[\/et_pb_text][\/et_pb_column][\/et_pb_row][et_pb_row column_structure=”1_3,2_3″ _builder_version=”4.9.10″ _module_preset=”default” custom_padding=”||0px|||”][et_pb_column type=”1_3″ _builder_version=”4.9.10″ _module_preset=”default”][et_pb_text _builder_version=”4.9.10″ _module_preset=”default”]<\/p>\n
4.1\u00a0 \u00a0 Mains Power<\/p>\n
[\/et_pb_text][\/et_pb_column][et_pb_column type=”2_3″ _builder_version=”4.9.10″ _module_preset=”default”][et_pb_text _builder_version=”4.9.10″ _module_preset=”default” min_height=”34.6px” custom_margin=”||29px|||” custom_padding=”||2px|||”]<\/p>\n
- \n
- Recall the voltage and frequency of the mains supply used in Australia.<\/strong><\/em><\/li>\n
- Recall the voltages and relationship between the Active, Neutral and Earth in a single phase mains.<\/strong><\/em><\/li>\n
- Recall the colour code of mains wiring.<\/strong><\/em><\/li>\n
- Understand the reason for the Earth connection (if provided) on mains operated equipment.<\/strong><\/em><\/li>\n
- Recall the purpose of the fuse and switch being in the Active lead of mains operated equipment.<\/strong><\/em><\/li>\n<\/ul>\n
[\/et_pb_text][et_pb_toggle title=”Mains voltage” _builder_version=”4.9.10″ _module_preset=”default” title_font=”|700|||||||” title_font_size=”14px” custom_margin=”-35px|||||” custom_padding=”||9px|||”]<\/p>\n
In 1980, the\u00a0<\/span>International Electrotechnical Commission<\/a>\u00a0<\/span>(IEC) rationalised the 220 V, 230 V and 240 V nominal voltage levels around the world to a consistent 230 V. This rationalisation was ostensibly made to improve the economics of making appliances by allowing manufacturers to produce a range of items with a rated voltage of 230 V. Not all countries have yet converted to the new standard.<\/p>\n
The nominal voltage in most areas of Australia had been set at 240 V in 1926. In 2000,\u00a0<\/span>Standards Australia<\/a>\u00a0<\/span>issued a system Standard AS60038, with 230 V as the nominal voltage with a +10% to \u20136% variation at the point of supply, i.e., 253 V to 216.2 V. A new power quality standard, AS61000.3.100, was released in 2011 <\/sup>that details additional requirements. The new standard stipulates a nominal 230 V, and the\u00a0<\/span>allowable<\/i>\u00a0<\/span>voltage to the customer’s point of supply is, as mentioned, +10% to \u20136%. However, the\u00a0<\/span>preferred<\/i>\u00a0<\/span>operating range is +6% to \u20132%. (244 V to 225 V).<\/sup><\/p>\n
In Australia, the actual voltages delivered to customers is set at the state level. As of 2019, all states have transitioned to 230 V standards, with the exception of Western Australia and Queensland.<\/sup>\u00a0<\/span>Queensland began the transition to 230 V in 2017 and hopes to be completed to the “preferred range” by July 2020.<\/sup>\u00a0<\/span>The reason given for Queensland’s decision to move was the increased use of grid-tied rooftop solar installations raising the grid voltage. By lowering the voltage to 230 V, additional headroom of 960 megawatts was created to accommodate future residential power generation from rooftop solar.<\/sup><\/p>\n
The voltage in New Zealand is also 230 V. In Fiji, Tonga and Papua New Guinea it is 240 V, and 220 V in the Solomon Islands. In China and Argentina the voltage is 220 V.<\/p>\n
The AC frequency is 50 Hz.\u00a0<\/p>\n
<\/p>\n
[\/et_pb_toggle][et_pb_toggle title=”Circuit conductors” _builder_version=”4.9.10″ _module_preset=”default” title_font=”|700|||||||” title_font_size=”14px” min_height=”16.6px” custom_margin=”-10px|||||” custom_padding=”||16px|||”]<\/p>\n
