Generator PTO Generator - Lights Flicker

teg33 · Feb 27, 2006

I just purchased a Tiger PTO 10kW Generator and put it behind my Kubota B2400 tractor. It ties through a transfer switch into a subpanel of my critical house circuits. The setup works fine with one exception, sometimes there is a noticeable flicker in the incandescent lights. The problem is worse under light loads and seems to diminish as you increase the load. In some cases, if you reduce the throttle a bit and then return to rated speed/frequency the problem diminishes. The volt and frequency meters all look good and an external power quality meter reading shows the Voltage THD is within/near the specified limit of 5%.

Anyone else see this problem with flickering lights on a PTO generator?

kubotaman68 · Feb 27, 2006

You are completely disconnected from the public utilities yes? I think that a b 2400 is marginal for 10 kw . I use a 12 kw behind my neighbors L3430 when the power goes out and i have no flicker except when things are being switched on in series

teg33 · Feb 27, 2006

Yes, I am completely disconnected from the utility. I also realize that I probably cannot get a full 10kW out of the B2400, however, I'm not running anything greater than about a 7kW load.

JoeR · Feb 27, 2006

Could be the A/C sinewave is not clean. You could have some noice induced or grounding issue from static build up on the generator. If you have an O-Scope you could see the signal, or look for signs of DC voltage. Ceiling fans make a unique sound when you get a square wave on the power A/C. Doesn't make the fan spin faster, but you hear a slight hum when the square wave comes through... I know this after finding that my power company was not doing the best job cleaning up noisy A/C. Somehow one of their capacitors would generate random noise, It drove me crazy for months! I still had 60hz, but is was similar to a square wave at times...

Joe

teg33 · Feb 27, 2006

Thanks Joe, I thought about that and did check it with an o-scope. It wasn't a perfect sine wave but wasn't too bad. When the lights were flickering and I viewed about 35 cycles on the scope, it did appear there was some low frequency (16Hz) amplitude modulation riding on the waveform but nothing really extreme.

Just wondering if anyone else has seen flickering lights with a PTO generator and what they did to resolve it?

KYMike · Feb 27, 2006

Don't know if this has anything to do with your problem, but I noticed some flickering if the PTO shaft is not straight in line horizontally & vertically. Universal joints are not constant velocity joints, so if they turn an angle (over 10-15%), there are vacillations in the RPM as the knuckle joints compensate. I needed to adjust the height of my unit on the trailer so it was at the same elevation as the PTO spline shaft.

DAP · Feb 27, 2006

I just purchased a PTO generator also. Gets here tommorrow in fact. The numbers are NOT matching up for you if I have the specs right. This assumes your Tiger generator is model PTO10 ....

I don't believe you are marginal at all. No, in fact, I think that your machine is clearly underpowerd to run a 10k watt generator. I believe that is why your power stream is inconsistent.

If your Tiger is model PTO10 it requires a MINIMUM 20hp at the PTO (not net HP). The B2410 is only 18hp and I suspect that your B2400 is at best equal to that. Correct me if I'm wrong. And yes, those 2 hp will make a difference, trust me. Further, running something like a generator at MINIMUMS is an invitation to lack luster performance.

Hopefully, I've got my assumptions wrong and/or you can return the generator.

Better still, buy a bigger Kubota! Sorry. I know it's not funny.

Hope it works out for ya somehow.

teg33 · Feb 27, 2006

Thanks for the shaft alignment tip, I'll be sure to check that.

john_bud · Feb 27, 2006

( Better still, buy a bigger Kubota!)

I like the way you think! /forums/images/graemlins/grin.gif

jb

teg33 · Feb 27, 2006

Doug, the B2400 is 18 PTO HP. The way it has been explained to me by various dealers, and seems to make sense, is that you need approximately 20HP to get the full rated current from a 10kW generator. However, if your load is less than 10kW then a smaller tractor will work just fine. In fact, some of the advice was to buy a bit bigger generator in order to improve the surge performance.

There is absolutely no indication that the tractor is working hard or loading down, even with 7kW of load. Also, as mentioned all spec readings (frequency, voltage, THD) are right on the money. I haven't seen anything to indicate there is a HP sizing issue. Would there be some other test you would recommend?

tillerkiller · Feb 27, 2006

Turn on your TV while on the generator and see how it looks, they are supposed to be notorious for showing poor power quality. I do not know what bothers them, just that they are finicky.

Shimon · Feb 27, 2006

What else is being powered at the same time as the lights?

Certain loads can cause problems for the voltage regulator in the genset such as reactive loads (fluorscent lighting, microwaves, motors). Your generator probably has capacitor excitiation which isn't very good at maintaining voltage. So when you have a motor starting then the engine droops which leads to loss of freq and volts until the governor on the engine gets the rpms back up. Capacitor excitation is cheap but slow to respond.

