I’ll ask a different question...

I have a dc motor

Volts 90
Amps 13.3
Hp 1.5
Rpm 3000

Assuming I can get the motor turning at 500 rpms how many watts will I generate?

Thank you for you help.

 

hi,
The Input power is the product of the applied voltage and the current thru the motor, it will not generate.
Look thru this link for more details.
https://www.micromo.com/technical-library/dc-motor-tutorials/motor-calculations

E

 

hi,
The Input power is the product of the applied voltage and the current thru the motor, it will not generate.
Look thru this link for more details.
https://www.micromo.com/technical-library/dc-motor-tutorials/motor-calculations

E

Hello Eric,

When I turn the dc motor by hand it lights up an LED. I’m not looking to power my house but to charge batteries and create power to light up multiple LEDS. I seen videos where two motors are used but I see from the answers there must be a secondary source of energy driving the first motor. I can get the flywheel turning by human power. I know that I will get 33v/rpm but I’m not able to work out the watts generated at 500 rpms.

I’m a blacksmith and play with electricity when I create artworks. My knowledge about circuits is very limited.

Thanks for your help, this site has been very helpful to me in the past.

 

... it will not generate.

How do you know? Some DC motors can act as generators, so why not this one?

If it does, the power output will be disappointing though. First, a motor used as a generator will not generate the same power it draws when run as a motor. Secondly, the power made is depends hugely on the rpm.

 

I know that I will get 33v/rpm but I’m not able to work out the watts generated at 500 rpms.

Did you slip a decimal point or two in there?

I think it'll be hard to predict the power without actually doing an experiment. This is because the power produced will also depend on the load applied, and whether the rpm drops when the load is applied.

The way to map out the power output is to run at a constant rpm and apply different known loads, such as power resistors that can take the power without overheating, while measuring the voltage across the loads. You'll find there is a sweet spot resistance where the maximum power can be drawn. A larger load will draw more current but the voltage will fall. A smaller load will draw less current and the voltage will rise, but not enough to make up for the reduced current.

 

How do you know? Some DC motors can act as generators, so why not this one?

I am fully aware that some DC motors can be used as a generator.
There is a recently closed Thread from this TS, which clearly reads as a free energy project.

I am in the process in trying to determine what the TS is trying to do, so that I can help him.

 

There is a recently closed Thread from this TS....

Ah yes, nothing beats prior knowledge. I had no idea.

 

Did you slip a decimal point or two in there?

I think it'll be hard to predict the power without actually doing an experiment. This is because the power produced will also depend on the load applied, and whether the rpm drops when the load is applied.

The way to map out the power output is to run at a constant rpm and apply different known loads, such as power resistors that can take the power without overheating, while measuring the voltage across the loads. You'll find there is a sweet spot resistance where the maximum power can be drawn. A larger load will draw more current but the voltage will fall. A smaller load will draw less current and the voltage will rise, but not enough to make up for the reduced current.

Thank for you response.

I found the information perhaps I’m wrong but rpm divided by volts is the formula I found. At maximum rpm I would get 33v/rpm and at 500 rpm I think I would only get 5.5volts. Not a lot of output....

 

Hi C,
I would have considered it cheaper and easier, if you have the power to drive a motor > generator > battery charger, to use a suitable mains driven battery charger unit.
Eric

 

Hi C,
I would have considered it cheaper and easier, if you have the power to drive a motor > generator > battery charger, to use a suitable mains driven battery charger unit.
Eric

It’s an art piece.....someone peddles a bike, walks or cranks the flywheel and things happen - lights and movement. Something for people to enjoy. I naively thought it was possible to add a second motor.

What does TS mean?

Thank you for your responses.

MOD: Thread Starter.

 

At maximum rpm I would get 33v/rpm and at 500 rpm I think I would only get 5.5volts. Not a lot of output....

5.5V at 500rpm would be just 0.011 V/rpm. Could be right.

What are you going to use to power your generator? There's no such thing as a free lunch. In other words, you might be better off using some other plan. There are a lot of losses in using a DC motor as a generator.

[edit] Ah, saw your post come in just before mine. TS = thread starter. Same as OP (original poster) used everywhere else.

