • Nickel oxyhydroxide battery • Oxyride battery • Organic radical battery • Paper battery • Pulvermacher's chain • Reserve battery • Silver-oxide battery • Solid-state battery • Voltaic pile • Penny battery • Trough battery • Water-activated battery • Weston cell • Zinc-air battery • Zinc-carbon battery • Zinc chloride battery Secondary cells or rechargeable batteries • Flow battery • Vanadium redox battery • Zinc-bromine flow battery • Fuel cell • Lead-acid battery • Deep cycle battery • VRLA battery • AGM battery • Gel battery • Lithium air battery • Lithium-ion battery • Beltway battery • Lithium ion polymer battery • Lithium iron phosphate battery • Lithium-sulfur battery • Lithium-titanate battery • Molten salt battery • Nickel-cadmium battery • Nickel-cadmium battery vented cell type • Nickel hydrogen battery • Nickel-iron battery • Nickel metal hydride battery • Low self-discharge NiMH battery • Nickel-zinc battery • Organic radical battery • Polymer-based battery • Polysulfide bromide battery • Potassium-ion battery • Rechargeable alkaline battery • Silicon air battery • Sodium-ion battery • Sodium-sulfur battery • Super iron battery • Zinc-bromine flow battery • Zinc matrix battery
Aircraft Electical Generation The power on an aircraft can be said to be generated in one of two ways, when on the ground we use a portable power generator or ground power unit as its better known, we mainly use this type when we want to test the systems that require power. The other method is by utilising the aircrafts engine to generate enough power, it does this by taking power from an alternator to power the aircrafts systems.
Distribution of Alternating Current On our aircraft electricity is transported across power lines which are known as Busbars. Many aircraft systems takes electricity from Busbars which take this electricity from our power generators. The Bus Bars may be tiered so that their importance to the aircraft can be designated as essential Busbars, non-essential Busbars, Avionics Busbars, emergency Busbars and finally cross-tie Busbars. Aircrafts can be fitted with Bus-tie breaker or Bus-tie contactor to allow for manual or automatic selection or de-selection of certain Busbars so non-essential systems don't cause a power drain during an emergency.
Conclusion So by reading through the information contained within this report it is the hope that a better understanding is gained regarding the fundamentals of power sources and their relevence to the aviation industry.
References Images www.science.aid.net – AC and DC Signals http://www.odec.ca/projects/2006/glaz6j2/battery_info.htm – Dry Cell Battery Image www.reuk.co.uk – Lead Acid Battery Diagram Image http://www.enotes.com/topic/List_of_battery_types – Table Of Battery Types Information http://www.autoshop101.com/trainmodules/batteries/101.html – Accessed 1/10/11
AC & DC SOURCES REPORT
Introduction Within this report we cover many aspects of the fundamentals of the portable power sources we use today in society. The information is to educate and help individuals understand how they are constructed and the way in which they operate. D/C and A/C Sources When talking about electrical fundamentals we must be aware of certain terms and understanding these terms will add to our explanations when asked to describe aspects about the subject. Within this report we are going to explore DC and AC sources, covering what they are and where they come from. First of all we must start with the abbreviations which are; • • DC - Stands for direct current, this always travels continuously in the same direction (Positive to Negative) AC – Stands for alternating current which means periodically over time it will reverse its direction
So to help explain this refer to the diagram, an AC current sine wave can be seen to have peaks and troughs whereas a DC current looks to be at a constant.
Current Current within a DC circuit can be said to be the rate in which the electricity flows, where the positively charged particles flow around the circuit from positive to negative terminals. The rate of flow or current is measured in "amperes" (A). Voltage Voltage is the difference in potiential energy or resistive load that is measured at any given point within the circuit, sometimes referred to as potiential difference (p.d.) and measured in "volts" (V)
Cell Construction Ayr college HND Electrical funamentals notes describes a "battery" as; " A battery is a voltage source in a single container made from one or two cells." Usually batteries are made up of cells, including electrodes and an electrolyte encased in a container, most containers are made from a material that is resistant to the electrolyte and mechanical shock as well as high temperatures. The case itself is vented to allow any detromental gases created to escape and evaporate in the air. When referring to a power source such as a battery we must be aware that it is made up of cells (although a single cell can also be a battery). When further broken down to its base contents it is made up of; 1)Electrodes - 2 Dissimular metal plates, one positively charged (Annode) the other negative (Cathode). 2)Electrolyte - The solution that acts upon the electrodes and allows the chemical reaction to take place 3)Container – The medium where the electrodes and electrolyte is housed.
Types of Cell Bearing this in mind we must be aware that there are two different types of cell: 1.Primary cell 2.Secondary cell The primary cell is the type where due to the chemical rection the negative electrode is damaged beyond repair resulting in a useless battery which cannot be recharged. However the secondary cell's electrodes can be returned to their origional state but reversing the current, therefor this means it can be recharged and used again.
Sizes There are many sizes of batteries available to us all providing different voltages and currents, the one which we choose to use is usually advised on the item we are using the power source in or within a user manual. The sizes are: -D cell -A23 Cell -C cell -AA Cell -AAA Cell -9-volt PP3 battery -Button Cells (CR2023 & LR44) -AAAA Cell
Batteries Connections When we have an appliance that requires a portable power source (i.e batteries) we require different sizes of batteries for different output voltages to ensure the appliance will work correctly. Sometimes we cannot use large batteries on small appliances otherwise we would compromise the size its casing so when this becomes a factor we use many small batteries aligning them in "series" (one after another in the circuit) so that the normal output has been added to so that it is sufficient enough so that applience will work. There are three ways in which we can connect batteries to attribute certain qualities we wish a circuit to have. 1.Series – Cells connected in series which provides a higher voltage with no change in current. 2.Parrallel – Cells connected in parrallel to provide an increase in current or the same current but for a longer duration with no increase in voltage. 3.Series-Parrallel – Cells connected in parrallel but in series also this provides increased current and voltage than a singular cell.
