replacement brushes

[listerengine2006]

Can anyone tell me where to source replacement parts for my ST Generator.?
Need new brushes.

Key Information from the Nameplate:
Type: ST-5

Power Rating: 5 kW
Voltage: 120/240 V
Current: 41.6/20.8 A
Frequency: 60 Hz
Speed: 1800 r/min
Excitation Voltage: 49 V
Excitation Current: 2.6 A
Insulation Class: B
IP Rating: IP 21
Phase: 1
Manufacturer: Power Solutions
Serial Number: 6104026
Date: 2006

Key Information from the Nameplate:
Type: ST-5

I live in Ontario Canada.

[Randybee1]

Central Georgia Generator ( in USA) sells them along with a few other ST related items such as rectifiers, slip rings etc.

[listerengine2006]

Received parts from Central Georgia, took about weeks ( https://www.centralgagenerator.com )  Kit arrived with brushes, holders, insulators and a spare set of brushes.  Assembly required reuse of the existing bolts/washers (not included ) but other than that installation went well.  I originally started down this path to replace the brushes, as I experience considerable voltage drop under load, and the old brushes are 20 years old.  Unfortunately, I still have the issue of voltage drop after installing the kit.

Considering adding an AVR, although I suspect my real problem is loss of RPM under load.  (680 RPM, 63 Hz) no load, 610 RPM (59 Hz) at 3kW.  linkage, all works well, no sticking.  Mechanically, the belt to pulley arrangement is strong, no slips.  Not sure how to better stabilize the RPM between no load and full load.  Any suggestions are appreciated.

[BruceM]

Your rpm drop under full load is reasonable, but you didn't list the voltage at no load and full load.  You also didn't mention whether your ST head required a resistor to down regulate the harmonic winding output or whether you are running full open.

There is huge variability in the ST heads imported by CG from different vendors over the years, and sadly not better over time. Some will not operate adequately without an AVR, and some will need the AVR to operate off the mains, not the harmonic if the latter is too weak to provide full voltage under load.  At one time I had three ST-3 apart on my bench and no two had the same rotor or stators.

Many of the better units will regulate acceptably well off the stock harmonic system.  Some not.  I run my ST-3 on an AVR, as does a neighbor.  My homebuilt AVR is run off the mains to reduce the classic single phase ST "harmonic hump" distortion.  which depends on your luck of draw for rotor and stator.  My neighbor's setup uses one of the cheap brushed AVRs from China, and you should get a spare.  They seem to fail every 3-4 years, though this setup does see a LOT of engine run time.

[listerengine2006]

No load, 132V, 63hz, Full load, 3000 watts, 116v 58.5 hz. The ST head is as basic as it gets.  Simply rectifier mounted inside the bell end, and brushes connected directly to the rectifier, no capacitors/resistors.
With the new brushes installed, I did not see any change in performance, and I can only attribute my voltage drop to the fact that the old girl is working hard, and its all I can ask of her to maintain the RPM.  I imagine if I could live in the 1000 - 2000 watt range, I would be ok, but I tend to need more than this old girl has to offer.

[BruceM]

That performance is about what you should expect from a good stock ST setup. The stock harmonic is good for high capacitance, low PF loads like a low PF charger or cheap welder. An AVR will not work as well for those loads since the cheap ones do not do true RMS voltage regulation.  If you want tighter regulation for normal loads, you will need to connect the AVR to the mains, as your harmonic winding doesn't have extra capacity for the fully loaded situation.  The AVR can only limit the excitation source. 

ST heads which have excessive voltage (unlike yours)  require adding power resistor to reduce harmonic excitation, and can use the harmonic as excitation for an AVR.  They will do well with the AVR on the harmonic (with no resistor) since even under full load the harmonic will have sufficient power.  Some stators (like mine) have harmonic winding configurations that have output waveform distortion called the "harmonic hump" when the harmonic is used.  Some have found adding capacitance to the rectified harmonic output reduces this acceptably.  That may also boost your voltage somewhat (not varied by load). Just remember that the harmonic peak voltage is quite high- (it is spikes, not a sine) and I have measured my ST-3 harmonic voltage peak for starting a well pump load at 400VDC despite a faceplate harmonic voltage of something like 24VDC.  On some heads, capacitors did not change the harmonic hump, but using and AVR off the mains works well.  (Motor run capacitors are the safest to use for this.)

