OT-Automobile alternator rotation direction

for example.

One factor that should weigh in, IMHO. This is automotive parts where cost at high volumes is absolute king. I don't know that alternator diodes are made on the same lines, with the same goals as usual power semis. I have not decided how that will affect things in this case. [I know almost nil about power semi manufacturing/costing etc.]

Reply to
David Lesher
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[Only one wire of the cord will be black; the others will be white and green.]

Here we differ greatly. I'd NOT connect to car harness at all; it gains you nothing. I'd disconnect the battery hot lead; and connect the other generator out directly to the battery positive.

After you unplug the alternator field; NOTHING in the car is part of the loop. Not the ECU, the stereo, the dome lights, nothing. Worst case, you'll take out the alternator diodes, and after the bears eat you; your survivers can get the car fixed cheaply.

Cook the computer{s}, however, and you'll be stranded and poor.

Reply to
David Lesher

I wasn't clear. We stripped out and cut the 'hot' wire in the extension cord within a couple feet of the 'socket' end. We will have one black wire that connects to the 'plug' side and another black wire connecting to the 'socket' side. The white and green wires are not disturbed.

It would tend to protect the truck's electronics.

I'd disconnect the battery hot lead; and connect the

If you disconnect *at* the battery terminal, the ECU, stereo, dome light etc. wouldn't have the battery's low impedance to protect them from voltage surges produced by the generator. Plus ungood. All that stuff should remain in parallel with the battery.

Have a look at the second 'alternator' diagram.

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Mmm no. Unplugging the field gains you nothing. All the downstream loads would still be connected to the battery regardless if the alternator field is connected or not. 'Tis a herring of great redness.

Not for long, if the bears are having me for dinner! :)

--Winston

Reply to
Winston

With the car (and alternator) out of the circuit the 115 volt "alternator" can NOT charge the battery. The battery requires DC, the

110 volt generator/alternator only puts out AC. Keeping the alternator in the circuit uses the diodes in the alternator as a half wave rectifier - giving the battery the DC it needs.
Reply to
clare

Now that's a good idea. Drills (AC powered) are usually universal motors. So they won't mind running on DC. The battery battery will only 'see' the current that the drill motor passes, which should be in the neighborhood of 5 to 10 amps.

Connecting a 110 V (rectified) source to a car battery directly, with no voltage control is less likely to damage the battery than trip the gen circuit breaker.

Reply to
Paul Hovnanian P.E.

[snip]

It wouldn't matter either way. Using this method to charge, the generator isn't producing anything, as it isn't turning. And while there's little need to protect anything in the vehicles electronics (the battery will act as a very good low impedance voltage clamp), it will take little extra effort to pop the (+) lead off the battery.

Reply to
Paul Hovnanian P.E.

Actually -- that is not a bridge rectifier to convert three phase AC to DC, but rather a bridge of mosfets to convert DC to three phase AC -- as in a VFD. (It will need more logic to drive the gates to do it right, but that is at least a start.)

Not at all sure that the voltage ratings there have any bearing on what would be found in an alternator. Instead, it is described as being to drive things in the automobile which *need* three phase

Enjoy, DoN.

Reply to
DoN. Nichols

The {13.8v} ALTERNATOR is not turning.

The {120vac} GENERATOR is..

Reply to
David Lesher

But the trigger speed is triac-based, and needs zero-crossing to work. I'm not keen on the drill as series limiter; it is added inductance and when the commutator switches, I can envision large spikes. I'm still thinking of using a headlamp as a series limiter......

The battery can take large amounts of current for ~1 min at a time, that is true.

Reply to
David Lesher

Before I bought my landlady's 85 Skylark, I used to warm it up about every second month (it was driven 3000 kilometers in eight years) no clock, mechanical pushbutton AM radio. I did have to put in a new battery in '96, along with new tires. Gerry :-)} London, Canada

Reply to
Gerald Miller

As I have said three or four times:

TAKE THE WIRES OFF THE CAR ALTERNATOR. ALL OF THEM.

TAKE THE POSITIVE BATTERY CABLE OFF. THAT'S THE BIG FAT WIRE THAT GOES TO THE STARTER AND FUSEBLOCK.