Ground<\/b>\u00a0<\/span>or\u00a0<\/span>earth<\/b>\u00a0<\/span>in a\u00a0<\/span>mains<\/a>\u00a0<\/span>(AC<\/a>\u00a0<\/span>power)\u00a0<\/span>electrical wiring<\/a>\u00a0<\/span>system is a conductor that provides a low-impedance<\/a>\u00a0<\/span>path to the earth to prevent hazardous voltages from appearing on equipment (high voltage spikes).\u00a0<\/span>The terms\u00a0<\/span>ground<\/em>\u00a0<\/span>and\u00a0<\/span>earth<\/em>\u00a0<\/span>are used synonymously in this section;\u00a0<\/span>ground<\/em>\u00a0<\/span>is more common in North American English, and\u00a0<\/span>earth<\/em>\u00a0<\/span>is more common in British English. Under normal conditions, a grounding conductor does not carry current. Grounding is also an integral path for home wiring because it causes circuit breakers to trip more quickly (ie, RCD<\/span>), which is safer. Adding new grounds requires a qualified electrician with knowledge particular to a power distribution region.<\/p>\n
Neutral<\/b>\u00a0<\/span>is a circuit conductor that normally completes the circuit back to the source. Neutral is usually connected to ground (earth) at the main electrical panel, street drop, or meter, and also at the final step-down transformer of the supply. That is for simple single panel installations; for multiple panels the situation is more complex. In a polyphase (usually three-phase)\u00a0<\/span>AC system<\/a>, the neutral conductor is intended to have similar voltages to each of the other circuit conductors, but may carry very little current if the phases are balanced.<\/p>\n
All neutral wires of the same earthed (grounded) electrical system should have the same electrical potential, because they are all connected through the system ground. Neutral conductors are usually insulated for the same voltage as the line conductors, with interesting exceptions.<\/p>\n
Live or Active <\/b>is a circuit conductor that delivers the supply current to a device.<\/p>\n
[\/et_pb_toggle][et_pb_toggle title=”Mains wiring colour code” _builder_version=”4.9.10″ _module_preset=”default” title_font=”|700|||||||” title_font_size=”14px” min_height=”25.6px” custom_margin=”-18px|||||”]<\/p>\n
\nBrown = Live\u00a0 (old Standard Red for fixed wired)<\/strong><\/p>\n
As previously mentioned, the brown wire has the function of carrying electricity to the appliance. There will be a risk of electrocution if the brown wire is live and not connected to the earth or neutral wires. You must ensure that there is no power source connected with the live wire before working on the wiring.<\/p>\n
<\/p>\n<\/div>\n
\nBlue = Neutral (old Standard Black for fixed wired)<\/strong><\/p>\n
The neutral wire colour is blue. The neutral wire transfers electricity away from the appliance to avoid overloading. It is located at the end of the circuit for connection after the electricity has flowed around the live and earth wires. It is highly unlikely that you will have an electric shock on contact with a blue wire. However, caution should be taken as the wire can run at a very high heat.<\/p>\n
<\/p>\n<\/div>\n
\nGreen and Yellow = Earth<\/strong><\/p>\n
The earth wire colour now features green and yellow stripes. It has the key safety function of connecting the metal casing of the electrical appliance with the ground. This means that the current of the live wire cannot be directly transmitted to the casing. Contact with the protective earth wiring should not result in an electric shock but exercising caution is always recommended.<\/p>\n
<\/p>\n
<\/p>\n
There should be some warning signage indicating installations featuring circuits and\/or fixed cables and wires of mixed colours. This warning should be very clearly designated on either the fuse board or the consumer unit.<\/strong><\/span><\/p>\n<\/div>\n
[\/et_pb_toggle][et_pb_toggle title=”Earth connection” _builder_version=”4.9.10″ _module_preset=”default” title_font=”|700|||||||” title_font_size=”14px” min_height=”43.6px” custom_margin=”-7px|||||” custom_padding=”9px|||||”]<\/p>\n
If there is a fault in your electrical installation you could get an electric shock if you touch a live metal part. This is because the electricity may use your body as a path from the live part to the earth part.<\/p>\n
