What is Alternator: Definition and 132 Discussions

An alternator is an electrical generator that converts mechanical energy to electrical energy in the form of alternating current. For reasons of cost and simplicity, most alternators use a rotating magnetic field with a stationary armature. Occasionally, a linear alternator or a rotating armature with a stationary magnetic field is used. In principle, any AC electrical generator can be called an alternator, but usually the term refers to small rotating machines driven by automotive and other internal combustion engines.
An alternator that uses a permanent magnet for its magnetic field is called a magneto. Alternators in power stations driven by steam turbines are called turbo-alternators. Large 50 or 60 Hz three-phase alternators in power plants generate most of the world's electric power, which is distributed by electric power grids.

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  1. Y

    Can Rainwater Power an Alternator? Exploring Sustainable Energy Generation

    'allo! I know it seems awkward that I posted an earlier thread about this topic, but roll with it. I would like to share what I (our group) am going to make for our science fair project. It is an alternator that uses collected rainwater to rotate the rotor. It will work like this: At the top...
  2. Y

    Formula for voltage output produced by an alternator?

    Hello! I have a science investigatory project issued by my school. For my (actually our) project, we decided we will make a some sort of concept alternator powered by water collected from rain. Our goal is pretty small, to power up a small 5-volt bulb. Assuming the rotor rotates 2-3 times a...
  3. N

    Car Alternator voltage is too high (16V+) Can it be reduced?

    My car alternator runs at 16 to 16.5 volts when I hit the gas, and 15v idling. This is scaring me and a new one is too expensive. It could be my computer or pulleys in the wrong too so I can't risk buying a new one and still having the problem. It turns off my speaker amplifier as soon as I hit...
  4. James O'Neill

    Can you make the drive shaft the alternator?

    I recently read a post on "How much energy does an alternator use?". So I read some more online articles and found that some people have thought of running their alternator on their drive shaft. This doesn't seem more economical to me, since you will still loose engine power . If the alternator...
  5. N

    Using a motor or alternator to generate electricity

    I'm looking into building a 7 1/4 gauge Diesel Electric Locomotive I will be using 4x 1hp (or 1 1/3hp) 24vDC permanent magnet motors for the traction motors. What I am looking for is someway of generating 24vDC with a 100-150A max output. (Im using a 3cyl 16hp Diesel engine to drive a...
  6. P

    Alternative ways to power hho cell without alternator?

    Hi my name is Patrick I have been trying to find new ways to power a hho generator in my car ,the problem is that yes you can have great mpg increase but you have to limit the amount of gas being produced ,to control the amount of amparge ,so it does not drag on alternator and thus decrease the...
  7. Selvven

    Upgrading a 12V Alternator to Produce a higher output Volts

    Hi could anyone please help with this:- I have a 12V 90Ah automobile alternator. is there a way to increase the output volts beyond the 14/13.8v to say 192v?
  8. smruti

    DC Generator Converted to Alternator

    can a dc generator be converted into an alternator?
  9. C

    Variable resistor & inductor connected to alternator

    A simple 2 pole alternator (a synchronous generator), is powered by a steam turbine. The amount of steam to the turbine is kept constant with a constant pressure ##p##, flow rate ##\dot{q}##, and power ##P##. If a variable resistor, inductor, and capacitor are connected in series to the...
  10. D

    Energy from bike riding used to charge phones/laptops

    Hi, I've been thinking up a project on harnessing the kinetic energy to use for charging or powering small deviecs around the house firstly my laptop and smart phone. I have a basic idea of what I'm going to use and have some of the things needed. My idea was to use a small brushless or maybe...
  11. K

    Max Output Power of 9 Phase Alternator

    I have simple 18 pole rotor, which I drive using another motor. I have 9 coils of 0.6 ohm resistance each, which generate open voltage of 1 V each. When I short circuit individual coils, I see current of 1.60 amp in each coil. All of these are randomly out of phase. I cannot group them as in...
  12. A

    Alternator Vibration During Excitation

    Hi guys, I'm new to this forum and this would be my first post :-) Hope you guys can guide me on what to do on this alternator that's having problem with vibration. I'm running out of ideas now on what to do with this alternator. The alternator was sent to our workshop by the client for...
  13. Q

    Wind turbine powering alternator of car instead of engine?

    So, my proposition is this: (Note that this is a purely theoretical project, and no models/experiments are necessary.) When a car moves forward, wind moves backward, right (relatively). So if we were to attach a small, retractable wind turbine to the side, connect it to the alternator, we could...
  14. D

    Can a Stationary Alternator Generate Current Like a Transformer?

    will an alternator produce current when both its field and armature windings are stationary(like transformer action), as ac current produces a changing magnetic field.is the field rotated for making more output?
  15. B

    Replaceable alternator rotor windings

    Has anyone ever heard of a rotor winding that can be interchanged with different shaft lengths? I'm trying to find a way to create a 3-phase alternator with a through shaft to attach pulleys on each end.
  16. H

    Alternator for thermal generator (Coal-fired generator)

    I am doing a project on coal fired generator and I don't really know how my Alternator will work. I'm currently trying to use a 2 pole stator, 5 former making 1 pole, single phase alternator. These are the problems : how do I calculate/obtain the power rating of my alternator/ generator does the...
  17. dean barry

    Calculating Cooling & Alternator Losses for Engines

    When dealing with power losses from engine to drive wheel(s) i ignored losses other than straight friction, can cooling and alternator losses be taken as roughly a percentage of the cars engine power ? Thanks Dean
  18. O

    Rotor Disassembly from Vehicle Alternator - How?

