So things have moved on a bit. Some good things, some bad things, kind of at a pause right now.
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Things got off to a bad start when I decided I needed to remove the pulley from the alternator to fit a different size one. Not having a large-enough impact wrench, I gave it to a guy at the local garage/auto workshop, forgetting to tell him the main nut was a left-had thread. I heard a loud snap and a sheepish engineer appeared, holding the alternator in two pieces. No repairing that, so I had to buy another alternator (it turns out Suzuki use exactly the same device, and it's cheaper because there's less demand than for Ford).
The alternators are nicely made - SKF bearing at the rear and the main one says "made in germany" so is likely to be good quality.
I have set up a test rig, driving the alternator using an old washing-machine motor with a speed controller so I can vary the rpm. I'm using a bench power supply to feed the field coils/rotor, so I can adjust the current, and running the output through a five-phase bridge rectifier (just two three-phase units in parallel) and watching the AC output with an oscilloscope and the DC output with a meter. It's open-circuit output - no load - but I reckoned it would be representative.
I do indeed get very clean DC out of it. However, I'm finding I need to get the RPM up *really* high. Here's a graph at 3600 rpm, showing how output voltage varies with field current :
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Current in Amps is along the bottom (x-axis) and you can see we've pretty much reached saturation by 10 amps - no useful increase beyond that.
So let's fix the current at 10A and then wind up the speed :
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Nice linear relationship, BUT we're at 5,000 rpm before hitting 24 volts, which means to get to 48 volts (or a bit beyond it, if we want to charge batteries) we would need to be at around 11,000 rpm. Hmm.
Looking at the car this unit comes from, the crank pulley looks roughly 2 x the size of the alternator pulley, so in order to charge the batteries, the engine would need to be doing over 5,000 rpm. That doesn't seem right ! How often will it be doing that ? The idea is it does this under braking, capturing waste energy, and you're not going to braking at 5,000 rpm unless you're on a race circuit.
So, where are we ? I could probably get this useful by running it really, really fast, but I don't want to do that as 11K rpm sounds excessive even if the device is rated for that. And I don't see how in it's intended application (the car) it can do anything useful.
Is it possible the big chunk of management electronics I took off this is doing something very clever like boosting lower voltages up to enough to charge a 48v battery ? Some sort of boost converter? I am next going to try wiring it back into the circuit and trying things, although I have a feeling it may need some sort of control input to tell it to go into charge mode.
Any thoughts appreciated, as usual, and I will let you know what transpires...
Richard
You cannot view this attachment.
Things got off to a bad start when I decided I needed to remove the pulley from the alternator to fit a different size one. Not having a large-enough impact wrench, I gave it to a guy at the local garage/auto workshop, forgetting to tell him the main nut was a left-had thread. I heard a loud snap and a sheepish engineer appeared, holding the alternator in two pieces. No repairing that, so I had to buy another alternator (it turns out Suzuki use exactly the same device, and it's cheaper because there's less demand than for Ford).
The alternators are nicely made - SKF bearing at the rear and the main one says "made in germany" so is likely to be good quality.
I have set up a test rig, driving the alternator using an old washing-machine motor with a speed controller so I can vary the rpm. I'm using a bench power supply to feed the field coils/rotor, so I can adjust the current, and running the output through a five-phase bridge rectifier (just two three-phase units in parallel) and watching the AC output with an oscilloscope and the DC output with a meter. It's open-circuit output - no load - but I reckoned it would be representative.
I do indeed get very clean DC out of it. However, I'm finding I need to get the RPM up *really* high. Here's a graph at 3600 rpm, showing how output voltage varies with field current :
You cannot view this attachment.
Current in Amps is along the bottom (x-axis) and you can see we've pretty much reached saturation by 10 amps - no useful increase beyond that.
So let's fix the current at 10A and then wind up the speed :
You cannot view this attachment.
Nice linear relationship, BUT we're at 5,000 rpm before hitting 24 volts, which means to get to 48 volts (or a bit beyond it, if we want to charge batteries) we would need to be at around 11,000 rpm. Hmm.
Looking at the car this unit comes from, the crank pulley looks roughly 2 x the size of the alternator pulley, so in order to charge the batteries, the engine would need to be doing over 5,000 rpm. That doesn't seem right ! How often will it be doing that ? The idea is it does this under braking, capturing waste energy, and you're not going to braking at 5,000 rpm unless you're on a race circuit.
So, where are we ? I could probably get this useful by running it really, really fast, but I don't want to do that as 11K rpm sounds excessive even if the device is rated for that. And I don't see how in it's intended application (the car) it can do anything useful.
Is it possible the big chunk of management electronics I took off this is doing something very clever like boosting lower voltages up to enough to charge a 48v battery ? Some sort of boost converter? I am next going to try wiring it back into the circuit and trying things, although I have a feeling it may need some sort of control input to tell it to go into charge mode.
Any thoughts appreciated, as usual, and I will let you know what transpires...
Richard