Sizing motor to pump 4

[vinic]

I'm in the process of setting up a rotary lobe pump for moving wine and wine must (skins and seeds still in the juice/wine).

The pump is a Tri-Clover brand TSR3 rotary lobe, and the only requirements I see in the manual are maximum RPM of 1000.

Already in place is a Saftronics drive that I can set to limit the RPM. This pump will not be run for very long periods of time per run (1-2 hours tops, more often, 10-30 minutes).

How hard is it on a motor to run it at this speed (no gear reducer) if rated for:
RPM of: 1140 or 1725

How can the HP requirements be determined?

I know these are pretty basic questions for this group, but help would be greatly appreciated.

Regards,

Clyde Gill

 

[electricpete]

An 1140 rpm runs 1140 rpm or higher. (slightly lower if the motor is overloaded). I don't think you can hook it up to your 1000 rpm max pump without a gearbox or belt or vsd.

How about a 900rpm motor?

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[Artisi]

"Already in place is a Saftronics drive that I can set to limit the RPM. "

Is this a variable speed drive - and can you set it to operate at 1000 RPM. If yes, I see no problem with operating a 60 hz 6 pole motor (nominal 1200 RPM) at 1000 RPM. As for the motor size I cannot advise as there is insufficient detail supplied.


Naresuan University
Phitsanulok
Thailand

 

[electricpete]

Sorry, I didn't see the part about the drive. I agree with Artisi.

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[vinic]

Thanx for the timely response.

The drive is a vfd (PC10). My intent is to not run the pump faster than the rated 1000 rpm, but my concerns at them moment are focused on what happens to a motor when run a less than rated speeds.

On this issue, wine pump motors are pushed pretty hard. Most operations will begin at very slow rpm (for less than a minute), then ramped up to full speed, and towards the end of filling a vessel, the speed is gradually lowered again to a stop. Again, I know this action is not good for the motor, but it's best for the wine, and motors are cheap compared to the product! Breakdowns, however, can be costly in time (and potential product damage). I'm thinking of setting up this pump with an old motor just to see how it responses to the horsepower rating. Not sure how else to determine the size needed, though I'll be trying to contact the OEM this morning.

As a side note (and another question), I've setup a radio remote to control the vfd. For this, the vfd must have an "up" and "down" function available for the control terminals. So far, I've only found that the newer Saftronics (fuji) and the yaskawa drives have this feature. Does anyone know of other brands that have this function available.

tia,

clyde

 

[quark]

It is foolish if I speak about motor characteristics in the presence of electricpete(and I am sure he will take care of them in his next post).

What problems do you foresee in running a motor at lower speeds than it is designed for? Almost all VFDs have ramp up function and it can be set depending upon your requirement to some extent. My question is 'how your motor comes to know that your vessel is close to full volume?' You have to have some sort of level transmitter and you can use this signal to control the VFD.

Regards,

 

[blutfort]

Most VFDs that I have had experience with support the up/down programming parameter. You will need to configure the drive's inputs for this setup.
As far as weather the motor will support the VFD, the easiest way to tell is see if the motor has a stamp or sticker claiming to me inverter duty. The vfd will produce large voltage spikes as it assembles the waveform, and I believe that this is what will eventually kill the shellack on the motor windings. Another possible killing point is the motor cooling. If the motor is cooled by a fan attached to the rotor, running at too low of a speed will result in triping on thermal overloads or motor meltdown. If your motor is designed for 1300 rpm and you are running it at 1000 it shouldn't be a problem however.

 

[blutfort]

Food for thought...
I don't have much experience with the wirless controls. There can be a lot of electrical noise near a VFD. Will the wireless controls be able to punch through it?

 

[vinic]

It's probably becoming painfully obvious, but I don't know a whole lot about motors and other applications- just enough to be dangerous, as they say. The pump I've been using so far with my wireless control tends to get rather warm when running about 1/3 the rated rpm. Running at real slow speeds (maybe 1/20 the rating) for very long (2-5 minutes) it will kick off the vfd with an overload error, which I assume is much better than frying the pump motor.


Blufort, I'd be interested in knowing what program/function settings would work on something like a Fuji FVR K7S. Again, it seems pretty straight forward with a Saftronics PC10 or the new CV10 (both of which I've used) and even with a Yaskawa VS mini J7 (by just looking at the manual).

As far as the RF controller, I've had little to no problem with any interference. Requires a fiberglass enclosure (if being enclosed). When I was just playing with the design, a simple garage door style trans/receiver worked fine. Also used a little key fob, build-it-yourself kit. But after getting the circuit designed, I went with a serious unit (Inmotion) that works from about 300 ft away. Controls up/down-fully variable, and rev/fwd.


clyde

 

[hydrae]

Vinic

To become the fool according to quark and venture into an area electricpete has vast more knowledge.

How can the HP requirements be determined?

Aid in this subject and help you understand about how theses systems work.

