Author Topic: Shorting an Amtek (Read 4535 times)

RanZ · « **on:** May 23, 2007, 03:57:19 AM »

I finally have all the parts for my Ametek 20VDC TDM project. This is just a project and I will occasionally use it on a fish house so I am keeping it pretty simple at the moment. I don't have a charge regulator and dumpload, I will just be connecting the 2 wires directly to a battery (it will have a diode) and using a multimeter to watch the charge. A few questions:

I will be using a multimeter to monitor the battery voltage so I don't overcharge... I would touch the leads of the battery to measure its voltage but how do I measure the voltage the genny is putting out?
Can I short out the genny while it is spinning in the wind or will that damage it? The diode I have is a 100v 25A diode but even when shorting the genny I don't think it will put out that much will it?
to measure the current the genny is putting out I would insert the multimeter to the NEGATIVE battery lead and the NEGATIVE genny wire correct?

Thanks! I will post pictures when I have this put together

Flux · « **Reply #1 on:** May 23, 2007, 12:47:11 AM »

Shorting a dc generator at speed in the real world is a disaster. Dc machines with commutators and brushes in general don't stand this treatment.

Small machines with more internal resistance and servomotors in general may survive some abuse but it is still a bad idea. Shorting them as a means of preventing them turning may be safe as long as they can't break free, but don't short them at any significant speed.

Shorting most electrical machines at speed is bad for them, but generally ac machines can survive it. Most larger alternators are designed to survive a short during fault conditions but this is never intended to be a regular occurrence, the forces on the windings is very great. Small alternators in the size used for wind can usually be shorted with little ill effect but not all will stop.

You can measure the output current in the battery positive or negative line( negative is a bit unusual but in a simple circuit it will be ok)

Flux

RanZ · « **Reply #2 on:** May 23, 2007, 07:34:24 AM »

So would some high resistance resistors work best to slow it down enough to disassemble?

Flux · « **Reply #3 on:** May 23, 2007, 07:42:24 AM »

OK I understand what you want now, I thought it was a form of control.

To stop it you can progressively load it with resistors and if you catch a lull in the wind you should be able to bring it to a stop. If it is already charging a battery the voltage should be down to about 12v so something in the region of an ohm should limit the current to a safe value for a once off stop. If it obviously isn't going to stop then you will need to wait for lower wind. You can connect the resistor before the blocking diode.

Flux

RanZ · « **Reply #4 on:** May 23, 2007, 07:57:22 AM »

I think what I'm going to do is put a toggle switch before the diode, that way I can just flip a switch instead of disconnecting wires. Basically I would like a method to either stop the generator or slow it down enough that I can walk up to it and turn it out of the wind for disassembly. Would something like this product work? If not could you recommend something?

http://www.weisd.com/store2/WOR25W0545.html

Would I need a few in a series? I apologize if this dumb question, I am a novice at this whole thing but am enjoying learning about it.

Thanks,

Dan

alancorey · « **Reply #5 on:** May 23, 2007, 10:13:31 AM »

If you can walk up to it and turn it out of the wind, why don't you just do that? It isn't likely to be flailing around much unless there's a lot of turbulence.

What some people do is use a connector of some sort on the leads to the battery, then when they want to keep the blade stopped they unplug the wire going to the battery and plug in a spare connector with a shorting wire in it.

Alan

AbyssUnderground · « **Reply #6 on:** May 23, 2007, 02:11:10 PM »

Bad idea. Ever seen anyone hit by a turbine? No? Thats probably because they died from the injuries. Id never go near a spinning turbine to stop it, especially in a storm if its going out of control.

ghurd · « **Reply #7 on:** May 23, 2007, 02:59:41 PM »

Not that I think it is a good idea...

But you don't want series, you want mostly parallel. And more like 200 total rated watts. 100W would do it I guess, but I wouldn't go that low.

Maybe 1 or 1/2 total ohms.

It would be a lot cheaper to go with a big pile of 20 cent surplus "sandstone" resistors, or a new single (giant) resistor.

Sorry, that $1.83 each makes my stomach hurt looking at it.

The surplus market is great for series parallel combinations toe get the proper ohms and watts for a lot less money.