CONNECT 120V CORD BETWEEN ALTERNATOR OUT ["White"] and BATTERY POSITIVE ["Black"]

Now, how exactly does ANY voltage get into the disconnected and powerless car wiring? Again, ALL the car's loads are disconnected from the car alternator; disconnected from the battery + as well. No connection.

If it makes you happier:

Unbolt and remove alternator from car. Unbolt and remove battery from car. Carry both ten feet away from car; over by the campfire... Put alternator, battery, and AC generator in series.

Will THAT smoke the car's radio, ECU, etc? If no, explain how it is different than the in-car approach.

See above....

NO, there is one single connection to the battery positive; one bolt, one connector terminal. Yes, that cable at some point splits into a) big wire to starter b) smaller wire to fuse panel;

BUT when you unbolt the battery terminal, everything is disconnected.

[If you have a car battery with two or more separate positive battery terminals; please put a picture up. No fair if it says "Lucas" or "Borgward"...]
Reply to
David Lesher

Please explain how the above are "permanently" connected to the battery. Every car I have ever seen [even British ones!] has a removeable, replaceable, battery. You unbolt either the old top post clamp; or the new banjo side terminal bolt. When you do, everything is disconnected. Pull both cables and the mounting bolt; you can take the battery out of the car!

[Of course, GM could have now come up with a car with a non-replaceable battery. They ARE the people who welded the doors in place on the Vega. And Apple sells iPods, iPhones and laptops where you have to junk the gadget when the battery dies; so are cars far behind?]
Reply to
David Lesher

On 5/6, you had the A.C. generator connected between the battery positive post and the wire that had been removed from it. All the downstream loads were still connected at the fuse block.

On 5/7 you said:"Plus, as I said, if I was risking what you propose; I'd isolate the system from the car by a) disconnecting the battery terminal and feeding the battery directly. b) Disconnecting the Alt field connections." No mention is made of disconnecting the alternator 'Bat' wire. The fuse block is still in the circuit because contrary to what you said, disconnecting the field will not isolate our lashup from the fuse block.

Later on 5/7 you said: "Disconnect BOTH!!!!" which changes the circuit dramatically, implying for the first time that the battery positive connection and the alternator 'Bat' connection should be removed.

This change *does* isolate the rest of the truck's electronics. I assumed wrongly that you were continuing to say that "BOTH!!!!" meant the connections to the battery positive post and the alternator 'Field' connector.

I didn't understand that you had changed the connections to the alternator, generator and battery from the plan in your earlier approach.

I see that you meant that the A.C. generator should now be connected between the depopulated Bat stud of the alternator and the depopulated positive post of the battery. Note that by doing that, the A.C. generator will see a short circuit every half cycle and the alternator will see current pulses every 8.3 mS that far exceed the forward current rating of the diodes. Let's hope the generator shuts down before it or the alternator short out. Will that get our intrepid cabin builder home? No.

On 5/8 you said: "I'd NOT connect to car harness at all". That could be construed to mean "the battery positive connection and the alternator 'Bat' connection should be removed before connecting the generator between the Bat stud on the alternator and the positive post of the battery." That's what you meant to say, right? That is likely to harm the alternator and / or the generator as outlined above. Our cabin builder is still cold and hungry.

I do concede that he can get underway the following morning after he is rescued and his truck is towed in for a new alternator and a battery charge.

--Winston

Reply to
Winston

I posted this diagram:

ALT+ ------Gen "Neutral" Gen "Hot"----------------------+ BAT term.

Note there is no real "field" connection on an integral-regulator alternator. The plug the car manual calls such is typically two wires -- sense and "red light" circuit.

That's been my thrust all along; if the car electronics are disconnected, they can not be cooked.

?Short? I do agree that current limiting will be a major issue. If only he had a 70W drop light; it would be easy. If he can get the generator to idle; that will be a big help. You can try using the drill, but the trigger speed control may object.

If he has a plastic bucket, water, and some salt [including that morning's used beer]; he can use a salt water bath resistor scheme. I know of a supersonic 10'x10' wind tunnel that uses that approach.

With no DVM, you could use a headlamp as a current indicator; dim will be several amps; full brightness is ~10A.

Reply to
David Lesher

(...)

