Post by thread:[EE] Alternator Regulators.

Hi guys, I'm in the late stages of replacing the alternator on my little 1 cylinder BMW Diesel sailboat engine. The original alternator hides behind the flywheel and no longer produces AC. Even if I did want to haul out the engine and pull the transmission and flywheel, the cost of BMW parts is far more than the cost of the 'free' permanent magnet alternator that a friend donated to the cause. However, I need a regulator for this puppy and I'd like to incorporate a 3 state charger. There is no field winding to control so there are two ways to reduce the voltage output (and hence the current). One way is to shut off the charger and let the alternator voltage climb. The other way is a shunt type regulator that dissipates the energy into a heatsink which therefore keeps the voltage low. What I was thinking of using was a bridge of SCR devices since the alternator just has a two wire AC output. Enabling the bridge via a PIC and PWM to set the current and letting the zero crossing turn off the bridge seems easy enough. I don't believe the alternator puts out more than 200VAC unloaded so my guess is that a couple of 400V 35A SCRs should be adequate. (The alternator is a 25A device). What I'm worried about is if there is a chance that when the bridge is enabled that the peak voltage might be kind of high. So the idea of a zero crossing detector to enable the SCR drive at effectively zero volts and then let the reverse bias turn off the bridge when the PWM stops. Or is it better to use a normal bridge rectifier and a shunt regulator to hold the voltage to some specific value as determined by the 3 state charging algorithm? Comments? Thanks, John Dammeyer Wireless CAN with the CANRF module. www.autoartisans.com/documents/canrf_prod_announcement.pdf Automation Artisans Inc. Ph. 1 250 544 4950 -- http://www.piclist.com hint: The PICList is archived three different ways. See http://www.piclist.com/#archives for details.

John Dammeyer wrote: > > Hi guys, > > I'm in the late stages of replacing the alternator on my little 1 > cylinder BMW Diesel sailboat engine. > 'free' permanent magnet > alternator that a friend donated to the cause. > > However, I need a regulator for this puppy and I'd like to incorporate > a 3 state charger. There is no field winding to control so there are > two ways to reduce the voltage output (and hence the current). Hi John, I remember when you posted about this before. My suggestion is to go to a motorcycle wrecker and find a shunt regulator from pretty much any small modern motorcycle that has a single phase alternator. They are mostly perm magnet, the bigger bikes use 3 phase, the smaller bikes generally single phase. There are only a couple of wires to connect, usually very straightforward. Cheap, quick and should be reliable. :o) -Roman -- http://www.piclist.com hint: The PICList is archived three different ways. See http://www.piclist.com/#archives for details.

Hi Roman, I posted the comments to a few lists before. I guess I forgot I did it here. However, a Motorcycle or car or tractor is vastly different from a boat. Boats do use little energy for starting the engine and then like a car sit at float mode very quickly until it's time to anchor. Then the power usage on the house battery goes way up till bedtime unless an electric autohelm is used while sailing. At night an anchor light is mandatory so there is a certain amount of current drain throughout the night. In the morning the battery needs to be recharged. A conventional automobile regulator will take as long as 8 hours to bring a 50% discharged 100AH battery back to 100%. That's because they charge at a compromise between float mode and a charge mode that doesn't boil the electrolyte away. In the marine environment, the 3 stage chargers apply enough current to the field to push in as much current as the battery can take (up to 40% of its amp hour rating) until it reaches the gassing state which is about 14.4V. Unfortunately the battery will be only about 50% recharged at this point because the electrolyte isn't uniformly mixed. Instead, pumping in about 25% of the amp hour rating into the battery until the 14.4V point is reached will put the battery at the 80% charge point. Next the voltage is reduced to a lower voltage like 13.8V and held there until the current into the battery reaches 2% of the AH. At that point the battery is almost 100% recharged. At that point if the engine still needs to run it can drop the voltage to 13.4V for a float where all it does is replenish the natural leakage. That's the three states: Current regulated, voltage/current Regulated, voltage regulated. A conventional car regulator runs at about 13.8V and that's a compromise between slow charge and not drying out the battery. But then cars aren't usually run for hours on end; for the most part. So if I take out 25AH at night, I'd like to be able to run the engine for under two hours to replenish the 25AH; it's a 25A alternator. So forgetting for a moment that I want a regulator for a boat, my question is really the best way to implement a permanent magnet based alternator regulator like the type used on some Wind or Water turbine generators for alternative energy. Shunt or Series pass? With FETs or SCR controlled? Forget the boat stuff for now as that wasn't my question. John Wireless CAN with the CANRF module. www.autoartisans.com/documents/canrf_prod_announcement.pdf Automation Artisans Inc. Ph. 1 250 544 4950 {Quote hidden}> > However, I need a regulator for this puppy and I'd like to > incorporate > > a 3 state charger. There is no field winding to control so > there are > > two ways to reduce the voltage output (and hence the current). > > > Hi John, I remember when you posted about this before. > My suggestion is to go to a motorcycle wrecker and find > a shunt regulator from pretty much any small modern motorcycle > that has a single phase alternator. They are mostly perm > magnet, the bigger bikes use 3 phase, the smaller bikes > generally single phase. > > There are only a couple of wires to connect, usually very > straightforward. Cheap, quick and should be reliable. :o) > -Roman > -- http://www.piclist.com hint: The PICList is archived three different ways. See http://www.piclist.com/#archives for details.

