ST or or YHG?

[glort]

I'm getting quotes from some chinese suppliers for generator heads. One company has notified me they do a Stamford YHG brushless type which they say is far better than the ST/C type I enquired about.
It's also a lot more exy ( surprise, surprise!)

I'm wondering about the difference and necessity of the brushless type over the ST models.

I have read some things that the ST type are only suitable for Lighting or resistance loads and that electronics etc requires a much cleaner and better regulated power. My practical experience has been different to that and I'm also wondering how much real world truth there is in that assertion and how much is just typical, " parrot the high road mentality without any hands on experience" as I come across on on the net all the time.

I have used a few very basic and poorly controlled generators on computers and electronic equipment and never had a problem. To me it seems that the power supplies in the gear I have seen, ( Computers, monitors, TV's, Electronic flash gear, stereo equipment and others) have very good regulation and filtering and either steps the voltage up or down and isn't particularly sensitive to frequency either.

I have never had a problem with the electronic gear I have had and I have run some good hours on some questionable generators but I'm wondering if others have any contradictory 1st hand, real world experience?

I am thinking of using one of the generators myself for a standby for home power ( meaning basically run everything)  and onselling some.  What I am really trying to find out is if the output from an ST is up to scratch for general, all encompassing use or if there is a real and tangible benefit to the output of the supposedly better heads?

George over at Utterpower seems to favour the Brushed type heads and I'm wondering what the benefits and drawbacks there are in practicality between the 2 types.

I also wanted to confirm that you can wire the links on an STC 3 phase head to give a "total" single phase output.
Can this also be done on a brushless head?

[Tom Reed]

We use an ST5 to power our entire off-grid home. As a software developer I have a bit more electronic stuff than most. The only item in the house that has any issue about the power is, strangely, the dishwasher. If the voltage goes even a bit over 126v it will pause the cycle and flash until it's restarted. The ST5 now has a balancing transformer on it, which probably won't be an issue for you, because an imbalanced load will cause low voltage on the loaded leg.

The ST5 feeds into a pair of Outback VFX3648 inverters that have a reputation of being picky about power, but there have been no issues here. The inverters function as an automatic xfer switch once generator power has been detected for a couple of minutes. The inverters do protect our electronics from low voltage by disconnecting the generator and going to inverter power when the voltage drops below 108v.

My eventual plan is to do direct DC charging to the batteries because the power from the inverters is so much cleaner than the generator.

[BruceM]

The output waveform of the ST head does vary greatly from unit to unit.  (Some guys built copies of my homebrew AVR and I've seen their oscilloscope images- mostly on ST-5s) Spikes and some ratcheting from the non-skewed rotor windings, mostly.  Most computer gear won't care, and in fact are so un-fussy that I'm able to use most equipment without modification on my nominal 120VDC (actual 120- 146VDC) off grid battery bank system.

I use my ST-3 head for all my AC needs: 1/2 hp submersible pump, central vacuum and washing machine.  It's been very reliable once I put an AVR on it and got rid of the factory diode bridge. 

Most equipment compatibility problems can be solved by putting a 40-60uF motor run capacitor on the output if ratcheting and spikes are a problem.  High frequency EMI from the bridge diodes can also be a problem.  This can be solved by adding a 0.1 uF metal film (AC rated) capacitor in parallel to each diode in the bridge. 

I think the ST's are a good value if you're on a budget and don't mind a project in replacing the stock bearings and diodes, removing the doghouse, adding an AVR.  If someone was buying it for me as a gift, I'd much rather have a Marathon head, with it's lovely voluptuous, clean sine wave output.

[Tom Reed]

That reminds me, I replaced the diodes after about 5 min of usage and the bearings at about 150 hours. It seems while some things may vary, those parts are universally crappy. Make sure you spec copper windings.

[BruceM]

My ST-3 stock diodes and bearings both failed well under 100 hrs.  The doghouse meter was broken in less than 20 hrs.
No problems but cleaning the slip rings and changing brushes since then. 6 years, 2000 hrs +. 

There is an Italian ? brand that dieselgman suggested was pretty good for a lower cost head.  Mecca ?  Mecco?  It is more $ but not in the Marathon class. 

[Ronmar]

Just about anything electronic these days uses a switching power supply capable of operating between 90 and 250VAC 50 or 60 hz for worldwide distribution. Some of the older ones might have a switch to shift voltage range, but I havn't seen one made in the past few years with the range switch. 

The first thing the switching power supply does is rectify the incomming AC into crude DC.  The circuit then switches this DC into a resonant circuit using pulse width modulation to deliver a regulated DC output.  This makes most everything pretty insensitive to input.  About the only thing you need is a relatively peak shaped sine wave as that is where a good chunk of the energy for the pulse is harvested from.  That is why square wave and modified sinewave inverters don't play well with switching power supplies.  Probably the worst thing you will have a problem with is a UPS.  Probably because they are supposed to be picky about input:) Mine has played well with everything I have hooked to it with UPS's showing the most sensitivity...

[BruceM]

The problem with some cheap inverters is more likely massive EMI or high frequency noise on the line output.  This can be bad enough to glitch out some equipment.  I don't think it's the fact that it's square or modified square wave, just really poor EMC design. 

Hold an AM radio tuned between stations near the output and you'll hear the EMI problem clearly. 

Same problem as the spikes and diode noise on the ST output with some sensitive (poor EMC design) gear, just a whole lot worse. 

[glort]

Thanks for the replies.
Very informative. I got another quote back today and there are more designations.

TFW, TFX, TKFX, TFS.
Dunno, don't really care what they mean.
It seems that the consensus supports my own conclusions that most things aren't as fussy as made out and, with a little modding, the ST type should be fine.

Ronmar makes a good point. I haven't seen one of those voltage setting switches in as long as I can remember either.  I certainly recall seeing 100-250V, 50-60 Hz on a lot of stuff. My new 50" TV has it as I noted the other day.  That's really quite a boon for the DIY power crowd because it allows us a lot of latitude in what we generate.
Wherever we are we can set our gennys right in the middle at 55Hz and whatever voltage that amounts to and have good leeway to play with.

Bit of a sag here when a load kicks in or an over shoot there when it cuts out, not a problem! 

Resistive loads like lights and heating elements aren't fussy and motors aren't either really as long as they are not overloaded.  I have seen plenty of VSD's on motors used to save power by under driving them and keep pumps in the sweet spot of their curves etc. as well as speeding them up to get precise speed on machinery.


Only thing I'm  really wondering about is should I get an STC for the one seldom every needed tool I have that runs 3 phase and in case anything comes along in the future or just stick to single phase?

Maybe I'm just biased because I love playing with 3 phase motors and making them into generators.
If I need I can run 3 phase motors off single phase by adding some caps I suppose.

Other than Copper windings ( which all the suppliers I have contacted seem to make a point of anyway) is there anything else to look at in this design and ask for?