# Questions tagged [alternator]

Electrical generators that produce alternate current.

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### I've designed a new style of ac alternator where both the stator and the rotor rotate oppsite directions so that rpms multiply by each other [closed]

My body of information is on a youtube video of nothing more than a hand drawn picture. In explanation of my actions I did this to publish to establish prior art. What I'm curious to know even if its ...
93 views

### What happens if you connect an AC generator to an AC motor? [closed]

An AC generator (or alternator) converts mechanical energy into electrical energy. An AC motor does the reverse. What would happen if we connect the two in such a way that the output rotational ...
49 views

### Actual Line-to-Line voltage from per unit value

In this question, I am able to find the per unit phase voltages using the symmetrical components. Taking the base MVA and base voltage to be the same as that of the alternator, \\$ (I_a)_1 = \frac{E_a}{...
49 views

### Can an alternator recharge a battery in an EV

Can you recharge a EV's electric battery with an alternator hooked up to the axle of the EV? This question came from a conversation with my Grandpa, and I was looking for an explanation for him of why ...
1 vote
259 views

### Looking for solution to energize a relay ONLY when the alternator is running

I added a DC-DC converter in my truck so that I can charge the Lithium batteries in my RV. To turn on the converter, I am using a relay that ties to upfitter switches in my Ford F350 truck. This all ...
• 19
82 views

### 24 V alternator to 24 V motor

I plan to run a 400 RPM, 400 W, 24 V AC alternator through a bridge rectifier, then through a 25 V smoothing capacitor, and then drive a 24 V, low-RPM DC motor. I would like advice on specifics. ...
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1 vote
60 views

### What is the net current through this LR circuit

Here is the problem which I was asked to do. I started by the method of phasors considering first the upper branch of the circuit Drawing phasors as follows : Then for the lower circuit i drew the ...
464 views

### Does Alternator Self-Excitation Require Rectification?

I am learning about self-excitation in alternators. My understanding is that there is residual magnetism in the rotor. As it spins, this generates a current in a stator which is then fed to the (...
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### Alternator's saturation in load and no-load conditions

When a ferromagnetic material is exposed to a magnetic field in which it moves, some voltage is induced in the material. If you increase the magnetic field, the voltage is increased up to a point, and ...
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### Alternator motor on 3 phase power

Hi was wondering would a alternator work as a motor if supplied dc power to the rotor and 3 phase ac to the stator. Have seen a lot of posts and videos turning it into a bldc motor but none on turning ...
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1 vote
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### Design principles that prevent overcharging of batteries in older vehicles without undercharging

This question is regarding older (10 to 30 years old) cars which did not have a smart solid-state or electronic charger built in. Basically, lead-acid batteries in such cars were (and in cheaper cars, ...
59 views

### Using bridge rectifier on failing alternator output?

I have a bridge rectifier (because it was what was readily available as an integrated part) rated at 150A which I'm using to protect against intermittent reverse current (battery draining) in an ...
1 vote
86 views

### Car battery > inverter > battery Maintainer > Same car battery = jumper cables in the trash?

I'm wondering if I have my car battery hooked up to a power inverter hooked up to a battery maintainer hooked up to the same car battery will it prevent me from needing to jumper cable my car? I ...
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1 vote
225 views

### Designing an automotive alternator's voltage regulator - how to avoid magnetic saturation in the rotor?

NB: See final edit. The question is based on a false premise Friends are making a test-bench for automotive ("Lundell") type alternators. They were supplied with an example alternator plus a ...
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### Three phase power supply for test purposes

I work in the electrical industry and deal with mainly three phase power. I'm trying to broaden my knowledge of scopes and power quality and the only time I really have to do this is at work and that ...
1 vote
101 views

### Can steel nails be substituted for the silicon steel laminate in a motor/generator/alternator?

This is as diagram of a generator/alternator in which steel nails are used in place of silicon steel laminates:
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### Honda CBX 1979 Regulator/Rectifier - Lipo (lifepo4) battery

I exchanged the OEM battery (PB) of the CBX 1000 motorcycle with a Lifepo4 12V battery. It is smaller, lighter and has a much better CCA. However, the connector (wires at the bottom side of photo) ...
• 1
66 views

### Charging battery using a three phase alternator

I want to charge a 672 VDC (182 kWh) battery pack using a 25 kW three phase alternator (679.8 VDC at 4000 rpm, current = 38.5 A). Can anyone suggest how to design the system? The alternator is powered ...
1 vote
117 views

### Why are all the phases connected together on this old alternator

I got my hand on an old car alternator. I can't figure out how it works. What bugs me is that it look like all the phases (and neutral) are connected together right at the output of the stator coils. ...
• 11
169 views

### Shape of magnets used in an AC generator and its relation with the obtained waveform

Suppose we are dealing with an elementary AC generator having a single coil armature located between the curved north and south poles of a magnet(like the ones found in toy DC motors-only two poles). ...
205 views

### 48V Lithium Battery Cutoff Detection Circuit

I'm building a power system using four x 48 V 100 Ah lithium batteries in parallel (48 V 400 Ah nominal). The batteries are already purchased, there is no going back. The cells cannot be accessed, ...
1 vote
231 views

### What is the intuition behind the formula P = 2n in computing alternator stator poles?

So from my reference for alternators and even in the Internet, it says that the number of poles P, produced in the rotating field is P = 2n where n is the number of stator slots/pole/phase. I've seen ...
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### How long should one let the motor turn (witout driving) to re-charge the car battery, after having using it to charge a laptop's battery [closed]

I'm going to spend 1 week with no electricity. I won't need any for everyday life (I do this each year), except to charge my laptop's battery (10.8V, 5.2Ah, 57 Wh) three or four times. I have a car ...
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1k views

### How does a lead acid battery accept more current when it is discharged than when it is charged if the resistance is higher when it is discharged?

