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VFD Ramp Up Parameter Optimisation

Clive603

Titanium
Joined
Aug 2, 2008
Location
Sussex, England
Friend Mike-the-Pilot has issues with a Hydrovane 502 compressor on start up. Three phase 2.2 KW, 3 HP, 2,800 rpm motor configureable in both wye and delta.

His main shop three phase is via a Transwave 5 HP rated rotary converter giving 440 V three phase. On the Transwave the Hydrovane start up is iffy, with a tendency to settle at half speed rather than run up to full speed. Most problematical in cold weather. I suspect the Transwave is running out of amps on the wild leg before the motor has run up properly. Its certainly slower to run up than mine is which gets proper 440 volts and jumps up to speed almost instantly.

I have a 2.2 KW rated Eaton DE-1 display-less VFD box waiting for its application to be ready. We tried running the Hydrovane off that on its factory default settings with similar results to the Transwave, although it was a bit less willing to settle at half speed. Testing the Eaton VFD on my Hydrovane 502 showed it to run just fine on factory default settings but my shop is a little warmer than his barn.

Factory default setting on the Eaton is 5 seconds ramp up and 3% low speed voltage boost. I'm guessing that shortening the ramp up period and raising the voltage boost will give a better starting kick hopefully pushing it up to speed before whatever causes it to bog down hits. Question is what combination of ramp time and voltage boost will give the best start-up kick. I assume that shorter start up ramp time and higher voltage boost will both drain down the DC supply side faster. Hence setting ramp up to minimum, 0.5 seconds, and voltage boost to maximum, 40%, is likely to be counter productive as it will demand too many amps too fast so the effective power could actually be less.

Tried a combination of 2 seconds ramp up and 10% boost settings on mine. Certainly livelier on start up. Road trip involved so be nice to have a better feel for whats going on.

Thanks.

Clive
 
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Power is power sir! Amps, volts, time. I would run the higher voltage boost and just have to roll back the accel time until you get reliable starts.

On real street, I would want to know what the hiccup is? Ya'll got meters? Surely this would be evident. It might well be the converter needs better tuned for the load, or you have a wire size issue. Motors want some amps at start up and people tend to not math everything out, including LONG runs of wire.

Look at voltage on all phases at start up. If you add capacitance on the converter, you will increase the unloaded voltage but if it just runs that one load, you need to be worried about voltages while running.
 
Huleo

Thanks for the reply.

Tuning the converter isn't an option unfortunately. The box works fine with everything else and have been specifically told by Transwave that extra capacitance won't help matters. Always seemed to me that Transwave converters are undersized on the rotary element so they suffer from both shortage of real amps on the wild leg and excess phase shift. That thing had wild leg problems on a Bridgeport so I'm less than impressed overall.

Which is where the VFD came in. The small Hydrovanes need to run up quickly to avoid back pressure issues during acceleration so can't make the ramp up time too long or it certainly will bog down. As the overload capacity in the VFD is finite its a matter of making best use of whats available. But I don't understand the trade-offs involved between voltage boost and ramp time.

Clive
 
The 'trade off' is less ramp time = more power. You will have to play with it. In the end, you may just not have enough power! The VFD can only do so much. It sounds like your converter is undersized but you are going to throw more wrenches in the mix. I'd probably start there.
 
Road trip and try-out this morning.

Left the Eaton DE-1 VFD box set at the 2 second ramp-up and 10% voltage boost I'd tried on mine.

His Hydrovane ran straight up from cold just fine and restarted perfectly when tank pressure dropped to the auto-switch limit. So I called it good and told him to get the same VFD box which I would fit and set-up for him.

Settings are probably not optimum but looks to be close enough. Messing about with parameters whose interaction I don't fully understand strikes me as being a good way to waste a lot of time without any significant improvement. If it does muck about when really cold we can always tweak things.

After this I'm even more certain that his Transwave RPC box has issues even though he got it almost new. But whatever works works.

Thanks for the help.

Clive.
 








 
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