    Good evening, Before I start, I'm sorry if this is in the wrong forum, I wasn't sure where to post such a question. I have an car alternator which I'm going to be experimenting with to generate electricity from the wind. It's a GM Valeo model, possibly taken out of a Vauxhall. Right now...
  19. A

    Low RPM alternator to charge 12V battery

    Hi guys, I am working on a school project. I have an inclined cart mounted on rails moved by a winch. I would like to install an alternator on one of the cart axis, so I can charge a 12V car battery - 20Ah. The wheel turns at 12 RPM. At that speed the alternator will not work, so I am also...
  20. R

    Sychronous Pernament Magnet Alternator under Load

    Hi I have a question about a Synchronous Permanent Magnet Alternator (Small Wind Turbine Alternator) I want to understand the ratio between RPM and the Voltage from the Alternator. I can't find any equation for that ratio , and I read somewhere on the web , that if I have a load ,than the...
  21. R

    Explain regulators and floating grounds to me, eg a car alternator

    I understand the basics but I am a bit lost on what happens in this example. In a car we have an alternator that charges the battery, if the battery is charged to stop it overvolting the regulator essentially shorts power to ground via SCRs (correct me if I'm wrong but this is my understanding)...
  22. M

    Alternator , generator efficiency

    Hi I've been looking in google although I can't find a definitive answer, what are the usual efficiency range for alternators, some talk about brushed ones in the range of 50 to 60 % , brushelss some say go as highas 75%, maybe some of you folks know from your experience what are the typical...
  23. A

    Is it possible for DC alternator using inverter directl without accu ?

    Hello, i am new here, and i hope there is someone here that could help me with this : Homework Statement I have a DC alternator and i want using inverter to make AC. Homework Equations Is there possible without using ACCU ? The Attempt at a Solution I tried directly without...
  24. M

    Which is better for low rpm power generation: generator or alternator?

    Hello there everyone. I was wondering about low rpm power generation. Is it better to get an alternator or a generator? I've been reading about both but I'm still a little confused about which would be best suited. This is going to be for a wind turbine. So the rpm and the power will be...
  25. S

    Permanent Magnet AC Alternator - No Load

    OK... so my understanding is that a DC generator under no load generates high voltages without any current, but does the same hold true for an AC alternator? What happens with current when the RPMs of the alternator exceed what is necessary for the current requirements?
  26. G

    Wasted alternator generated energy

    Sorry if this has been discussed before, I'm not a regular of the site and I have not found anything in a first quick search, if so just direct me to the relevant threads. Many millions of cars are driving every day with their alternators turning. Unless I'm wrong, once the battery is fully...
  27. K

    Build an Alternator: Calculate Requirements for Voltage/Amperage

    I understand that this question has been asked before, but I've seen so many different formulas that I'm questioning which one is applicable to my situation. What are the correct formulas I need to build an alternator to meet certain requirements? I need to meet a specific voltage and amperage...
  28. T

    Does an Alternator Really Take This Much Torque?

    Hi, I'm looking around for a replacement alternator and came across the specs which state max current available at 6000rpm and requires 47nm of torque. I was quite suprised with this needing that amount of torque. So I'm starting to imagine a typical diesel which most don't get up to...
  29. V

    Understanding Alternator Battery Charging: How Does it Work?

    I am wondering how can an alternator charge the battery if the rpm change constantly? Can someone please explain me how it manages to produce a constant voltage?
  30. D

    Is this possibile to do with a alternator?

    A friend of mine sent me this link over from Youtube. I really doubt it a lot... But the numbers from that meter keeps telling me other wise... Basic idea: Added more and more layers of Neodymium magnets to improve the supposed "output". From 10W to 40W as he claims.However, the meter shown in...
  31. R

    Alternator Pitch Difference for DG Sets Synchronizing

    hi all, please provide me the info that what is the maximum allowable pitch difference for synchronizing of DG Sets having different pitch?
  32. C

    Voltage spike in alternator when phases are shorted?

    inductive spiking as a viable electricity generation method? i have made a multi phase alternator to be used in a permenant magnet rotor setup , where the rectified DC output is 3V on average at the operating rate of rotation, as you can see in this video however, the AC wires leading to the...
  33. H

    3rd order harmonic distortion with PM alternator

    I have fashioned permanent magnet alternators with air cores and with iron cores. The air core units generate a sine wave (or something close to it), but the iron core units have third order harmonic distortion, (see waveform). Why is this?
  34. K

    Load angle of an alternator

    After going through the chapter of Alternator (i.e Synchronous Generator) I have come to know that if the steam input to the turbine which is coupled to the rotor shaft of the alternator is increased the load angle will increase.. but what is the reason behind this ? I want to know both...
  35. E

    Alternator Inductor Coil Output Equation (?)

