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How powerful of a motor do you need to run an alternator? Answered

From questions I have read and step by step’s I have read a question came to my mind.
How powerful of a motor do you need to run an alternator?
I checked the Delco Remy alternator series from 10SI in 37 Amps, to the 40SI durable brushless model, in 240, 275, and 300 Amps.
All their performance charts show rpm’s at the alternator not the motor.
The pulley on the crankshaft is considerably larger than the pulley on the alternator, giving you more rpm’s at the alternator than at the motor.
All their performance charts show rpm’s from 1200 to 8000 rpm’s.
All their performance charts show at 3000 rpm’s you get 13/16ths of max power.
The last 5000 rpm’s only gaining 3/16ths of power.
The thing is none of the performance charts say the horsepower to drive the alternator.

I decided to approach the problem from a different direction
Typical alternator efficiencies are in the 54%-60% range.
Brushless alternator efficiencies are in the 60% 70% range.
A typical 12v 60 Amp alternator produces 720 watts at 55% efficiency.
It needs just 1310 watts to drive it or a little under two horsepower at 1492 watts.
This does not account for mechanical efficiency of connecting the alternator to the motor.
With this in mind a three horsepower motor should drive a 12v 60 Amp alternator.
This is just an educated guess but I would like a horsepower chart.

720 watts would do well at charging a battery bank while you sleep; however I could not run my microwave and charge batteries at the same time.

Discussions

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iceng

Best Answer 7 years ago

Here is my mechanical 60 Hz  to 50 Hz sine wave  frequency changer.  
A 50 cycle MG set ( Motor Generator ),  The alternator has been modified
( no diodes ) to output 120 VAC at 50 Hz by virtue of the belt pulley diameters.
The drive is a 115 VAC induction motor drawing 9.6 Amps 60 Hz at 1725 RPM,
that's over a Kilowatt about 1½ HP of input Power. 
The alternator was rewound deliver over 6 Amps at 110 VAC 50 Hz. about 700 Watts.
There is a step-up 600 VA transformer is used to provide 220 VAC at 50 cycles.

The dual duplex outlet on the left provides 220 VAC and 110 VAC at 50 Hz.
The single duplex and motor power switch on the right is the 115 VAC 60 Hz side.
Efficiency of the whole system is a whopping 60%  but with it I can qualify designs
for the rest of the world including the UK :-)
There is a 12 sec video of it running.  The last pic is where it helps hold down a
Chinese metal lathe.

In my opinion a Transformer Rectifier would be a much better battery charger
then an MG setup...........................   A

ALT1.JPGmotorNamePlate1.JPG
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icengiceng

Answer 3 years ago

Trying a better video

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Josehf Murchisoniceng

Answer 7 years ago

Now that is neat, years ago I worked for a company that rebuilt electric motors.
We would get brand new motors from manual lath’s imported from Europe that ran on a variety of voltages and cycles, our job was to convert them to 600v 60cy. (Canadian Industrial Power) large electric motors are cheaper to rebuild then they are to buy.
That looks easier to build than a variable power inverter or rebuilding the motor without the specialised equipment. Especially if you cant buy just the right motor.

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KhalidM58

2 months ago

I plan to buy 7.5 hp 1800 RPM driver electric Motor to driven 5 kw AC alternator to support my electrical equipment load, of 4,500 watt and i want to use an inverter of 7 kw, then VFD to continous running in 48 hours, from battery source of 48 VDC if not what to do, and what is the best by pulley driven or direct to the shafting with the flywheel in.

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AndrewN152

6 months ago

Am please, to be here and have learnt a lot, but I need help, I have a 3kilowatt alternator, butbi din know the actual horse power and wattage of motor needed to run that 3kilowatt. And I will all be greatful to have more answer for the various ways to convert wattage to horsepower, so the stress of asking too much question will be less.thanks in advance.

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AndrewN152

7 months ago

Good evening here, now I start to imagine how simple it will be for me to have full mentorship with my mini innovative project, with the aid of the instructive team here. I firstly did a generator project that can run for over a week with out going off by using ordinary battery and other electronic stuff, but today I think of expand on that by providing electricity for me people living at the sub-sharan community, now How many watt alternator I should use to power over fifty houses as a start up and what would be the wattage and the strength of the motor to turn the alternator.

