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AVR quandry


Jun 4, 2009
Pearson 530 Admiralty Bay, Bequia SVG
It has been suggested that our older Onan 8 kw genset may perform better if we change from the old transformer regulation to a solid state AVR. Searching the web,I can find them from $23.28 on EBay to a thousand pounds in the UK.
It is down to nitty gritty time and I can't find a single reason to purchase one more expensive than the cheapest one. All the pictures except the most expensive two are identical, and the performance data on all are identical.
Can anyone suggest why I shouldn't just go with several of the cheapest ones (a few back ups)? One place on Amazon ($53.90) offers a one year warranty on theirs, but that seems relatively pointless if I store one and first one lasts more than a year.




Any input would be appreciated, thanks
Jun 2, 2011
Hunter H33 Port Credit Harbour, ON.
It has been a while since I have been working with the gensets (commercial rental) but we used to run Lister / Newage Stamford units with electronic AVR. They were expensive at the time and failed on a fairly regular basis. Epoxy cracks / vibration / suspected load spikes and many unknown reasons. They were not serviceable so it would be a replacement each time. The newer units (light towers) came with Kubota / Leroy Somer and were regulated by capacitor. I thought at the time that this was a little backwards but to run the light it seemed to work well. We still loose capacitors from time to time but the cost was much less than AVR units.

Electronic AVR produces a much more stable voltage output than Capacitor or Transformer regulation due to the constant field voltage adjustments. This is better for sensitive electronic equipment.

Frequency is mostly controlled by the engine speed so the governor control plays a big role. Mostly in the reaction time between the load change cycles. Sophisticated systems may be able to manage the frequency but I doubt these AVR have that capability.

If you are looking for better voltage stability the electronic AVR is the way to go. There may be a difference in the net accuracy between the more expensive ones versus the less expensive ones but that is just a comment, I do not know for sure. If I was making the choice I would go with the less expensive unit and mount it separate from the genset to minimize the vibration impact and keep it dry. I would try it before adding spares to my inventory and I would keep the original transformer system as the back up.

Hope this helps.
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Jun 4, 2009
Pearson 530 Admiralty Bay, Bequia SVG
Thank you.
The idea of vibration dampening is a great tip; thanks again. As we are a charter boat and far from (time wise) suppliers, I'm going to buy a back up or two for now; can't really lose @ $24 to $54 each, but will certainly keep the old transformer set up. Plan to store the spares in vacuum sealed bags.
Jun 15, 2012
Hunter 50 AC Greenport, NY
2 months ago one of the regulating capacitors in my Mase generator failed. It took about an hour to open up the unit to get to the capacitor and replace. I thought how nice it would be if the capacitors were mounted remotely in a simple plastic electrical box (which is now on my "to do" list). I never thought of the other benefit, the reduction in vibration. Now I wonder if the bursting of the capacitor top may have been partially due to vibration as the capacitor are mounted directly on the alternator of the generator.