I am trying to work out how the wiring on a newly acquired (secondhand) mower works. I have what are supposed to be the wiring diagrams for it but none matches exactly.
The current (ha, ha) conundrum is the meaning of the letters on the regulator. It's a Hatz diesel engine and has an alternator with a separate external regulator. I have the Hatz manual but that is no more forthcoming than the mower wiring diagram.
The regulator has terminals marked with the letters G G L C W. I can work out that the G G terminals are for the output from the alternator but the others have me rather stumped. The W terminal is not connected in any of the wiring diagrams I have. The C connector seems (in most cases) to be connected to switched battery +ve, i.e. it will get 12v on it when the ignition is turned on. The L connector has me totally confused, it's connected to the engine hours meter and thence via an 82 ohm resistor to something that will be at 12v when things are running normally. The regulator is connected to ground/0v by its case. The alternator has a connection direct to battery +12v in addition to its two G G connections.
The Hatz engine is German so the letters may mean something in German.
I'm not at home at the moment so I can't provide a picture or much more detail.
Any information or pointers would be most welcome.
Although every car alternator I've seen incorporates the regulator into the alternator itself, that's not necessarily true of the 24v alternators used on trucks and HGVs. I used such an alternator obtained from a scrapyard as a replacement to the dynastart on the 2 cylinder auxiliary petrol engine on my father's 30 foot ocean going sloop some forty odd years ago.
This engine also had provision for a standard electric starter motor with which it had been equipped so the dynastart was only being used for the dynamo function alone. Dynamos being the inefficient things that they are, it seemed a good idea to uprate this aspect of battery charging with an alternator to reduce fuel consumption when running the engine just to top up the battery and power the electrical systems (radio, navigation lights etc).
The battery power system on the sloop was just your standard 6 cell 12v LA type but this wasn't a problem since I merely had to design and build a 12v (14v actually) regulator box to connect to the alternator. The main six diode 3 phase full wave rectifier pack with the usual additional 3 auxiliary regulator diodes were, as with all such alternators, built into the alternator itself so it was simply a matter of making connections from the regulator box to the two slip ring brushes and the auxiliary rectifier, along with a common earth connection, with the negative side of the ignition light that had formerly gone to the dynamo's regulator now being connected to the auxiliary diode's connection on the regulator box swiftly modified with an extra on/off switch for a reason that will shortly become apparent.
The dynastart double V grooved pully was only about 2 or 3 inches in diameter[1] and was driven by just a single V belt, rather than the two required to handle a starting torque load, wrapped around about an 18 inch diameter flywheel. This gave something like a six to one speed advantage for the dynamo function whilst providing the converse torque advantage for the now unused starting function. The gearing up was necessary because, iirc, the engine maxed out at a mere 1800rpm or so, maybe ticking over around the 3 to 4 hundred rpm mark. This meant we needed to run the engine at a wastefully higher than normal idle speed just to recharge the battery despite the six fold faster rpms of the dynamo, circa two or three thousand rpm to get maximum output.
Using an alternator designed to produce some 28v for charging a truck's
24v battery meant we could get a useful charge at the normal tickover speed without wasting as much fuel. Obviously, the torque loading from generating current at such slow tickover meant the engine actually had to do a little more work than merely overcome its own frictional and pumping losses (and that of the drive belt) but we only had to open the throttle a tad extra to compensate whilst running no faster than the normal idling speed which was a way more efficient and quieter way to generate electricity than before.
The only issue was that if the alternator load was allowed to kick in straight away on startup, it would usually bog the engine down due to one of the cylinders failing to fire up straight from cold. Without such loading the engine could get up to tickover speed, allowing the reluctant cylinder to start firing shortly thereafter. The solution was that additional on/off switch to prevent the regulator exciting the field winding via the slip ring connections, thus eliminating the torque loading otherwise produced when trying to send charging current to the battery.
It was an effective modification since it took only a minute to warm the engine up, especially if we throttled up to a higher tickover speed and then enabled the alternator since the torque loading reduces with speed for a given current output and we'd have both cylinders working with a productive load to both help accelerate the warm up period at a still modest engine speed and swiftly replenish the battery of the energy just taken by the starter motor.
We hadn't suffered such a problem with the dynamo since it needed a very fast tickover to get its regulator to kick in to start generating any current at all. The use of a 24v alternator to generate 12v meant it was producing at least as much as the dynamo could do at full chat, if not more at tickover speed alone.
Not a major problem if *both* cylinders were firing at that speed but since it placed a torque drag loading at less than idling speed, it was a problem I'm happy to say since it demonstrated we were getting more efficient use out of the engine when it was being used just to produce electricity. Having to fit a switch to overcome this cold starting issue was a tiny price to pay in upgrading the battery charging system efficiency. :-)
As for those GGLCW connections, I would guess GG are the slip rings, and of the remainder one will be the 60 to 120 amp rectifier output terminal (obvious from the sheer size of the nut and thread used), another will be the auxiliary diode output to energise the field winding excitation circuit and provide the voltage reference to regulate the voltage on the main rectifier output. The leftover terminal might be a thermally operated output indicator (I have a vague recollection of such a 5th terminal on some alternator connection diagrams but it was a good forty years ago since I last saw such diagrams - perhaps I should try a search engine? :-)
I've just checked out a pdf on truck alternators and there was mention of a connection to an AC output terminal intended to operate a relay (of the thermal class since it works just as well with ac as with dc) or else a tacho sensor (presumably as an alternative method to the classic ignition light confirmation that the alternator is being driven and producing output).
