Have 12v AC, converted to 12v DC, motor slow

[Mikel_NY]

Two or three 10,000's should do. More won't hurt.
Capacitors have a rating for AC current . It's called "Ripple Current".

Do i understand that I will be installing the caps on the DC side, parallel with the fan?

Now I read that caps have a rating for AC ripple ... Do I install two different types before and after the rectifier? ... I'm only asking for clarification.

 

[jim hardy]

The fan would not turn. I only saw the fan quiver when switched on/off when connected directly to Yellow Brown from stator.

Correct. Fan is probably a permanent magnet motor. They won't run on AC like the "universal" motor in your Skilsaw or drill.
Yellow to Brown is AC . And it's regulated.

What i'd like to try is:
Regulator and lights disconnected.
Yellow - Brown connected to AC terminals on bridge
Fan connected to DC terminals on bridge, voltmeter same place to read fan voltage. Note fan won't be grounded.

Then start engine, observe fan voltage (and current if you have an ammeter?) at idle
then gingerly increase engine speed until you see almost 15 volts on fan, note RPM. (and fan current?). Don't overrev engine though.
Now we'd know the raw capability of the alternator .
And can figure out a test to determine whether that half wave regulator is appropriate.
Baluncore questioned that way back in the thread.

Do i understand that I will be installing the caps on the DC side, parallel with the fan?

Yes. Exactly.

Now I read that caps have a rating for AC ripple ... Do I install two different types before and after the rectifier? ... I'm only asking for clarification.

No. Not yet, anyhow...
Rectified AC makes a lumpy wave with peaks as in Kavik's post #3. The capacitor's job is to store current between the peaks , to fill in the valleys if you will pardon that informal phrase.
So current rushes into the capacitor on the peaks and dribbles back out between peaks. That's AC. And it's called "ripple". (see http://en.wikipedia.org/wiki/Ripple_(electrical) )
So your capacitors go on the DC side.

Try adding some capacitors across fan with the setup you have now, regulator in place. You might find some in a junk computer power supply or TV set from a trashpile just for an experiment.

I hope this project helps you understand the snowmobile alternator. It's an interesting device, closely related to the synchronous machine. We learn fastest by doing.

old jim

 

[Mikel_NY]

And can figure out a test to determine whether that half wave regulator is appropriate.
Baluncore questioned that way back in the thread.

I'm eager to see where this comment will be going, sounds like "2 ways to skin a cat". ( my interest is peaked). Are you thinking that the factory regulator is the cheapest production item that served the original application and there may be a better regulator for my current application depending on if the stator makes enough juice? (just a guess)

Edit: Just reread Baluncore's post 24, (that must be where I got the idea from)

Jim, I will do some more testing tomorrow and report results.

 

[jim hardy]

Edit: Just reread Baluncore's post 24, (that must be where I got the idea from)

Yep. I'm unabashed - will steal a good idea anywhere. Balun is a cornucopia of them.

Thanks Balun - as usual i was a day behind...

old jim

 

[Mikel_NY]

What i'd like to try is:
Regulator and lights disconnected.
Yellow - Brown connected to AC terminals on bridge
Fan connected to DC terminals on bridge, voltmeter same place to read fan voltage. Note fan won't be grounded.

base test:
Fan RPM of--1840 --(Directly hooked to a 12V battery at battery V of 12.4 sat overnight, not fresh charge)

Fan RPM is--1680 at 12.30-12.40V AC / 9.7VDC engine at 1500rpm idle regulator hooked up

Fan at 15V DC, unhooked reg/no bulbs tach 2800, fan speed 2250

Fan speed: 1720-1730 @ 10.3VDC engine idle 1500, reg plugged in, one 35V 10,000 mfd installed DC side in parallel
same engine speed, fan RPM increase of 40 RPM w/ cap.


Sorry, no amp readings at this time. Please ask or reask a question if more information is needed.