Example...

http://www.goldmine-elec-products.com/products.asp?dept=1124

Use Watt' and Ohm's Laws to determine the resistance and watts of the dump load you are considering.

Two switches may be a good idea, bringing the difference in a bit slower.

G-

RanZ · « **Reply #8 on:** May 23, 2007, 05:35:31 PM »

http://www.goldmine-elec-products.com/prodinfo.asp?number=G14510

so if I bought 6 or 7 of these how exactly would I hook them up? Before the diode would I connect the positive wire to one and then connect them together in a series and then the negative wire to the end of that series?

CmeBREW · « **Reply #9 on:** May 23, 2007, 06:13:11 PM »

What I do for my treadmill generator is hook it directly to one of those 12VDC car heaters.(below) It stops it and/or keeps it in STALL very well until a 40MPH+ wind hits it and even then it just turns on the heater and some heat comes out. Make sure you get the type with the BRUSH blower fan motor in it and not the BRUSHLESS type blower motor.(with transistor) The brushless type will burn out from the varriing voltage, but the BRUSH type won't. The photo below is the BRUSHLESS type after it blew up and I added a little fan on top. I believe it is far better than just frying your generator brushes by dead shorting the leads. These little auto heaters are seasonal items though. I got mine for half price as spring was approaching.

RanZ · « **Reply #10 on:** May 23, 2007, 09:46:16 PM »

Those are cheap little heaters, I think I will go that route. I'm assuming you just cut the cigarette lighter end off of it and twist the fan wires to it? Does it matter which wire is the positive?

RanZ · « **Reply #11 on:** May 23, 2007, 10:17:10 PM »

http://cgi.ebay.com/ebaymotors/PORTABLE-AUTO-CAR-HEATER-DEFROSTER-12V-Volt-PLUGIN_W0QQitemZ190077671
519QQcmdZViewItem

something like that work?

AbyssUnderground · « **Reply #12 on:** May 24, 2007, 05:07:04 AM »

The positive wire often has a white strip down it.

CmeBREW · « **Reply #13 on:** May 24, 2007, 06:15:57 PM »

The problem with ordering one by the internet is you don't know if it has the correct BRUSH(s) type blower fan in it or not. This is what I use now.

It is 12vdc / 12.5 Amps / 180 watts (600 BTU).

Like i said before it works great for those mega hurricane like winter days and all thunderstorms. So as long as your Ametek don't go over 200watts. I'm not sure how to read the Ohms, but here is what it says on the 2 ohm scale of my meter. It has to be very low ohms to STALL my DC generator as it does. It is probably less than 1/4th of a ohm. Amazingly, this is made in the USA!!

I have another one (new,never opened) exactly like the one I use if you want it. You can have it for what I paid, half off was $15 and about $5 for shipping. (I have daily UPS pickup for my business) Just email me if you want it. I don't think I will need it, I am making my own multi-element, multi-switching heater. (electronic controlled according to load on mill)

Here are the insides:

It has a simple straight heating element and blower. Of course, the heating element is the same as a big resistor I believe. You can see the little brushes thru the hole there. If you buy one from the store, take it apart and make sure it has BRUSHES and NOT the type that is a Brushless blower fan with transistor. The voltage drop goes down to around 7 volts when hooked up to your genny in a big wind , so this always blows out the little transistor in the little blower motor. So like the photo I had previously posted with the extra blower fan taped on top (I don't use it no more actually).,, that one is a pain in the neck, because that fan is also a brushless type and i had to hook it to my 12v battery bank SEPERATEly and let it run all night even if there is no thunderstorm.

The far better way is the BRUSH type blower which turns on only when it has to...when the heating element turns on during a very strong wind gust.(40mph+) It is completely self-contained and wastes no power. I should have never showed the first picture with the taped on fan. I hope I'm not confusing anyone. As for the polarity question, I don't know,,,I identified the positive wire from the center of the cigarette socket thing and put tape on the wire to keep polarity the same. It would probably work both ways on the BRUSH type blower fan, but NOT on the transistor type BRUSHLESS blower. And yes, you simply cut off the cigarette socket. -Hope this helps.

