M-803a load exercising

[jcollings]

Was trying to get thoughts on 803a generator underload and having equipment starts pegging to 125% then coming back what is considered okay 30% to 75%. anybody's input would be appreciated.

Thank you

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[Scoobyshep]

The general rule of thumb I most hear is 80% is a good normal load. Sizing for big spikes is tricky, Instead of going bigger I try to look at the big spikey things and find ways to make them less agressive. soft starts, VFDs, load shedding, or other creative controls.

On the other end of things if the sets too big and it starts wetstacking just do a load banking now and then to burn the crap out

 

[jcollings]

No I get the wet stacking analogy.
Just when running 30% load a sprinkler pump Kicks on getting that spike and return back to normal. what's considered acceptable without stressing the system out.

Thank you

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[Scoobyshep]

No I get the wet stacking analogy.
Just when running 30% load a sprinkler pump Kicks on getting that spike and return back to normal. what's considered acceptable without stressing the system out.

Thank you

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Electric motors are really good at that. they can draw up to 12x their rated load on startup.

These things are rather good about protecting themselves, That inrush surge isnt likely harmful if the breaker isnt tripping.

If it will help you sleep better, a softstart will reduce that spike and they are relatively cheap

 

[jcollings]

No not worried about it, just trying to get some input, I know my UPS doesn't like it inside it alarms briefly.

Thank you

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[Scoobyshep]

No not worried about it, just trying to get some input, I know my UPS doesn't like it inside it alarms briefly.

Thank you

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Thats most likely due to the sudden drop in voltage or frequency

 

[jcollings]

I've been kind of easy on it since when I first got it, everybody said oh yeah they're bulletproof , well I put it through the paces and the flex plate cracked which led to a whole new gen head, that was fun

Thank you

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[Scoobyshep]

I've been kind of easy on it since when I first got it, everybody said oh yeah they're bulletproof , well I put it through the paces and the flex plate cracked which led to a whole new gen head, that was fun

Thank you

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Sorry you went trough that. Generally they are pretty bulletproof.

 

[jcollings]

Could have been a hairline factory crack in the flex plate, but it was bad when it happened and depressing.

Thank you

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[Guyfang]

Have you got any idea how high, (KW or % wise) the spike pushes the generator?

 

[jcollings]

Going the by the percent of load meter it looks like 125% Spike then right back down after. Load was running at 30% at that time the other motor kicked on (sprinkler pump)

Thank you

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[Guyfang]

Short Circuit/Overload Relay, (K. This device will activate when the set output current in any phase exceeds 425±25 percent of the rated value.

If the K8 is not shutting it down, I would not worry about it too much. To echo what Scooby wrote, maybe a soft start would be a good idea.

 

[jcollings]

Thank you so much for that information, that clarifies the information I was looking for. the likelihood of putting a soft start on a sprinkler pump is unlikely.
The water plant I used to work at before retiring had a lot of soft start equipment on a 120, 300,25 horsepower but nothing like a 1 horsepower. although some chemical feed were variable and did have that type of setup.
Thanks to everybody for your input.


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[Scoobyshep]

They are quite different animals. I used to work with some 300hp soft starts, if they were my only perspective on them I would be rather hateful towards them.

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[jcollings]

Haha yeah....

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[Coug]

on my 802 5kw I was messing around with a 3 ton ECU and ended up dumping the heater circuit onto it without realizing how much load it was.
The heat coils draw over 9kw, plus some more with the blower fan motor so over 10kw.

Generator bogged down to about 40hz and kept chugging along until I realized what I did and turned it off. That was a couple of minutes.
I've put hundreds of hours on it since then, and no signs that the extra load did anything harmful.

For the most part these units are overbuilt to the point that you have to do something extremely stupid to actually hurt them, and have enough safety built in to make that difficult.

 

[2Pbfeet]

Thank you so much for that information, that clarifies the information I was looking for. the likelihood of putting a soft start on a sprinkler pump is unlikely.
The water plant I used to work at before retiring had a lot of soft start equipment on a 120, 300,25 horsepower but nothing like a 1 horsepower. although some chemical feed were variable and did have that type of setup.
Thanks to everybody for your input.


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There is always a VFD for a 1HP sprinkler pump; just program the VFD for a reasonable start up current ramp, and you could even do a ramp down to make life super easy on the generator controls.

All the best, 2PbFeet