Mikel

 

[Mikel_NY]

Side bar question ... I have the on/off Fan switch on the Positive AC line going to the rectifier, then from the rectifier DC going to the fan and cap ( in parallel ).

Is this an accepted method of install? (my first w/ caps)

 

[Mikel_NY]

here is the best description of the one Cap that was installed: (about 1.5"dia, 5" tall)

Mallory Type CGS
10000MFD 35VDC
POS+85C
MAX surge 45VDC
CGS103U035R4L3PH
235-8406A

Bottom listing in pic.

 

[Mikel_NY]

while sitting back and thinking about this project I think I come to realize that the stator Hz is directly related to the RPM in that when I calibrate the Tach with a tone generator from my laptop that I use a tone of 500 Hz for a tach reading of 5000 and a tone of 820 for a tach reading of 8200.

In post #6:

To use a capacitor instead of a battery;
An 80W fan on 12V will draw a current of 80W/12V = 6.67A
What is the frequency of the AC? If 100Hz then period T = 10msec.
C = I * T / dV; For a 1.0V droop in the capacitor during the cycle;
C needed will be C= 6.67A * 0.01sec / 1.0V = 0.0667F = 66.7mF, rated at 15V or better.

the engine's AC Hz is RPM divided by 10.

Maybe buy ten x 10,000 uF capacitors. US$2 each.
Wire them in parallel to give 0.1F that will handle the current at the stator output voltage peaks.

Does this still apply now knowing that the motor will be run mostly at 820 Hz and sometimes at 150 Hz?

 

[Baluncore]

Does this still apply now knowing that the motor will be run mostly at 820 Hz and sometimes at 150 Hz?

Maybe. The time / frequency dependent values must be designed for the lowest frequency.

I do not know how your regulator works, or what load it is under now, even before the fan load is added. I am working here on the assumption that the alternator and regulator have sufficient capacity to drive the fan.

If you keep the regulator output chassis referenced, then only a single high current schottky diode is needed to rectify the regulator output into the capacitors. If you do use a single diode then you will need to design for the lowest RPM, giving 150 Hz, period T = 6.67 ms.
For 1V of ripple you would need C = 6.67 * 0.006.67 / 1.0 = 0.044 F = 44,000 uF.
I would then recommend ten x 4,700. uF capacitors in parallel.

Ideally you would take the alternator output before the regulator, then use a switching regulator. But if the existing regulator is doing things like shorting the alternator output to ground on negative half cycles, it would be impossible to use the alternator output while the original regulator was present. That would require a replacement switching regulator, and I see no cheap off the shelf solution for a 55V maximum input. I would build a switching regulator from available components, but I certainly don't recommend that for beginners.

An alternative solution could be to change the permanent magnet alternator for a more sophisticated three phase alternator, with a regulator to control it's field current.

 

[Mikel_NY]

To my knowledge, there is not an option of 3 phase replacement for my application.

I just completed a test of running the setup with:

no caps at idle 9.3V DC
1 cap at idle 9.8V DC
2 caps at idle 10.3V DC

Each cap rated at 35V 10,000MFD.

I'm thinking that this setup is very usable and if no one sees a safety issue, I'm going to try and run this setup at a track and see if it prevents overheating of the engine.

This is not to end this project ... I'm just itching to try the setup.

Is there anything wrong with using 35V caps? could 25V caps gain me a return?
I will look into sorcing 2 more like caps to gain the 44,000uf that you are stating I need.


When I go to the test, the 20,000uf that are installed now, what should I look for? maybe overheating?

 

[Baluncore]

Each cycle requires the current to flow into the capacitor and then out again to the fan, so ripple current is going to be very high. It is therefore better to use more capacitors of smaller value. Up to ten would be sensible. If possible use low ESR, high temperature capacitors designed for power supplies.

Capacitor weight, volume and cost are proportional to the voltage rating.
If the voltage will never rise above 16V then a 16V rating is OK. The same goes for 25V, 35V and 63V.
Capacitor dielectrics are optimised to operate between 50% and 100% of their voltage rating.

