ST GENERATOR PAGE

This page is left herre for reference only, utterpower no longer sells ST parts:

NOTE: March 23, 2010,


The ST is a KISS design. It is a simple generator head that operates on the same principle as about 95% of all generators made. It is a simple, reliable, time tested design, and some versions do not employ expensive voltage regulators that are often the fault of generator failures. I recently read a posting on a public forum where a self proclaimed expert said it was not a problem to stock a spare regulator, tell that to Darren Hill in New Zealand, he was recently quoted near $1000 NZ for a replacement voltage regulator for a Kubota Generator he likes.

Fact is, this simple and basic ST generator head works for DIYers and Electrical Engineers alike. Are there better Generator heads? You bet! open your wallet wide, lay out 10 times as much, and you'll likely have a better Gen head, but you better lay out even more for some of the expensive and proprietary spares you'll want on the shelf if you want to assure it's going to work when you need it most. People who dismiss KISS, usually have a storeroom of something else to sell.      

 Scroll to the bottom of this page for FAQs, and LINKS.

Update: 01/22/07 NEW PS (Power Solutions) GEN Head is now shipped with Utterpower modifications installed! I asked the Power Solutions Ware House to send me a Randomly selected ST5 generator head from the new shipment of Heavy PS heads. As I have mentioned, the PS ST5 weighs 80 pounds more than other ST heads I have weighed here. This particular head weighed 232 pounds. These new heads arrive with a higher quality western style rectifier located in the bell housing where they sink heat well. High quality spade connectors are used to make connections at the rectifier.  Other mods include the sealed bearings with proper grease, and a QC tag on each head with other items of importance checked off, and signed by the factory inspector.  The leads are brought out under the steel plate, and the problem dog house is left off! I know of several DIYers who have invested a day in making these modifications and replacing the cheap bearings, or at least cleaning out the yak fat and repacking with a proper grease.  As I have mentioned, this thick grease might make it at 1500 RPMs, the 50hz Chinese standard, but at our 1800 RPMs, the grease is way to thick, and the bearings travel thru it like some sort of plastic, heat builds, and failures happen. 

Power Solutions has permission to distribute the (Utterpower ST manual), this manual is also part of the Utterpower CD, and should not be confused with the basic manual you can Download for free somewhere on this site.           

Above: This is a picture of the famous "YakFat Man" best to avoid his grease!

Picture copyrighted 01/2007 Tony Dovy

I have inspected one head at random, but I am also asking others who sell this new PS_ST with the new Utterpower mods to make some simple inspections and report back. This particular head certainly met my expectations. 

  Update: 07/23/06 The world is changing fast, there are a number of Americans who wish to try their hand at importing. There is much to learn, and many pitfalls. In an attempt to steer clear of these problems, I have involved myself in the development of the PS Brand. We have been providing feedback to the manufacturer to eliminate design flaws, or quality issues for some time, and soon their will be additional changes made that eliminate some of the more common troubles reported. (this is now the case) 

This page was getting verbose! Trust that there are differences in ST heads, and I think more of them each month, not all of them are good, Erica has sold a number of metal fans to replace the plastic ones found on some brands, as I may have said elsewhere, plastic fans are failing, and some heads are overheating unattended.  

Update 12/08/05

Update: there are a good many questions about voltage regulation. Ask a man who sells only one brand and make, and he's likely to tell you that his is best. If you wish to make an informed decision.... , what you are looking for is percent voltage droop from no load to full load, and is this acceptable? how the gen head does this is a secondary matter, a good many designs don't need the VR to provide adequate service, 99.9 percent of all generators sold don't use them, and they are not in the circuit to fail. Imagine what it's going to be like 5 or 10 years from now to get your electronic voltage regulator, how long has your vendor been in business? what relationship does he have with the manufacturer?  How much is that VR part, and should you order a couple spares with your original purchase? I have received three emails about non functioning AVRs in the STs alone! if you become convinced this is what you need, get a spare with the Gen head, and get it from the Vendor, if he has no spares, that's a bad sign.

