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New PTO Generators
You sort of have to wonder about specs these days. Watts and HP are both measures of work and 750 watts = 1 hp. I get 16.4 hp for a 12K load. Maybe the 16 theoretical hp tractor actually is beefier or maybe a whopping flywheel is assumed to push an engine passed very brief surges.
It's probably a decent generator for the money but I don't think I'd depend on one for bringing very large electric motors up to speed. Lugging an engine when an AC motor is the load isn't good.
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Looks like part of AC's message is missing. I think there are a few other chopped ones. I wonder if there is a length limitation on posts as Dennis is trying to manager the problem of traffic and server costs. Maybe I get to blab because I paid my $20. I couldn't find any length limit notices. If there is a limit, it might be good to trap long messages and provide warnings rather than just chopped messages. Even I could learn to shorten up my ideas and not try to get a whole subject in one post, but a warning that I need to shorten things up would be good.
I did miss reading the rest of AC's post. I think it was going to talk more about surge specs. Yes, I think heating is the main limitation, and a another spec (the duty cycle) usually goes along with purge specs to indicate how long surges can be maintained. If there's no duty-cycle speced, the surges talked about may be only momentary load spikes. Duty cycle is important to people who want to use generators for arc welding.
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I have the whole message now.
My original interest in MarkH's post was if the pto generator with a 16hp tractor would result in a situation where the generator load might be capable of lugging the engine.
I'm aware that if rpm decreases both the frequency and voltage of the output decrease. Lower frequency power creates less impedance in a motor, which would result in increased current at the original voltage. Of course, since the voltage also declines which would decrease current at the same frequency through a motor. I don't know the net result of current change or if there's any potential for low frequency generator power to burn up motors under these conditions. It sure would through the accuracy of electric clocks off though.
I used 746W/HP instead of 750W for the 12,000W-surge rating and I get 16hp and very small change. That leaves me wondering if the surge rating might be theoretical and simply calculated from an assumed tractor HP. I also wonder if the 16 hp is engine, pto or theoretical.
I run my own Honda backup generator with a 6500W surge rating through a bit over 100' of 10-gauge wire to a transfer panel, and then there's the length of wiring from the panel throughout the house. That's basically minimum code adding 2-gauge for the extra length run. If I did it again I'd use 8-gauge. When it's running I juggle loads to minimize one motor starting when others are running. Neither the generator nor the motors like it much when left to their own devices.
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Yes, I think it's more likely that the tractor spec was obtained from a calculation of the max load permitted by the generator's breaker rather than the other way around. I just noticed that the tractor hp and surge specs were too close to think that it was coincidental, and as you say if the specs came from calculations they might not say much about how a generator would actually perform if driven by a 16hp tractor.
About the freq thing; when I was teching in the USAF a long time ago. We had a mystery transformer in surplus. We wondered what its output voltages were so we connected it to an AC source. It burnt up before we could get a VOM on the outputs. Turned out that it was an aircraft part that used a 400 HZ AC system.
I've got the loads fairly well balance across the phases in my house wiring. I put heavy circuits and motors on both phases--'cause a 200A service turns into a 100A one if everything's on one side. Balancing of course is more critical when working with limited capacity backup generators. There is a related issue here for use of generator and especially pto generators. Grounding is crucial and a ground always should be provided for portable generator operations.
Lack of a ground can result in neutral potentials that are different than ground and can create mild to severe shocks from equipment cases. A heavy load on one phase without adequate grounding can produce 220V on the other phase. There's been a few generator powered sound systems with poor grounds burn up when starting up heavy amps on one phase. We should think about that sort of thing if running a 110V arc welder from a generator. A radio plugged into the other side may not fair well.
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Welcome to the Board. We were spared the outage here except for a few drops that wiped out about an hour of computer work so I didn't need my generator. I have a stand-alone myself and I'm a great believer in back-up generators--stand-alone or pto. Our oil dealer has a generator for his fuel pumps so if we had the failure here we still could have gotten gas or diesel, which is a problem some people had. The thing about a stand-alone in my case is that my wife might start it and switch over the power herself but she'd rather freeze in the dark than learn to hook up the tractor.
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