Alternator Dyno

[zapmk]

Hi all,

Been working on building a dyno to do some alternator testing with.

And now Iam starting to think about what kind of tests that need to be run.

Like what am I going to use to load the alt with, to get some kind of meaningfull

output figures.

I already have a way to the track RPM, and the torque on the stator.

Here is a couple of pic of my progress,I can vary the RPM from 0 to 600 +

with the change of a pulley and belt. still need to weld on some tabs on the stator bracket and frame for the 100 pound digital fish scales.

I did weld on some flat plate and put on another idler pulley in place,

just in case I decided to start playing with these,  bought at an action about

week ago.

 -Zapmk

[willib]

Zap , is that a standard size pail , under that lathe?

holy crap !

please refresh my memory on the dia of those rotors?

[SamoaPower]

Neat setup Zapmk. I've been thinking along the same lines myself for an upcoming alternator. I will also use a geared down 5 Hp gas engine to drive it.

Your past post indicates you will be doing 24 volt battery charging rather than just making heat. It's interesting to note that the 10 kW Bergey machine is derated to 7.5 kW (I think) for battery charging. I think this amplifies the point that testing with simple resistive loads won't give you the same results as batteries.

The problem with testing into actual batteries is that the batteries state-of-charge (and other things) will determine the current into them and the terminal voltage. What you don't want while testing is to have another variable or two to worry about.

What's needed is a battery simulator that will maintain a set voltage. When faced with these kind of issues, I usually turn to electronics for a solution since I'm comfortable with it. A simple shunt regulator will do the trick. I say simple because the circuitry is straight forward but the higher power levels present a few problems. Multiple FETs, large heat sinks, large resistors and fan cooling will be required at these power levels.

I still think it's the best way to go for meaningful results.

 

[harrie]

Hi zapmk, Wow neat looking set up, and nice shop too !! . What do you think about the square tube staton support, it looks real sturdy. What size tubing is it.

great fun, Harrie

[zapmk]

Willib,

Is that a standard size pail , under that lathe?

holy crap !

please refresh my memory on the dia of those rotors?

I beleve its a 2.5 gallon pail.

The rotors are 24 inches, I had taken all the mag off so I could beadbast the rotors and get everything mocked up for the dyno, with out worry of getting them stuck   (or me)in between them when Iam by my self.

 -Zapmk

[zapmk]

Hi Harrie,

Wow neat looking set up, and nice shop too !! . What do you think about the square tube staton support, it looks real sturdy. What size tubing is it.

Thanks, been working hard to get the dyno setup, and the shop too. Finely got the 30 HP 3 phase converter wired up last week, so I could use the lathe and some other equipment I have around here.

The tubing is 1.5 by 1/8 wall, it has a large torrington roller bearing in the center that rides on the main shaft, so it can rotate, so I can get some torque reading on the stator when it under load. I think it will work just fine.

 -Zapmk

[zapmk]

Hi SamoaPower,

Your past post indicates you will be doing 24 volt battery charging rather than just making heat.

Yes, I will be charging a 24 volt battery bank, and would like to use any excess power after the batterys a full for some hot water per heat.

I have been in the process of building commandas, dump load controler for just this purpose.

The problem with testing into actual batteries is that the batteries state-of-charge (and other things) will determine the current into them and the terminal voltage. What you don't want while testing is to have another variable or two to worry about.

Thats what Iam thinking also, Thats why I was looking into some other possibilities for loading, instead of just using batterys for the load.

Hmmm- How that I think of it, couldn't I just use commandas load controler and a battery bank for the load. would this not be a good way to test the alt, for the current output of the Alt ?

 -Zapmk

[Flux]

I agree that you need a battery bank as a load or something that simulates a battery exactly.

A battery bank with shunt regulator will do fine. Without a regulator you will have a messy job keeping the volts reasonably constant.

You could do it near enough if you have resistors to nominally load each step, especially if you don't work the batteries fully charged. Once they are fully charged you will need to change the resistors for each step even if you are quick.

You can manage with a smaller shunt regulator if you set it to 13v rather than 14v. It will discharge the batteries between readings and the battery will help hold the rise even with fairly big currents if you are quick.

I use a big linear shunt regulator, but you will not likely be lucky enough to have a whopping big power transistor with screw mounting, rated at 50A that I use in series with some big resistors to keep the transistor dissipation within 300W.

Flux