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

[tbone1004]

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.

1. Cheaper than a single phase motor, soft starter, and rewiring the box. Also generally easier for most people to install than trying to rewire the whole box.

2. Not with single or even twin cylinders, but they are used in high cylinder counts which tends to balance the torque surge. They are used in Europe on all of these compressors that are sold new for soft starting and phase conversion.

3. Phase converters aren't appreciably cheaper and when you add in a soft starter they are more expensive.

4. The Toshiba in the original post is rated for drive duty, we use that series at work, though any of the big motor manufacturers really don't make non-drive rated 3p motors anymore. They have different grades of drive rated depending on what you're doing with it *mainly if they're going to be working on the bottom of their RPM band*, but everything now is rated for drive duty.

5. it's not, it's just often more expensive than putting a VFD on these things. For a 5hp unit you're in for ~$400 motor, ~$400 soft starter, and probably $100 in misc wiring to convert the box to single phase. Call it $900 to convert to single phase. A 10hp VFD to run the thing is about $600, and a rotary phase converter is about $1200 not including installation of the thing. So the whole thing is cheaper and easier to install and yes you are using it as a phase converter and soft starter instead of the full capabilities of the drive, but you can also use the io controls to add controls to the unit for different cutoffs if you want without having to cut power to the motor and basically have the pressure cutoff act as an E-Stop which is not great for anything.

 

[Cio]

1. Cheaper than a single phase motor, soft starter, and rewiring the box. Also generally easier for most people to install than trying to rewire the whole box.

2. Not with single or even twin cylinders, but they are used in high cylinder counts which tends to balance the torque surge. They are used in Europe on all of these compressors that are sold new for soft starting and phase conversion.

3. Phase converters aren't appreciably cheaper and when you add in a soft starter they are more expensive.

4. The Toshiba in the original post is rated for drive duty, we use that series at work, though any of the big motor manufacturers really don't make non-drive rated 3p motors anymore. They have different grades of drive rated depending on what you're doing with it *mainly if they're going to be working on the bottom of their RPM band*, but everything now is rated for drive duty.

5. it's not, it's just often more expensive than putting a VFD on these things. For a 5hp unit you're in for ~$400 motor, ~$400 soft starter, and probably $100 in misc wiring to convert the box to single phase. Call it $900 to convert to single phase. A 10hp VFD to run the thing is about $600, and a rotary phase converter is about $1200 not including installation of the thing. So the whole thing is cheaper and easier to install and yes you are using it as a phase converter and soft starter instead of the full capabilities of the drive, but you can also use the io controls to add controls to the unit for different cutoffs if you want without having to cut power to the motor and basically have the pressure cutoff act as an E-Stop which is not great for anything.

1. You still need to rewire the box, incoming power has changed; the VFD needs to be integrated to the existing starter and only takes care of the motor, the controls still need to be powered correctly. (the existing incoming 480 most likely goes to a transformer for conversion. ) Same work here no matter which way you go.

2. VFD balancing torque surge? I'm referring to speed, it is best to keep the manufactures fixed speed and not vary it. (seems like we are in agreement on that) Are there benefits to using a VFD with regards to loads and such, arguably, yes. (you can use a fancy overload and get most of that functionality BTW) But I still don't know any recip manufacture that would bless a variable speed recip, no matter how may cylinders it has, it is about harmonic vibration and wanting to stay with a tested speed that doesn't create them.

3. When I say phase converter for this application, I am referring to basically a solid state fixed speed VFD, these items are sold for this exact purpose and although not way cheaper they are less expensive than a VFD. Soft starters are VFDs, there are units sold as soft starters that can do this all by themselves.

4. the motor being rated for drive duty is not the same as it being correctly sized for the application. It is uncommon for a machine to be properly converted to VFD without replacing the motor. VFD requires larger motors than a hard starter would. Running the VFD at and only at OEM speeds does alleviate this to some extent but does not account for the soft start loads which are more strenuous on the windings than hard starting. (you'll have to wait a little bit for a failure)

5. Your a cave diver, fault points. VFDs break, add to that, that this is a non OEM configuration, not approved by a drive engineer and you have a recipe for a break down. (not likely to be quick either, the motor will take a beating for a while before failure. )

 

[BRT]

1. You still need to rewire the box, incoming power has changed; the VFD needs to be integrated to the existing starter and only takes care of the motor, the controls still need to be powered correctly. (the existing incoming 480 most likely goes to a transformer for conversion. ) Same work here no matter which way you go.

