PMG FAQ

Note: The following information was retrieved from UtterPower’s archived pages. All information is republished for educational purposes. Any mention of parts or prices are outdated and no longer applicable.

Why do you rate the smaller PMG at only 3.0KW continuous when you say you have ran it all day with a 4.2kw load on it? Aren’t you losing customers by under stating the capability of the alternator?
One of the first deployments for the PMG was part of a mission critical multifunctional APU (auxiliary power unit) that might see 150F temperatures in the compartment it lives in.  It was a concern as to how much load we could place on it and still assure it ran cool enough. In our tests, we find that running 4KW is no problem at all as long as the ambient temperature is reasonable, I think if you have the alternator out in an open space where air can flow around it, and the temperature is reasonable, then a 4kw continuous load could be reasonable. Some think they might need more generator to handle the peak current required to start an induction motor, following are two screen screen shots that show you just how good the voltage is even with 5.55 KW of load on the unit! Yes, that’s right, the unit is still supplying 224 volts (112 when wired parallel) at this load.

PMG 5.56 KW Load

Shown above is 3KW unit on the Utterpower Test Bench.  Note the load is pure resistive (PF=1.0). Almost 50 honest Amps and still well above the voltage allowed by the ANSI standard. If I find a hydro site where fuel or cost of electricity is not a factor in conducting a two week or longer test at let’s say 4.2 KW, we might raise the continuous ratings, but for now, I think the people who frequent here know that there are generators sold that will flat burn up at their advertised ratings or the voltage will be so low that they’ll be afraid to run at those advertised loads. Bottom line… don’t compare this head to other heads rated at only 3KW unless it’s designed for the military

Does the PMG run and make power all by itself?
I get this question more that you think… Answer is NO, you need some source of power, like an engine, hydro wheel, wind turbine, etc.  This is not a magic device, there are no free lunches in physics.  Want the promise of a free lunch? Talk to a politician or find the many scams on the internet that discuss HHO generators and other things designed to remove money from your pocket and give you zero return on your investment.

How much horse power do I need to run the PMG?
This depends on what you expect to get out of it in the way of power, a rule of thumb is two horsepower in for every corrected (honest) 1000 watts out. Be careful what you read on the internet!  I have seen a number of claims where people put 3000 watts of lighting on a generator and claim they have a real 3K out and far less horsepower in than 2HP per KW. Always do the math and don’t be fooled by those who don’t know what they’re doing or attempt to deceive you in order to sell you stuff.

Why a PMG?  Aren’t there enough generator choices out there already?
For those of us who want assurance we can make back up power in emergencies; there are all too few generators that can survive being run weeks or months in service without problems. If you own the Utterpower PMG, it’s easy to replace the engine if necessary and keep on running.

What voltage does the PMG operate at?
North American Standards allow us to operate as high as 127/254 volts, or as low as 110/220 (at the end of the distribution point).

The PMG produces 127/254 at 60hz no load, and at a severe overload of  140% the PMG is still within the Spec for voltage droop.  This is all done without a failure prone voltage regulator. Of course voltage droop is far better than just meeting our standard when we observe the continuous rating of the PMG (3000 watts continuous), but the 4000 watt plus overload never seemed to get the unit very hot in our low ambient summer temps here in Western Washington. The very low (extremely conservative) rating assures that this unit can run in a very warm and harsh environment and still meet its rating.

What about high temps and low temps?  Can this damage the magnets used in the PMG?
The PMG has been run at rather extreme temps inside a box with heat added.  The temp that would cook out any properties of the magnet is significantly hotter than any temperature we will see in a machine room or in a natural environment. As per cold, this only increases the performance of the magnets AND the copper windings, it does not affect the magnets or their properties to cycle them thru bitter cold temps.

Are there any serviceable parts inside?
Not really.  The front bearing on the shaft end (the one that sees the load) could be ‘changed out’ in the field with a few minutes of training.  This can be done without pulling the rotor.  In countries where there is not yet a repair facility, we plan to work with DIYers to allow them to safely change the rear bearing (requires removing the fan first). We are assembling with high grade bearings, and we expect these to run for many years before a bearing change is necessary.

