Quincy 10 HP compressor and VFD

Hi. Just for reference, our 5 hp, 220 volt 3 phase, compressor seems to have zero ramp up. At least it's not detectable when it starts. Seems to go from zero to full speed instantly. The tank is 60 gal. So, really don't think acceleration on your compressor should be a consideration.

Best regards, Paul

Presumably you're feeding your compressor "real" three phase power. When using three phase from a VFD functioning as a phase converter from single phase power in a residential setting a little soft start helps reduce the lights dimming and SWMBO bitching.

Iggy - Are the unloaders speed or time controlled? If speed, your plan sounds good, if time, get things up to speed in time for the unloaders to kick in. Either way I doubt there will be much benefit to a ramp up of more than 1 second. You can always put an amp probe on it and see what peak current is with zero ramp up and at different ramp rates and see what is the best fit.

My plan, to be exact, is to put this compressor on a VFD so that it can be run without any phase converter. My setup features a 10 HP compressor motor, 15 HP head (spun 33% slower), and a 25 HP rated VFD.

Just to be a little redundant, I did call Quincy today and gave them my serial number etc, they confirmed that this is a 15 horsepower head, properly slowed down so that it can be driven by a 10 HP motor.

So, I want the VFD to take 1 phase in, and to make 3 phase out for the motor to run.

I would guess they are speed controlled.

1 second seemt to be the best all around spin up time, to me personally. Not too slow, not too fast, does not startle people as much and is gentle on everything. i

If one is using a VFD to drive it, and the VFD has ramp-up capabilities, might as well use them - if nothing else (and there are other things, such as lubrication distribution) it reduces the starting surge of current drawn from the wall. If you're building compressors and trying to maximize profit, there won't be a VFD there, so there won't be a ramp on start-up. Turning one-phase into three-phase to power surplus equipment changes the economics, and thus the options...

Then you get into other neat things you can do with a VFD, if you get the control electronics (and more sensors than are typical) lined up right - run the compressor faster or slower depending on how much air you are using (well, probably based more on tank pressure, or rate of change of tank pressure, really), idling it down (and perhaps unloading, if the unloaders are electrical) without shutting off until some period of time passes so it's not shutting off and turning on in the middle of work, etc. All much fancier than the standard setup, and somewhat violating KISS...

Just a ramp up is fine with me. Running it slower may create motor cooling issues.

i

Depending on the unloader system, it may be entirely pneumatic time delay, or hydraulic. Especially if hydraulic, it will not be at a specific time. The first start of the day will take longer. Just set the ramp up so the lights don't dim too much when spinning up. Roughly one second might be a good starting guess. I can't see any reason to not be fully at speed (60 Hz) before the compressor gets loaded.

Jon

I don't believe Quincy has ever used a centrifugal unloader control. The two (non-electrical) systems they have are pure pneumatic (where the motor pretty much runs all the time, and the control unloads the compressor as the primary pressure control mechanism) and hydro-pneumatic, where the unloader cuts out and allows the pump to work when the oil pressure is built up. This usually takes about 2-3 seconds, depending on how long the pump has been stopped. On your pix from a couple days ago, I didn't see anything that looked like electrical controls for the unloader. Since the unloaders are pneumatic (I think) you could always control them with a solenoid valve and a time delay relay.

Jon

I called Siemens, spoke to their engineer and he confirmed that this drive should work with this motor. I expected that, but it is good news.

i

Jon, I will double check tonight if I get some free time. Thanks. I have no idea how unloaders work. As for hydraulic control, that would require the oil pump? But this compressor is splash lubricated.

i

1 second is definitely what I will start with. My mill also has a 1 second delay, it feels very nice. i

Um, that reply was to the other poster re: his 3ph compressor with no VFD or soft start.

Seems unlikely given the other replies.

1 Second is probably good, however if this is your winter project, some peak amp numbers at different soft start rates would make an interesting post...

Yes, you are right.

Looks like I was wrong here, too.

I went through this once with my phase converter. I will report my results once I get somewhere.

i

Ignoramus705 wrote: {big snip}

Splash lubricated Quincy? Really?

Really. QR series pumps are pressure lubricated, most others are splash.

i

Really!

Just below Pressure Lubricated and above Oil-less.

I'd be tempted to call Quincy and ask them.

Joe Gwinn

I called Siemens actually, their engineer did not seem like the utmost expert in the field, but he said that it will probably work. I will see. I am going to post a separate message about how I ran this Quincy today.

i

You want the motor to get up to speed before the unloader cuts off. You should have the vfd acellerate as fast it is able to do without tripping the breakers.

John