VFD For 3 Phase Equipment, not just motor

[Ron Boulton]

Malcolm is correct. It is not good ( Very Bad?) practice to disconnect, or connect, the load from a VFD while the VFD is powered up. Sure fire way to destroy the VFD. This is what will happen if you use the normal controls on the AD941.
Only option is to leave the VFD permanently connected to the motor in the Felder AD941 and rewire the control on the Felder AD941 to switch the VFD as suggested by Jack.

Really the best option is a suitably sized Rotary Converter. If you oversize the RC you can also use it for other 3Phase machines that might become available

By the way a Felder AD 941 is a Planer /Thicknesser not a Saw
Ron

[jack forsberg]

I hadn't seen more than 5hp rating for a 1>3ph VFD but I had heard Jack had options for more, apparently a lot more. Not surprised about the amperage necessary for a 20hp drive, I think most 20hp (starting) RPCs need even more than 100 amp service.

actually only 90 A but most people can’t find a breaker that size . I see some people here are still talking about the reading and puts on three phase VFD’s. Mine are Custom made with front end is large enough for single phase input But more importantly parameters are for single phase So there’s no little tricks like disabling phase loss.

[Dan Friedrichs]

All of that makes sense, except that since VFD's are programmable, I don't see why designers wouldn't include a "dumb converter" mode. As far as demand, people do sell and want phase converters - why is anyone using rotary anymore when the hardware needed to do it solid state is so cheap?

I suppose they could (and FWIW, I'm an EE who works in power electronics...). To be honest, I'm not sure why they don't exist.

I don't think the feed rollers have separate motor(s). So you really only have the main motor and the electronics. The electronics are also certainly DC, so there must be a power supply in there. That power supply is almost certainly single-phase (although it may just be wired to 2 legs of the 3-phase supply).

I'd encourage you to go for it. I don't think the problem is that daunting.

Absolute worst-case, you buy/build an RPC.

[John Halsted]

John, are you sure the motor isn't 4 kw rather than 4 hp? Felder generally spec'd their single phase motors at 4 hp and the smallest three phase was 4 kw or 5.5 hp. Dave

You almost got me, had to go back and double check myself, but yes it is 4hp, not 4kw.

[Dan Friedrichs]

actually only 90 A but most people can’t find a breaker that size . I see some people here are still talking about the reading and puts on three phase VFD’s. Mine are Custom made with front end is large enough for single phase input But more importantly parameters are for single phase So there’s no little tricks like disabling phase loss.

Jack, I'd be curious to hear more about this. How are you getting "custom made" VFDs for what appears to be a hobby business? And what does "parameters..for single phase" mean (are you just saying that the input rectifier is sized for a single-phase input?). I'm genuinely curious, as my professional life has me buying electronics, and I sure can't get custom power converters made at quantities in the hundreds (or even thousands) of units/year...

I would think the regulatory hurdles associated with certifying and safety testing a custom design for on-line connection would require a fairly sizable investment...

[John Halsted]

I suppose they could (and FWIW, I'm an EE who works in power electronics...). To be honest, I'm not sure why they don't exist.

I don't think the feed rollers have separate motor(s). So you really only have the main motor and the electronics. The electronics are also certainly DC, so there must be a power supply in there. That power supply is almost certainly single-phase (although it may just be wired to 2 legs of the 3-phase supply).

I'd encourage you to go for it. I don't think the problem is that daunting.

Absolute worst-case, you buy/build an RPC.

I'd concluded about the same and I'm going to take this as the winning answer. If I get a good deal on the 3 phase 941 there are a few routes of attack to solve the power problem, the most expensive of them being a rotary converter which may very well be useful for other things. Though as someone who also has done a lot of fairly recent power electronics design, I still feel silly using a mechanical spinning thing to do what can now easily be done solid state.

I'll see what I can get it for. In the meantime if anyone had a 941 (or 951) and feels like jumbling around inside and telling me how it's wired, that'd be great.

[jack forsberg]

I'd concluded about the same and I'm going to take this as the winning answer. If I get a good deal on the 3 phase 941 there are a few routes of attack to solve the power problem, the most expensive of them being a rotary converter which may very well be useful for other things. Though as someone who also has done a lot of fairly recent power electronics design, I still feel silly using a mechanical spinning thing to do what can now easily be done solid state.

