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Running coolant pump with vfd

joehunt1

Plastic
Joined
Sep 25, 2014
Trying to get my new to me Tos sn32 up and running, I have a 220v main motor and vfd ordered.
Just wondering if it would be acceptable to run this coolant pump wired for the lower voltage on 240v with a small vfd.
I only have 240v single phase available.
Thanks for the help and sorry for my ignorance.
Joe
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Should not be a problem running the pump on a separate VFD at 240VAC/60Hz. KB Electronics sells some inexpensive simple VFD drives that work well in this application if you have an enclosure, there are of course the usual generic ones on Amazon and eBay, you have the option to turn on the pump when powered up with 240VAC, or using a switch to activate a run input.
 
Should not be a problem running the pump on a separate VFD at 240VAC/60Hz. KB Electronics sells some inexpensive simple VFD drives that work well in this application if you have an enclosure, there are of course the usual generic ones on Amazon and eBay, you have the option to turn on the pump when powered up with 240VAC, or using a switch to activate a run input.
Thanks a bunch. I will give it a try.
Joe
 
Check the motor voltage please....
The 288V is higher than 240, yes. That will be a bit more current for the same power output. A pump usually has a fairly consistent power requirement, but we don't know how much it actually uses in your machine. It is probably a standard unit that was selected as "sufficient" for the machine, and may have more capability than needed.

Smaller motors often handle a bit of extra current better than larger ones, since the surface area is larger per watt of input.

You can monitor the current input with the VFD or an ammeter, and check for overheating, at least externally. At 90W and 0.29A input, it is only around 1/8 HP.

You do have other options, including stepping up the voltage after the VFD. I don't think there should be a big issue, though.
 
Ok I’ll test it for amps. I really don’t have anything to loss. It if no use if I can’t run it on 240. Probably cheaper to buy a new pump then have this motor rewired for the correct voltage. I’ll look into a small transformer but my understanding is it have to be transformed before the vfd not after.
 
You can do either, but "after" means a 3 phase transformer. "Before" needs only a single phase type.
 
The pump may run a bit slower than rated speed, but as a coolant pump it should not be a significant issue running it at a slightly lower voltage. I would not measure the current, the VFD limits the current. If one wanted to diddle with the VFD settings, one could set the volts to 240VAC and the Hz to 50 on the VFD which would maintain the V/Hz ratio. Often in these type of situations, it is easier and less expensive to replace the pump with a single phase 240VAC one, but small 1/4Hp VFDs can be purchased for not much, and this is a simple application.
 
Measuring the current is just a way of estimating the actual load on the pump when running.

If at or lower than the full load number on the tag, there will be no issues. If above the FLA on the tag, then some adjustment may be necessary, to flow rate, voltage, etc.
 
The coolant pump on my ATW is 240v/3ph so no voltage questions but a small VFD drives it just fine. If there are concerns about current the VFD thresholds can always be set to inhibit overcurrent. Speed control of the coolant pump wasn't very useful but it does work.

After getting that working I found the flood a bit too much so mounted and plumbed a 120v diaphragm pump w/ bypass so I could tailor the flow w/ increased pressure which permitted a more targetted application, eg thru coolant tooling. I'm just finishing a ER32 based system for the tailstock, which works for thru coolant drills.
 
The highest load on a centrifugal pump tendst to be when it's operating at maximum flow. If the flow is throttled at all, the load will be lower. Normally coolant systems on manual lathes aren't working anywhere near the maximum flow rate of the pump (unless you are wearing a diving suit and mask! )
 
Remember, that pump is 90W, between 1/8 and 1/10 HP. Current is 0.29A.

The smallest VFD is generally around 1 HP, corresponding to about 4A or so. The available steps of current limit may not be fine enough to set very closely to the motor limit.

Yes, open flow is the highest power mode. A current measurement would show if the pump is being overloaded, which is possible due to the lower than spec voltage.

If needed, a valve can be put in-line to limit the max flow, if desired. I doubt it will be an issue, but ...................
 
Running a .5hp VFD driving the 1/3rd HP pump on my lathe right now, just not much room for drama in such a small system. I ran a 1.5hp 440v lathe drive motor from a 240v vfd for years, likewise no detectable drama.

A centrifugal pump will probably benefit from a bypass back to the sump on the far side of the pump vs constraining overall flow. If a small trickle is desired a different pump is probably indicated.
 
There are quite a few 1/4 Hp VFD's, I have used the KB's, Hitachi (WJ-200-002SF), DuraPulse (GS11N-20P2), WEG and a few others, one can adjust the output current to ones likings, and in some cases dialing down the flow rate may be desirable, otherwise one can use a tank return with a valve or a valve on the flow line which is what I use on my bandsaw.
 
The other option is for a transformer, if desired to get the voltage perfect and a capacitor. It'll probably be perfectly happy with just a correctly sized capacitor. No need to go overboard on such a simple application.
 
If you can get a small VFD, then you will be fine. They are less common, and often more money per watt.
 
Thanks for all the input.
I will advise on how it works. Just going to try wiring the vfd straight to the pump.
Joe
 
I run a small coolant pump off the main hydraulic pump VFD on my grinder. I just turn the pump on and off with a separate switch when using it rather than leaving it powered and running with the flow valve off. The pump motor is small enough that the VFD doesn't even notice it going off and on. Could always add an overload/interrupt inline if you're worried about it, as others have mentioned.
 








 
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