Anyone running 3 phase coolant pump on single phase?

[Com_VC]

Hi all,

Just wondering if anyone has had any luck running a 3 phase coolant pump on single phase, it seems you can get them working with a capacitor. https://www.youtube.com/watch?v=RLaBVY1yN44
The pump I have is 85 Watts and can be configured for either 415 or 240V.

I do have a small 0.25kw VFD that I can use but it seems a waste to use it on a coolant pump, I have no desire to have variable speed at all.

Thanks

[Com_VC]

Here is a photo of the name plate376430

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[BobL]

I'm running one on 240 but it's via a small VFD.

At least your motor is 240V 3P convertible - the Y -> ∆ conversion on mine involved wires that were almost as thin as human hair. The pump on mine was a solid ball of corrosion and needed a lot of work to get it back to operational.

After going to all that trouble I have used it a grand total of once because I am using an coolant misting system with ATF and this is works more or less OK. I can see on some cuts it night still be useful to have flood coolant.

Pumps are funny things - you can't derate them much so running the 3P pump motor via SP plus a cap may not provide the grunt required but it should be worth a try. Pump motor may also run hotter - you'd need to watch this.

[Com_VC]

I might give it a try, what size cap would be best to use? It will be used on a drill press so it won't be on for long periods of time.

[BaronJ]

Hi Com_VC,

85 Watts is not a lot for a drill press ! Unless you're only going to use it for little drills, say 1/8" or less.

Anyway I would try 15 to 20 uf for a start.

[Com_VC]

Hi BaronJ,

It will be used as a coolant pump on the drill press :D

[BaronJ]

Hi Com_VC,

Actually using a coolant pump as a coolant pump never occurred to me :doh: I did think "small drill press" though, I have seen one designed to drill holes in pcb's using a 135 W brush motor.

If you get stuck for capacitors, old fluorescent fittings usually have one of about 8 uf. If the capacitor you have is too small you can connect another one, two or three in parallel to increase the value. Capacitors in parallel add their values together.

[Com_VC]

Would these be the ones?376454

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[BaronJ]

Hi Com_VC,

No ! They are glow starters for starting the tube. The capacitors will be inside the body of the fitting and are usually round cylinders and silver in colour. The other Item in there will be the choke, which is basically a coil of wire around a laminated iron core.

Their will almost certainly have the capacitor value and a voltage rating marked on them.

I actually had one in my hand earlier today whilst looking for something else.

[Com_VC]

Thought they looked a bit unusual. Will have another look tonight. Think I should have something around.

[Com_VC]

So I had a chance to have a play around with this today after work. I found two light fixtures, each had a 4 uf cap. So I figured I would grab one of them for now and wire it up to see what happens. What do you know, it actually works, it spun right up and sounded healthy. I only ran it for 10 seconds as it is dark now.

I want to do some proper testing with some water and run it continuous for 30 minutes to see how it flows and if it develops the height I require. Also to monitor the temperature.

[BaronJ]

Hi Com_VC,

The motor speed is determined by the frequency of the supply voltage, so irrespective of the capacitor value it won't alter the motor speed.
What will alter is how hot the windings will get ! So keep a close eye on the temperature. I think 4 uf might just be a little small, but at least you now know that it works and pumps OK.

Re temperature. The winding that has the full voltage on it will be the coolest. The capacitor value will determine the current through the other windings.
Under ideal conditions the current through each winding should be the same under load. One way to measure this is to use a clamp ammeter on each power lead in turn, and adjust the capacitor value to get even current on all three leads.

[OxxAndBert]

And do that tuning while it's under load i.e. Pumping, not just spinning freely.

Steve

[Com_VC]

I just ran it for a full 10 minutes in a bucket with some water in it and it didn't get hot at all, just slightly warm. So either I fluked it or the value of the cap is pretty close. I am still going to measure it just to make sure it is 100%.

Then I am faced with how I should mount the cap, is it OK to mount it externally or should I modify the motor terminal box to somehow incorporate the cap and wiring all together?

[BaronJ]

Hi Com_VC,

Depending upon how big the capacitor is, you could just use a plastic cap to cover the terminals and mount it anywhere reasonable. Or a plastic box, like those project boxes with a lid that is secured by a screw in each corner. Don't forget to make sure that you have a safety earth connection to the motor and include the capacitor case if its metal.

[BobL]

I just ran it for a full 10 minutes in a bucket with some water in it and it didn't get hot at all, just slightly warm. So either I fluked it or the value of the cap is pretty close. I am still going to measure it just to make sure it is 100%.

Then I am faced with how I should mount the cap, is it OK to mount it externally or should I modify the motor terminal box to somehow incorporate the cap and wiring all together?

Did you get it to pump to full working height and not just round and round in the tank?

[Com_VC]

Thanks BaronJ, will work something out.

BobL, no it was just sitting in the tank. I will try again tomorrow to see if it reaches the required height.

[Com_VC]

BobL: Just tested it with the hose attached, I was thinking that I might have to prime it but within 5 seconds I had a continuous flow of water coming out at 1350mm height.

[Pete O]

I've been running the 1/4hp 3-phase coolant pump on my lathe for about 5 years on 240v with capacitor start, very simple system that a friend set up for me when I first got the machine. I have the standard on/off switch plus another rotary switch that I converted to a 'normally open' momentary switch. I hold the momentary switch for a couple of seconds whilst starting, this brings the capacitors in to kick-start the pump. Rough as guts and works a treat. The pump also supplies my milling machine via about 3 meters of garden hose with around 1m of lift. I did essentially the same thing with my recent disc sander build, but using a timer and contactor to bring the capacitors in for the start cycle. From what I have read, 70uf per horsepower is about the right value as a starting point.

[Com_VC]

Is the momentary switch required, can't the cap remain connected full time?

[Vernonv]

Is the momentary switch required, can't the cap remain connected full time? He is using a "start" capacitor, not a "run" capacitor. Start caps shouldn't be left connected for extended periods.

[BaronJ]

Hi Guys,

It really shouldn't matter whether the capacitor is left in circuit or not. The thing to do is start the motor and disconnect the cap, see if it slows down or stops. If it caries on running normally, you could use a normally open push button to connect the capacitor for as long as the button is held down, when first switching the motor on.

I've a 1Hp three phase motor that requires 48 uf to start it running, but it slows down and will stop under load if the cap is disconnected. It really could do with a bigger cap, but I don't have another large value one.