I'm just trying to get my head around the above question. It doesn't seem to follow Ohm's law. Could someone please explain what I am missing in this? Below is a chart I found of the changing ...
• 75
998 views

### How can I test the rotor winding of a single phase brushless alternator on a generator?

Context Generator runs but no power output from the alternator. The manual gives Ohm readings for the stator, excitation and rotor windings. The stator and excitation coil are to spec and have no ...
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163 views

### Current limiting at 100 amps

What options exist for limiting current in this scenario? I have been searching for an option and it looks like I need to reduce the field on the alternator but I don't understand enough to know if ...
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### Selecting Capacitor to reduce AC ripple from Car Alternator - LED Indicators only work when Engine Off

My neighbour has recently installed some aftermarket LED indicators, when the engine is switched off the units work as expected, switching from white headlight mode, to blinking yellow mode. When the ...
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208 views

### Why does a change in excitation of an alternator affect only kVA and not kW?

http://www.brainkart.com/article/Effect-of-Change-of-Excitation_12208/ The explanation is there but I feel too dumb to be able to understand it and connect it to the visual. Can someone explain it in ...
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1 vote
240 views

### Car alternator broken soldering joint

so it was very cold in my country last week and my car alternator died. I took it out and I found that one coil wire, which connects to rectifier is broken and there is no contact (I guess it could ...
148 views

### How is it that the induced EMF in an alternator is in quadrature with the main flux?

Looking at the simplified diagram of an alternator, the flux "linked" with the conductor is maximum at 90, 270 degrees, is also when induced EMF is maximum. So isn't the main flux in phase ...
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### Counter torque in alternator supplying reactive power

When an alternator(assume zero armature resistance and iron loss) is supplying purely lagging/leading current, which means there is no work done by the current supplied, does that mean the counter ...
1 vote
75 views

### How can you predict the power an electrical generator (alternator) produces?

We have to design an electrical alternator in a multiphysics software, but we can't seem to figure out how to deduce the power it will produce. We need to charge a capacitor to 1000 joules (at 2000V) ...
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1 vote
110 views

### Car Battery Voltage

Why is the voltage of a car battery rated for say 12V around 14V when the car is running? Is it because of the alternator?
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### Regulating voltage from an alternator [closed]

I asked a question about voltage regulators but didn't get a proper answer, so here's a new one. So i have this motorcycle with an alternator. The alternator gives out about 3 volts at idle speed, but ...
531 views

### Determining number of poles on permanent magnet alternator

I was able to buy a cheap used permanent magnet alternator, however the seller was not able to tell me much about the specifications. I could determine that it has a built in voltage regulator, ...
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### Which form between solar panel and wind turbines requires less cost in servicing?

I found that the average life of a solar panel is about 25 years and that of the the wind turbine is also somewhat close to 25 years. But the wind turbines require alternator in order to generate ...
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1 vote
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### How can I calculate the internal resistance of an alternator?

I have a 12V, 90A alternator. I wanted to know how can I calculate its internal resistance. The specifications sheet I received from the manufacturer is a simple image, as shown below: I This ...
220 views

### Using rectifier + inverter to get 50Hz AC output

I am currently in the theoretical (until I am very sure that it is safe) situation that I have an alternator powered by a gasoline engine that provides 220V 1500W AC power with RPM dependent frequency....
367 views

### What determines the frequency of alternating current?

I am certain this question has been asked before but I search and cannot see anything just yet. I read most AC current is 60 cycles per second in the United States and some say 50 but that does not ...
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### Old lead-acid battery inrush charging current

Can an old lead-acid battery have an usually high inrush charging current, such that the alternator belt squeals for the first 30-90 seconds after the engine is started? It is worse in hot weather. ...
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### Is the calculation of weight to be suspended inorder to produce electricity from an alternator correct or not?

I bought a alternator with the following specs: power: 5 hp rpm: 1800 voltage: 220V The formula for finding the horsepower is: horsepower= (RPM X Torque)/5252 By substituting the value of horsepower ...
• 9
559 views

### Alternator output rating

Overview: I am currently working on a project that requires a 24v alternator, which is powered by a mower engine. This engine in particular runs around 3,000 RPM, and does not exceed 3,200 RPM (based ...
2k views

### Tantalum Capacitor Explodes When Engine Starts

I designed a circuit using a SMPS voltage regulator based on the tps65261rhbr triple synchronous buck converter. The circuit is rated for up to 18V. It is connected to a 12V lawnmower battery, which ...
84 views

### An AC generator can 'lock up' if its timing is off? [closed]

I believe I read elsewhere on Stack Exchange (Physics or Electrical Engineering) about how an alternating current generator can seize up if the frequency of the current does not match something else ...
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### Modifying brushless alternator for external regulator

I'd like to modify a Delco Remy 38si or 40si brushless alternator for use with an external voltage regulator. For a brushed alternator, I'd just need to pull the field out external to the case. My ...
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1 vote
59 views

### Selecting the right PMDC motor and battery

I'm looking at generating electrical energy from a mechanical input being used to rotate the shaft of a Permanent magnet DC motor. However, i'm a bit stuck with selecting the right motor and battery ...
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### Attempt to build DIY high current power supply from car alternator?

Recently I had posted about a thread related to a bench DIY high current transformer 12VDC supply that I'm trying to built. But due to some transformer and diode rectifier limitations that project may ...
1 vote
2k views

### How can excitation be used of an alternator to control the power factor?

Looking for ways the excitation of an alternator can control its power factor?