# Need to understand power rating.

Discussion in 'General Electronics Discussion' started by Ganther, Nov 11, 2015.

1. ### Ganther

3
0
Nov 11, 2015
Hi, I am not electrically inclined but trying to learn by doing small projects. I have a 10hp motor where the stator puts out 12Vac, I am looking at powering a LED light about 5,000 lumen here is the power rating for the light rated at 4 A from 10-30 VDC.

I understand I need a full bridge rectifier, to convert to DC. I am wondering if this will be enough to power the light I am looking at. Or should I look at a smaller light or is it possible to go bigger.

Any help would be great, hate to throw money at a LED light only to not have it work.

2. ### Minder

3,102
664
Apr 24, 2015
What is the technology of the AC motor that puts out 12vac?
10HP motor to produce 120w?
What are you driving the motor with? at what rpm ?
M.

Bluejets likes this.
3. ### Ganther

3
0
Nov 11, 2015
It is a older snowblower, with a 10HP gas motor. When I connect my volt meter to the plug ( I can get a photo of) I am reading roughly 12 volts. I am not sure of the RPM.

4. ### Tha fios agaibh

2,166
726
Aug 11, 2014
A good place to start would be to look at the power rating of the original light. You know it puts out 12v, but we don't know the maximum current its capable of delivering.

Bluejets likes this.
5. ### Tha fios agaibh

2,166
726
Aug 11, 2014
At first I was thinking...Holy Cow, 10hp is a huge electric motor for a small project!

Bluejets likes this.
6. ### Bluejets

4,978
1,045
Oct 5, 2014
A hp is 746 watts. Not that you will get 10 x 746 = 7460w out of it due to losses such as heat amongst other things plus the old snowblower probably wore out a few horses ....

Your loading is a bit vague (4A @ 10-30 volts) ...but lets say 4A @30 v around (4 *30 = 120W roughly)

I think you can see where this is going with reference to your supply system.

I tend to go with other quotes here...wow...and holy cow......

A model aeroplane engine would be more appropriate I think.

7. ### Minder

3,102
664
Apr 24, 2015
How are you getting generation of AC? what type of motor, the normal motors fitted to a portable application are P.M. DC brushed due to the need for no external excitation needed.
The only alternative I could think of is a 3 phase gen with P.M. rotor, but this would be 3 ph?
M.

8. ### Y2KEDDIE

259
15
Sep 23, 2012
I would check to see if its AC or DC with your volt meter. Either AC or DC will run an incandescent light. Current may be quite limited, Like suggested earlier, see what the bulb current was on the original light, if good use an ammeter to check.

9. ### Tha fios agaibh

2,166
726
Aug 11, 2014
I'm thinking it's a small magneto thats driven by a 10hp gas engine (Not electric)
This magneto generates the power for the accessory lights.

10. ### duke37

5,364
772
Jan 9, 2011
There is a problem with english, I think he has a petrol engine, not a gas motor!

Small motor cycles often have an alternator with no voltage limit. The current is limited by the leakage inductance of the alternator, thus they will produce the right voltage when loaded with the right bulbs.
If the load is less than designed, the voltage will be high and if the load is more than designed, the voltage will be low.

A circuit diagram would help.

The light output may be fairly constant regardless of the led size. The colour will not vary with a change of light output.

11. ### Ganther

3
0
Nov 11, 2015
Wish I could supply a circuit diagram and provide more info than what I have.. This is a used snowblower from what I have researched most of the snowblowers use a stator.. I will see if I can find anymore info.. As for the light I am looking at 4 A from 10-30 VDC is what it says for power rating..

Thanks for the help guys, like I said I will see what I can find..