small portable gas generator under voltage issue - StormCat 63cc

Thread Starter

Serge3125

Joined Oct 31, 2019
7
Hello,

I have small StormCat 63cc gas generator that I bought for power backup some six years ago.
It has been broken in for some three hours and then stored in my garage until recent times when we start having outages here in NorCal.
When I pulled it and started engine it was not producing any power, I've used the drill trick to excite generator. After that it produces 60V only instead of 120 that is supposed to.
Next I've adjusted engine RPM and measured frequency at 60Hz, the output still 60Volts.

I've opened it up and checked Capacitor - it is ok, checked windings for short to ground and between them - both were ok with no short, also both windings have some resistance which looks good.

Now I am confused, what else can be faulty in this little beast? The diagram (attached) shows it has two windings one connected to capacitor and another to output. I'd trow it away but since the gas engine works perfectly it may worth some more troubleshooting.

Thank you in advance for help with this.
 

Attachments

drc_567

Joined Dec 29, 2008
738
... does the capacitor at the smaller generator coil have a measurable DC voltage on it? Occasionally, capacitors will age, especially if not in use. ... If that capacitor is not working as it should, try replacing it.
... Observe the + and - polarity of the capacitor. It will be marked.
 

debe

Joined Sep 21, 2010
1,142
Its a very basic brushless generator, the capacitor has AC voltage on it & controls the out put voltage. I would try a new capacitor first, making shure you get the same size capacitance & voltage.
 

drc_567

Joined Dec 29, 2008
738
... I was thinking that capacitor at the generator would be the polarized electrolytic type, but I could certainly be mistaken. .... As suggested above, replace with the identical part.
 

PGB1

Joined Jan 15, 2013
110
I must be missing something in the drawing as I don't see the capacitor on the generator circuit. Is there just one in the exciter circuit, or also one in the output circuit? Or, are they shared? (Not common)

But, if it has one in the generator circuit- DeBe is spot-on. They do degrade over time, especially in storage. You've already verified the frequency is correct, so voltage should follow.

Be sure, with this type of voltage control, to use a good surge suppressor and don't connect it to electronics. (I'd also be worried about powering expensive motors.)

I used to service the electrical portion of megawatt + size generator as part of my career and co-workers would often ask me to check their portable putt-putt units. Once in a while, adding a load for a minute or two would kick voltage regulation back into compliance. Try a non-motor, non-electronic load such as a space heater or clothes iron. It is important to operate any generator at least every 3 months with a load on it. This will also keep you from having to punch up the exciter.

I've also seen several of the house brand units with voltage regulating circuitry. Sometimes they are buried in the generator's body, sometimes next to the exciter components. The wiring diagrams often ignore them. Unfortunately, many of the boards are epoxy sealed so you can't get in to service them.

There is one more, not unheard of, possibility: One of the leads in the windings could be corroded or open. These are usually 18 lead units, sometimes 36. (If it is 3600 rpm, it is 18 lead. 1800 rpm = 36 lead.) That is not usually fixable on these machines. Or, one of the external leads or receptacle terminals could also be corroded, but you would probably have seen this.

To find a portable with a good voltage regulator is sometimes a challenge. Honda & Wacker are known for good regulating circuits & proper sized engines to help prevent surge dips & recovery spikes. (I don't know if this is still true, but Honda used to use German made Wacker generators and Wacker would use Honda Japanese made engines. My old Wacker is like that.)

I hope you can get this operating without too much expense or time. Be sure to enjoy the project!
Paul
 

Thread Starter

Serge3125

Joined Oct 31, 2019
7
I got the capacitor and replaced it. No fortune so far. Tried to connect iron and run for short time- now it does 80 to 95 volts, can power a 50watt bulb, however if I connect anything more power consuming the voltage drops to 35volts. Any suggestions ? -Thanks
 

PGB1

Joined Jan 15, 2013
110
If you can't find a voltage regulator, your machine is what's called "self regulating". Only the rpm controls the voltage (with frequency to follow). In those, the capacitor isn't for regulating voltage from your generator. Its primary task is to "start" voltage flow. Its real job is to privide field excitation.
However, if the capacitor is bad there will be little, or no, output with or without a load.

Since you have proper voltage when there is no load, but low voltage under load, my next check would be to find out if the rpm drops under load. Even a small drop will send the voltage down, so you will need a meter or point-and-shoot tachometer. And, when the load is lessened, the voltage will over-shoot when the engine catches up & over-revs for a fraction of a second (or more). That's why these are poor choices for powering electronics.

If the rpm drops, my first thought would be that the generator is being overtaxed. Failing that, perhaps the engine has a bad piston ring, leaking valve, partly clogged fuel or air filter. There are probably a bunch more causes, but I know very little about small gasoline engines.

After that, it will be time to take the alternator apart for a look. Perhaps the windings' insulation is cracking and when the wires get warm, they short. To evnision how this changes the voltage, picture a transformer. Shunt some coils and the induced voltage will change accordingly. Also, there could simply be dirt or an insect nest shunting. And, there is always the possibility of a corroded connection.

The unfortunate part about taking the alternator apart is that many house brand portables use nylon (or even plastic) bearings & seals. If one breaks you may not be able to find a replacement.

If you have time & the inclination to learn some technical data, do a search for US Patent 4786853 (uspto.gov). That document has a good explanation of a brushless generator.

I hope you have good fortune in your repair project. It will be great to have the machine up and running again!
Paul
 

Thread Starter

Serge3125

Joined Oct 31, 2019
7
Thank you all for support and Ideas on how to fix the little beast. I gave up on this, and decided to let it go. Bought a new Firman 3607 instead on amazon.
 

PGB1

Joined Jan 15, 2013
110
Congratulations on your new Firman Serge!

Firman makes their own equipment, often labeled for some house brand's higher end models. It seems they decided to put their own brand on their units. The giant firm Sinomach owns them, so they aren't going out of business in our lifetimes.

Since Firman makes Firman you can not only buy parts, but get technical support as well. (On many brands, parts are impossible because whomever ordered it, for example Harbor Freight, sends the specs to dozens of manufacturers. They may end up with the same model number made by 3 companies with 3 different versions of the same repair part.)

Once I helped a friend with a Kohler branded small unit that turned out to be a Firman. It was very well designed & quite robust. One thing I noticed is that the windings were heavier than the circuit breaker, so if the breaker ever fails to trip, the windings won't burn. Nice Touch!

You can probably sell your old unit on craigslist quite readily, especially since winter is apparently here (14-F tonight in Detroit. Yuck!) I once listed a trash picked house brand from Harbor Freight on craigslist. I put in the ad that it had a thrown rod in the engine and a burned alternator winding. Within an hour, I had a dozen calls.

Again, Congratulations on your new generator. Hopefully you will never have to use it!
Paul
PS: Be sure to run it under load every few months. Before storing, I recommend running it until it stalls from lack of fuel (no load- breaker off) Then pull the starter rope until firm resistance is felt. This way, the valves are closed and no moisture can get to the cylinder. Plus, follow the manufacturer's storage instructions, as they may have additional requirements.
 

Thread Starter

Serge3125

Joined Oct 31, 2019
7
Thanks Paul!
You've just reassured my good choice! I sold the old one for 20$ on craigslist today :) and the new one will be here next week.
 
Top