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Electrical Engineering
Electrical engineering is a field of engineering that deals with the study and application of electricity, electronics and electromagnetism.
23,056 Questions
Where can one purchase old Transformer videos?
Old Transformers videos can be purchased from some stores and websites that offer them for sale. While rare, they can be bought from stores such as eBay.
Explain what current grows gradually when an inductive circuit is switched on?
The AC current grows gradually when an inductive circuit is switched on. This specific current, also know as a electromagnetic field, is slowly growing, then shrinking, and changing, because of the wire current.
Are the windings in a transformer linked?
Yes, but the secondary coils function by induced magnetic currents- they have no wired connection to the rest of the apparatus. In some cases , on railroad ( big leagues,here not Lionel) There are controls in the cab that can pre-selected transformer functions- for example when starting the let-down from high speed running, the engineer will call off: Primary Coils- Half Flux- thus makes a peculiar noise, the transformer seems to be yawning, Thus it is ( set) for a lower gear, without ,say changing the throttle setting. There are usually only two settings for the Transformer output- Half flux and Full Flux, and an overhead switch controls this. Boy does this bring back memories.
I usually look at the data plate on the side of the motor, or inside the terminal junction cover. If neither are there, a motor rewinding shop could open it up and tell.
Different manufacturers are known to use their own color codes. Esp. if it's a foreign make.
Why armouing is not done in single core cable?
On the contrary, armouring is common on single-core conductors. Frequently, high-voltage underground cables are made up of three, individual, single-core, line conductors. These are most definitely armoured to protect them against penetration by the trench backfill and to protect workers who may accidentally hit them with tools.
How do you calculate temperature of a motor?
The basic equation that will enable you to determine the temperature of any electrical machine is:
(W - Q) = m c (Tf - Ti)
Where, W = work done on the machine, Q = heat transfer away from the machine into its surroundings, m = mass of the machine, c = specific heat capacity of the machine, and Tf and Ti the final and initial temperatures of the machine respectively.
But there are so many variables involved that it would be very difficult to apply this equation in practise. For example, the ambient temperature (Ti) is variable, and you would need to know the mass and specific heat capacity for every component of the machine.
So the simple answer would be to simply measure it with a thermometer!
What is charged by having a one way current flow through it?
A battery is charged by having a DC current flow through it.
How do you calculate voltage and watts electric outlet heaters on low setting?
All of the information is on the nameplate that is located behind the heating element or the units junction box. The wattage and voltage of the baseboard heater will be shown stamped on the plate. The high to low setting on the heater has nothing to do with the wattage and voltage of the unit. All the control does is limit the time that the unit is in the on position. In the low position the heater will cycle on and off until the lower set point is reached to shut the unit off. When the heater is in the high position the unit will stay on and cycle longer until the higher set point is reached. The longer the heater stays on the more it costs to operate. The wattage remains the same regardless of whether the setting is on high or low.
What is the LM-80 for LED Lumen Maintenance Test?
IESNA-LM-80 (Measuring Lumen Maintenance of LED Light sources) is an approved method by Lighting Engineering Association of North America (IESNA) for the third generation SSL products; it mentioned the measurement standard and method. The main purpose is that measure and records the LED lumen maintenance change along with time, in other word, it is applied to test LED aging life.
Compare with the traditional light source, theoretically LED life can reach to 50000 hours. So it is hard to test the LED life, because it is impossible to light up the LED till it dies, and it is also unworkable because there are so many different types and different power of LED, if the problem can not solve, it will become a big resistance to develop and push LED products. Considering the real situation, IESNA passed the LM-80-08 approved method, which provides the guidance and specification for measuring and recording LED lumen vs time, and calculate the life time of LED luminaires in the end. Also it solves an urgent problem for LED industry.
When we say LED lumen maintenance and LED aging life, we will talk about LM-80, TM-21, TM-82 and etc. so it is necessary to explain them. LM-80-08 put forward the measurement method and then obtains the data, TM-21 put forward the calculate method and then obtains the data. In those standards, they mentioned L70, L50, L30 And etc. that means the time to 70% lumen maintenance, time to 50% lumen maintenance and time to 30% lumen maintenance. From the data, we can find lumen changing along with the time. Generally speaking, time to 70% lumen maintenance will be defined as the LED life. According to LM-80, the test time should be no less than 6000h, and 10000h is recommended. And during the test, temperature is limited at three points, first one is 55℃，second one is 85℃，and the third one is depends on the manufacturer. And generally, the test report should includes the following information: number of LED light source test, description of LED light source, description of auxiliary device, operating cycle, ambient conditions including airflow, temperature and relative humidity, Drive current of the LED light source during lifetime test, Initial luminous flux and forward voltage at photometric measurement current, Lumen maintenance data for each individual LED light source along with median value, standard deviation, minimum and maximum lumen maintenance value for all of the LED light sources, Observation of LED light source failures including the failure conditions and time of failure, LED light source monitoring interval, Photometric measurement uncertainty, Chromaticity shift reported over the measurement time.