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SolaceplusAndrewN152

Reply 6 months ago

Hello Andrew! I’m interested in this, perhaps you can put me through. I want to be able to produce an electricity to power my small house, with the aid of an alternator, battery and a motor, and other electronic stuff. I have a 3kva alternator. No electric motor yet as i dont know which electric one to use for now. I really need to make this work without the use of piston engine motor that uses fuel. I wan the electric one. Thanks in advance. You can also email me at laurex_bb@yahoo.com

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Josehf MurchisonAndrewN152

Reply 7 months ago

Just to give each house 1000 watts (enough for a computer and some LED lighting) a 50,000 watt generator and a 100,000 watt or 140 horse motor.
The average home here in Canada with all the modern conveniences uses 50, 000 wH a month. (Watt Hours)

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princeadeosun

6 months ago

I have a mandate to produce a power generator that will supply 3kva for domestic use;using a motor,alternator and battery; can someone help me with the accurate rating of;alternator,motor and battery that will give me this?and can it be noiseless?

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Josehf Murchisonprinceadeosun

Reply 6 months ago

Noiseless is not likely, even wind turbines make noise.
To be noiseless solar is best.
A 3kva generator depending on its efficiency will need as much as twice the output or 8 horse power motor.

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princeadeosun

6 months ago

I need someone to help me out please;I have a mandate to produce a 3kva power for domestic use using electric motor,an alternator and battery;please what is the motor rating I can use,battery rating,alternator rating meanwhile I want it to be noiseless.

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LymM

7 months ago

I need some help my project is to produce 10kw generator .10kw alternator and 27hp motor.

How much energy is left to use? Thank.

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Josehf MurchisonLymM

Reply 7 months ago

That depends on the efficiency of the alternator.

1 horse is 746 watts

10,000 / 746 = 13.4 horse.

If the alternator is only 50% efficient, that is 26.8 horse just to run the alternator.

13.4 x 50% = 26.8 horse

However if the alternator is 75% efficient

13.4 x 75% = 18 horse

At a 50% efficient alternator all the energy is used to produce electricity.

At a 75% efficient alternator only uses 18 horse to produce electricity and you have 9 horse or 6714 watts left over.

You can get brushless alternators that are 90% efficient.

13.4 x 90% = 15 horse leaving 12 horse unused.

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VictorR54

9 months ago

yes, you can run the microwave. It would simply draw from the batteries and genset at the same time.

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PeterA226

1 year ago

JOseph or iceng.what if i use a flywheel,can a 1hp motor run a 5kw alternator,ill use my hand for to initiate motion.would this be possible?

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Josehf MurchisonPeterA226

Answer 1 year ago

Not to full power.

A 5 kw alternator needs 5 kw plus efficiency.

So if your alternator is 50% efficient you need a 10 kw motor minimum to get to full power. About 14 horsepower.

1 horse power is 746 watts.

A flywheel doesn't add horse power it only adds stable load torque.

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solaimans1

1 year ago

When synchronized 5kva alternator and driven motor are same frequency,speed,& rating how to needs ?

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JamiluM

1 year ago

Hello please can any body help my how to construct flywheel free enargy? I have 3kva altanator 1500rpm and 2hp 1400rpm

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paulo148

1 year ago

an alternator with AC and DC phase, can the DC output use to charge a battery that is powering DC motor that is driving the same alternator effectively?

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Hammerhead46paulo148

Answer 1 year ago

NO!
That would be perpetual motion.
Not possible with what we know today.
Friction loss in bearings alone would prevent it.

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Josehf MurchisonHammerhead46

Answer 1 year ago

You know; I originally asked this question because, I wanted to power an alternator with a gas engine, and wasn't sure about gas to alternator efficiency.

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paulo148

1 year ago

Please, am a student, my project is to produce 5kva using DC motor,
What HP or motor do I need to drive 5kva alternator
Thank

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Josehf Murchisonpaulo148

Answer 1 year ago

Ok 5kva to watts is 5000 watts.

1 horse = 746 watts.

5000 / 746 = 6.7 horse.

So for a 5kva alternator that is 100% efficient you need a 6.7 to a 7 horse motor. However most alternators are not even 90% efficient, most are only 50% efficient so you may need a 14 horse to power that alternator.

What is the efficiency of your alternator.

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paulo148Josehf Murchison

Answer 1 year ago

Please I find out that the output from the alternator was not enough to drive the motor(DC) continually, as the battery went down.

So what do I do to ensure that that the alternator charges the battery very well and generate 5kva

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Josehf Murchisonpaulo148

Answer 1 year ago

Of course not; you are using up to 10,000 watts, to make 5,000 watts.