I'll see what I can get it for. In the meantime if anyone had a 941 (or 951) and feels like jumbling around inside and telling me how it's wired, that'd be great.

I’d rather not share my bussness connections with the manufacture nor do I think it’s Any of your concern. Parameters are for single phase Input drive And are relevant to their particulars. I wouldn’t worry about me too much As I can’t see someone like you ever buying my VFDs

[Malcolm McLeod]

actually only 90 A but most people can’t find a breaker that size . I see some people here are still talking about the reading and puts on three phase VFD’s. Mine are Custom made with front end is large enough for single phase input But more importantly parameters are for single phase So there’s no little tricks like disabling phase loss.

Sounds like a slick set-up (i.e. you've taken the devils out). I try to keep up because of my shop, but not much time lately.

I deal with larger VFDs in the industrial world (last 2 weeks was commissioning of 4 x 150Hp + 1 x 400Hp + 300 I/O + PLC). We've got about 30 of these setups in the next year. In about 6 weeks or so, we shift efforts to the big ones (>2000Hp). ...Not much 1-phase stuff out here.

[Van Huskey]

the most expensive of them being a rotary converter which may very well be useful for other things.

Check out Phase Perfect for a step up from RPCs in price. Speaking of Phase Perfect most people I know with 3ph WWing machines run something similar to the American Rotary AD series BUT my 3ph machines are dumb (pretty much the only electrical things I own that aren't smarter than me), I have gotten the impression that modern Euro machines need or might benefit from the higher level RPCs with better balance and voltage stability. However, if Dan is correct and they are using rectified DC for the brains it might not be an issue. Anyone care to comment?

As for the RPC what I like about them is how simple they are and how enticing they make further 3ph purchases. Once you run your 3ph circuits you just plug the newly acquired 3ph machine in and spins like it is designed to. No need to add the extra cost of a VFD to the cost benefit analysis, but you do lose the cool feature set of a VFD.

Stepping back to the question of why no dumb VFDs I can only assume that there is little or no price benefit to producing them. Look at some of the multimeters like Fluke, often the boards are the same on lower level units compared to next couple of models up and people are learning to "hack" them to get the higher model's features. It is cheaper for Fluke to just disable the features but put them in a different case vs building boards without the features.

Also, Jack I doubt Dan meant any offense at all nor did he want to dissect your business or circumvent your connection. My guess is he was simply intrigued. As for the single phase parameters, it might well be a language gap much like attorneys degreed engineers often speak in their own language and use lots of terms of art. I just don't want the thread to go wonky as it is interesting and should be full of information for the future.

[jack forsberg]

Sounds like a slick set-up (i.e. you've taken the devils out). I try to keep up because of my shop, but not much time lately.

I deal with larger VFDs in the industrial world (last 2 weeks was commissioning of 4 x 150Hp + 1 x 400Hp + 300 I/O + PLC). We've got about 30 of these setups in the next year. In about 6 weeks or so, we shift efforts to the big ones (>2000Hp). ...Not much 1-phase stuff out here.

Those must be the size the lockers. Really trying to feed the market of those trying to operate three-phase machinery from household so that limits us to about 40 hp drives. Most people are just simply confused as to what drive to get and how to wire the controls and set parameters. We have a system of walking you through step-by-step regardless your experience. We make it so easy monkey could do it. lol

[jack forsberg]

Also, Jack I doubt Dan meant any offense at all nor did he want to dissect your business or circumvent your connection. My guess is he was simply intrigued. As for the single phase parameters, it might well be a language gap much like attorneys degreed engineers often speak in their own language and use lots of terms of art. I just don't want the thread to go wonky as it is interesting and should be full of information for the future.

All good I wouldn’t worry too much about it we only sell about 300 units a year to the United States

[Matt Mattingley]

It has already clarified (and I’m not trying to beat a dead horse but...).
1 Hp = 0.745 hp or... 1 kw = 1.34 hp. And you always want your feed line/branch distribution to be 20% bigger. I Believe this is required under the NEC.