Be careful to check for aluminum rotor windings.  They do not hold up well, and it can be hard to spot with the red electrical varnish.  My neighbor got one of these from CGG, and one rotor winding failed open in less than a year. The bearings need to be replaced with high quality ones like SK.  The "better" Chinesium bearings we got from CGG were noisy under load.

I added info on the common variations of the ST single phase heads in hopes it may help some others new to these simple, cheap workhorses.  I have gotten great service out of mine with some effort but I don't recommend them for newbies without some technical skills as they vary greatly and some are not  problem free.  Stamford clones were recommended here and have been reported  to be trouble free with good waveform, but are expensive relative to the ST heads.

Best Wishes,
BruceM

[listerengine2006]

All in all, I can't complain about the performance of my setup, although the load that tends to complain is the UPS for the computers.  frequency drops UPS pops on, and frequency returns in a few seconds, UPS drops out, and this cycle repeats.  On lister power, I simply take the UPS out of the loop, and the computers seem to be ok, but it makes me uncomfortable to run electronics without the UPS.  tried looking for ways to adjust the UPS so its not so sensitive, but didnt find any options.

It might be I need to invest in a higher quality UPS, that offers power conditioning.  I think the magic of the old girl thumping away far outweighs the issues around voltage drop, and even if I have to do without computers, maybe its a sign to get out and enjoy nature, and away from the screen.  All very helpful info as always, thanks.
Mark

[BruceM]

The typical UPS is looking at the normal frequency drop during the compression stroke of the CS and thinking it should do something.  You might have better luck with an AVR in that the voltage will be better regulated, but the frequency drop will still be there- the AVR can't do anything about that. 

Increasing the threshold for voltage and frequency variation of the UPS is just what you need, as you noted, but it's a stinker as a DIY project due to lack of documentation and access change embedded software.  An alternative would be your own homebrew UPS using a cheapo 12V inverter which you could control with an Arduino or analog circuitry monitoring voltage and frequency. In the data center world they got rid of the inverters and went to straight higher DC voltage straight from the battery system, since they found that their 230VAC computer switching supplies could handle 350VDC just as well with no conversion losses.  I use that approach to run my off grid computer gear on my main 125V battery bank sans inverter. MOST switching supplies are happy with my 125VDC main battery bank supply. (Some switchers have startup circuits which insist on AC input. Fewer of those these days.) I only run my 125V input inverter when I need AC for the washing machine, well pump, etc. But without that source of higher voltage DC, a cheap inverter from a 12V is likely the simplest solution.  If you need more of a time buffer to have the inverter start up, then creating rectified HV DC from the AC for the computer gear, with sufficient capacitors to allow for inverter start up might be a good solution. In this case, the computer supplies will be operating on about 180VDC all the time.  The inverter could be replaced with a DC to DC boost converter.  Most computer switchers allow for 100VAC operation these days. Looking at the bulk DC voltage for the computer, and turning on the inverter or boost converter if it starts to get low is viable solution. 

Simpler is often better as you noted.   I mention this stuff just because it is an area I have dabbled in and use myself for my own off grid power system.

Best Wishes,
BruceM

[listerengine2006]

I looked at putting inverter/batteries charged from the grid, to deliver 3000watts, and keep the batteries charged with lister power or grid.  the total cost to install 3000 watt inverter/batteries, plus charging and transfer switch was just a bit pricey, all to keep a few computers and internet alive.  If I could find a way to do this on the cheap, I might go for it, but batteries/inverter alone are prohibitive.
https://sigineer.com/product/6000-watt-24-volt-to-120240-vac-split-phase-inverter-charger-pure-sine-wave/

[old seagull man]

A while back i was looking for a 70amp charger, for my 48v system, and i found a second hand Victron Multiplus, was cheaper than the dedicated  that i was looking at. Just a thought.