RanZ · « **Reply #14 on:** May 24, 2007, 07:35:00 PM »

Thanks much for the details and pictures. I am assuming I connect this BEFORE the diode correct? I will put a selector switch on my positive wire so if my battery is full I can flip the switch so the power would be going directly into this heater and not into the battery. What happens if I switch it to the heater if the motor is putting out 14 or more volts? Will that cause harm to the heater?

CmeBREW · « **Reply #15 on:** May 24, 2007, 07:49:42 PM »

I just saw Ghurd's post and I must say his suggestion is even better. Thats a nice cheap electronic source i didn't know about. Nice. Thanks Ghurd!! Where have i been???. Yes, I like Ghurd's suggestion to simply solder 8 to 10 of those 20watt resistors in parallel on a little circuit board (only $1 there I believe) and then there is no need for a fan of any sort. The auto heater fan (BOTH types/brushless and brush)could eventually quit and then the heating element would possibly overheat, burn out, and your mill spin out of control. And the Second reason the resistors are a bit better is if one of those 20watt resistors ever burns out, then the other resistors will still easily keep the mill in STALL. With the auto heater, if the one heating element burns out then your mill will spin out of control, probably in a thunderstorm. And personally, making wood blades is not exactly one of my 'favorite things'.(to do)

RanZ · « **Reply #16 on:** May 24, 2007, 08:02:57 PM »

Would the following picture be the correct way to setup the resistors?

CmeBREW · « **Reply #17 on:** May 24, 2007, 08:31:34 PM »

Yes, BEFORE the diode is the way I do it. The switch is what I do too. That is the basic set up I have been doing also. When the batts reach full (for me it is 13v when the ammeter says 2amps/ but everyones set-up is different) , I switch it to the auto heater to 'shut-down' (Stop/stall) the gennerator. 14volts won't hurt anything. Like I said, after you directly hook the heater to the genny, even if its as high as 30 volts (open voltage/free spin for experimenting) or just 15v hooked to batts, it will immediately drop to 7 volts. I did many 'heating' experiments with my heater and it keeps working fine. You can actually hook two of these type car heaters in SERIES and get alittle bit of heat from them both during wind gusts. Two heaters in series doubles the resistance which will bring the windmill alittle bit more out of STALL and allow it to make alittle heat during 20-30mph wind gusts. It won't heat up a bedroom, but it helps some. However, If there is going to be more than 30mph gusts, You need to STALL the mill better by hooking to only one heater or both heaters in PARALLEL. BOTH methods mentioned (auto heater or plain resisters) will work fine. I don't think the heater(and fan) method will burn out because its hardly ever running anyway. The auto heater is quick and easy is why I chose it.

CmeBREW · « **Reply #18 on:** May 24, 2007, 08:49:19 PM »

Yes. That is similar to mine. Except I have a full wave bridge rectifier instead of a diode myself. I hook the two leads from the dc generator to the two ac input leads of the bridge. I believe your diagram is correct. If anyone sees something wrong or something better please speak up. I always keep forgetting the polarity of the diode symbol!(which direction the current flows)

RanZ · « **Reply #19 on:** May 24, 2007, 09:03:14 PM »

Thanks for all the info! Eventually I would like to make this more complex but since this is a first time project and will only be used for short periods of time I cant justify spending large amounts of money on charge controllers and things. I hope this works out because then I want to build a more powerful generator out of a treadmill motor or one of these: http://www.windbluepower.com/DC_540_Low_Wind_Permanent_Magnet_Alternator_p/dc-540.htm

1 more question. How can I measure the power the wind generator is putting out? If I touch the leads of the battery w/ the multimeter wont it give me the reading from the battery?

CmeBREW · « **Reply #20 on:** May 24, 2007, 09:38:18 PM »

Be very selective about choosing a treadmill motor for a windmill. Most of them are NOT very good. You want higher voltage (above 100) in relation to as LOW of an RPM as possible. Good ones are hard to find. Stay away from anything like 130v@6550rpm.

I glanced at that alternator and at first glance it doesn't look that good either. They said:

"On our test stand with a 12 Volt battery connected the PMA produced 15 Amps at 2000 RPM."

A 4 or 5 foot wind mill rotor(blades) usually don't go much over 1000rpm in high winds, I believe. (4 or 5 foot rotor) My 4 footer when it is generating usually goes 300-800 rpm. I STALL it anything much over 1000rpm.

