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. rossc12


    I’m looking at designing a portable propane electric generator that’s light for camping ect’ What ideas on how to improve the efficiency on the alternator and the inverter from dc to could I improve upon or incorporate? Thanks Rosd
  2. K

    Odd box that connects to alternator and produces 120 volt DC....

    First off, not an engineer, just invading your forum as no one seems to be able to answer this problem. I have an ambulance/fire marshals vehicle, a 1992 Ford E350 with 7.3 IDI diesel. Pre Powerstroke. It came with a red box in one of the compartments that has no labels or identification. It is...
  3. E

    Alternator run at zero power factor lagging

    Hello, I'm wondering if it's possible to make an alternator run at zero power factor lagging (purely inductive). I was researching this topic and apparently by shorting the leads of the alternator the output will become fully reactive. Yet I've attempted this on a small scale and the most I can...
  4. O

    Tiny wind turbine alternator

    Hi, I am trying to rewind an existing Chinese alternator, it comprises of rotor with 12 magnets and 18 poles (stator), the original design produced virtually no power , aluminium windings have been removed and I have replaced with copper 20 gauge wire, 7 turns per pole, I spin it and nothing...
  5. Y

    System design for charging battery from turbine alternator

    I am designing a hydro power system that will tie into an off grid solar system. I will be using a 48v carbon AGM battery bank. Will be using the Sol-Ark 12kw inverter/charger, which has 2 built in MPPT charge controllers for solar. Assume the hydro power will be around 5 kw potential, and...
  6. J

    Honda 50 Alternator: Voltage Output From Windings?

    Have a motorcycle that has alternator under flywheel where the magnet spins around the outside. Looking at wiring diagram one end of windings goes to ground center tap goes to charging battery and third tap or longest part of winding goes to lights and battery, switch determines which part of...
  7. Grinkle

    How can I safely energize a suspect alternator

    I have a "house" alternator on my van. The 12V rail waveform is attached. The 5V drop-outs are not right, imo. The alternator is controlled by a Balmar 614 regulator. http://www.balmar.net/PDF/regulator%20info%20s/MC-614.pdfThe spacing of the drop outs leads me to suspect they are...
  8. D

    Alternator Field Winding Question

    I have an older 12 volt battery-charging 1979 Sencenbaugh wind generator that I am testing. It has an 3 phase alternator with a field winding that must be excited, as opposed to the newer "permanent magnet" alternators. The manual says that 60 watts maximum should go to the field winding...
  9. J

    Electrical Automotive Alternator with External Regulator Light stays on all the time

    My problem started when I took my alternator apart to grease bearings when I put it back to together dash light came on so took it apart seen wire to one of the brushes was broken soldier back together it work for a short while the light was back on seen soldier had broke again so I changed...
  10. S

    3 phase alternator is generating a voltage, but no current

    I made a permanent magnet alternator out of a 3hp 3 phase induction motor. I am getting voltage, but no current at all. The alternator is wired delta and feeds a capacitor bank wired in a wye, to create a neutral. I have even tied the neutral into the alternator and still no current. I connected...
  11. Fdtroya

    Which factors determine the power output of a permanent magnet alternator

    To be more precise the generator has to be able to produce around 1.5 Watts from a person spinning its axis, which is why I was thinking of putting a gearbox in my design but I need to know how much Torque would it take to spin the axis and at what rpm would the generator be effective.
  12. M

    I Why is the Alternator Alternating?

    Hello, let us define the Alternator $$Alt(T)$$ where T is a multilinear function $$Alt(T):= \frac{1}{k!} \sum_{\sigma \in S_n} sgn(\sigma) T (v_{\sigma(1)},...,v_{\sigma(k)}))$$. Further recognize that $$S_n$$ is the group of permutations and sgn the signum of the permutation. May...
  13. M

    Car reading 17V+ in the battery when running, how to fix?

    Hi, I have a 2004 Toyota Matrix with 270 000km. It's working great but today when i started my car the battery was going up to 17.2V (i have a battery voltage reader in the car at all time). It's the first time it went up there, it usually stays in the 13-14V. I know something is wrong and I...
  14. B

    Computing Alternator Back EMF as a function of load current

    I am attempting to make a basic model of an alternator and determine terminal voltage levels at several different current levels. The alternator design looks like this: 900 RPM fixed, 60hz, single phase 2000 gauss permanent magnet Flux Density, Magnet circumferential velocity 9.58 m/sec, 4...
  15. B

    Simulation Software for a Permanent Magnet Alternator Design

    I am looking to try some design ideas using PMs for alternator design. I am a retired EE so I do not have corporate capital for simulation software. Does anyone know of low to medium cost simulation software that might be workable for basic flux/emf/etc calculations and modeling? Or other...
  16. DonKiwi

    Voltage Doubler help: 6V ac 36W alternator in ~ 12V dc out

    I am trying to build a Voltage Doubler to use a motorcycle 6 Volt a.c. alternator's dedicated headlight coil (which presently runs a 36W incandescent headlight bulb) to provide 12 Volt d.c. to drive a commercially-bought 12V LED headlight unit (also rated at 36W). Frequency will be (1500 ~ 5000...
  17. J