Earthing is used to protect you from an electric shock. It does this by providing a path (a protective conductor) for a fault current to flow to earth. It also causes the protective device (RCD or similar) to switch off the electric current to the circuit that has the fault.<\/p>\n
For example, if a cooker has a fault, the fault current flows to earth through the protective (earthing) conductors. A protective device (fuse or circuit-breaker) in the consumer unit switches off the electrical supply to the cooker. The cooker is now safe from causing an electric shock to anyone who touches it.<\/p>\n
[\/et_pb_toggle][\/et_pb_column][\/et_pb_row][et_pb_row column_structure=”1_3,2_3″ _builder_version=”4.9.10″ _module_preset=”default” custom_padding=”||0px|||”][et_pb_column type=”1_3″ _builder_version=”4.9.10″ _module_preset=”default”][et_pb_text _builder_version=”4.9.10″ _module_preset=”default”]<\/p>\n
4.2 Potential Difference and Electromotive Force<\/p>\n
[\/et_pb_text][\/et_pb_column][et_pb_column type=”2_3″ _builder_version=”4.9.10″ _module_preset=”default”][et_pb_toggle title=”Fuse or circuit breaker” _builder_version=”4.9.10″ _module_preset=”default” title_font=”|700|||||||” title_font_size=”14px” min_height=”54.6px” custom_margin=”1px|||||” custom_padding=”19px||4px|||”]<\/p>\n
\nThe fuse or circuit breaker must be connected in the live wire side of a domestic circuit\u00a0<\/span>to ensure that it keeps high voltage from reaching the user, or surroundings<\/b>, if a fault develops.<\/span><\/p>\n
In a mobile installation circuit breakers and switches are required to be double pole, meaning opening the live and the neutral conductor, because it cannot be guaranteed that the outside connection is of correct polarity.<\/span><\/p>\n<\/div>\n
[\/et_pb_toggle][et_pb_text _builder_version=”4.9.10″ _module_preset=”default” custom_margin=”||-4px|||” custom_padding=”||2px|||”]<\/p>\n
- \n
- Understand the difference between potential difference (PD) and electromotive force (EMF).<\/strong><\/em><\/li>\n
- Understand the concept of source resistance (impedance) and voltage drop due to current flow.<\/strong><\/em><\/li>\n
- Understand the relationships between voltage, current, resistance and power. Calculate any one when any two other elements are known.<\/strong><\/em><\/li>\n<\/ul>\n
[\/et_pb_text][et_pb_toggle title=”EMF – voltage” _builder_version=”4.9.10″ _module_preset=”default” title_font=”|700|||||||” title_font_size=”14px” custom_padding=”10px|||||”]<\/p>\n
Potential Difference<\/strong><\/p>\n
For a potential difference (PD) to exist there must be an excess of electrons at one point and a lack of electrons at another point.\u00a0 It is the difference in potential between two points that gives rise to the force that creates a current flow when the points are connected.\u00a0 PD is measured in volts.<\/p>\n
Electro Motive Force<\/strong><\/p>\n
Electro Motive Force (EMF) is the force created by a potential difference.\u00a0 It is the force created by a potential difference that causes a current to flow. \u00a0EMF is measured in Volts and is often referred to as voltage.\u00a0 The symbol or abbreviation is E.<\/p>\n
Eg.\u00a0 EMF = 5V or E = 5V.<\/p>\n
Voltage<\/strong><\/p>\n
Voltage is actually the measurement of potential difference or EMF.\u00a0 One Volt is the PD or EMF required to create 1 Ampere of current through one Ohm of resistance.<\/p>\n
Because PD, EMF and Voltage are so closely aligned the terms are often technically misused and interchanged.<\/p>\n
Often a current source (battery or other supply) will be shown as V=12V rather than E = 12V.\u00a0 Similarly a resistor is said to have a voltage drop across it rather than a potential difference between either end.<\/p>\n
Current<\/strong><\/p>\n
