Ways to stabilise a non AVR generator?

[Memmeddu]

Hi everyone ,I hope you're all well.
So I would like to know if there's something I can do to stabilise the auxiliary power output from my engine driven welder.
It has a Brushless ,three phase,self excited alternator , driven by a gasoline engine.
No AVR or electronics at all
Voltage/welding current is regulated by the throttle ,so engine RPMs will dictate welding current,load and no load voltage on the welding circuit, auxiliary power output voltage.
Any idea to improve this 50 years old welder generator?
I've seen there are voltage regulators for photovoltaic panels, or those servo motor Variable transformer.
I'd like eventually to connect electronic devices to it ,like a plasma cutter or something like that

 

[voipio]

It should be possible to repurpose a generator inverter module. These normally take three phase A.C. input and generally give a single phase A.C output, which may be pure or stepped sinewave. Not a cheap option, though, especially one with sufficient power to drive a plasma cutter. There may be a few hacks needed to fool it into "thinking" it is fitted to its intended generator. Have you measured the 3-phase output voltages under various operating conditions? It might be all too easy to exceed the safe input voltage to these modules, which normally incorporate some sort of throttle control output.

 

[Matrixx]

It will be complicated and not cost effective to try to redesign the excitation control system, for a smooth regulated output you could just stick a UPS on the output.

 

[Ubique]

The simplest method, in terms of technology, would be to increase the weight of the flywheel. The practicalities......

 

[GRW]

It sounds like the set was intended to be a welder primarily.
You'd need a Governor to maintain engine speed and stabilise Frequency for openers. That would give you a stable offload voltage. However, once you applied a load, without any form of voltage regulation, you'd still not have a workable output.

 

[reb78]

for a smooth regulated output you could just stick a UPS on the output.

Does this work? I have read conflicting things. Dad has three old UPS's with knackered batteries and I wondered about using them on my generator to make the output better for modern equipment - everything has a cpu of some sort now - even my fridge freezer!

 

[awemawson]

Most modern quality generators take raw output from the windings, presumably rectified, and fed into an inverter circuit to produce the 240 volts 50 Hz or whatever. This way the electronics determines the voltage and frequency and the engine can turn the alternator at it's most economical speed rather than be limited to 1500 or 3000 rpm to get the frequency correct.

 

[Memmeddu]

There are some big capacitor inside for phases balancing (connected directly to the windings )
Welding and auxiliary power are on the same winding circuit
I believe they are 500μF each connected in series between themselves and in parallel to the windings (Delta configuration for the capacitors )
The welder is a GenSet 5/170 CX from the middle 70's
I've used it to run my grinders which have electronic modules inside
But soft start might have helped little bit

 

[Ubique]

Putting a reasonable resistive load (like an electric convection heater) on the output can help smooth out switching transients to a point, of course, it is also a load so would reduce the effective available output.

 

[GRW]

Most modern quality generators take raw output from the windings, presumably rectified, and fed into an inverter circuit to produce the 240 volts 50 Hz or whatever. This way the electronics determines the voltage and frequency and the engine can turn the alternator at it's most economical speed rather than be limited to 1500 or 3000 rpm to get the frequency correct.

"Most" quality gens is over-stretching things rather a lot tbh.
Industrial generators of quality don't employ Inverters. Electronic AVR's yes, but that's it.
For frequency sensitive loads you fit an electronic engine governor.
A machine with this kit on (sized properly for the load) offers much tighter voltage control than you'll see off the utility (which is allowed +/- 10%, where a good genset regulates to +/- 0.5%).

 

[Jack_K]

Does this work? I have read conflicting things. Dad has three old UPS's with knackered batteries and I wondered about using them on my generator to make the output better for modern equipment - everything has a cpu of some sort now - even my fridge freezer!

It depends on the UPS, most are line interactive and simply switch a relay to the inverter when the input fails. Expensive ones are called "online" and the load is constantly run off the inverter. There is also the fact that only the expensive ones are a pure sine wave.

 

[GRW]

Does this work? I have read conflicting things. Dad has three old UPS's with knackered batteries and I wondered about using them on my generator to make the output better for modern equipment - everything has a cpu of some sort now - even my fridge freezer!

UPS are generally pretty "fussy" regarding input voltage and frequency.
Instead you could use Off-Grid Inverter-Charger units that are designed with a much wider tolerance for both volts & hertz (& their data sheets usually list the range).
Still a very costly way of doing it though.
Really it'd be cheaper & better to get a different generator altogether if you really need one.

 

[reb78]

Thanks both ^^ this is an old 2.5ish kW generator with an equally old 5HP briggs and stratton engine. I just bought it as it was cheap (£30) as it wasnt working and thought it might be useful for powering freezers etc in the event of a powercut. The more I have read on here though the more nervous i have become about using it on anything more modern than a light bulb! I do run the cement mixer and power tools off of it occasionally too (it has a 110v output too).

 

[Geoffm]

Does this work? I have read conflicting things. Dad has three old UPS's with knackered batteries and I wondered about using them on my generator to make the output better for modern equipment - everything has a cpu of some sort now - even my fridge freezer!

I tried running the office from my 2.2 kva generator, which is not an inverter type and 30 years old or more. The ups units did not like the dirty power at all and sat there beeping alarm codes at me and didn't work.

 

[GRW]

I tried running the office from my 2.2 kva generator, which is not an inverter type and 30 years old or more. The ups units did not like the dirty power at all and sat there beeping alarm codes at me and didn't work.

Most frame type 2.2kva sets in the UK that aren't Chinese or Japanese built (alternators) are capacitive voltage control.
Great for their intended loads e.g. power tools, they don't regulate super-well.... but UPS and non-linear loads cause harmonic interference onto small gensets that actually affect the output (in simple terms the UPS causes the problem and then refuses to accept the result).
Also (I guess it's to do with the high freqency switching) non-linear loads seem to rapidly age and cause the capacitor to fail anyway in the alternator.

 

[reb78]

‘An equally old B&S engine‘ likely means it was ‘flash’ rated and would not maintain that output for more than the test time, so I doubt it would run that alternator at 2 1/2kW. Might just about manage it if the generator was specified in kVA.

My first generator was either driven by a 1 1/2HP B&S or was maybe a 1 1/2 kW generator. I had to over-rev it to get the freezer started (approx 150-160W). I soon sold that when I bought a 4 1/2 kVA Stamford armature-wound generator with a Hatz E75 diesel engine. No such problems since.

oops. Sorry, I meant 2.5kVA, not 2.5kW!!

 

[Matrixx]

Modern inverter type UPS's can run on a wide range of frequencies and voltage's and output a stable voltage/frequency, none are ever a pure sign wave, not even close.

older ups's had a very tight voltage/frequency window, as the power would flow straight through and if the input was out of limits would switch to rectified battery output, on the newer type the output is constantly through the rectifier,

 

[Farside]

I tried running the office from my 2.2 kva generator, which is not an inverter type and 30 years old or more. The ups units did not like the dirty power at all and sat there beeping alarm codes at me and didn't work.

I've run my UPS (a Smart UPS 1000kVA) from my cheap'n cheerful 3kW genset and it doesn't mind at all. Keeps the PC, monitor, LAN and wireless modem all going happily.
However, there's no way I'll risk running my big telly from the genset, just in case.