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

[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

 

[jim hardy]

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

that'd be good.

We've got to figure out how to not blow up expensive regulators...

 

[jim hardy]

Mike let's try an aftermarket regulator made for this job

check your "conversation" button...

 

[Mikel_NY]

reg unplugged, no bulb, 16V DC at 2700-2800 engine rpm.

reg plugged in, no bulb, 16V DC at 4500 engine rpm. fan speed at 1860 rpm.

I "assumed" the reg was not working when testing, the voltage would reach 15. For the above test, the voltage climbed until about 15.2 then the regulator was at its controlling limit as the voltage was bouncing all over till it reached high 15V then steady climb with engine rpm to 17V DC. ( I lost engine control, it leaned out a bit) it was at 17V for a very short time, I don't think any damage occurred.

 

[jim hardy]

Good test .

Well, so much for the fans being enough load to hold voltage down !

Caps will take brief overvoltage, no sweat.

Let's see what the aftermarket regulator does... next week...

 

[Texashorsepower]

Hello Gentleman! I just signed up and so far this thread has been a wealth of great information!

I have a snowmobile project almost like this and have some similar questions. I don't however, want to hijack Mike's thread.

Since there has been no additions to this topic for a few months does anyone have an objection to me adding a few questions of my own, directly related to the topic?

Thanks!
Russ

 

[Mikel_NY]

I don't have a problem with a parallel question . I have restarted my conversion and have received a different voltage regulator from Jim and have started rewiring it. I should be done this weekend or next.

 

[Texashorsepower]

In my project I'm converting to HID headlights. Factory setup is (2) 65watt incandescent bulbs.
I have a 2002 Polaris Edge 800 snowmobile. It has the same "clipping" style AC regulator with a half wave rectifier built into send a charge to my 12vdc starting battery.
The battery ground is common to chassis/engine ground.
The hid ballasts (2), each have an input voltage of 9-32VDC, Nominal 12.8VDC @ 3.2A, 6A max draw at startup

Initially I powered the HID lights directly from the 12vdc starting battery but, not sure of the actual charging capacity of the half wave system, drained the battery after a few hours of opperation.

My next line of thinking was if I could run the ac lighting wires through a full wave rectifier and send the rectified dc + & - to the battery to charge better than the half wave output coming from the factory regulator/rectifier. Then the power to the HIDs would continue to be smooth being powered directly off the battery. (I use rectified voltage from the headlight harness to "trigger" a 12vdc relay to provide power to the ballasts from the battery only when the sled is running), just in case you were wondering how the lights would turn on/off.

I do however remember someone saying you CAN NOT have a full wave rectified dc ground be common with an ac system ground so I'm not sure if this idea would work...

I suppose I could try running rectified dc from the headlight harness directly to the HID ballast with some caps parallel on the dc side but I don't think there would be enough capacity for the initial startup amperage required of the ballast.

I appologize if this sounds a little scatter brained, I've been interrupted a couple times while trying to write this post.

As Mike mentioned earlier, I greatly appreciate the chance to learn from those that have worlds of knowlage in this area. I know enough to get me knee deep in a fun project but the information you've provided above is awe inspiring.

Lastly, thank you Mike for letting me get some additional information on top of what I've learned from your project!

Russ

 

[Mikel_NY]

Jim sent me a regulator that changed to an ungrounded stator so both stator wires go directly to the regulator. The regulator has a 3rd wire out that is a 12 v DC positive. That would go to the battery and in my case I will be wireing 12v pos to fan motor, then founding fan 2nd wire to frame ground. The reg body will be grounded as well. The caps these people sized for me will be wired in parallel to the fan load. All this is DC. I will have to find a way to wire the tachometer to stator so it can see the rpm signal. Not clear if that part will work but so far these guys are spot on.

I hope they will stop in and help you out and finish up my project. I have been unexpectedly dealing with family matters and am just getting back working on my project.

Side note to Jim, I have not forgot about it, just sidetracked.

 

[jim hardy]

Hi Mike
i'm still in Idaho with very sparse internet availability... i am relieved you're not waiting on me !

Am thinking "what next" if that Briggs regulator doesn't do the job. Probably we'll have to go to higher voltage caps and a buck regulator, which is way more trouble.

Good Luck, and Thanks for your patience and perseverance.

old jim