I need some help. I have connected these following two parts together and had let them run. While running I went to toilet, and when I came back, the DC Motor catched fire. My home was stinking badly, I even could not breath. I connected this two parts:
An absolute beginner would have made a block diagram showing exactly how you had all this connected together. Since you expect someone on the internet to know how you connected it all, you are before an absolute beginner.
Please start over so someone can perhaps help you figure out what you did and what the problem was.
By the way connecting what you described cannot possible heat up or catch fire. You obviously had some sort of power supply connected. What is it?
That's a series-wound motor you're thinking of - not relevant here as the motor is a permanent magnet DC motor (PMDC).
Most DC motors are perfectly happy run no-load at rated voltage continuously - the power dissipation is much greater under load,
so I suspect the motor was loaded or seized - usually a motor's
internal fan is plenty for no-load.
Bearings in a new motor would not seize by them selves.
The volt meter is absolute okay. Please anser these:
could the 30V voltage damage the DC ?
I allways knew that the power supply allways should have more current output than the DC or etc... again, I am a beginner, so again a stupid question: could it be that the 4,5A Output current damage the DC ? I know certainly that the maximim current input for the DC is 2,1Amps (51 Watts). So should I use a power supply with 2,1Amps ??? <-- maybe it is a stupid question
How it usually works is that the motor - at any given voltage - will try to draw a certain amount of current ... so the power supply needs to be CAPABLE of supplying that amount of current.
So if 24v is the correct voltage for the motor - and it draws, say, 2 amps at 24 volts then all that matters is that the power supply is capable of supplying at least 2 amps at 24 volts. So long as it's 24volts then the power supply could be capable of delivering 20000 amps and it would still be fine.
Ohms law tells us that for a given resistance, current (and power) will increase in proportion to the voltage.
So lets put that in the context of your motor;
It's supposed to run on 24v and dissipate a maximum of 51 watts. p/v=i (p = power, v = voltage, i = current) so 51 watts divided by 24 volts equals 2.13 amps.
v=i*r ... so v/i = r (with r being resistance). So 24 volts divided by 2.13 amps = 11.29 ohms.
Assuming that the motor load is purely resistive and doesn't change (don't ask!) then at 30 volts it'll be drawing 30 volts / 11.29 ohms = 2.66 amps.
And 30 volts at 2.66 amps would be a power dissipation of 30 * 2.66 = 79.72 watts - which would be 56.31% over it's rated maximum.
But having just said all that, what the motor ACTUALLY draws (thus how huch heat it puts out - thus how hot it gets for a given amount of cooling) is also going to depend on it's load.
So in the context of your project:
you can probably throw that motor away since it's been smoked (it'll have damaged insulation and will probably fail again)
You need to decide if you want to take a chance on another one the same (but only feed it a maximum of 24v) or re-think it and use something else. From my experience with high-power RC helicopter motors it's to be expected that they'll get hot if run under load for a few minutes ... but the difference is that (a) they have fans built in to pull air through and (b) they're designed to take it (they can be far too hot to touch right after a flight). Other than that I probably can't help a lot unfortunately.
@anon12459472 <--- what a great explaination !!! Thanks. Everything you calculated sounds consistand and smart! okay, I have to put a fan to cool it down. Because, the motor will run for 8 hours a day. Maybe I will use resistors to pull down the amps (because I do not need such a speed). As example, this:
Thanks - feel free to "reward me" by using the like button (so the system thinks I'm wonderful)
Adding resistors are probably not the way to go; you'll still end up dissipating a lot of heat - it'll just be spread over the motor and resistor instead of just the motor.
I think the fastest way forward is probably to start by taking 3 steps back and make some better design choices. Plenty here who can help with that but first of all we need enough information to "fill in the blanks" - so perhaps you could start by telling us exactly what you're trying to achieve?