If a Single phase VFD has output of 40 A, you multiply this by 1.73 then add 20%. By my calculator shows 83 A. This would take it to the next breaker size which is 90 A and feedline adequate. A feed line should be 125% of device load or to a maximum of 250% if properly distributed with fusing.

-SPC (or Static phase converter) do their job at starting a three phase motor, but once started only have 2/3 of the nameplate power. You are single phasing a three phase motor. This is the cheapest solution.


-VFD (or variable frequency drive) these are generally designed to run one motor at a time (but are not exclusive). A Vfd can run two or three motors… Vfd’s can be specifically set up for single phase or three phase input. The beauty is is they are fairly cheap and... if you only have two or three machines or you’re looking for variable speed, Soft start, breaking... multiple station controls and a array of sensor commands. A Vfd could be beneficial for not just conversion. Generally the second cheapest but wiring is required. Of course this is AC to DC back to AC pulse wave modulation and some pretty high-tech computer programming behind it.

-RPC (or rotary phase converter) is the good old bulletproof way that farmers have been doing it for 50 years. Electrical companies even longer. Very few moving parts, A few capacitors for starting a few capacitors for balancing and a few heavy contacters... you don’t need to be to brilliant to keep this up and running. You need a good test metre and you need to check your system a few times a year. The nice part about this system is... with a proper set up you can step up the voltages. The problem with the system compared to the PP or VFD’s is there a waste electrical power through heat and mechanical mass while running in idle. Usually about 2 to 3 kW per hour. What do you pay for a kilowatt hour??? Are you really worried about $.18 per hour(or whatever you pay), Times two or three???

-PP (Phase Perfect) is the cream of the crop. Initial cost is about $3000. This system allows for the two single phase natural lines to be completely passed through the device and it uses hall current measuring devices and creates pulse wave modulation at 208 V to ground perfectly no matter the amperage to the third leg (or generated leg, similar to an RPC but, not in a wild form). This system can be sent through transformers similar to RPC’s to step up the voltages but they generate a cleaner/more consistent third leg.

Both RPCs and PP’s you need to be concerned with contactors/Transformers in a machine to not receive the 120/208 improperly. This is a Delta/Wye situation. Any EE, E technologist or industrial electrician can walk you through this kind of situation if it applies to you.

I presently run...
1=> 5 hp RPC with the transformer to suit my needs.
1=> 20 hp homemade RPC with a transformer to suit my needs.
My Air compressor, Lathe, Tablesaw, 2 Drill press’s (and soon my ventilation hood) are all run by single phase VFD‘s. The crazy part is my air compressor has 4 different speeds depending on my demand for air. I have different pressure sensors for different call commands to the VFD through the parameter settings. Just remember you don’t need an engineer to set these things up.

Yes the PP would be great.... but I am just like the good old farmer. Technology is going to get pretty advanced and I hope to keep up.... I have a single phase 243 V fed property. I have 240 V three-phase and 600 V three-phase. Vfd’s have been a good compromise (in my opinion) for my needs.

My opinions are just my opinions and are open to any questioning. Sure there’s a lot to think of..... and there’s a brilliant brains here to help you choose your best solution. Sift through them to best suit your needs.

[John Halsted]

You almost got me, had to go back and double check myself, but yes it is 4hp, not 4kw.

Hah! The seller actually got it wrong when he said 4hp. Nameplate on the machine says 4kw.

[Bill Dufour]

Seems like two VFDs might work one constant HZ for the low power stuff, with a big load reactor. I assume the low power controls are intermitant use only. And a separate one to only run the main motor using low voltage controls direct to the vfd.
My 3Hp lathe came with 1hp VFD which worked fine for light loads. It just means the motor can only supply 1hp. As long as the vfd can supply enough power to run the motor at idle it should be able to do some work.
Obviously Tesla has figured out how to make VFD run off of a dc supply direct to the dc buss. Several hundred horsepower of vfd there. I think all the other motors are standard 12volt dc?
Bill D.
Bill D

[Bill Dufour]

I wonder how prices are getting on solar inverters that make ac from dc? you could just throw a bridge rectifier in to supply it with 180 volts dc from your house single phase supply.
Bil lD.