Alternators are only 50 to 80 % efficient; for a 5,000 watt motor to drive a 5,000 watt alternator then to power a 5,000 watt motor it would need to be 100 % efficient. Then to do some other work the alternator would need to be 100 % + efficient.

The only thing over 100 % efficient is geothermal heating; and it dose not convert electricity to heat, it just moves the heat from one place to another, so you put 1,000 watts in and you get 3,000 watts heat out of the system.

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icengJosehf Murchison

Answer 1 year ago

You are correct, that is a more realistic value for efficiency !

Paulo you will need 14 of these devices pictured below ;-)

FMT34D9GPZ9R7XQ.MEDIUM.jpg
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Josehf Murchisoniceng

Answer 1 year ago

OK I have got to ask, What did you google to get that PIC.?

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icengJosehf Murchison

Answer 1 year ago

Nine years ago I was a good skier..

Now I'm building this using a 1/3 HP 3 Phase Motor

Sinv.jpg1in Tumbler.jpgStrong2.jpg
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Josehf Murchisoniceng

Answer 1 year ago

What about a racing bike air tube some of them can be quit small in diameter.

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icengJosehf Murchison

Answer 1 year ago

Water hose but it was new wound and has bumping..

I may have to search out old garden hose.

Grip2.jpgMix1.jpg
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icengpaulo148

Answer 1 year ago

5000 VA / 746 HP/W = 6.70 HP

Now assume 80% conversion efficiency.

6.70 / 0.80 = 8.38 HP DC motor is your answer.

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BTW next time ask your own question, so you may award the best answer and more iblers will see your comment rather then the few who have left a watch command to a 6yr old question.

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paulo148

1 year ago

Please, am a student, my project is to produce 5kva using DC motor,

What HP of motor do I need to drive 5kva alternator

Thank

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Ianne-PH

2 years ago

Hello. Please give us advise on our school project.

We are trying to make a generator using motor and alternator. If our target is to produce minimum of 1000 watts of electricity, is an 85amps alternator already good enough? what is the compatible volts, amps and hp of motor do we need to find? We'll appreciate any expert response from anyone in here.

- Student Ianne

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Josehf MurchisonIanne-PH

Answer 2 years ago

You are going to need about a 3 to 3 1/2 horse power motor depending on the alternator. Some car alternators are only 50% efficient. So 2000 watts / 746 watts = 2.68 horse + 1 for mechanical.

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JohnA391

2 years ago

I'm in need of some help, I'm working on a project including a steam powerer tesla turbine which I want to harvest surplus energy going into a boiler, it'll also serve as backup power generator in winter when the P.V.s slow down.

I'm looking at a 2m long, 300mm dia boiler witha 100mm dia flue running through it, not sure what sort of pressures I'm looking at. This comes after a thermal mass rocket stove style combustion pipe burning wood. The tesla turbine will be ally plates in oil drum based housing (572mm, 22.5" dia).

Any ideas what sort of alternator would be suitable and should I be thinking about any gearing?

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Josehf MurchisonJohnA391

Answer 2 years ago

Since Tesla turbines are very efficient and high RPM you should be able to connect an alternator direct to the turbine.

I wouldn't go with a car alternator most of them are only 50 to 60% efficient.

I would go with a brushless alternator or a brushless generator some of them are 80 to 90% efficient.

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chirag prajapati

2 years ago

I have a technology for produced
the free energy by alternator...i can do
that..but still working for the experiment.

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AinuddinS

3 years ago

how much current produce when a DC altinetor works 1800rpm or 1200rpm and volt 60vlt or 120 volt

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icengAinuddinS

Answer 3 years ago

How many pounds is the alternator weigh ?

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AinuddinS

3 years ago

how much current produce hen a altinator work 1800 rpm and volt 120volt or 60 volt

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cuyler1

3 years ago

i know from experience as i had a 35 amp alternator combined with a 3.5 hp b&s over 20 years ago. if i had a huge amperage draw the engine would stall as the alternator came up to match the output. i used this to charge the race car battery between rounds and had 1- 500 watt halogen floodlight and a box fan to cool me off. Just about any other device such as a small tv connected to it would stall it. purchase a 5-6.5 hp engine and a 350 sbc crankshaft pulley then connect to the ( i'd run a 6.5hp harbor freight engine on it) engine and this would overdrive the alternator. i've viewed the diy generators on youtube but what they don't tell you is the engine has to be started in a no load alternator situation.

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Josehf Murchisoncuyler1

Answer 3 years ago

Not surprised combine 50% efficiency with up to 25% mechanical loss and you do not have much left for generation.