In reading that pdf, I noticed mention of variations such as a seperate negative output terminal and a sense wire option terminal so it can all become rather more complicated than that truck alternator I was using 40 odd years ago. If two of those terminals are both equally large heavy duty types, that would suggest seperate positive and negative output connections rather than the use of the casing as a common ground connection.
[1] The truck alternator's pulley was, I think, a little larger in diameter, maybe 4 inches or so and, of course, just a single V groove. Nevertheless, this was going to be running some 5 times faster than the engine, allowing it to produce useful output even at tickover, unlike the dynamo half of the dynastart unit it was replacing.
Most definitely there is, apart from anything else the AC has to be turned inton DC to charge the battery. Most car alternators simply have the regulator (+ diodes for rectification) built into the alternator but this little Hatz diesel has a separate bit of hardware to handle rectification/regulation.
I outlined the problem to someone else as well and, as very often happens, I think that has led me to the answer:-
G G - these terminals are the alternator field coil which the regulator drives to vary the alternator's output. The alternator has a separate B+ output which actually charges the battery.
C - This is the switched +12v feed from the battery, it provides power for the regulator electronics and also tells it the battery voltage.
L - This is L for L[amp]. It would normally have a lamp between it and the C terminal. When ignition is turned on there is 12v on the C terminal and 0v on the L terminal so the lamp lights. When the engine runs L goes up to 12v and the lamp goes out. On my Hatz there is an 82 ohm resistor instead of the lamp (between L and C) and L is also connected to the hours meter. The hours meter is thus only running when 'the lamp is out', i.e. when the engine is running and the alternator producing output.
W - I still don't know what this is.
I don't know why 'G' means field, translating to German doesn't help. L for Lamp makes some sense, C for battery +ve doesn't.
First alternator I had was Lucas on a P6 Rover. The regulator for that was external.
There is an advantage. The regulator is far more likely to fail than the alternator itself. And an external one is easier to change. So saying, keeping the regulator away from the heat of the alternator may give it a longer life anyway.
Oops! Then WTF isn't it just using a pm 3 phase with full bridge rectifier alternator driving a switching converter instead of a needlessly complicated and inefficiently dc excited rotor field winding automobile styled alternator then?
Re-reading the OP, maybe it is but the W lead suggests possibly not. I'm a bit confused as to whether the terminals are those on the regulator box or on the alternator itself (or maybe even both?)... What was the question again? :-)
So no other similar heavy duty terminal for the B- output then, just relying on the alternator frame to provide the common ground connection?
That's normally the function of the L connection in the typical truck and motorcar usage case.
That corresponds to the auxiliary diode pack output that provides a lower current rated duplicate of the main rectified voltage output of the alternator to both act as the voltage feedback needed to regulate the output voltage and to provide the energy required by the regulator to drive whatever current is needed to excite the field winding on the rotor.
When the ignition is switched on, the ignition warning lamp provides current which the regulator passess to ground via the slip rings and the
3 or 4 ohm field winding which saves the need to kick start the self excitation process by revving the bollocks off the engine to ultilise the rather weak residual magnetism, if any, in the rotor core.
It's this, typically 180mA, lamp current which bootstraps the build up of voltage to the regulator's power/voltage sense input terminal. Once bootstrapped, the voltage on both sides of the lamp equalises and the lamp extinguishes.
That will almost certainly be an ac output as surmised by Tim and Bill who mentioned frequency/tacho connection and, from my vague recollection from 40 years ago, a reference to the use of a thermally operated relay to sense when the alternator is turning and producing power instead of relying on the traditional ignition warning lamp circuit. I suspect in this case it's simply surplus to requirements and unused (BICBW).
I only surmised slip-ring field connections from the fact that there was a pair of them and only the field connections, whose polarity is entirely arbitrary in this case, made up a pair of anything to be found on an alternator without a - or + subscript. :-)
BTW, just how big is this diesel powered mower that it needs what seems to be a full size car/truck alternator? :-)
No, just a big lump of screwed together aluminium castings (not always absolutely reliable in my experience).
OK, yes, I agree. 12 volts across 82 ohms is around 160mA.
It's not particularly big but it is verging on commercial. The Hatz
1B50 engine is 8.5kW output (around 11 BHP). It drives a three rotor
125cm wide cutting deck but there are loads of electrical accessories. The cutting height is electrically adjustable, there's a cruise control (!), an electrically operated rear PTO and a power connection for a sand spreader.
The W doesn't seem to stand for anything, "Drehzahlsignal" meaning rotation count signal is completely W-free. But then a couple of manufactureers use "61" for the "L"-amp connection...
They're probably entirely arbitrary designations so I wouldn't bother pursuing any further the idea that German translations of F for field and G+ for Generator output terminal and the like will answer your question any better than what's been arrived at in this thread by the usual 'detective/educated guesswork'. :-)
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