DC Motor Generator: Understanding Voltage and Current | FAQs

[wiiman3893]

Ok, I'm new to electronics and have some pretty simple questions that I can't seem to find answers to elsewhere. Let's say I have a DC motor that I want to use as a generator with the following specifications:

130 VDC
17 A
5950 RPM

I know that in order to generate 130 Volts, that would mean spinning the motor 5950 times per minute. Which would mean that spinning the motor at around 46 revolutions per minute would generate 1 volt. But I'm not sure how the current would work in this situation. Do I need 5950 RPM in order to create that 17 Amp current? or is this another proportional thing?

Thank you for your help!

 

[vk6kro]

As you might expect,... "It all depends"

You would get less than that even if you spun it up to that speed.

Quite probably, this is a series wound motor which will create problems if you try to use it as a generator.
The field current will depend on the armature and load current, so the voltage will actually rise with load.

All this may become unpredictable, so I would anchor it in a vise and put a 110 volt lamp on its output and drive it with an electric drill. Gradually bring the speed up and plot the voltage.

Have a look at this site:
http://nuclearpowertraining.tpub.com/h1011v2/css/h1011v2_93.htm

 

[wiiman3893]

I see... Now, how about using an alternator connected to some kind of water wheel? If I were to rectify the current into DC to charge a battery, then would that be any better?

Let's say there was a 12V, 105 A, 5000 RPM alternator. Would that make this any easier dealing with AC current?