 

[Mikel_NY]

There seems to be many types of capacitors avalible. Would you please recommend the best type for my application.

I know a local source that has 16V , 1000 uF by the hand full. They are about 1/2" dua. And 1" tall with two wires at same end . The two wires are different lengths. I will look and see if they are "low ear" and high temp.

Thank you.
Mikel

 

[jim hardy]

Sorry to be gone so long from thread - some things piled up on me . ANd Balun's electronic expertise is better than mine, I'm kinda a fundamentalist able to help out with basics.

That CGS you picked looks like a very good capacitor with 5 amp ripple capability. I was hoping you'd find something like that but inexpensive on surplus market.

Does this still apply now knowing that the motor will be run mostly at 820 Hz and sometimes at 150 Hz?

You'll have more capacitance than you need at high engine RPM. If you don't spend much time at idle you might get away with two - that gives you around 10 amps of ripple capability ?

Is there anything wrong with using 35V caps? could 25V caps gain me a return?

Nothing wrong so long as your voltage doesn't go higher. I'd stay with the higher voltage caps. If you use capacitors at 70% voltage they last a lot longer than at 100%.

When I go to the test, the 20,000uf that are installed now, what should I look for? maybe overheating?

Yes. If they're getting warm it's almost surely that AC current heating them from inside. With only 8 amps of fan load i think you could be okay but not much margin left.
That's a little tricky to calculate because as Balun said current rushes into the capacitor then back out. So it's a long way from sinewave current, instead it flows in in big gulps on the voltage peaks. Those short bursts of high current have a higher heating value than a slow steady current and to try and put a number on that i'd be guessing ... there's something called "Crest Factor" we'd need to measure... meh - just feel of 'em and see if they're getting hot. One experiment is worth a thousand expert opinions.

I'm thinking that this setup is very usable and if no one sees a safety issue, I'm going to try and run this setup at a track and see if it prevents overheating of the engine.

You'll want to make a measurement of the voltage across fans with engine at track speed. That can be brief, just long enough for fans to get up to speed. I don't like to rev up an unloaded engine... What you want to know is your alternator doesn't apply 55 volts to a 35 volt cap and 12 volt fans.
Now - your fans being non-electronic just plain brush type motors will probably take some abuse, mild overvoltage. If you find your alternator making up around 25 or 30 volts perhaps we could rewire the fans in series ? Back in the days of DC railroad locomotives we had gigantic relays that switched the traction motors between parallel and series connection as needed ... that'd be a complication for your fans but not a major one.
I'm thinking that as your engine speed comes up and so does voltage, fan speed will increase giving more cooling at high power where the engine needs it . If you're real lucky you might just get away with no regulator !

Go ahead and give it a try .

Lastly, for now, i thought you'd be running lights too? They'll be less tolerant of overvoltage than the fans... perhaps we could regulate them...

Glad to hear of your success so far.
Golly i was going to butt out and let you guys have at it. Please forgive my "old fire-horse behavior". Old habits die hard.

old jim

 

[jim hardy]

Just an aside -- stumbled across an interesting hobbyist webpage describing a home-made voltage regulator .

http://members.iinet.net.au/~cool386/regulator/regulator.html

 

[Mikel_NY]

Hello all, an update.

I have ordered a few 4700uF,16v caps from one state away and they will be here Saturday at the earliest.

Jim, I will read the post you put up.

I have not " left the building" , I'm just waiting on parts.

What will changing my regulator type gain me? Maybe run a more powerful fan, an electric weight jacket. Lots of things I could convert to DC. ( The fan would be continuous, but a all else would be intermittent)

If there is good gains to be had, I have four or five snowmobiles that will be converted. It would be nice to keep phones charged while using them for GPS guidance.

 

[jim hardy]

What will changing my regulator type gain me? Maybe run a more powerful fan, an electric weight jacket. Lots of things I could convert to DC. ( The fan would be continuous, but a all else would be intermittent)

I try to worry ahead... was trying to figure out what to do if your voltage at track speed is too high for your fan motors.