Better VRs are available, and we will discuss the reasons you might want one in the future. Bill Rogers has already fitted a readily available VR to the ST head, and found the output improved, if you think you need it, it's not all that hard to fit.  

Most of the folks selling generators don't know ohms law, and couldn't talk you thru a repair if their life depended on it. If it isn't there, it won't break.  KISS engineering wins in the long run for the small guy, there's nothing worse than really needing that power, and finding that the electronics in it are broken.

I just talked to DIYer Brandon Wright, commercial power is out, and he was not making  220 out of his ST Gen head, it took a few minutes to find the trouble and have him up and running, if you have a spare rectifier and a set of inexpensive brushes, there's little that will stop you from making juice when the kids and wife are counting on you to pull a rabbit out of the hat. Brandon called back, and said he had 220,  the well pump was running, the house fridge was on line, and the AC was running. No doubt Brandon's wife is glad that Brandon spent the money to build a Gen set, and went the KISS route, it was during a heat wave, and there are times when it's more important to be cool than to eat.. 

What's right for you, you need to determine, I will be running without AVRs, as I have for 30 years.  

The ultimate answer will be a generator that can run in KISS mode, and with a VR. Bill Rogers has found an aftermarket commercial regulator that is working well in the ST, and I hope to cover his story here in the near future.



115 at full output or 115/230 volt operation...  (this usually requires 4 or more leads out of the stator)

Dual Brushes per ring on 5KW and up models

Sealed bearing on the fan end

After years of tearing into ST heads, you learn what to look for.

PS brand ST generator heads are built like tanks, the main ingredient is cast iron.   If you read a lot, you probably know that cast iron really is a wonder metal. Where weight is not thee principle concern, it is hard to beat it's performance. The down side is the shipping weight, you will end up paying for Cast Iron. This unit uses dual brushes for the field.

Insert: 4/2004, visitor feedback

- On the ST page, you say something about a Honda having
"only" a single brush per slip ring, with an exclamation point,
as if that's a terrible thing.  That struck me as maybe "going
over the top" a bit.  There are countless old Gennys out there
running single brushes, and working just fine, decade after

I just did a fuel-injection repair on a 1948 Cat D13000
50kw set which is used 7 days a week for running irrigation
pumps on a large ranch.  It's a typical single brush head, and
the owner told me that the last time he put brushes in was 1978 !

Richard- Medford, OR.

The ST design is simple and time tested, farmers and untrained persons in the field have managed to keep these heads running year after year in areas that have next to nothing in the way of repair material and spares.   

 rotor1.jpg (52701 bytes)

Above is a picture of the rotor, it's a hefty piece at 72 pounds on the bathroom scale. or about as much as the complete consumer type head! The rotor laminations are1mm thickness.  Notice that fan, high tech plastic? Not a chance; it's real cast metal, and it's held in place with a real spring steel 'C' clip. On the left is the slip rings, in the center is the four poles that allow the generator to function at the lower speed of 1800 RPMS versus 3600 RPMS of the typical 2 pole head used in consumer Generators.


shftsd.jpg (55478 bytes)

Here's the inside, notice the housing, it is also made of good ole cast iron, the ends are precision machined and fit snugly into the stator housing, This allows for a nice tight air gap which adds a generous amount of efficiency to the design. I didn't measure the gap, but it's plenty close. The laminations in the stator were .5mm thick, which should add to the efficiency of the design.

Notice that all the windings are copper....

shftsd2.jpg (42127 bytes)

Here's the end bell for the shaft and fan side, notice the generous openings for cooling and access on each side. Keep the screens in place to keep mice and other critters out, consider adding  a screen across the bottom section for the same reason. Mice; their nesting material, and their urine can wipe out machinery in no time.

rngsd.jpg (42520 bytes)

Here's the 'slip ring side' bell housing, yes this is cast iron too. There's a bearing cover on the inside to assure that no grease finds it's way into the electrical windings and rings, it doubles as a sturdy mount for the brushes, I'll get a picture of this some day. Note the size of these openings! The cover is removed with one positive clasp, no matter how big your hands are, you can get them inside the slip ring end.

bearing.jpg (61943 bytes)

The stock bearings are of the 'open' type; the shaft side has a massive standard 6310 bearing, the slip ring side has a smaller 6309 standard bearing. Most bearing houses will have these on the shelf. I compared the bearing size of the ST 12KW  to a well known 'upper end' 12KW 3600 RPM head, the ST bearings are twice the size! 