2. VFD balancing torque surge? I'm referring to speed, it is best to keep the manufactures fixed speed and not vary it. (seems like we are in agreement on that) Are there benefits to using a VFD with regards to loads and such, arguably, yes. (you can use a fancy overload and get most of that functionality BTW) But I still don't know any recip manufacture that would bless a variable speed recip, no matter how may cylinders it has, it is about harmonic vibration and wanting to stay with a tested speed that doesn't create them.

3. When I say phase converter for this application, I am referring to basically a solid state fixed speed VFD, these items are sold for this exact purpose and although not way cheaper they are less expensive than a VFD. Soft starters are VFDs, there are units sold as soft starters that can do this all by themselves.

4. the motor being rated for drive duty is not the same as it being correctly sized for the application. It is uncommon for a machine to be properly converted to VFD without replacing the motor. VFD requires larger motors than a hard starter would. Running the VFD at and only at OEM speeds does alleviate this to some extent but does not account for the soft start loads which are more strenuous on the windings than hard starting. (you'll have to wait a little bit for a failure)

5. Your a cave diver, fault points. VFDs break, add to that, that this is a non OEM configuration, not approved by a drive engineer and you have a recipe for a break down. (not likely to be quick either, the motor will take a beating for a while before failure. )

Soft starts are not VFD's. They don't have the capability to change frequency, only to clip voltage.

 

[PBcatfish]

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.

I'm going to need to put a pin in this & respond in greater detail when I have time, but just a few quick comments for now -

VFD's are nice because they give you a soft start & variable speed. The soft start can, under certain circumstances, give you a lower starting current & allow you to run a compressor on a smaller capacity circuit without tripping a breaker. If you run at a lower speed, you may enjoy lower noise, a cooler running compressor & less wear. You may also overheat the compressor, if the compressor is now getting insufficient cooling because the fan is also running slower. Running above nameplate RPM would give reduced torque & likely cause problems, especially at higher pressures.

I have used VFD's on a lot of reciprocating machines including reciprocating saws, punch presses, & compressors.

I could write a book about harmonics. That's a big can of worms to open. The electrical codes still haven't caught up to the physical realities of all the drives that are out there. This is not a 5 minute discussion and probably belongs in a different forum.

Drives are so cheap now that they can sometimes be had for maybe 30% more than the price of a static phase inverter. That being said, I priced out a static inverter last night & may use it for a simple application that I have in the shop right now. They still have their place in this world, although it has shrunken quite a bit.

Non drive rated motors don't beat on the drive. The drive beats on non-drive rated motors. Read up on Corona effect. Here too, I could write a book. The bottom line is that any time you use a drive, you are supposed to use a drive rated motor. 90+% of the time, you get away with running a regular motor on a drive for several years with no problems.

I used to disallow a lot of warranty claims on drives. 90+% were either for wiring mistakes, or people that went inside the part of the box that they were told not to. People who set the acceleration rate to 0.1 seconds were treated on a case by case basis. I didn't deny any claims over motor type, but hey, maybe somebody else did. I would not honor a motor warranty on a non-drive rated motor that was run off of a drive, especially if the windings were burned in small areas.

If you can get a single phase motor of the same frame size as an original 3 phase motor, then a single phase motor swap is easy. You just need to add a jumper wire in the magnetic starter to keep all three phases of the overload relay properly energized and make sure that the control wiring runs off of the two phases that are still hot.

If you add a drive or phase inverter, rather than changing motors, then you have the option of running off of single phase or three phase in the future. Three phase generally gives a little better performance & is usually cheaper to run.

 

[PBcatfish]

Soft starts are not VFD's. They don't have the capability to change frequency, only to clip voltage.

Please check on that.