    Hello!I'm working on an experimental alternating current generator project and need specific equations to calculate voltage and current output from a permanent magnet driven inductor, so I will have an idea what to expect before I commit real money to expensive materials. the only variables...
  36. W

    Can I run a 12v alternator with a 12v motor?

    The situation is this, I would like to power a Delco 1 wire 100 amp alternator with a 3/4HP 12v DC motor, I would have an automobile battery to start the motor, and for the alternator to maintain, plus I would like to have enough power to run an additional 30 amps (max) of accessories. I can...
  37. sophiecentaur

    Optimal 12V Alternator Speed for Diesel Engine Boat

    I have looked all over in the search for the optimal speed to run a 12V alternator. I have a diesel engine on my boat which is never run above 2500 revs and I have a feeling that the drive pulley is too large - so the alternator runs slower than optimum. Does anyone know the speed range that I...
  38. B

    Vertically stacked Stators and Rotors Permanent Magnet Alternator

    Greetings, I fabricated a PMA using vertically stacked stators and rotors. I tested the unit on a lathe and was able to gather the following data at different RPMs. The design uses the flux lines from both ends of the magnet. This configuration allows the stators and rotors to be stacked...
  39. V

    Motor and alternator in same shaft

    Sir, Should we make both Motor and Alternator on same shaft? the Motor will run at 12V and it should not consume >2 Amps and tha same time Alternator should produce 220 V 300watts. Please reply
  40. B

    Is a 1968 Alternator Guage unit rebuildable?

    The 1968 alternator gauge is 'smoked' The replacement Stewart-Warner gauge is different - it reads "Amperes" instead of "Alternator". I would like to save the casing on my unit...There is a detent on the rim of the casing and looks to me like the main cap would "pop-off", like a watch case. If...
  41. C

    'levitating alternator' electricity generator question

    hey all, i recently had an idea to combine the concepts of a magnetic bearing i.e. using the repulsion of magnets to lift a rotating object so that the object may rotate without mechanical friction , as well as an axial-flux alternator where coils of wire are exposed to a regularly fluctuating...
  42. F

    How Do You Calculate Power Input for an Alternator at 3000rpm?

    Homework Statement An alternator runs at 3000rpm and produces a sinusoidal output voltage with an amplitude of 100V. Calculate the power input required to turn it. Homework Equations Ohms Law: I=V/R, R=V/I, V=IR, Watts Law P = VI Lenz's law regarding back EMF. The Attempt at a...
  43. G

    Alternator Theory: Questions & Answers

    Hello all! Ive been thinking about car alternators... and have a few questions! Does a car alternator have to be able to supply max power at engine idle speed? My thought being that you could turn on all electrical devices in your car at this speed. I do notice however that when you turn...
  44. B

    Exploring the Potential of Vertically Stacked Permanent Magnet Alternators

    Greetings, I have been working on a permanent magnet alternator, axial flux configuration. It has been configured with vertically staked stators and rotors. The traditional fabrication technique the stator is one large diameter with a large diameter magnet rotor above and the below the stator...
  45. F

    Question About Series-Hybrid Drivetrain Alternator ?

    My friend said he read someone claiming on his blog that in a series hybrid drivetrain consisting of a small engine and an alternator connected by a shaft & belt, the alternator acts as a motor at all times except the power stroke ? I wanted to know if anyone has experimented with this and...
  46. S

    Alternator energy consumption?

    Would someone be able to explain the physics behind how an alternator consumes energy? Obviously there is friction but what force is pushing back on the rotor? How does getting the electrons moving in the wire push back on the magnetic core?
  47. J

    Alternator efficiency question

    Hi guys, Currently just looking through a few concepts for wave energy converters and I noticed that a few designs use bi-directional rotating turbines (or linear action) meaning the alternator has to continuously keep rotating in one direction, stopping, rotating in the other direction...
  48. E

    De-Rectifying Automobile Alternator

    Hi, Automobile Alternators produce AC currents which are converted to DC currents by a diode bridge known as the rectifier.The question is. How does one remove the rectifier so the Alternator produces AC current only. How can it be connected to a Transformer Is there any adverse effect on...
  49. J

    Alternating poles in the stator of an alternator

    I have run into something i don't understand while working with an alternator. I purchased a magnetic pole detector to identify the poles of some magnets and tried to see if i could detect the changing magnetic field of the alternator in my car while it was running by placing the pole detector...
  50. F

    Choosing the Correct Terminal: Understanding DC Alternator Stator Assembly

    Hi there, I have a question on DC generators stator assemblies?? I've been given a standard DC alternator wye wound stator assembly wiring diagram as attached. The question states: terminal at point A is nominated as, answer, (A) "STA", (B) "AUX" or (C) "POS"?
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