Note: One of the leading causes of electric motor and generator head failure is over greasing. The builders of the ST heads must know this, there is no external means over grease bearings. More often than not, this is a good thing, but adding a grease fitting would be easy. I did tear down one brand of ST 12KW head and found the bearing on the fan side was open to the elements towards the fan . If you bought an ST with this situation, you might rig up a cover for that side or replace the bearing for a sealed one. 

As for the shaft size, the ST10 and ST12 have 42mm shafts, this is a standard, you should have little problem ordering a bushing through the bigger parts houses in North America.  42 mm is about 1.635 inches. You can compare it to 1 5/8 inches which is 1.625 inches. If you're really bothered by metric, you could pull the rotor and have your local machine shop turn the rotor to 1 5/8, a simple job for them to perform. The ST15, uses a massive 48mm shaft, (about 1.9 inches)  although I haven't ordered bushings and pulleys for a 15 yet, I'd bet they're in the warehouse in North America  as well.

For those that have a few years under their belts, we remember a time when things were built to be repaired. To throw something out just because it quit working was unheard of. The ST Generator Heads are from our past; ''when people bought things and expected them to last their life time". There's nothing inside you can't figure out or replace when it breaks. If you're off the grid, or you just want to be independent, the old way is worth a look.

Closing thoughts? Any generator head is heavy, this will make a 'repair and return' expensive.  Being able to fix it yourself, or have it rewound locally could be a major cost savings over time.   

I have received several emails explaining that replacing the diodes in a brushless head requires one to pull the rotor because they are mounted on the rotor, I don't know if this is common.   In the ST design, they are in the control and wiring box on top of the machine for easy access.

This is not the most sophisticated generator head in the world, it's really a step backwards into our past. Some of us will welcome the simple non-electronic design, others won't.  In simple terms, it runs everything from my induction motors to my DSS dish and TV, it's all I need.

In closing.... Have you heard of an EMP?  Electro Magnetic Pulse ?  Some folks think that the use of  EMP tactical weapons becomes more likely everyday. One EMP could wipe out all the electronic devices, your car wouldn't work, your microwave, TV, radio, etc;  would be junk... How about that solid state ignition system on your trusty Briggs and Stratton? It would most likely be junk too. 

But... a generator built like the ST, powered by a small diesel with no electronics could be brought back on line in the matter of minutes.   Does it make a person radical to think about these things? Today.... I don't think so.

Cons: The connection box that sits on top of the generator head is a bad idea. I recommend removing this box and mounting a small connection box in it's place if you will run long hours, mount your volt meter and other stuff on the wall.

There are better heads to buy than the STs, but these are doing a good job for lots of DIYers for a fraction of the cost. People who bad mouth them are often those who are selling something. Want to find the experts? Visit the public forums :-)  

Additional info:


 ST Manual Pushing this button will give you access to R.G. Keen's BASIC Engrish to English ST Manual Translation in PDF, RG has given me permission to share this with utterpower visitors; thanks RG! There is a far more in depth manual as part of the utterpower CD

Providing the best ground for your generator head   NEW

What's a normal voltage to run?

utterpower's exposure testing 

 Panel Meters

How to trouble shoot the ST Gen Head.

ST Voltage Excitation (How it works)

How to inspect or replace a bearing in a ST Head

Recommendations for ST Head Installation.


What about the insulation class?

Installing brushes

ST Owner's Installations

Playing with power

Converting center tapped  heads   for full output at 120 volts!