pm motor

[greenkarson]

Just found this pm motor at the local surplus store.  Wondering what everybody thoughts are on it.  tag only shows the following      vdc 24,   hp 1.3,  rotation ccw. Is that enough specs to get a rough idea of watts?  I did some crude testing connected it to a electric motor at roughly 1300 rpm it hit 22.5vdc .  Tried it on my lathe at 600 rpm it hit 6.5 vdc.  maybe I have this wrong but I was thinking it was going to put out ac volts and have to rectified to dc.  But it seems to put out dc already.  Tried to test amps but i think i fried my multimeter.    Any thoughts or input on motor?  looks to be really well built with bearings.

[taylorp035]

Well, to get you started, the 1.3 hp = 746 * 1.3 = 970 watts
970 watts / 24v = 40.4 amps.

Now the question is, is it 1.3hp continuous or peak.
Also, voltage tends to be linear based on rpm, but your numbers seem to show otherwise.  Maybe you fried your voltmeter too.  I know my 200v dc setting on one of my meters is not accurate by about 20%, which was probably caused by shorting the amp meter on a lawnmower battery.


Either way, your motor is either 50 to 100 rpm/volt, which is kind of high for wind / slow hydro.  Maybe on a pressurized hydro, because I have seen people have success with higher rpm/volt wet ups.


What are the dimensions?  And the weight?

[greenkarson]

to be honest i just assumed the electric motor i was using  was around 1375 rpms.  the demensions of dc motor is 7.5"dia 4.5" thick 7/8" shaft . 

[ghurd]

You tried to test Short Circuit Amps?
Yup.  The meter is probably toast.

DC PM motors usually make DC output, like Ameteks.

A lot of my 12V to 30V DC PM motors are not linear on the open voltage output at lower RPM.
Do not feel lonely about them causing confusion.

Is the lathe RPM accurate?
I have a variable speed Harbor Freight $400 mini-lathe with a DC motor and a twist knob for RPM.
The margin of error is huge.  The slightest load slows it down a lot.

I am with Taylor.  Seems pretty high RPM to get useful 12V out.
Might make a great fan?
G-

[greenkarson]

615 rpm with tack =6.5vdc   never tacked the electric motor.   what open load volt is ideal for 12v charging or is open load irrelevant?

[12AX7]

Hello.

I've not seen a DC motor that specs it's direction.

I always thought the main advantage of using a DC motor is the ease of changing rotation direction.


ax7

[greenkarson]

i forgot to add there is a small black wire and a small purple wire on the motor as well.  Anybody know what they are for?

[ghurd]

The extra wires are either a thermal fuse, or maybe some kind of sensor.
0 ohms makes it a thermal fuse.

Open voltage must be over about 15V, at an RPM suited to the blades.  And the blades must be suited to the motor.
15V at 300-400RPM is probably what most people like in a 4' diam blade set.
My mini-ECM was about 15V at 675 RPM, which was great for 25" dia blades, but they would hardly be a good match for a motor with a 7/8" shaft.

Something else you can try is connect the motor to a 12V battery to get the RPM, them you need to spin about 15% faster than that to start charging.
That does not always work out either, but usually.
G-