Current is the number of electrons moving past a point in a given time and has the symbol I.\u00a0 It is measured in amperes (A).\u00a0 I = 2A.<\/p>\n
Note that current flows in all parts of a circuit at the instant the circuit is made (switched on).\u00a0 Like water in a pipe if you add water at one end, water immediately appears out of the other end because there is water already in the pipe. Current is the same.\u00a0 As an electron joins an atom it bumps an electron out of orbit in that atom to the next which has the same effect.\u00a0 It is the bumping effect that can cause a switch in Sydney connected to a light globe in Perth to light instantly when the switch is<\/span> made.<\/p>\n
[\/et_pb_toggle][et_pb_toggle title=”Resistance – voltage drop” _builder_version=”4.9.10″ _module_preset=”default” title_font=”|700|||||||” title_font_size=”14px” custom_padding=”10px|||||”]<\/p>\n
Resistance<\/strong><\/p>\n
Resistance is the opposition to current flow and has the symbol R.\u00a0 It is measured in Ohms and uses the Greek letter omega (\u03a9).\u00a0 R = 20\u03a9.<\/p>\n
Voltage Drop<\/strong><\/p>\n
When ever a current is flowing through a resistance some energy is used to ‘push’ the electrons through the resistance.\u00a0 This creates a difference in voltage across the resistance, known as the voltage drop or Vd<\/sub>.<\/p>\n
[\/et_pb_toggle][et_pb_toggle title=”Ohms law” _builder_version=”4.9.10″ _module_preset=”default” title_font=”|700|||||||” title_font_size=”14px” custom_padding=”10px|||||”]<\/p>\n
The Ohm\u2019s Law Triangle<\/span><\/strong><\/h2>\n
Every electrical engineer has seen the Ohm\u2019s Law triangle at some point in their education. It\u2019s the \u201cgo-to\u201d for teachers when trying to help visually explain the formula. As a quick refresher, the triangle is a visual representation of the mathematical relationship between\u00a0<\/span>voltage\u00a0<\/strong><\/span>(V, sometimes represented as U or E),\u00a0<\/span>resistance\u00a0<\/strong><\/span>(R), and current (I) in a circuit. This triangle is an easy tool for new engineers to remember the three main aspects of electricity.<\/span><\/p>\n
<\/span>
![\"0916](\"https:\/\/static4.arrow.com\/-\/media\/arrow\/images\/miscellaneous\/0\/0916-ohms-law-fig-1.jpg?mw=290&hash=42E4FA3AF6E8BCC7DCC57147F808AA38A398EA14\")
<\/picture><\/p>\nOhm\u2019s law triangle includes three sections<\/span><\/strong>: The top half must always be voltage. The bottom half is then split into two smaller halves for current and resistance \u2013 current is usually on the left with resistance on the right, but the order doesn\u2019t really matter. It just seems that because most people remember the formula as V = I*R, they write it in the triangle as such.<\/span><\/p>\n
To solve for one of the variables, cover the letter being solved for and use the remaining line separation to give you the mathematical expression.<\/span><\/strong>\u00a0For example, when solving for resistance (R), cover the R and all that is left is V and I. Then use the line that separates those two variables as an indication to use division. The same is true when solving for current (I). The only tricky part is when solving for voltage (V); the line separating I and R then represents multiplication because the items are next to each other.<\/span><\/p>\n
The three resulting variations of Ohm\u2019s Law are:<\/span>\u00a0 \u00a0\u00a0<\/span><\/strong><\/span><\/span><\/p>\n
<\/strong><\/span>V = I * R<\/strong><\/span><\/h2>\n
I = V \/ R<\/span><\/strong><\/h2>\n
R = V \/ I<\/span><\/strong><\/h2>\n
This leads to easy manipulation of a circuit. For example, if resistance were to decrease in a circuit with the voltage held constant, the current increases.<\/span><\/p>\n
In the end, Ohm\u2019s Law is not very complicated, but it is essential for circuit design. If two out of the three values are known, the missing value can be easily calculated. The inner workings of every circuit, no matter how simple or complicated, rest on this cornerstone of electrical engineering.<\/span><\/p>\n