 

[Cio]

I'm going to need to put a pin in this & respond in greater detail when I have time, but just a few quick comments for now -

VFD's are nice because they give you a soft start & variable speed. The soft start can, under certain circumstances, give you a lower starting current & allow you to run a compressor on a smaller capacity circuit without tripping a breaker. If you run at a lower speed, you may enjoy lower noise, a cooler running compressor & less wear. You may also overheat the compressor, if the compressor is now getting insufficient cooling because the fan is also running slower. Running above nameplate RPM would give reduced torque & likely cause problems, especially at higher pressures.

I have used VFD's on a lot of reciprocating machines including reciprocating saws, punch presses, & compressors.

I could write a book about harmonics. That's a big can of worms to open. The electrical codes still haven't caught up to the physical realities of all the drives that are out there. This is not a 5 minute discussion and probably belongs in a different forum.

Drives are so cheap now that they can sometimes be had for maybe 30% more than the price of a static phase inverter. That being said, I priced out a static inverter last night & may use it for a simple application that I have in the shop right now. They still have their place in this world, although it has shrunken quite a bit.

Non drive rated motors don't beat on the drive. The drive beats on non-drive rated motors. Read up on Corona effect. Here too, I could write a book. The bottom line is that any time you use a drive, you are supposed to use a drive rated motor. 90+% of the time, you get away with running a regular motor on a drive for several years with no problems.

I used to disallow a lot of warranty claims on drives. 90+% were either for wiring mistakes, or people that went inside the part of the box that they were told not to. People who set the acceleration rate to 0.1 seconds were treated on a case by case basis. I didn't deny any claims over motor type, but hey, maybe somebody else did. I would not honor a motor warranty on a non-drive rated motor that was run off of a drive, especially if the windings were burned in small areas.

If you can get a single phase motor of the same frame size as an original 3 phase motor, then a single phase motor swap is easy. You just need to add a jumper wire in the magnetic starter to keep all three phases of the overload relay properly energized and make sure that the control wiring runs off of the two phases that are still hot.

If you add a drive or phase inverter, rather than changing motors, then you have the option of running off of single phase or three phase in the future. Three phase generally gives a little better performance & is usually cheaper to run.

Reciprocating saws and punch presses are not examples that reflect the type of vibrations we are discussing, surly with you book writing skills, you are aware of this. compressors; screw type are not reciprocating but rotating so not applicable to this discussion (they do benefit from VFDs) and reciprocating compressors, are not meant to run at varying speeds, that's a fact and why most use unloaders and none come with VFDs.

Running at lower speed will not reduce wear, it will increase it, if you look at it from a wear to CF produced. This is because at lower RPM you will have increased slip and lower efficiency. You also won't know when to change the element or you will be changing the element before it is is due on a CF processed basis so filtration cost is up as well. (there are non worthwhile solutions to this but lets keep the approach reasonable ). Also, you forget about oil pressure? I guess that's not so important....

speeding it up will not reduce torque to any real extent, torque load is developed by the pressure on the piston faces and is primarily related to outlet pressure (which still won't affect torque all that much since it is only varies one stage and still needs to meet a minimum pressure) , all that remains relatively constant. So , actually, HP demand increases, torque remains very much the same. You are right it will cause problems, most importantly, you are increasing the heat load so proper cooling will not occur which has nothing to do with pressure and everything to do with mass flow and cooler sizing.

Running one of these compressors at a speed not on the nameplate or varying the speed is dumb and the argument for such operation is nonsensical. A legit book could be written on how this affects the different systems and therefore ill advised. (oil, fan cooling, heat rejection...)

His compressor is 480, its not as simple as you state to convert, there is likely a transformer. not difficult but not just a jumper either.

As far a being able to write a book on harmonics, I am not capable like you are, but I know that a reciprocating compressor can create harmonics and it is best to run nameplate RPM to avoid running in the magic RPM. Please reference a manufacturer that runs a recip at varying speeds, three conditions, the manufacturer is a reputable one, not one from Alibaba, the machine has some commonality (reciprocating) with what we are discussing and the VFD isn't simply used top meet a code and is then run at steady speed. I don't think this is a staunch recipe for destruction but recommending that the operation speed be changed is bad advise in general, recomending it on a thread to a guy who isnt sure how to change phase requirements is piss poor advice.

