Micro CoGen.

I guess that depends on ones wallet but I was thinking $1,500/ea.

Tom,

56V isn't the max. This one could go a bit higher. I just set it there for a good charging voltage to play with. At no load 3600 RPM the output voltage is @ 70vdc.

The alternator stators can be wound to achieve any desired voltage. We used to use some that ran at 300Vdc+ that we would then attach to an inverter and build variable speed AC generators with.

Hi Bob,

I can't say I've had any issues with the diodes at this frequency. I've built a lot of units using these modules and never have had a rectifier problem. What type of alternator were you using? What diodes were you having problems with? Have you looked at the AC wave form coming off the alternator? Does it have a lot of high frequency noise that could be the problem? Noise Spikes?

I believe this would make a great cogen application if one had a liquid cooled engine. I don't have much experience in the heat exchanger area but I know my way around a PMG and engine control system. I'd be willing to work with some body if they are looking to but something together.

Hi Bob,

1. I just use standard speed rectifiers. 24 pole at 3600 RPM produces 720 Hz. No need for high speed rectifiers for that. I use rectifiers from Vishay, Powerex, Crydom. Look at a VSKD91.

2. I manage to regulate both the voltage and the current by the speed of the engine. In a battery charging application you can lower the charging current by reducing the charging voltage. What I do is monitor both the voltage and amps. If the amps is greater than the limit then I regulate on the current or in a constant current mode. If the current is less then the limit I increase the speed until the limit is reached or the voltage becomes the regulated limit 56Vdc in this case. At that point I regulate the speed of the engine to maintain a constant voltage. I don't use any SCR, IGBT or MOSFETS.

3. At the moment they are not in production. That is subject to change. I have a number of them in house. I don't have the exact numbers but they are close to 90%. You would then need to add in the rectifier losses. Your 82-83% would be close. I have a source to get some of this information. I'll see what I can dig up on the eff. I haven't seen anything affordable to beat the efficiency of this design. Since you have a direct couple there isn't any loss in a belt drive, no bushes or bearings either. Use of Schottky diodes would reduce the rectifier loss, but you are very limited on the voltage rating of the Schottky.

BTW you can get @ 10KW out of this size generator. It measures about 11" OD and 4" thick. Weighs @ 40lbs.

Hope this helps

SteveU

Thank you for your kind words. I appreciate any referrals you wish to give.

I do have a diesel unit on my YouTube channel. It worked out to be a very nice package too. I also did a similar generator to this Kohler diesel using a Kubota DF972 on LP. I'll have to get it posted up there too.

EA

Thob,

I used 2 different controls. One controller does the engine speed control. It uses a stepper motor to move the throttle and senses the engine speed. The other controller which is in the small box in front of the generator tells the engine speed controller what speed to run the engine at. This controller then measures the output voltage, output current and adjusts. I even incorporated the ability for remote battery sensing (to make up for cable voltage drop) and temperature compensation but I haven't integrated those features in yet. I used Atmel 8 bit AVR controllers.

EA

Below is a link to a video showing a 48Vdc battery charging generator I have been tinkering with for a while. I used a 8 HP Honda engine and a 24 Pole PMG. I electronically control the engine speed to regulate the output of the PMG according to the load. For this setup I programmed the charging voltage to 56Vdc and the charging current is limited to 75Amps so peak power is 4200 Watts. Attached to the generator is a load bank and 48Vdc 200 A/hr battery string. At the beginning of the video I apply 60 Amps of load to the battery to start discharging it. I then start the engine. It has electric start and auto choke. The engine idles for a short period and then begins to increase the engine speed to raise the output voltage of the PMG. It does this slowly to walk into the charging load. The control system monitors the output current via a shunt. It will limit the charging current to 75 Amps so to not overload the engine. I then begin to turn off some load and the engine speed increases to raise the voltage but yet maintain only a 75 Amp charge. Once the voltage reaches 56Vdc the controller maintains 56Vdc regulation and the charging current begins to taper off. As I drop more load you can hear the engine speed slow to keep regulation.

http://www.youtube.com/watch?v=1CvYcCUZqOI

Henry,

I use them in my generators. I have them custom built for me. I could sell you one if interested. Attached is a 3D view showing the extra clearance it would provide.

EA

The muffler you have on that engine is a standard B&S catalog muffler. This clearance is closer that I'd like to see but in reality when running it won't be that bad. The main thing that will need to be done is to make sure the alternator can pull in cool air. The alternators fan will pull air in through the end where the terminal block is attached. The air is then pushed out through the cooling fins. Unfortunately the engines cooling air moves the opposite direction. It blows its hot air at the alternator. When the engine is running there should be enough air moving by the muffler to keep the heat transfer to the alternator at a minimum. When the engine stops and the air stops moving you will then see some heat soak into the stator housing. I have attached some pictures of some mufflers that I have that would elevate the position of the muffler away from the alternator.

As for the magnets they are class H. With as much capacity (HP) as the engine has you won't stress the alternator enough to over heat it. You should be able to get @ 5KW on LP. DanG is right about the danger of the alternator closely attached to the crank case. The alternator will absorb the heat of the engine. The alternator was designed with this in mind. Again the key thing will be to baffle the alternator so that it pulls in cool air and not recirculate the hot engine cooling air. If you do that you shouldn't have a problem. It has been done like this for a lot of generators.

I mounted a low voltage alternator to it this morning and ran some data. See the chart attached. First run I had the throttle wide open or @ 3900RPM no load. I ran out of load bank switches before the engine began to really load down. I then set the no load speed to 3600RPM and added load followed by no load set point of 3300 RPM.

The unit measures 30 x 20 x 28 inches (L x W x H) and weighs @ 180 lbs. The enclosure and base are all aluminum. The fuel tank is about 1.5 gallons.

Let me know if you would like any other information.

Looks good Henry. Did you run a feeler gauge around the rotor to check for clearance? Or just spin the rotor by hand to make sure nothing is rubbing? Since the stator is mounted to a J609 mounting face it shouldn't be a problem but always good to be safe.

Let me know if you have any other questions.

Eric

Okay. Where should we start? I can get you a LxWxH and weight. I might even have a Power vs Voltage curve on an alternator I could put on. Let me know what else you want to see and I'll try to get if for you.

Eric

Sure do if the engine runs at 3600 RPM.

I'm pretty familiar with these PMG alternators. They are a 24 pole design. I don't know the details of these particular ones as there are many variations in the stator windings to produce different outputs for each application they were built for. This sized alternator can produce about 12KW spinning at 3600 RPM. Typically the stators were wound for dual output voltage configuration. With 12 leads you can connect them in a parallel wye and get 24Vdc and put them in a high wye configuration for 48Vdc. That is quite the setup to parallel 2 of them.

Hello, I have 2 enclosed diesel generators I'm wanting to part with. They have a Yanmar L70 engine, 24 Pole PMG and inverter. As configured they output 3.0KW 120Vac/60Hz. Engine runs at a set 3600 RPM. These are old military prototype units. They have very low hours but were built in mid-90s. I started them for the first time in a couple of years the other day and both started on the first pull. They do have electric start but is set up for 24Vdc.

I do have access to some low voltage PMG alternators I could swap on the units to allow for battery charging possibly through a solar charge controller to regulate the output. If you have some interest in something like this let me know and lets see what we can put together. I hate to see some nice generators sitting on the shelf doing nothing.