I would run the genset with only resistive loads to see if the flickering goes away. Plug in as many electric heaters and incadescent light bulbs to see if you still have flickering. If you do then work on the pto shaft alignment. If the flickering goes away then start to add your reactive loads (motors and fluorescent lights) and see if the problem shows up. If it does then you will have to live with it.

cheesehead · Feb 28, 2006

What is loading the line when you see the flickering? This information would investigate three "guesses":
1.) Too little load for the regulation circuitry. Some solid state regulation schemes need 10% load (1000 watts in your case) of load to form enough circuit feedback to properly regulate.
2.) Your flickering could be caused by a load that is varying it's current/power factor requirements. This situation will be very visible if you're running at or above the current carrying capacity of connections between the generator and your load(s). In this case, it would be good to know how you are connected to between the generator and what length and size wire run you have going to the load(s).

You probably already know that sizing motor starting currents on a generator require allocation of around 2.5kW per rated electric motor horsepower. This drives a need to manage loading when switching in things like well pumps and air conditioners as then have very high surge requirements.

teg33 · Feb 28, 2006

Good ideas, let me respond to all.

1) A flicker when a motor starts or the load changes wouldn't bother me, this is a constant flicker but with varying intensity from quite annoying to almost not there.

2) I've tried various loads. Starting with pure resistive load drawing 500W on one side and 800W on the other side. Flicker worse at these light loads. After more load, a mixture of resistive (water heater) and reactive (refrig and freezer compressors), the flickering was reduced. I tested the microwave by itself and didn't notice much difference.

3) Chuck might be onto something. I am temporarily wired into the generator feed circuit that was previously used for a 5kW generator. Although I have a #6 gen cord, the house wire it connects to is only 12-guage NMB. Length is ~50 feet. Could this cause the problem when running light resistive loads?

4) I have tried the well pump but not as part of the flicker checks. No AC connected. I did start the refrig and freezer seperately and the system watt meter showed the surge and then returned to a steady state which indicated to me everything started okay.

Keeps the thoughts coming.

teg33 · Feb 28, 2006

One other thought...

Maybe it is a two fold problem: not enough load to keep the voltage regulator working at light loads, then too small of a wire to eliminate the problem at higher loads??

DAP · Feb 28, 2006

( Doug, the B2400 is 18 PTO HP. The way it has been explained to me by various dealers, and seems to make sense, is that you need approximately 20HP to get the full rated current from a 10kW generator. However, if your load is less than 10kW then a smaller tractor will work just fine. In fact, some of the advice was to buy a bit bigger generator in order to improve the surge performance.

There is absolutely no indication that the tractor is working hard or loading down, even with 7kW of load. Also, as mentioned all spec readings (frequency, voltage, THD) are right on the money. I haven't seen anything to indicate there is a HP sizing issue. Would there be some other test you would recommend? )

Under these conditions, the tractor is not the device that might bog down.

The only test I would recommend would be to slap that badboy onto a pto shaft that is providing 22 or greater hp.

I disagree with the 'tail-wagging-the-dog' comments by the dealers - they have their incentives. Just seems to me that if you don't meet the specifications then you wont meet the performance numbers.

Keep us posted ... and when I get my 7500 watt hooked up, I'll let you know the outcome ... I should be mounting the unit on a carry all fork within the next coupla days ... (gotta cut a PTO shaft methinks)...

Soundguy · Feb 28, 2006

( And yes, those 2 hp will make a difference, trust me. Further, running something like a generator at MINIMUMS is an invitation to lack luster performance.
)

While he can't runit at full load, if he runs it at a lower load.. one using less than his pto is rated for.. should be fine.

Nothing wrong with having more gen -or- more tractor than you need. I'd rather run a 13kw gen at 8kw than run an 8kw gen at 8kw. etc..

And having more 'tractor' than you need helps with hi-wattage loads that kick on and off.. like motors. For instance.. If I use my ford 5000 to run my 13kw genny, there is -0- change int he engine running when i drop a motor load on it. Same test with my 8n makes the governor jerk to compensate..e tc... that's the difference in running it on a 27hp machine vs a 71 hp machine..

Soundguy

Soundguy

DAP · Feb 28, 2006

Ummm ... while there could be lots of reasons, he WAS complaining about the product (electricity in this case) performance.

It certainly is a possibility that either the tractor, the generator or BOTH are undersized.

teg33 · Feb 28, 2006

More food for thought....
I'm wondering if the tractor governor could be at least part of the problem. I believe the B2400 has a mechanical type governor (does anyone know for sure?). How well do these regulate the engine speed (which determines PTO speed) and could this be causing a flicker?

Thanks again

George2615 · Feb 28, 2006

3) Chuck might be onto something. I am temporarily wired into the generator feed circuit that was previously used for a 5kW generator. Although I have a #6 gen cord, the house wire it connects to is only 12-guage NMB. Length is ~50 feet. Could this cause the problem when running light resistive loads?

Are you saying your #6 gen cord is connected to a 12 Gauge 50' lead cord? If so that could be your problem. 12 Ga. is only rated for 20 amps. If you have an ammeter, check each leg in your panel box where it's connected. I think you'll see over a 20 amp load when you see the lights flickering.