Which would indicate from that statement that it would be only doing 5 or 6 amps in a pretty good wind. In lower wind it looks like it will do almost nothing. Also, it may cog. If it does, thats not good. The open voltage they show don't mean much I believe. What matters is the POWER it makes when hooked to the 12v battery, and it don't look too impressive. My piss-ant treadmill generator does more than that.

Better is to MAKE your own alternator. Get ALOT more power ,,especially in the lower winds which happen MOST of the time. Of course, thats just my opinion. I just now am making a couple of decent alternators, and once you know the basic principles, its not too difficult.

CmeBREW · « **Reply #21 on:** May 25, 2007, 07:33:49 AM »

"How can I measure the power the wind generator is putting out? If I touch the leads of the battery w/ the multimeter wont it give me the reading from the battery?"

I don't believe so. That only gives the voltage. I use two meters. One for the voltage reading accross the battery terminals and another one as an ammeter(measures amps) in SERIES. (I use the negetive side) Those "cheap" multimeters have a 10A (amp) max ammeter function. For now, thats what I use. Or, just use the one multimeter as an ammeter. (since you already know the battery is going to be around 13or 14volts when charging. Soon, I'm buying a 60 amp ammeter. One more thing, I was wrong about the 'circuit board' for the power resisters. I forget, but its something LIKE a circuit board only higher amps??. Just look in that catalog. Or you could simply solder wires on the leads if you use a heat sink tool of some sort.

RanZ · « **Reply #22 on:** May 25, 2007, 07:51:21 AM »

Will those resistors heat up pretty bad? I was going to just mount them to a board and solder the wires onto them.

I was going to measure the battery's voltage to know when it's full. Do I need to disconnect the generator before measuring it's volts to get an accurate reading?

ghurd · « **Reply #23 on:** May 25, 2007, 08:03:03 AM »

The can get pretty hot, depending on how everything is set up.

They won't get hot if the windmill is about totally stalled.

I like to keep the worst-case watts below half of the rating.

G-

CmeBREW · « **Reply #24 on:** May 25, 2007, 08:34:51 AM »

Measuring the charge on your battery while it is charging is a little tricky, but I do it often. It takes two multimeters though as I stated. One to read amps(in series) and a meter to read the voltage at the same time. For my "cheap" marine batteries, I know they are fully charged when the volt meter says 13volts when at the same exact time the ammeter says 2 amps. (which is a common amp output for my pissant generator) I sometimes verify it is full with my 120vac (12v charging) battery charger(led comes on), and it is always correct. Of course, if you want to know total watts output of the genney,you simply multiply voltage times amps.

Concerning those power resisters,, i always thought the ceramic around them is designed to disipate the heat. Maybe Im wrong, but I thought they are made to get hot. The good thing is, if one does ever burn out, your generator is still safe and then you will know to add a cooling fan or even more resisters. But I'm no expert on anything. I am more of a trial and error kind of guy.

RanZ · « **Reply #25 on:** May 25, 2007, 08:43:17 AM »

could I just wire in a 12V PC case fan to the parallel circuit to blow some air on them?

CmeBREW · « **Reply #26 on:** May 25, 2007, 09:42:33 AM »

Yes,Only if it is wired separately to the 12v battery though. I believe most if not all those type fans are BRUSHLESS type with a transistor. The transistor will burn out, I believe, if it is hooked to the varriing voltage of the wind generator by itself.(in parallel with resisters)

Some of those little fans can be upto 5watts which adds up when it has to be on all the time hooked to a battery. I'm not sure about the voltage drop across the resistors so as to hook a 12v BRUSH type fan in parallel. You'll just have to experiment i guess. Sorry i don't know more.

RanZ · « **Reply #27 on:** June 05, 2007, 02:13:49 PM »

Would 5 2 ohm 25W ceramic resistors work for the dump load? The 2ohm are alot cheaper then the 1 ohm

CmeBREW · « **Reply #28 on:** June 05, 2007, 03:02:57 PM »

RanZ,

Yes, I believe the 2ohm will work also, but if your mill does not furl out of the high winds I would play it safe and get a couple more resisters in parallel myself.

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Author Topic: Shorting an Amtek (Read 4535 times)