A shunt regulator after the bridge might work but would need a diode between it and the capacitor&fan , just as in that article about Model T Ford regulator, so capacitors don't backfeed into it..

Just musing really. Let's see what happens when you try your setup.

Buck regulators hold promise too. I'm not familiar with these 'off the shelf' ones. Have wanted for a long time to learn about them for use on motorcycles.

old jim

 

[Mikel_NY]

I try to worry ahead... was trying to figure out what to do if your voltage at track speed is too high for your fan motors.

old jim

I just want to clarify that I my setup now is a stock stator that outputs up to 45V AC. It is rated at 230 Watts
-- the unit was designed to run a handful of light bulbs rated at 12V and totaling about 150 watts or a little more and can run 45 watt warmers w/o dimming the bulbs.
-- The stock voltage regulator is installed and regulates the AC voltage at top RPM all day long without blowing the light bulbs. That would say that at top RPM the AC voltage does not go over, say 15V or the bulbs would blow. ( I have not measured the voltage at top RPM to confirm.)

Now the modifications

-- I have removed about 120 watts of light bulbs and have installed an 80 watt brush 12V DC fan
-- I have installed a bridge rectifier to change some AC V to DC voltage to run one fan.

and the question

-- the motor will idle at 1500, this puts stator at 150Hz. To add capacitors in parallel on the DC side of the bridge rectifier without changing the regulator, is it still the 44,000uF that is required?


I respect all your expertise. I guess I'm missing something here. I would "assume" that wattage is wattage. Is there a difference in the load if I change from AC bulbs to simple DC brush motor?
If there is no difference than I have lightened the load on the regulator and would ask why I would need to change it? I ask only to understand.

 

[jim hardy]

I guess I'm missing something here. I would "assume" that wattage is wattage. Is there a difference in the load if I change from AC bulbs to simple DC brush motor?
If there is no difference than I have lightened the load on the regulator and would ask why I would need to change it? I ask only to understand.

By just inserting a bridge between the regulator and the load you haven't basically changed anything. When you add capacitors it does change something.With light bulbs before the bridge, that is right on alternator wires,
what does the alternator see?
It sees a load that draws current whenever any voltage is present.

With light bulbs after bridge but no capacitors, what does alternator see?
Alternator still sees same thing. Lights now see DC with lots of ripple instead of AC

Now add capacitors. What happens on DC side of the bridge?
The capacitors charge to some voltage on every peak then discharge a little bit waiting for next peak. Balun sized capacitors for 1 volt sag between peaks at lowest frequency.

So - what does the alternator see now?
It sees a load that draws no current until alternator voltage gets higher than whatever is leftover on capacitors from last peak. Then it draws a big gulp of current. That'll happen on every voltage peak.
So - the current demanded from the alternator has changed:
from a replica of the voltage wave (assume it resembles a sine as in Kavic's post #3)
to a series of short but very big gulps one at every peak.

Those big gulps of current will flatten out the voltage peaks. But I don't know how much.
That's why I was interested in voltage readings with capacitors installed and fans running and regulator disconnected. I think you posted them...
I'll go back and look what those numbers were after dinner - Fair Anne just set it out..

thanks

old jim

 

[Mikel_NY]

I received my order, can I use this style?

Lelon
16V 4700uF
RGA 105 degree C
H032(M)

I went to LELON's website and the only match I could find stated the cover is Black and White. I received green case with black print.

On the page that listed color, it stated if ESR is needed then use another style than RGA.EDIT: Jim, Thanks for clarification on what has changed. If these caps are usable, I will install 10-4700uF caps and disconnect the regulator and retest the voltage w/ fan on and report at what RPM the engine reaches at just before 15V DC at the fan.

