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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.

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iceng
iceng

Best Answer 9 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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iceng
iceng

Answer 5 years ago

Trying a better video

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Josehf Murchison
Josehf Murchison

Answer 9 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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Snoj
Snoj

27 days ago

Pls what capacity of single phase motor or motors can drive alternators of the following range 15w to 30w or better how can i design a motor driven alternator that can generate between 15w to 30w. I need all important parameters stated clearly to assist my design.

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Josehf Murchison
Josehf Murchison

Reply 24 days ago

OK if you want to power an alternator, you need to know a few things about your alternator.
1. Watts, the output of the alternator in watts, every 746 watts equals 1 horse.
2. The efficiency of the alternator, I recommend brushless alternators they are as much as 95% efficient.
3. How these work.
As an example a car alternator it is about 50% efficient. (I picked this for the easy calculation 2 in 1 out.)
So for every 746 watts (1 horse) out of the alternator, you need a minimum of 1492 watts (2 horse) to power the alternator.
So an AC Delco 334-2114 alternators output of 12 volts 100 amps, has an output of (12 x 100 = 1200 watts)/746 = 1.6 horse.
1.6 x 2 = 3.2 so you would need a minimum 3.2 horse power engine to power an AC Delco 334-2114 alternator.

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Robert Ose
Robert Ose

5 months ago

Good Day Sir, Please just neended some clearifications, What's the minimum capacity of Electric Motor required to run 50kva Alternator, would appreciate more if paramiters are listed side by side. Thanks.

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Snoj
Snoj

Reply 27 days ago

Please i need this answer to help me design my own motor generator

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georgeaina7
georgeaina7

4 months ago

hello, please am a novice in this discussion, but in this attachment, can u tell how many horse power can carry the alternator perfectly? And is this kind of invention good for home use and office?

gen.jpg
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Ajide01
Ajide01

4 months ago

Good day I av a 3hp 24v DC motor, 2.7kva alternator, 12volt battery, 12volt car alternator for charging the battery. can i use this setup to power a 1hp pumping machine for like 10hours,will the power of charging alternator be effective,? Please I really need us help. Thanks

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weri812
weri812

7 months ago

thank you this helps

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sh4dows
sh4dows

7 months ago

Hi everyone. This seems like a good place to pose an interesting question:
OK... for a medium sized, twin diesel engine boat application. Most planing boats are overpowered because they need plenty of power for the hole-shot (getting the boat up onto it's plane'). Once you're up out of the water at cruising speed you've got a couple of big HP diesel engines running extremely uneconomically.

So - how about pulling one engine out - converting to electric motor direct drive to the propeller, and using the remaining diesel engine to run alternator / generator to power an electric motor that has immense torque to drive the propeller?

OK - so we pull 1 diesel engine out of the boat and reconfigure the hull for a singe propeller shaft. Now we have a single diesel engine producing 450hp / 331kw and 1464Nm (1080 lbf. ft) @ 1510rpm. (motor rated@ 2700rpm).

What's the best & cheapest way to convert this diesel power into electric power that can drive an electric motor direct drive to the propeller?

I'm sure some of you will wonder why we would want to do this - electric motor power is delivered far more effectively because of high torque...

Let's forget about battery banks as they're still rather expensive.
Let's look at: Diesel motor > Alternator Generator > Electric motor drive as a configuration like a diesel electric train setup - and see what numbers we can come up with :-)

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amahe1979
amahe1979

1 year ago

What transformer can I use to power 1hp, 12VDC, 3000rpm motor. For effective working and without reducing motor speed. Pls kindly reply

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justforus2005
justforus2005

Reply 9 months ago

30 AMP TRASFORMER TO MAX IT OUT MAY NEED 60 AMPS U RAN TWO TRASFORAMERS WITH FANS ON THEM I HAPPEN HAVE TWO SUCH TRASFORMERS THEY FAR FROM CHEEP NEW BUT I HAVE NO USE FOR THEM BUT U WILL HAVE CONVERNT THEM DC IF INTERESTED THEY 30 AMPS EACH 12 TO 14 VOLTS THEY ARE VERY VERY HEAVY COST NEW ON EACH WAS 1200,00 TAKE 500,00 FOR BOUTH AND U WILL NEED RUN FANS ACROSS THEM THEY DO PUT ENOUF POWER OUT TO KILL IF NOT SET UP RIGHT, THEY COULD BE USED IN HAM RADIO OR SUCH, U EATHER NEED BY 12 VOLT AC DC CONVERTER OR IF U KNOW HOW USE DIEOES