    Alternator in parallel new critical clearing time

    Homework Statement Homework Equations critical clearing time proportional to square root of (H / (P times frequency) ) equation 1 Power remains same as alternator at 1p.u Frequency is also same H will increase. It's not given so we can assume machines swing together, so H = H1 + H2 = 2H since...
  18. J

    Alternator connected to a long line

    Homework Statement [/B]Homework Equations I think right answer should be A. Long line on no load is like capacitor so due to ferranti effect the terminal voltage is high. Now when alterator is disconnected the terminal voltage will drop to Ef The Attempt at a Solution Book says answer is D. It...
  19. Oladapo Babatunde

    How to recharge a 12V battery using an Alternator

    I am working on a rural project that requires continuous use of 12v battery as a single unit,to keep the project running i need to recharge the battery . How do i connect an alternator to recharge the battery while the batteries is in use. or can i use a Capacitor instead. My thinking is since...
  20. W

    Maximizing Alternator Efficiency: Does RPM Affect Permanent Magnet Alternators?

    Hello Wizards! Does permanent magnet alternator efficiency increase with RPM? Would an alternator with small magnets turning at high speed be more efficient than and alternator with large magnets turning at low speed. Frequency of output is not a concern, ( converting to dc ) Thanks for...
  21. J

    Joe McFadden magnetic rotors

    I’ve come to this forum because for some reason in my later part of my life I’ve become fascinated with magnetic forces... a dream has driven me to “ let’s get some magnets spinning “ attitude. I am looking for answers and guidance regarding magnetic motors and generator systems.
  22. T

    Increasing the number of pole shoes on an alternator rotor

    Would like to know how to determine if 2 additional pair of rotor pole shoes can be added (re-designed) to rotor for existing 72 slot alternator stator. Present claw pole rotor has a total of 12 and I would like to have a total of 16. Any assistance would be appreciated. Thank you.alternator...
  23. T

    Does an alternator obey Ohm's law?

    Do alternators obey Ohm’s law? The alternator output voltage is proportional to the rotor excitation current. When reducing rotor excitation, the output voltage drops and the load resistance stays constant. Can why still use ohm law to determine the output current. Example alternator 480 v / 4...
  24. T

    How do I calculate the output current of an alternator

    Do alternators obey Ohm’s law? The alternator output voltage is proportional to the rotor excitation current. When reducing rotor excitation, the output voltage drops and the load resistance stays constant. Can why still use ohm law to determine the output current. Example alternator 480 v / 4...
  25. J

    Why Do Railcars Use Inverters with Alternators?

    Hi everyone I am currently working with diesel railcars. To power the electrical systems, we have engines connected to alternators, which then connect to static inverters. The auxiliary power system runs off the static inverters, initially at 415V AC but distributed throughout the railcars at...
  26. A

    Can a Car Alternator Function as a Battery to Power a Motor?

    Hello, Is it possible for a car alternator to work like a battery and power a motor?
  27. J

    Can You Use Resistance to Fix Alternator Output at 2 Amps?

    I have a 10SI delco alternator the voltage regulator and diode trio test open to all points I put it togather this way I know it will not charge unless you ground the one side of the brushes then the alternator will put out maximim output. What I want to know if you put resistance between ground...
  28. G

    Static test of Denso 12 V alternator

    I know a real test of this unit would be to mount it and run, checking DC and AC voltage, current etc. The plan is to mount it on my Super Dexta, but this would need some work as there's currently a dynamo which is starting to fail. I was given the alternator free and would like to bench test it...
  29. J

    Directly power house with alternator

    My plan is to reduce electricity use supplied by the grid by having a waterwheel partially power a house. From my simple research I've learned that hooking an alternator up to the waterwheel would work. Since a house runs on 120V AC and an alternator produces (correct me if I'm wrong) 13.8 -...
  30. jlmccart03

    Find alternators magnetic field?

    Homework Statement You're an electrical engineer designing an alternator (the generator that charges a car's battery). Mechanical engineers specify a 10-cm-diameter rotating coil, and you determine that you can fit 250 turns in this coil. To charge a 12-Vbattery, you need a peak output of 16 V...
  31. T

    Negative and zero sequence impedance of alternator

    To measure negative sequence impedance of an alternator, we short the white and blue phases, measure the current and then divide it by the voltage of the red phase. Then to measure zero sequence impedance, we short the rotor and connect the stator in open delta and inject a current. My...
  32. J

    Which is the correct diagram (synchronous alternator varying PF)

    Hi, Sorry this question may be silly but I have an exam on 11th Feb on machines, maths and electronics. Book had two diagrams for alternator external characteristics. But then which one of 2 diagrams is right? Book says: For zero pf loads, it is seen V(t) = E(f) +/- I(a)X(s) It's minus for...
  33. srinaath

    What are the effects of changing the speed of alternator?

