Question Bauer Capitano II 480V 3 Phase to 240V Single Phase Help

[JayPBC]

@happy-diver operating model of what? single phase to 3-phase VFD? tons of youtube videos

ding ding except you want to run a VFD when you can for compressors since AC-DC-AC is done with no moving parts and minimal efficiency losses. Overall still more efficient than a single phase motor believe it or not.

The conversion to single phase is complete and it turned out great.

 

[JayPBC]

This kind of circuit with capacitors is quite inefficient and provides no control on speed, nor avoids the big current absorption at start.
Furthermore your description seems applicable only for those few sites where 220V is provided by two opposite phases. Usually 220V is provided by just a single phase and the neutral wire, so you need that the circuit generates TWO missing phases, not just one.
A good VFD avoids all these problems and runs with efficiency better than 95%. I do not see why this simple, cheap and reliable solution is facing such an opposition here...

I converted the compressor to 240v single phase and its working great.

 

[Gone for diving]

This kind of circuit with capacitors is quite inefficient and provides no control on speed, nor avoids the big current absorption at start.
Furthermore your description seems applicable only for those few sites where 220V is provided by two opposite phases. Usually 220V is provided by just a single phase and the neutral wire, so you need that the circuit generates TWO missing phases, not just one.
A good VFD avoids all these problems and runs with efficiency better than 95%. I do not see why this simple, cheap and reliable solution is facing such an opposition here...

Not disagreeing, vdf sure are nice, I have done it a bunch of times,
When you have machine shop style equipment sometimes a roto is nicer,
Especially when there are 220v, 375v, 475v, 600v.

But I have had a 600v 2 speed 3phase motor. The motor was a really weird thing, with a 10 inch shaft coming off it,

I stepped up 220v to 600v single phase, then input it into a 600 vdf, works like a charm,

 

[BRT]

When I think of a rotary phase converter,
I am not thinking of that style.
I am thinking of a 220v 3phase motor with a contol box with capacitors,
There is a bunch of start caps to get it running, then those drop out of the system, once spinning the 3phase motor will run and create a simulated third leg,
That a simple roto phaser, it's like a spinning transformer,
To make it better , capacitors are added to the 2 hot 220v to balance out the missing third leg and get the voltage up,
If you need high voltages, install a step up transformer,, the more motors spinning on the 3 phase side the more true the 3phase becomes,,,
I have built a few of these, work well if you have multiple motors to run,
Look up static phaser, that's as basic as it gets, then you just add more capacitors,

If you have one compressor only, go vdf much simpler and nicer,

Only provides 2/3 of the motor capacity.

 

[Gone for diving]

For a single motor, only


The more motors spinning on the 3 phase side the more true the 3phase becomes,,,
If you have multiple motors start the smaller ones first, they clean up the 3phase, and act as rotary batteries to help the big one,

Again it's not that way with a single motor,
Except for the spinning roto phaser

 

[PBcatfish]

This kind of circuit with capacitors is quite inefficient and provides no control on speed, nor avoids the big current absorption at start.
Furthermore your description seems applicable only for those few sites where 220V is provided by two opposite phases. Usually 220V is provided by just a single phase and the neutral wire, so you need that the circuit generates TWO missing phases, not just one.
A good VFD avoids all these problems and runs with efficiency better than 95%. I do not see why this simple, cheap and reliable solution is facing such an opposition here...

Wiring in the US & Italy is different. In Italy, you have single phase 220vac 50hz for house power & no 120vac. Industrial power is most often 380vac 3phase 50hz.

In the US, there is 120vac & 220vac single phase 60hz for house power. The 120 is one leg of the 220 going to a neutral. The 220 is two hot legs & requires a double breaker. The US also has many voltages of 3 phase, all 60 hz. They include 208, 220, 240, 480. Somehow 277 single phase is a by-product of one of them.

When electrical equipment is shipped from Italy to me in the US, I always try to check the neutral circuits before applying power. They are almost never wired correctly to US code. It seems that the US system is not well understood in Italy, even when speaking with electrical engineers that I know over there.