ALL light bulbs are on AC side. there will be 2-7 watt bulbs on at all times, 2 may be continuous or intermittent. 28 watt total. on the DC side, the 80 watt fan will be on always and another DC 12V motor very intermittent. ( a drill motor to move wing )

 

[jim hardy]

from post # 35:

Fan RPM is--1680 at 12.30-12.40V AC / 9.7VDC engine at 1500rpm idle regulator hooked up

Fan at 15V DC, unhooked reg/no bulbs tach 2800, fan speed 2250

Fan speed: 1720-1730 @ 10.3VDC engine idle 1500, reg plugged in, one 35V 10,000 mfd installed DC side in parallel
same engine speed, fan RPM increase of 40 RPM w/ cap.

So at idle, if i understand:
with regulator hooked up the alternator made 9.7 volts at idle while driving the fan,
unhooking the regulator and adding a capacitor raised that voltage to 10.3 at idle.

The capacitor held the voltage up a little bit between peaks. That's probably why DC value came up.

At 2800 RPM your alternator makes 15 volts while driving the fan with no capacitor... doubtless the peaks are higher.
It'll be interesting to see what a few capacitors do for it above idle.

hang in there - call this R&D . Experimenting is one step at a time.

old jim

 

[Mikel_NY]

the install of the capacitors is done and there is no heat at idle. I retested the DC voltage and have blown another voltage regulator.

what is my next step to replacing the current type of regulator with one that will work?
i would like an off the shelf part if possible.

Please help if you can.

Known information:
-- stator output 10V AC through 45V AC
-- stator output of 150Hz at idle and 850 at top rpm
-- DC converted by a Bridge rectifier and has 10 - 4700uF capacitors in parallel.
-- current regulator is a "shunt" type wired in parallel
-- Load is 12V DC, 80 watt brush fan motor and a couple of 7 watt light bulbs continuous and very intermittent use of a 18V DC Craftsman drill motor (used to move a wing front to back on a sprint car).

 

[jim hardy]

and have blown another voltage regulator.

Another ? I missed the first one(s?)

How's it connected ?

- current regulator is a "shunt" type wired in parallel

Is it in parallel with the capacitors, on capacitor side of the bridge ? That'd explain its untimely death, trying to dump all that stored charge. See post 46.
Another caution: If it's on that side of bridge, both its wires need to be on that side = its 'ground' connected to bridge & capacitor negative not frame.

I've still not heard what is voltage with no regulator, capacitors installed after bridge, lights disconnected so they won't blow, fans on and motor at track rpm...
If that voltage doesn't hurt the fan motors we only have to fix the supply for the lights.
If that voltage is too much for the fan motors, we'll have to fix their supply as well.

A little series regulator like this should in theory handle the 7 watt lights
http://www.ebay.com/itm/High-efficiency-DC-DC-8-48V-to-12V-5A-60W-buck-step-down-power-supply-module-/301317578007?_trksid=p2054897.l5668
that one's five amp,

.

a bigger one like either of these should handle the fans, they're ten amp.. Hopefully the fans will be okay without one because they 'eat' three volts..
meaning fans will be slow until capacitor voltage reaches about 15. Hopefully that'll be just above idle.

http://www.ebay.com/itm/High-efficiency-DC-DC-15-45V-to-2V-12V-10A-buck-step-down-power-supply-module-/351180611037?_trksid=p2054897.l5659

http://www.ebay.com/itm/High-efficiency-DC-DC-15-45V-to-2V-12V-10A-buck-step-down-power-supply-module-/291247866998?_trksid=p2054897.l5658

I think Amazon sells them too.
I've never used any of those modules, hopefully somebody who has used them can chime in with reality based advice.

