Franklin MonoDrive VFD

Ponderosa

New Member
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Jan 17, 2021
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5
Can anyone provide advice on an inverter that will work with the Franklin MonoDrive variable frequency drive submersible pump controller? Franklin says some inverters will work and some not so much but won't advise as which one. Need one with the truest, true sine wave. Maximum amps drawn would be 11 amps at 240v. If someone is running a Franklin MonoDrive Connect series with solar successfully, please advise.
 

FilterGuy

What, me worry?
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Nov 26, 2019
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Your situation has a couple of ugly complications. I can't give you a recomendation, but I can give you some background on the situation

1) VFDs typically have really bad power factors. Some of them are as bad as 60 or 70%. That means that if your pump needs 200W, the inverter might have to supply ~280W.

2) Motors in general have a very high start surge. A rule of thumb is that the start surge can be 3 times the normal runtime load. Furthermore, pumps can have a start surge that lasts a reasonably long time (Till the pump comes fully up to speed).

Your system has both.... that means your inverter may have to handle a surge of 3.4 (or more) of the normal runtime load. Does the documentation with your pump tell you anything about power-factor or start surge?

In general, you should be looking for a low-frequency inverter. These will typically have a surge rating of around 3x inverter continuous rating
When you select the inverter, Make sure to select one that has a runtime continuous power rating well above the runtime power needs of the pump (a factor of 2x would be my starting point, but I get conservative on this type of thing. You might be able to get away with less)

Finally, if you put a reactor in front of the VFD, it will improve the power factor rating some.
 

MichaelK

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Mar 21, 2020
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1,319
My 1hp well pump has a Franklin controller on it, though I'm not sure whether or not it's a MonoDrive variable frequency controller. It draws 10A while running, but the measured startup surge is ~38A. My Schneider XW+6848 handles it without a single complaint. I used a clamp meter with "in-rush current" capacity to measure the startup surge.

Here are a few extra numbers you may find interesting. While powering the well with my 240V generator, it pulls 10.0-10.1A while running, and pumps 275 gph. With the inverter it draws 9.4A and pumps 300 gph. This is testing over an 8 hour time period. An engineer friendd explained that the Schneider is producing cleaner AC than the generator is, so it uses fewer amps to pump more water.
 

Ponderosa

New Member
Joined
Jan 17, 2021
Messages
5
My 1hp well pump has a Franklin controller on it, though I'm not sure whether or not it's a MonoDrive variable frequency controller. It draws 10A while running, but the measured startup surge is ~38A. My Schneider XW+6848 handles it without a single complaint. I used a clamp meter with "in-rush current" capacity to measure the startup surge.

Here are a few extra numbers you may find interesting. While powering the well with my 240V generator, it pulls 10.0-10.1A while running, and pumps 275 gph. With the inverter it draws 9.4A and pumps 300 gph. This is testing over an 8 hour time period. An engineer friendd explained that the Schneider is producing cleaner AC than the generator is, so it uses fewer amps to pump more water.
Thanks for the input, I'm looking into the Schneider. That is interesting about the generator vs the inverter.
 
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