Then again, I had a hard time understanding "Ring Circuits" that are used in homes in the UK, so it would seem that the problem is not isolated to any one group of people.

 

[PBcatfish]

Phase inverters come in 2 flavors, static & rotary.

The static ones are cheap. They are small & weigh little. Phase-A-Matic is the most common brand name. They generate a “synthetic leg” for the third phase. They need to be correctly sized to a particular motor, not oversized. They don’t handle heavy start loads as well as rotary phase inverters. They do not provide soft start nor variable speed. I ran an old Bridgeport milling machine on one for many years.

Rotary phase inverters are large & heavy. They look like electric motors without an output shaft. They are duel wound inside the case. There is both a motor & a generator on the same armature. These are very tolerant of having multiple motors running off of a single source. They easily tolerate individual motors being turned on & off while others are still running. Ronk is the most common name brand. Feel free to oversize these if you want to, but these are not so cheap. They are very durable. They are usually the best choice only in a very limited number of multi motor applications.

Variable Frequency Drives (AKA VFDs or Drives) are a class of electronic motor controls that come in a wide variety of types. The ones you would typically use in this type of application are among the most simple. They would be the volts per hertz type. Even these simple ones are programmable. I could easily fill 10 pages with details on drives, but I’m going to keep it as short as I can here. Drives can give you variable speed, variable torque or control over other variables. When running a motor at speeds below the nameplate RPM on the motor, a drive can deliver full rated motor torque. Above nameplate RPM, torque decreases. Drives can give you variable acceleration & deceleration rates. Rates below 5 seconds beat on the drives. Rates below 1 second rally beat on the drives badly & often cause failures of the output thyristors. Almost all AC drives run 3 phase motors. Some require 3 phase primary power. Some use 1 phase primary power. It is sometimes acceptable to run a 3 phase primary drive on single phase primary power if you derate the output by around 50% Only a few types of drives require fuses between the drive & motor. Most modern ones are able to self limit current. In some applications, it is required to install line reactors between drives & mains or drives & motors to cut down on EM radiation. For this application, you can probably sneak by without that. It is often advisable to select a drive with a HP rating one size above the size of the motor you actually plan to use. If not, the drive will likely die long before the motor.

A soft starter is a device that is sort of a stripped down drive. It allows you to have the gentle acceleration, & sometimes also deceleration, that a drive gives you but it does not allow the other types of complex control that you get from a drive. Since the prices of drives have come down so far in the 30+ years that I have been buying them, & the prices of soft starts are now so close, I seldom consider a soft starter anymore.

 

[tbone1004]

@PBcatfish you forgot 600v which is standard in a lot of the older industrial locations. Very common to have 600v switchgears in the ~50+yr old buildings.

 

[Angelo Farina]

Thanks @PBcatfish . Your posts clarified everything. Particularly interesting the differences between European and US systems. I was aware of the 60 Hz vs 50 Hz, but I was thinking that also in US the 220V circuits were single phase + neutral. Now I understand how, already having two phases, it is possible to create the "third leg" with a proper passive circuit.
Still, your discussion about VFDs indicates that also in the US this is the viable solution. Here we use them for EVERYTHING has a motor: pumps, fans, HVAC systems, drills, etc...

 

[Cio]

Why all the recommendations for VFD's?

VFDs are not to be used for reciprocating machinery, there is a reason that not one manufacturer I can think of offers VFDs on recips. ( You can find harmonics with VFDs and destroy the comp head)

Using a VFD as a phase converter and not to vary speed is perfectly OK in practice, but why use such an expensive device when phase converters are available inexpensively? It's like giving grandma a corvette.

Also, the motor that comes with it is not sized for VFD duty, no drive company would sell you and warrantee a drive for this motor unless you got lucky and the motor is oversized quite a bit. Maybe you'll get away with it for homeowner duty but that doesn't mean it's technically correct.

Why is a single phase motor swap so bad? (not to a crappie motor but to a good quality on one the same frame size. ) I do this regularly and as long as you know how to adapt the cabinet to it, it is a no brainer and looks OEM when done.