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justforus2005
justforus2005

9 months ago

people here are right and they wrong, we looking at how effecent things are, so i give u all something work on, i have a 250 amp 3 phase motor and 250 amp genarator now at peak they go 20 pecent above this, now we know for fack 3 factors in a motor that a 250 amp is full load, motor, and 250 is at full load gen, now, say my home takes 60 amps run, now we talking 3 phase here now if we convert numbers to two phase we now need 40 amps run home, so we need 40 amps from genarator to run my home, now quistion be put to all you will the motor run at under 200 amps, if only 25 pecent load was appled to it, and if it will guss what u made system will run its self, now, we do need keep few things in mind fist getting united this size started with no load, once started swich to genartor, now i talk to people who make what is call feq converters they make these systems to change feq. but they to will run at 60hz range, also a home can run off 3 phase juse as easy as 2 phase, so lets do math motor 250 amp 240 volts genarator same so we know for fack we get 250 amps out it these devices has magents in it now there is a winding in genarator to start it to make power, so we have specks of power now at max home will drap no more 60 amps at two phase or some call single phase, now we go back to unit we ack run 100 pecent of power off one windings back to motor, 3 phase motors dont need 3 phase keep running, they will run off single phase once started, so we have current requirements for home single phase 60 amps 3 phase will drop to 40 amps, now to max out the gen we need go 8 times this amout, so we need go 8 time this amout to max out the motor, even if home ran at 80 amps at 240 volt i matain that motor will only run at 40 pecent of ratatd out put , there for there is enofouf power to keep the system running, i talk to people who build these they told me the idea might work but never tested in that configeration, nor would they ever test it, . so i give it all to you all can such a system run, and math and all people who do this work say most likely yes, so tell me why it would not ? maybe lack trainning in how hell would such system be wired up to or above code, i have add, i cant spell or know gramer to wire this i cake to me, i got milatery genartor hardware to my home, it pass inspecktions, why any code they got well suppoase it, has gfi at 150 amp duke engery them selfs say cant be done i did it, useing a device never consider, never used in home found on ebay, and solve all my porbems, so lets for get my spelling and gramer and tell me why this wont work good luck

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WalterO1
WalterO1

11 months ago

Hi Mr Joseph , I have a 12.5hp 3000rpm engine ,and I want to buy a brushless alternator of about 7kw , but I don't know what rpm the alternator should be , please can assist thanks .

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automatipc
automatipc

1 year ago

Sir, what is the ideal RPM of the alternator of gasoline generators (say TIGER of 2.5KVA)?

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Arimint
Arimint

1 year ago

Hello Joseph how do I determine the efficiency of the alternator... Does it appear on the label?

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Dauda-M-Kamara
Dauda-M-Kamara

1 year ago

Is self running generator real. If you have a 50kw alternator, how much kW motor do you need to run it to produce enough power to power itself and other appliances. Thanks

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Josehf Murchison
Josehf Murchison

Reply 1 year ago

Self running is not possible for one reason.
Generators are not 100% efficient.
At best a brushless generator is 90% efficient.
It takes 100 hp to make 90 hp.
90 hp won't run 100 hp.
Even if generators were 100% efficient it would serve no purpose because it would only run itself.

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Dauda-M-Kamara
Dauda-M-Kamara

1 year ago

Hello Mr. Joseph, please I want help I have a 100kw 1800rpm brushless alternator and I want to use it to give electricity to my village people, please what kW motor should I use, how many HP and what will be the power that will be leftover to supply 70 houses? Thanks.

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Josehf Murchison
Josehf Murchison

Reply 1 year ago

Brushless alternators can be very efficient up to 90% efficient.
746 watts per horse.
100kw = 135 horse + efficiency
You will need at least a 150 horse gas motor at 90% efficiency.
Just remember the less efficient your alternator the more horsepower you will need.

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Dauda-M-Kamara
Dauda-M-Kamara

Reply 1 year ago

Please what will be the voltage required to run the motor and what will the kW of the motor and can I be able to run a self run generator with it. What will be leftover current.

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Dauda-M-Kamara
Dauda-M-Kamara

1 year ago

Hello Mr. Joseph, please I need help here, I have 100kw 1800rpm brushless alternator I wnat to use it with motor to generate electricity for my village people, what type motor do I need, how many kW and HP and what will be my remaining power to supply to them?

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Josehf Murchison
Josehf Murchison

Reply 1 year ago

1 horsepower is 746 watts.
Watts are volts x amps.
So a 3.5 kva alternator is a 3500 watt alternator.
3500 watts divided by 746 watts is 4.69 horse.
Depending on the efficiency of the alternator you will need that much more horse power to drive the alternator.
So if the alternator is 50% efficient it would need a 10 horse motor to drive the alternator.

How many horsepower / RPM motors do I need to drive 3.5kva to 3.8 kvaAC alternator professionally?

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engr clement omowale
engr clement omowale

Reply 1 year ago

How many horsepower / RPM DC motors do I need to drive 3.5kva to 3.8 kvaAC alternator professionally?
And what is the battery capacity to power the DC motors professionally?.

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KhalidM58
KhalidM58

1 year 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
AndrewN152

1 year 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
AndrewN152

2 years 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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Solaceplus
Solaceplus

Reply 1 year 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 Murchison
Josehf Murchison

Reply 2 years 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
princeadeosun

2 years 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 Murchison
Josehf Murchison

Reply 2 years 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
princeadeosun

2 years 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
LymM

2 years 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 Murchison
Josehf Murchison

Reply 2 years 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
VictorR54

2 years 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
PeterA226

2 years 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 Murchison
Josehf Murchison

Answer 2 years 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
solaimans1

2 years ago

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

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JamiluM
JamiluM

2 years 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
paulo148

2 years 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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Hammerhead46
Hammerhead46

Answer 2 years 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 Murchison
Josehf Murchison

Answer 2 years 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
paulo148

2 years 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 Murchison
Josehf Murchison

Answer 2 years 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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paulo148
paulo148

Answer 2 years 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 Murchison
Josehf Murchison

Answer 2 years 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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iceng
iceng

Answer 2 years 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