A squirrel cage induction motor is a torque limited motor (generally) that is, when operated at normal frequency the motor will spin near synchronous speed and as the load is increased the motor will slow down slightly which increases the rotor field which increases the torque, this works until the field is saturated after which if additional torque is added to the load the field breaks down, the motor will slow way down or stops depending upon if the load is a variable or constant torque respectively. The HP rating of the motor is a percentage of the breakdown torque times operating speed.

When the motor is operated on a drive, the limiting factor is the amount of amperage the motor can take, (with adequate cooling) a motor operated at 30 Hz will produce the same torque as a motor operating at 60 Hz, the torque is directly proportional to the amperage draw, therefore the hp available is directly proportional to the operating speed. So a motor will drive a constant torque load on a drive without overloading the motor or the drive as long as there is adequate cooling of the motor.

Now to look at your load: you are using a rotary lobe pump which is positive displacement so the torque requirements are directly proportional to the change in head, your flow is fixed, each revolution of the pump will produce the same amount of gallons of wine et al.

Since this is a constant torque load, the drive will need to be sized and programmed for constant torque.

So to answer your question when will the motor be overloaded?
If the change in head exceeds the available torque of the motor by either pumping against a closed valve or pumping to too high of a tank
If the pump is operated at a slow speed for a long time without external cooling of the motor, that fan on the motor is a centrifugal pump which pushes a whole lot less air through those tiny passages at slow speeds.
If an obstruction prevents rotation of the pump. how likely is the wine must to clog the pump? how much torque is required to grind up the must if they do get clogged?

If you are concerned about RF interference, the drives I have worked with (AB, ABB, SqD) all use an RJ45 connection between the drive and controller panel, so connecting the remote can be extended using an off the shelf Ethernet cable. Check the instruction manual though.

Hydrae

 

[Artisi]

hydrae (Mechanical)has put it all together for you in a nice package. All you need to do now is contact the pump supplier or manufacturer to asertain the power requirement for the application and to contact the motor supplier or manufacturer for the tech data on the motor - ie, power output / torque / current / pf. etc at the speed you need and advice on the cooling capabilities of the fan at the running speed.
Also check with the motor manufacturer if there are any fan options available (if required)or alternately if there is a potential problem with o/heating a seperate powered fan may be in order, as you said the hardware is cheap compared to product and downtime.

Naresuan University
Phitsanulok
Thailand

 

[vinic]

The help here has been nothing short of tremendous!

The pump I just purchased showed up today in fine condition. It was purchased second hand but looks brand new (no marks on the drive shaft).

I wanted to have the pump in hand before starting to build a frame to hold the motor and pump. There's a few old motors around here that I'll start with (common 56c frame) just to see how it works, then look into purchasing a washdown version... quite possibly one that is rated for vfd control, now that I know they exist (thank you very much). Gist is, it may be a few days before I have more questions, but chances are high that I *will* have more questions!!

To answer some questions that have been asked of me, the pump will never be bogged down completely with must. This is the main reason for using rotary lobe in this application. It also doesn't tend to "grind" the material, which again is why this style is used. The objective here is to move the skins and seeds with as little breakage/damage as possible, which tends to degrade the wine quality. If there's to be any clogging, it would occur in the hose, but these pumps are so powerful (absolutely positive displacement), that it would tend to blow the hose (fittings most likely) before putting any kind of undue strain on the motor. Quite possibly a small motor would aid in this scenario, as the motor might send an overload to the vfd before any physical damage (exploding hose) could occur.

I have quite a bit of background in the operation of these types of pumps, but have only now started to look into what drives them. Specifically, this design of radio remote control is new to our industry (as far as I know, I've built the first in our country), and I'd like to learn more about what might be required to make this system work best and be safest.

This has been a great place to start/continue my education. I'm willing to go farther both here and in the bookstore, if anyone has any more comments or some suggestions for literature for a beginner (with basic electrical/mechanical background) in this field.

Thanx all,

clyde

 

[vinic]

Reading back through the post I see Quark's question about the top of the tank issue. This is exactly why I'm using the radio remote control. Most wineries have a wide variety of vessels. Many size tanks, sometimes in a wide array of positions/levels and then there's usually wine barrels. I suppose a portable limit switch could be attached to the bung of a barrel, but my solution is this radio control. No wiring to the pump or the tanks. The operator stands over the pump, as the level gets close to the top, the speed is reduced and then stopped completely at full up (hopefully just from line of site.

clyde

 

[hydrae]

Vinic
One more thing VFC rated motors have two additional features over normal motors, the windings have additional supports (more glue and strapping) to prevent them from vibrating at the high frequencies of the carrier waves from the drive and the have a grounding ring to ground out stray currents between the rotor and the stator also due to that carrier wave. Motors from 15 to 40 years ago will fail in 1 to 3 years of VFD use. Realy older motors I have found live longer because of the additional iron in their construction and oversizing of every componet inside the motor.

Hydrae

 

[MortenA]

I couldnt see if this had been pointed out but:

You should be sure that the motor cooling is suited for VLT. If not then when the VLT slows down the speed then the fan might turn more slowly and perhaps provide inadequate cooling.

Best regards

Morten