 

I would have considered it cheaper and easier, if you have the power to drive a motor > generator > battery charger, to use a suitable mains driven battery charger unit.
Eric

That may not be what he is wanting. When you look at this quote by the TS he may be doing "interactive" art.

I’m a blacksmith and play with electricity when I create artworks. My knowledge about circuits is very limited.

Edit - looks like it is what he's after.

 

It’s an art piece.....someone peddles a bike, walks or cranks the flywheel and things happen - lights and movement.

Well that's OK, efficiency is then a minor concern. You might consider a pulley or something to make the motor spin faster. This would give you more voltage and make it easier to power stuff. Or a different motor designed for lower rpm and lower voltage operation.

As for wattage, consider that a typical bicycle dynamo for lighting is a 6W generator. This is low enough to not put too much drag on the rider. A healthy rider can hit 100W or more for some period of time but I'd say that's the upper limit I'd look for from a random person in an art exhibit. Yeah, some guys can burst to more than 1000W but only very briefly

 

It’s an art piece.....someone peddles a bike, walks or cranks the flywheel and things happen - lights and movement. Something for people to enjoy. I naively thought it was possible to add a second motor.

hi C,
Sounds like a fun project.
As its a manually driven generator, I would have thought a small generator less that 200Watts would be a power limit.
E

 

hi C,
Have you considered using the motor from a electric powered pedal cycle.?
They IIRC they are about 250Watts , nominal 36Vdc, which is a safe working voltage.
Convert the motor to a generator.?
E

 

hi C,
Have you considered using the motor from a electric powered pedal cycle.?
They IIRC they are about 250Watts , nominal 36Vdc, which is a safe working voltage.
Convert the motor to a generator.?
E

No I haven’t but I’ll keep my eyes open for one. I currently have the one treadmill motor (v90, 13.3amps, 3000rpms) that I was hoping on using. Will this motor not work or be safe?

Www.kinghorn.ca or www.kinghornblacksmithing.com

 

I’ll ask a different question...

I have a dc motor

Volts 90
Amps 13.3
Hp 1.5
Rpm 3000

Assuming I can get the motor turning at 500 rpms how many watts will I generate?

Thank you for you help.

Generally speaking, machines constructed as DC motors tend to exhibit markedly less efficiency in 'generator service' (and vice-versa). Although such is, to some extent, compensable via adjustment of 'brush angle', native provision for such adjustment is seldom incorporated...

As an aside, please be advised that a 'DC motor' featuring a PM field may, as a practical matter, be regarded as a parallel (shunt) connected machine...

Best regards
HP

PS -- As our resident 'motor guru' perhaps @MaxHeadRoom would care to chime in?

 

I currently have the one treadmill motor (v90, 13.3amps, 3000rpms) that I was hoping on using. Will this motor not work or be safe?

--Emphasis Added--

(Note: based upon the above quoted description, a PM field (stator) arrangement is implied/assumed)

It'll 'work' howbeit with the requirement of rather high AV operation is anything approaching reasonable efficiency desired...

Best regards and good luck!
HP

 

... rpm divided by volts is the formula I found. At maximum rpm I would get 33v/rpm and at 500 rpm I think I would only get 5.5volts.

You got the formula right, but you are using it wrong. 3000RPM / 90V = 33.3RPM/V, and it is not the same thing as 33.3V/RPM.

 

It’s an art piece.....someone peddles a bike, walks or cranks the flywheel and things happen - lights and movement. Something for people to enjoy. I naively thought it was possible to add a second motor.

What does TS mean?

Thank you for your responses.

MOD: Thread Starter.

OK and actually sounds like a pretty cool art project because it affords some interaction. As to a generator suitable for use in your project? Anyone who has ever peddled a bicycle or turned a hand crank to generate power knows just how difficult it can be. As the load increases the leg and arm muscles really begin to feel it. You may want to keep things small, for example a small permanent magnet DC motor as a generator. Use the power to illuminate several small incandescent light bulbs or create a small village and illuminate with LED lights. You may want to consider an old style analog volt meter and current meter as people like meters with a moving needle. A Google of DC 12 Volt Generator will bring up some examples on Amazon. You also have the issue of gears to get from a bicycle or hand crank RPM to a usable RPM to spin the generator. When I mentioned a village I had in mind something you would see with a small train set.

Ron