[\/et_pb_toggle][\/et_pb_column][\/et_pb_row][et_pb_row column_structure=”1_3,2_3″ _builder_version=”4.9.10″ _module_preset=”default” custom_padding=”||0px|||”][et_pb_column type=”1_3″ _builder_version=”4.9.10″ _module_preset=”default”][et_pb_text _builder_version=”4.9.10″ _module_preset=”default”]<\/p>\n
4.3\u00a0 Resistance<\/p>\n
[\/et_pb_text][\/et_pb_column][et_pb_column type=”2_3″ _builder_version=”4.9.10″ _module_preset=”default”][et_pb_text _builder_version=”4.9.10″ _module_preset=”default” min_height=”78.4px” custom_margin=”||-12px|||” custom_padding=”||2px|||”]<\/p>\n
- \n
- Understand and apply the formulae for calculating the combined values of resistors in series and\/or parallel.<\/strong><\/em><\/li>\n<\/ul>\n
[\/et_pb_text][et_pb_toggle title=”Resistors in series” _builder_version=”4.9.10″ _module_preset=”default” title_font=”|700|||||||” title_font_size=”14px”]<\/p>\n
Resistors in Series<\/h2>\n
When\u00a0<\/span>resistors<\/a>\u00a0are connected one after each other this is called connecting in series. This is shown below.<\/span>
![\"resistors_in_series_1\"](\"https:\/\/resources.kitronik.co.uk\/images\/blogs\/2014\/01\/resistors_in_series_1.png\")
<\/a>To calculate the total overall resistance of a number of resistors connected in this way you add up the individual resistances. This is done using the following formula:\u00a0<\/span>Rtotal = R1 + R2 +R3<\/em>\u00a0and so on. Example: To calculate the total resistance for these three resistors in series.<\/span><\/p>\n\n\n\n
\n ![\"resistors_in_series_2\"](\"https:\/\/resources.kitronik.co.uk\/images\/blogs\/2014\/01\/resistors_in_series_2.png\")
<\/td>\nRtotal = R1 + R2 + R3<\/em>\u00a0<\/span>= 100 + 82 + 1 Ohms<\/em>\u00a0<\/span>= 183 Ohms<\/em><\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/div>\n [\/et_pb_toggle][et_pb_toggle title=”Resistors in parallel” _builder_version=”4.9.10″ _module_preset=”default” title_font=”|700|||||||” title_font_size=”14px”]<\/p>\n
Resistors in Parallel<\/h3>\n
When resistors are connected across each other (side by side) this is called connecting in parallel. This is shown below.\u00a0<\/span>
![\"resistors_in_series_6\"](\"https:\/\/resources.kitronik.co.uk\/images\/blogs\/2014\/01\/resistors_in_series_6.png\")
<\/span><\/p>\n<\/h3>\n
Two Resistors in Parallel<\/h3>\n
\n\n\n
\n To calculate the total overall resistance of a of two resistors connected in this way you can use the following formula:<\/td>\n ![\"resistors_in_series_7\"](\"https:\/\/resources.kitronik.co.uk\/images\/blogs\/2014\/01\/resistors_in_series_7.png\")
<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/div>\n
- Understand the concept of source resistance (impedance) and voltage drop due to current flow.<\/strong><\/em><\/li>\n
- Recall the voltages and relationship between the Active, Neutral and Earth in a single phase mains.<\/strong><\/em><\/li>\n
![\"resistors_in_series_8\"](\"https:\/\/resources.kitronik.co.uk\/images\/blogs\/2014\/01\/resistors_in_series_8.png\")
<\/p>\n![\"resistors_in_series_10\"](\"https:\/\/resources.kitronik.co.uk\/images\/blogs\/2014\/01\/resistors_in_series_10.png\")
![\"resistors_in_series_11\"](\"https:\/\/resources.kitronik.co.uk\/images\/blogs\/2014\/01\/resistors_in_series_111.png\")
<\/a>![\"resistors_in_series_12\"](\"https:\/\/resources.kitronik.co.uk\/images\/blogs\/2014\/01\/resistors_in_series_12.png\")
<\/p>\n![\"4](\"https:\/\/learnabout-electronics.org\/Resistors\/images\/resistor_4_band_code.gif\")
<\/p>\n![\"Examples](\"https:\/\/cdn.sparkfun.com\/r\/600-600\/assets\/4\/0\/3\/a\/e\/511948ffce395f7f47000000.png\")
<\/a><\/div>\n![\"Vout](\"https:\/\/cdn.sparkfun.com\/assets\/e\/7\/6\/3\/c\/511968d9ce395f7c54000000.png\")
<\/a><\/div>\n