The phase control scheme may work but imho do not allow the alternator to free run, provide a resistor to limit the voltage at all times. 200V may be too much for the insulation of that device. Also, the frequency could be 400Hz-ish or more so you need a SCR scheme that works at that voltage. Me I'd rectify and filter the voltage directly and use a buck dc/dc converter to regulate rail voltage and a second with current and voltage settings for charging, with switchover through FETs used as switches. I suppose that 25A is @24Vac or such, not at 200. Peter -- http://www.piclist.com#nomail Going offline? Don't AutoReply us! email spam_OUTlistservTakeThisOuTmitvma.mit.edu with SET PICList DIGEST in the body

On Sun, 14 Jul 2002, Roman Black wrote: >Hi John, I remember when you posted about this before. >My suggestion is to go to a motorcycle wrecker and find >a shunt regulator from pretty much any small modern motorcycle >that has a single phase alternator. They are mostly perm >magnet, the bigger bikes use 3 phase, the smaller bikes >generally single phase. > >There are only a couple of wires to connect, usually very >straightforward. Cheap, quick and should be reliable. :o) Always assuming that there are small bikes with 25A alternators. Else it will be a shunt *ignition* regulator. Peter -- http://www.piclist.com#nomail Going offline? Don't AutoReply us! email .....listservKILLspam@spam@mitvma.mit.edu with SET PICList DIGEST in the body

Peter L. Peres wrote: . . > Me I'd rectify and filter the voltage directly and use a buck dc/dc > converter to regulate rail voltage and a second with current > and voltage settings for charging, with switchover through FETs > used as switches. I suppose that 25A is @24Vac or such, not > at 200. . . I think, it's a good idea of using single regulated DC/DC converter. It should produce 13 to 15V DC. I doubt about alternator's 200VAC unloaded. It is diesel sailboat, not jet fighter. In order to be used effectively alternator should produce somewhat 14AC at min rpm. For a sailboat diesel max/min rpm is aprox 3, I think. So 14-40V to 13-15V regulated switching DC/DC converters aren't rare things on a market. After all, for what heck do this PICs have PWM? Mike. -- http://www.piclist.com#nomail Going offline? Don't AutoReply us! email listservKILLspammitvma.mit.edu with SET PICList DIGEST in the body

Hi Peter, I pulled the 200VAC from the BMW D13 manual where they say the two phase alternator produces as much as 200VAC open circuit. These little Shibaura alternators may be far less. I'll connect up a 1/3HP electric motor to the alternator and run it at 1725RPM just to see what comes out. I'm leaning toward a two SCR plus two regular diode bridge setup where the SCRs are triggered with PWM from a PIC. I'll start with a 6.3VAC transformer to test out the circuit and then migrate up to 36VAC just to ensure that things are working correctly. I will post the circuit design when the testing is done. John Dammeyer Wireless CAN with the CANRF module. www.autoartisans.com/documents/canrf_prod_announcement.pdf Automation Artisans Inc. Ph. 1 250 544 4950 > {Original Message removed}

John, you design should avoid the chance of the alternator running open-circuit for any periods of time, this is the main cause of alternator insulation breakdown, and will kill your alternator. The SCR type regulators are designed to keep the alternator volts down, by loading the thing into the battery/load or shorted through the SCRs. If you are going to use a PIC to control SCR firing it might be prudent to add a hardware safeguard circuit, where a cap is charged through the cycle, and if reaches a setpoint automatically turn on the SCR. So if you get an open-circuit load, (blown fuse, PIC glitch etc) the alternator has a minimum load. Probably the last 1/3 of the cycle (60') should be enough as your hardware safeguard. -Roman John Dammeyer wrote: {Quote hidden}> > I pulled the 200VAC from the BMW D13 manual where they say the two phase > alternator produces as much as 200VAC open circuit. These little > Shibaura alternators may be far less. I'll connect up a 1/3HP electric > motor to the alternator and run it at 1725RPM just to see what comes > out. > > I'm leaning toward a two SCR plus two regular diode bridge setup where > the SCRs are triggered with PWM from a PIC. I'll start with a 6.3VAC > transformer to test out the circuit and then migrate up to 36VAC just to > ensure that things are working correctly. I will post the circuit > design when the testing is done. -- http://www.piclist.com hint: To leave the PICList .....piclist-unsubscribe-requestKILLspam.....mitvma.mit.edu