Your tenacity is noted and applauded.
The permanent magnet alternator is a difficult thing to co-ordinate because its voltage sags a lot with load..
They built a special purpose regulator for their needs. I'm still scratching my head over its clipping only half the cycles...
Hang in there ! "Things are lookin' up" : (courtesy Nate Owens)

http://www.sketchoholic.com/uploads/userfiles/13890/c3bcd100d2_LOOKNUP_cropped.jpg

old jim

 

[Mikel_NY]

Is it in parallel with the capacitors, on capacitor side of the bridge ?

the stator outputs AC, yellow, brown ... the regulator is in parallel at this exit of wires from the stator. the wires then go to the light bulbs still AC. the wires are then branched off and feed the bridge rectifier. the caps and fan are on DC side. the caps and fan are parallel after the BR

 

[Mikel_NY]

Is it in parallel with the capacitors, on capacitor side of the bridge ?

The reg is on AC side, the caps are on DC side

 

[Mikel_NY]

I've still not heard what is voltage with no regulator, capacitors installed after bridge, lights disconnected so they won't blow, fans on and motor at track rpm...

The voltage as it sits now is 15.2V DC at fan when the motor is at 3000 rpm.

How would I test the voltage at top RPM when I have 16V caps installed? Can I overvolt them without damage?

I could test RPM to 16V and reply with an rpm w/ regulator unpluged, fan on and no bulbs.

 

[Mikel_NY]

I saw this on eBay:

http://www.ebay.com/itm/SUPERNIGHT-...501?pt=LH_DefaultDomain_0&hash=item35ce07c19dThis is a 48V DC to 12V DC regulator (for golf carts). I didn't post this before as I thought it only for the DC side, I would still need to control the AC side voltage.

The tach works by sensing the pulses from the AC stator signal. I would have to leave this part original so I know how fast the motor is running. I do not know if the tach would burn out if I sent unregulated AC to it for a long duration and installing the above regulator to control DC voltage and wire the bulbs to the DC side.

If the tack can have uncontrolled AC, I would think all else would run DC and regulated from the above regulator.

 

[jim hardy]

got it. Thannks... I'm mystified by regulator blowing.

been looking for off the shelf regulators...

some motorcycle forums are happy with this unit
http://podtronics.net/

instructions from somebody who sells them :
http://www.britcycle.com/Manuals/Podtronicinst.html

another outfit, Tympanium, seems to have become these folks :
http://www.trombetta.com/voltage_regulators.cfm
they are an oem for the industry. Briggs&Stratton i think uses them...
but i can't find where to get them.
This one looks interesting, 15 amps for single phase alternator
http://www.trombetta.com/voltage_regulators.cfm?id=60

i never saw either one, so can't endorse.

From post 35:

base test:
Fan RPM of--1840 --(Directly hooked to a 12V battery at battery V of 12.4 sat overnight, not fresh charge)

Fan RPM is--1680 at 12.30-12.40V AC / 9.7VDC engine at 1500rpm idle regulator hooked up

Fan at 15V DC, unhooked reg/no bulbs tach 2800, fan speed 2250

Fan speed: 1720-1730 @ 10.3VDC engine idle 1500, reg plugged in, one 35V 10,000 mfd installed DC side in parallel
same engine speed, fan RPM increase of 40 RPM w/ cap.

Did the extra capacitors change that very much ?

 

[jim hardy]

Your ebay gizmo is the same sort of device i was hunting.

Tach... we know nothing about it except it hasn't blown yet... Got a spare to maybe sacrifice?
What's it read with an ohmmeter ? Could work up a simple zener protector... three parts.

 

[jim hardy]

uh oh did you read fine print on that ebay golfcart regulator? I'm afraid it's for DC in from golfcart batteries..

Input range: 40V to 60V

need one that's got a wider input range... or is already made for the job like those Trombetta units.
Might find one of them to try out on a big riding lawnmower.

 

[jim hardy]

http://www.scribd.com/doc/55972644/Brigg-Stratton-Vanguard-16-Hp-Basic-Wiring-Diagram
493219 looks like that Trombetta 16 amp with charge indicator

Handy page here... http://www.briggsandstratton.com/eu/en/support/faqs/~/media/files/faqs/briggsandstratton/pdfs/alternator_specifications.pdf