Alkaline Cell The alkaline battery is simular to most types out in the market today it is made up of electrodes, electrolyte and a container. The main differences are that the electrolyte used its of potassium hydroxide as opposed to the acidic electrolyte used by zinc-carbon batteries, which allows it to have a higher energy density and longer shelf life in comparison. The cathode is made of maganese dioxide, whereas the annode is created of a zinc powder which allows more surface area to allow an increase in the rate of reaction resulting in increased electron flow. To way in which this battery works is basic to every cell and battery the annode and cathode are made up of two dissimular metals (i.e zinc and copper), connected via a wire and then placed in an electrolyte within a container. A chemical reaction will take place in which the positively charged particles flow from one metal to the other negatively charged particles on the other peice of metal. It is this flow of current created from the moving of the particles and the burning of the negatively charged metal (Zinc) that creates our charge or electricity.
Lead Acid Cell The structure of the lead acid cell is simular to the others except usually larger and it containes a different electrolyte (dilute solution of sulphuric acid) and the negative electrode is comprised of a sponge lead and the positively charged electrode is comprised of lead peroxide. When the chemical reaction is taking place between the three chemicals it forms lead sulphate on the electrodes and the acid becomes water but by recharging the battery it reverses this change to the origional chemicals.
Nickel-Cadmium Cell Within the cell make-up, Annode is created from nickel hydroxide, Cathode of cadmium hydroxide and the, Electrolyte is an alkaline solution made up of potassiom hydroxide and distilled/de-ionised water. However the electrolyte is not playing an active part in the chemical reaction but is used to provide a path for the current flow instead. Whilst charging the cell an ion exchange takes place where oxygen is removed from the negative electrode and then is transferred to the positive electrode which means the electrolyte is acting as an ionised conductor resulting in the positive electrode being at a higher state of oxidisation. When the charging process is finished all the oxygen is driven out of the negative electrode leaving only metallic cadmium and the positive electrode consisting of oxidised nickel hyrdoxide. Toward the end of the charging process gassing begins to occur and as a result of electrolysis which reduces the water content, which means the water must be refilled periodically.
Types Of Cells Primary cells or non-rechargeable batteries • Alkaline battery • Aluminium battery • Atomic battery • Optoelectric nuclear battery • Nuclear micro-battery • Bunsen cell • Chromic acid cell • Clark cell • Daniell cell • Dry cell • Earth battery • Frog battery • Galvanic cell • Grove cell • Leclanché cell • Lemon battery • Lithium battery • Lithium air battery • Mercury battery • Molten salt battery • Nickel oxyhydroxide battery • Oxyride battery • Organic radical battery • Paper battery • Pulvermacher's chain • Reserve battery • Silver-oxide battery • Solid-state battery • Voltaic pile • Penny battery • Trough battery • Water-activated battery • Weston cell • Zinc-air battery • Zinc-carbon battery • Zinc chloride battery Secondary cells or rechargeable batteries • Flow battery • Vanadium redox battery • Zinc-bromine flow battery • Fuel cell • Lead-acid battery • Deep cycle battery • VRLA battery • AGM battery • Gel battery • Lithium air battery • Lithium-ion battery • Beltway battery • Lithium ion polymer battery • Lithium iron phosphate battery • Lithium-sulfur battery • Lithium-titanate battery • Molten salt battery • Nickel-cadmium battery • Nickel-cadmium battery vented cell type • Nickel hydrogen battery • Nickel-iron battery • Nickel metal hydride battery • Low self-discharge NiMH battery • Nickel-zinc battery • Organic radical battery • Polymer-based battery • Polysulfide bromide battery • Potassium-ion battery • Rechargeable alkaline battery • Silicon air battery • Sodium-ion battery • Sodium-sulfur battery • Super iron battery • Zinc-bromine flow battery • Zinc matrix battery
Aircraft Electical Generation The power on an aircraft can be said to be generated in one of two ways, when on the ground we use a portable power generator or ground power unit as its better known, we mainly use this type when we want to test the systems that require power. The other method is by utilising the aircrafts engine to generate enough power, it does this by taking power from an alternator to power the aircrafts systems.
Distribution of Alternating Current On our aircraft electricity is transported across power lines which are known as Busbars. Many aircraft systems takes electricity from Busbars which take this electricity from our power generators. The Bus Bars may be tiered so that their importance to the aircraft can be designated as essential Busbars, non-essential Busbars, Avionics Busbars, emergency Busbars and finally cross-tie Busbars. Aircrafts can be fitted with Bus-tie breaker or Bus-tie contactor to allow for manual or automatic selection or de-selection of certain Busbars so non-essential systems don't cause a power drain during an emergency.
Conclusion So by reading through the information contained within this report it is the hope that a better understanding is gained regarding the fundamentals of power sources and their relevence to the aviation industry.
References Images www.science.aid.net – AC and DC Signals http://www.odec.ca/projects/2006/glaz6j2/battery_info.htm – Dry Cell Battery Image www.reuk.co.uk – Lead Acid Battery Diagram Image http://www.enotes.com/topic/List_of_battery_types – Table Of Battery Types Information http://www.autoshop101.com/trainmodules/batteries/101.html – Accessed 1/10/11