228 A through a 50 A alternator. Until a real short shows up, this will do nicely. :)

The only weakness in Pete and Paul's otherwise brilliant solution is that Clack implied that we cannot change the voltage coming from the generator:

"(...)power from the generator which is making 110 volts AC(...)"

I suspect that the drill will run happily (at significantly reduced RPM). It has a source of DC that pulses from 0 to ~150 V to 0 every 16.66 mS. We only need it to run for a few minutes so cooling shouldn't be an issue. Lock the trigger down full and try the headlights in a few minutes.

Because our cabin builder was wise enough to leave the battery connected at the post, he can shut off the drill and generator and try the starter. If she don't start, he can crank up the generator and drill to buffer up some more Joules in the battery. This process might take as much as a minute to complete. Way faster than buttoning everything up to see if she starts, particularly if she doesn't.

Drill is *much* safer and much faster to implement. And *way* more pleasant to be around.

Or one could look at the drill motor nameplate and subtract ~60%.

--Winston

Reply to
Winston

The same circuit can be used as an active rectifier. It has the advanage of a lower Vf, which reduces the heat generated in the alternator housing. It also means that trying to use it as a straight single phase rectifier won't work.

Reply to
Michael A. Terrell

Three phase synchronous rectifier? Very kewl idea!

But,

1) They appear to be using the MOSFET body diodes to do ~ 10% of the rectification rather than using them as voltage clamps (protection devices). This appears odd.

2) Though the MOSFETs *are* bidirectional, they are shown installed 'backwards' from conventional usage. During power production, the drains are negative in relation to the sources. Strange.

3) I didn't see the gate drive circuit for the MOSFETs. I assume it includes a charge pump to keep the high side MOSFETs saturated during peaks.

4) This is a bridge all right but it's really to be used as a source of 3 phase power, not a rectifier. Look at it that way and items 1 and 2 are non - issues because the current would flow in the opposite direction.

--Winston

Reply to
Winston

What is shown in a data sheet is never the full schematic. they always have errors, on purpose, to prevent a direct copy.

Synchronous rectifiers have been around since at least the '40s, in the form of synchronous vibrators. More that one OEM mentions FET power rectification in their automotive sections.

Reply to
Michael A. Terrell

So your portable one-lung generator will source 228 amps? At 120V that means 27 KW. The small portable gas generator in my garage is a lowly

0.75 KW; I'm jealous..

A friend has a 7.6KW model for his house; when his that Clack implied that we cannot change the voltage coming from the

Based on 20 years of listening to Click & Clack; I'd say their Puzzler limits are not THAT cast in stone. (But then, I just watched Kirk beat the Kobayashi Maru exercise.) After all, it is described as an "electric drill" he has, not an "electric motor with chuck that can drill holes OR spin the alternator.."

One issue on the drill is while its nominal reactance is well suited for our needs; it will draw a lot more in locked rotor mode. If it does not quickly get out of that mode and to a reasonable RPM, will it still be a suitable current limit....?

Salt water resistors are used in some interesting places. For example, for the 87,000 HP drive motor system on a NASA wind tunnel.

I suspect the salt in new beer is sufficient...but agree it would be a sin to waste beer..

Lamp is at least resistive, and linear over the DCish waveform.

Reply to
David Lesher

The generator is an unknown. Is it a 6 cyl. diesel behind the cabin or a nice little Honda inverter?

All we know is that our intrepid cabin builder will get nowhere fast by connecting it to the truck without any current limiting. The generator is not going to 'grunt and supply'. It will fail safe or short out or it will take out the alternator and attached wiring. None of these options will get our guy back on the road and to dinner.

It will be out of 'locked rotor' mode very quickly. As you point out, these drills use phase modulation to control speed. I figure that 90% of half wave should spin the drill at about 40% of maximum RPM with no mechanical load. That'll do and it'll charge our guy's truck battery at a fast, yet safe rate.

(...)

I didn't see a lamp in the inventory. A headlamp will have only 10% of the resistance we need anyway.

I am embarrassed for not suggesting that our intrepid cabin builder just swap out his battery for the charged one in the back of his truck. If you can materialize objects into the scenario, I can too, right?

MR. SPOCK: Say again, captain? You want me to beam down a *truck battery*?

CAPT. KIRK: Yes and don't suggest that I should mine some lead and begin looking for some lemons.

:)

--Winston

Reply to
Winston

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