    Homework Statement What are the effects of changing the speed of alternator? (elctrical synchronus generator) Homework Equations Ns=120*f/p; p-poles f-frequency Ns-synch speed E=4.44*f*phi*T phi-max flux linkage T-turns f-freq E- generated voltage The Attempt at a Solution from the above...
  34. H

    I What causes alternator waveform shape?

    I have a permanent magnet alternator. It does not produce a sine wave output, but rather a sort of distorted triangle wave. I did a frequency analysis on it and it showed a series of harmonics. The strongest was the third, with each odd harmonic getting progressively less powerful. It also...
  35. J

    What is tangent of power factor angle for an alternator?

    My book had these two solved examples that gave contradictory replies. The power output of an alternator is 100 kW. Now if the tangent of pf angle is 0.8 lagging, the KVAR rating must be -80KVAR. I drew phasor and got this. I took it that since tangent is negative. Now tangent is opposite...
  36. J

    Does Reversing the Field Current Change the Phase Sequence of an Alternator?

    Homework Statement A three phase alternator has a phase sequence of RYB for its three output voltages. In case the field current is reversed, the phase sequence will become (A) RBY (B) RYB (C) YRB (D) none of the above. Homework Equations Faraday's Right Hand Rule The Attempt at a Solution I...
  37. G

    Potential difference in an alternator

    Hi, In a current generated by an alternator, can we really say that there is a potential difference like in a battery? The magnetic field exerts a force on the electrons which makes them move. We can calculate the work done to the electrons in joules, and we can divide this energy by the...
  38. J

    What happens when alternator load is increased

    So I'm studying synchronous machines and what happens when load is increased. In case of alternator(synchronous generator) if the load is increased, like more lamp is added in parallel, then the armature current would increase. But where does this extra current come from? The rotor cannot go...
  39. R

    How to specify an electric alternator....

    how we can specify an alternator (which converts rotational energy into electricity) . how we can calculate the charge given out by alternator in its one revolution .
  40. B

    AC Alternator Load Loss on Engine Performance

    I'm trying to determine the amount of load (power loss) a theoretical engine will suffer from an AC alternator, such as one you would find on an automobile engine, they produce something of 40 amps with 110 volts I believe? To be specific, I'm curious to know how much a theoretical engine would...
  41. cnh1995

    Rotor and negative sequence impedance of alternator

    When an alternator is supplied with a 3-phase voltage and its rotor is rotated in opposite direction to that of the stator rmf, the ratio phase voltage/phase current is the negative sequence impedance of the alternator. My understanding of this is as follows: When rotor is rotated in opposite...
  42. cnh1995

    Negative sequence currents in an alternator

    We recently performed one experiment regarding measurement of negative sequence impedance of an alternator(unloaded) in our lab session. The alternator was star connected and we shorted Y and B phases together, leaving R phase open(an L-L fault). How does this arrangement generate negative...
  43. cnh1995

    Synchronization of an alternator to the grid

    When an alternator is synchronized to the grid, its voltage and frequency are same as those of the grid. So, it shouldn't take any load at that instant. How is it brought into operation then? What is the procedure followed practically? My book says prime mover is given some extra energy so the...
  44. Metals

    In an Alternator, is the armature an electromagnet?

    Hey, I'm lightly studying 'Generating' as a topic in my Physics curriculum. I have just been introduced to an AC Generator, an Alternator, and I have a simple question: Is the armature in an alternator an electromagnet? From my understanding, there is a U-Shaped length of wire(s) which...
  45. P

    Maximizing Current Output of BLDC Generator for Power Generation Project

    I'm using the following BLDC motor as part of a project to generate power: http://www.rcdude.com/Cobra-C-3520-18-Brushless-Motor-p/c-3520-18.htm I'm able to spin this motor to about 3000 RPMS which gives me about 5 Volts. This is to be expected given that the motor is rated at 550 KVs. I'm...
  46. A

    Car Alternator & Battery: How it Charges & Works

    How car alternator charge battery..?? Both equipment are connected with same cable so why battery power does not reached at alternator?? If you guys have any animation it would be helpful..
  47. D

    Book or free video course on alternator design

    Hi All, Does anyone perhaps now of a book or free video course on alternator design, Like where I can learn about how to design alternators? Sorry if I posted the question in the wrong "apartment" of the site. Thanks Dilan
  48. cnh1995

    Reactive Load and Alternator Speed: Exploring the Relationship

    A motor driven alternator connected to local load (in lab), say a lamp bank, slows down due to power consumption by the load I.e. nonzero power angle δ. But should it slow down when δ is zero i.e. with purely reactive load(like in SC test and ZPF test)?
  49. I

    Engine torque: Can an alternator increase ICE torque?

    Hi there. What would happen if, while generating electricity with a fixed inlet power from the ICE, the alternator suddenly increase the out put demand by increasing the voltage? Does the engine would augment the torque while reducing RPMs? consider a self excited alternator, the voltage is...