I received my unit with a pulley.  Where do I get a belt for it and why don’t you sell them?
We adopted the “K” Section Automotive belt because it can easily carry the max load and it’s very easy to source the belt at reasonable cost.  We recommend the 8 rib belts, but many use less expensive six rib belts without any problems.  Remember, using readily available parts is part of KISS engineering. To use an industrial belt because you think it is better just sets you up for a sourcing problem.

Can I spin the alternator either direction?
Yes!

Why do you use a tapered bushing pulley? What’s the advantage?
Taper Locks are popular in commercial applications because they make it VERY easy to place a pulley and to remove it, even with gloves on in sub zero temps. There are several ways to install these pulleys, but I recommend that you place the pulley on the shaft, and then put the Bushing (taper lock) on the outside. Use the Metric bolts AND the metric threaded holes in the pulley to secure the pulley to the shaft. Tighten evenly, each bolt a little bit at a time in a circular pattern, and don’t use two hands on the wrench!  There is no need to get them really tight, as they lock up pretty solid ‘snugged up’.  The jacking holes (threaded holes) are normally used to remove the pulley. Once you learn the advantages of taper locks, you’ll find it hard to use anything else. One trick in installing the taper bushing:  Insert a screw driver in the slot, tap it in with a hammer to spread it a little, and it will slide on the shaft easily.

How do I check the Stator wiring? I want to be sure it’s right before I run it.
See the charts that show open circuit voltage output at rated output and verify that your stator puts out the same voltage. Also check out the PMG Testing Page.

How do I check stator wire designations?  I want to be sure they’re right.
This is a good idea, although I don’t expect you to find trouble with the PMGs, I have found several ST generator heads with the wrong designations on the leads from the factory.  Here’s how I quickly test and wire PMGs.

Use a 12 volt light bulb, an incandescent tail light bulb or similar is all you need to make the basic checks and then wire correctly. Start with all leads separated, if any are strapped together, then remove the straps. You can find the ends of the windings by putting the light bulb across them, a simple twist of the shaft, (do it fast), and the bulb will light bright. Find both Stator windings one at a time. Note, if you short the ends of one winding together, it’s hard to turn the shaft!

1-////////////-2  should be the first winding.

3-////////////-4  should be the second winding

After you’ve proven the above combinations light your 12 volt incandescent bulb connect up the following

1-////////////-23-////////////-4  (make sure 2 and 3 are strapped together

With the above configuration, place your 12 volt bulb across one and four, give the shaft the same quick twist, the 12 volt light bulb should get a lot brighter! If this is not the case, swap 1 and 2 and try again.

Notice that the setup above is what you’ll use for 120/240 service, 2 and 3 strapped together become your neutral. You will also note that only half the load (approximately 1500 watts can be carried between neutral and either terminal 1 or 2 in this configuration, this is typical of all generators wired for 120/240 single phase operation.

If you will be using your PMG for 120 volt only, arrange the windings in the following configuration

1-////////////-2
|                 |
3-////////////-4
|                 |
|                 |

In the above configuration, the two stator windings are in parallel, and the full 3000 watts can be supported, this is necessary when you have one LARGE single 120 VAC load.

Put your light bulb across these pairs and give it a twist, if you had the two windings opposing each other, the shaft should be hard to turn. If this were the case, you’d swap 3 and 4 and try again. It should now be obvious a person could lose all the designations, and quickly sort out the leads.  Also check out the PMG testing Page.

How do I wire in a fuse box or breaker panel?
See the ST pages.  How you wire it should be the same, except for breaker sizing and lead designations.

What’s going on with the new 6KW unit?
Not many have been sold up to the date of this writing because it has taken about three years longer to get this design out of the lab where it was fully flogged. We were planning on rating the generator higher than 6KW, but we decided to take the same approach as we did with the 3K unit, and stay on the conservative side. After we got though with the torture testing in the lab, I arranged to send our first production unit to Moe M. in Canada. Moe has a PhD in physics and a background in Electrical and Mechanical with hands-on experience. Moe is plenty happy with the performance and finds it a good match for his 12/2 off grid power plant. The new unit meets all of his expectations.