LPCE-2(LMS-9000A) high accuracy spectroradiometer and integrating sphere test system, this system not only meet the requirements of CIE, EN and lm-79 clause 9.1, and also meet the requirements of LM-80. Base on the normal function, Lisun's engineer developed new software to meet the requirements of LM-80. So LPCE-2 has two software, one is to test the luminous flux, color temperature, color rending index, wavelength, spectrum, light efficiency and etc. the other is to test and record the data of lumen vs time, according to the data, we can generally predict the LED life. But the main function for this system is to test the photoelectric and colorimetric parameters of LED, so it is not a standard way to test LED life, the test result and test report can not regarded as the final evaluation. But along with the technology developing, LISUN push LEDLM-80PL LED lumen maintenance and life test system into the market, this system is designed according to LM-80-08, TM-82, TM-21 and etc. so it is completely meet the relevant standards.
LEDLM-80PL is developed base on the mature system of LPCE-2 (LMS-9000A). In the hardware, LEDLM-80PL still adopts the high accuracy CCD spectroradiometer to keep the high precision. And the most important is the software, the software absorbs the essence of the LPCE - 2, and then combine Arrhenius model to build a newly reliable LED life predict software. Users will only need to test the lamp for hundreds of hours under certain temperature, then the software will calculate the time to 70% (50%, 30%) lumen maintenance at this temperature, it will greatly help to improve the test efficiency and the accuracy and reliability of LED lumen maintenance testing.
Please fill this blank Almost all the digital signals are Options1 Periodic Option 2 A-periodic?
Signals are aperiodic because they are not repetitive.
Think it through. You are adding a second path for current flow.
Current flow will increase to some extent.
Therefore, with more current flow, resistance must....
What are high efficiency motors?
The efficiency of a motor is the output power divided by the input power. The difference is the lost power which appears as heat usually. High-efficiency motors produce very little lost power. But they tend to be more massive and expensive to make, so that most motor designs have to compromise on efficiency.
Can solid cores be used in transformers?
Yes but a solid core is not recommended because it allows large eddy currents to flow, which greatly increases the power losses in the iron core.
That is why a core is usually made from insulated iron stampings.
Another Answer
No. A solid core would get very hot and damage the windings' insulation. As far as the primary winding is concerned, the core is simply another winding -a single-turn winding. So a large circulating current ('eddy current') will be set up within the core, leading to a large energy loss ('eddy current loss'). Laminating the core restricts eddy currents to flow within each lamination which, because of their small cross-sectional area, means that the eddy currents will be very small, and the losses also very small. The eddy current losses are inversely-proportional to the square of the number of laminations (approximately. anyway) so, say, 100 laminations mean that the losses will be 10 000 times lower than for a solid core.
How can you measure the power or voltage of a potato clock?
A voltmeter would measure the voltage. If you measure the voltage drop over a known low resistance you get a kinda-sorta idea of the power available.
What action can be taken if an industrial consumers power factor is too low?
The deterioration of the power factor in an industrial setting is almost
always the result of running a lot of motors ... that is, a lot of inductive
loading. That's corrected by adding utility capacitors across the lines,
at the transformer that feeds the industrial plant. The power enters the
plant with a big leading power factor, which compensates for all the lagging
loading of the motors inside.
Does the current in home wires oscillate due to oscillating ac voltage in homes?
Yes. In almost all cases, the current follows the voltage waveform.
The peak amplitude of the current depends on the device or appliance
that's drawing the current.
What does MNA in AC motors stand for?
The meaning of MNA is Magnetic Neutral Axis. It can be defined as the axis along which no emf is produced, as the armature conductors moves parallel to the field flux lines. The scope of how it works is to great an explanation for this site.
Does miliamperes increase as does battery voltage when put in a series configuration?
The current in a circuit, expressed in milliamperes, is
1,000 x (battery or power supply voltage)/(resistance connected between the power supply terminals)
If you increase the voltage of the battery or power supply, the current in the circuit
increases proportionally, at least until something in the circuit gets hot, melts, fuses,
and opens the circuit.
A natural gas generator connected to the grid has its voltage and speed (frequency) stabilised by being connected to the grid.
All generators on a grid run synchronously, and it happens because if one generator has a tendency to lag behind it will produce less power and thereby maintain its speed.
How do power pools increase the reliability of a power system?
Because if there is only one generator and it develops a fault, the lights go out. If the generator was part of a pool, the other generators in the pool can take up the extra load while it's repaired.
Why desiel is used in transformers?
Transformers use transformer oil as an insulator and to conduct the heat away from the windings. The oil usually flows through a radiator in a closed circuit on high-power transformers.
Used in this context, 'R' probably stands stands for 'red'. This is one of three colours used to identify the lines(not phases) of a three-phase system. The other two lines are coloured according to the standards used in your country. In the UK, for example, the colours are red, yellow, and blue -which also represent the positive phase sequence of the three-phase supply. Other methods of identifying lines include letters, e.g. 'A-B-C', numbers, e.g. '1-2-3', combinations of the two, e.g. 'L1-L2-L3', or other colours, e.g. 'brown-black-grey'.
'R' could also represent one of the letters, 'R-S-T', which has been used in Germany to represent the three lines of a three-phase system.
Is there any necessary to mark polarity on capacitor?
For electrolytic capacitors, yes, as ignoring their polarity can damage them.