Peter L. Peres wrote: > > On Sun, 14 Jul 2002, Roman Black wrote: > > >Hi John, I remember when you posted about this before. > >My suggestion is to go to a motorcycle wrecker and find > >a shunt regulator from pretty much any small modern motorcycle > >that has a single phase alternator. They are mostly perm > >magnet, the bigger bikes use 3 phase, the smaller bikes > >generally single phase. > > > >There are only a couple of wires to connect, usually very > >straightforward. Cheap, quick and should be reliable. :o) > > Always assuming that there are small bikes with 25A alternators. Else it > will be a shunt *ignition* regulator. Good point, the larger bikes are 25A+, not sure about the smaller ones. Typical running current on a small bike is well over 15A with lights and ignition. Most bikes now are required/designed to have lights on at all times. -Roman -- http://www.piclist.com hint: To leave the PICList EraseMEpiclist-unsubscribe-requestspam_OUTTakeThisOuTmitvma.mit.edu

>I pulled the 200VAC from the BMW D13 manual where they say >the two phase alternator produces as much as 200VAC open >circuit. These little Shibaura alternators may be far less. Don't count on it. Did you manage to run your original alternator open circuit at some stage? This may well be why it has died. I believe that many of the original alternators on motor vehicles would die if run without a load because the rectifier diodes used did not have the Reverse Voltage rating to withstand open circuit use. More modern alternators may well have moved on from this situation now high current/high voltage diodes are more common than they were then. -- http://www.piclist.com hint: To leave the PICList piclist-unsubscribe-requestspam_OUTmitvma.mit.edu

> > >I pulled the 200VAC from the BMW D13 manual where they say > >the two phase alternator produces as much as 200VAC open > >circuit. These little Shibaura alternators may be far less. > > Don't count on it. Did you manage to run your original alternator open > circuit at some stage? This may well be why it has died. The manual states the procedure on how to test the output of the alternator and that's what I did. At maximum engine RPM the alternator produced about 3VAC. It's possible that at some point I may have inadvertently shut off the Master Battery switch while the engine was still running. This would have disconnected the battery from the alternator output and blown the regulator which in turn took out the windings. It's a common problem on boats with master switches and Diesels that don't care if they have electricity for operation. This "Load Dump" can be prevented by putting a hefty transorb on the output of the alternator regulator to keep the voltage within some safe point. Given that this diesel is from the mid 70's the chance of it surviving a Load Dump is pretty unlikely. So more than likely I shot myself in the foot. That's one reason why I would like to have a system that has high voltage diodes and regulator transistors to be capable of with standing the Load Dump voltages. Sigh.... John -- http://www.piclist.com hint: To leave the PICList @spam@piclist-unsubscribe-requestKILLspammitvma.mit.edu

John, test the alternator at that RPM, it is intended for. If you have 6v 3000 RPM motorcycle alternator then it is OK. Find 12v alternator of low RPM engines or change if possible transmission ratio from engine to the alternator to increase RPMs. Cheer up. Mike. John Dammeyer wrote: {Quote hidden}> The manual states the procedure on how to test the output of the > alternator and that's what I did. At maximum engine RPM the > alternator > produced about 3VAC. > > It's possible that at some point I may have inadvertently shut off the > Master Battery switch while the engine was still running. This would > have disconnected the battery from the alternator output and blown the > regulator which in turn took out the windings. It's a common problem > on boats with master switches and Diesels that don't care if they have > electricity for operation. This "Load Dump" can be prevented > by putting > a hefty transorb on the output of the alternator regulator to keep the > voltage within some safe point. Given that this diesel is > from the mid > 70's the chance of it surviving a Load Dump is pretty > unlikely. So more > than likely I shot myself in the foot. > > That's one reason why I would like to have a system that has high > voltage diodes and regulator transistors to be capable of > with standing > the Load Dump voltages. > > Sigh.... -- http://www.piclist.com hint: To leave the PICList RemoveMEpiclist-unsubscribe-requestTakeThisOuTmitvma.mit.edu

Hi Mike, Well sad news. Finally mounted the alternator on my super little cast aluminium bracket. It looks so professional sitting in there, snugged up beside the engine. Even milled a slot into a piece of stainless strap to adjust belt tension. I get 12.9VAC open circuit at full power in gear. I'll measure current into the battery later but it looks like I'm going to have to make up a pattern and cast a gearbox casing/bracket assembly. All it costs is a bit of time, 13 minutes of propane at 250,000 BTU and time to let the casting cool. Then the gears, bearings etc. Looking more and more like I should pull the engine and find out what went wrong with the alternator buried behind the flywheel. Sigh.... John Wireless CAN with the CANRF module. www.autoartisans.com/documents/canrf_prod_announcement.pdf Automation Artisans Inc. Ph. 1 250 544 4950 > {Original Message removed}