I don't need to read up on corona effect to understand basic VFD/ motor principals, I did not state the drive would get beat up, it is, as you say, the motor that will take the beating. My statement was that the motor should be a drive rated motor, AND be sized correctly for the application. a 75HP drive rated motor is rarely used on a 75 HP machine, it is more likely a 100HP motor. Due to operational conditions, the windings may need to be sized to handle more amperage than a 75 can handle. This is application specific and if a VFD is being used as a steady state drive with soft start, it is less applicable but it still remains poor practice to simply add a VFD to an existing motor and think it should be fine. In the case of this compressor we are discussing, compressors have higher than typical parasitic loads on startup, I'd imagine that would push the application up a motor size.

Your a nice guy, allowing warrantee claims on VFDs due to incorrect wiring or dumb techs with screw drivers, I should buy drives from you. (I'm serious) My experience has been that VFDs are overall very reliable and warrantee claims just don't happen unless it happens when the unit is very new. Most issues fail from dirt and dust, warrantee claims are finger pointing contests and the customer pays for a new drive (typically, rightfully so) . The big issue with VFDs is that when they break, you can't just go get a starter and fix it that day like a hard start. I'm in NJ so we can get drives repaired locally but equipment is still down for days. VFDs do have their place but they are overused and the cost/ benefit isn't there to justify it's use.

I agree three phase is better in general but adding a VFD or phase converter of some kind negates most of the advantage vs a hard start single phase.

I also agree on your please check on that @PBcatfish needs to call his local drive guy and get some updated soft starters. I have herd of these types of soft starters but never saw one or understand how it could work reliably, maybe they do exist?

 

[tbone1004]

@Cio
his 480v compressor is easy to switch to 240v by changing the jumper configuration in the motor. If you look at the dataplate it has 230/460 on it so will happily run at either voltage.
I don't believe any of us have recommended using a VFD to vary the speed, only to take advantage of phase conversion and soft start/stop.
With regards to a reciprocating compressor run at different speeds. Bauer, need we say more? The Junior II is sold in otherwise identical configurations with nameplate RPM from 1500rpm up to 2300rpm. Same pump, just different rated RPM's based on the motor configuration. The Vertecon 4-stage is sold from 1180 up to 1420rpm *admittedly a narrow band*, and the K14 was sold in configurations *and this is from memory so don't shoot me if it's a bit off* from about 950rpm up to 1500rpm. Again, these are all fairly narrow RPM ranges because cooling, splash lubrication, and the oil pump have fairly narrow RPM ranges where they work effectively, but they are out there. For this though, we aren't talking about changing the RPM though, so I don't know why you're harping on that.

I will agree with you that the simplest course of action is to hard start a single phase motor and if your electrical system can handle it then by all means, it's not really going to do a whole lot, but one of my friends was talking about his 5hp compressor and that it starts fine at home but blows breakers when travelling. His shop is wired a bit overkill and can handle the huge inrush current of starting a compressor under full load from 0, but most can't. Most people will try to find pumps that maximize output based on their breakers that are already wired in and the harsh reality is that a 5hp motor rated to pull 20a on a 1p/240v circuit will most likely trip a standard 30a breaker so you need to soft start them. This is very different than looking at industrial applications where you have 3p power already and you also have the infrastructure to handle hard starts. I went down this path after talking to the drives engineer that did all of the work at the mill and what the best course of action was when dealing with the compressor build that I wanted and while it's not the simplest, it's certainly the best especially since it allows full PLC control if you want to head down that path *which I did with temp/pressure measurement on each stage as well as the nitrox stick*

 

[Cio]

@Cio
his 480v compressor is easy to switch to 240v by changing the jumper configuration in the motor. If you look at the dataplate it has 230/460 on it so will happily run at either voltage.
I don't believe any of us have recommended using a VFD to vary the speed, only to take advantage of phase conversion and soft start/stop.
With regards to a reciprocating compressor run at different speeds. Bauer, need we say more? The Junior II is sold in otherwise identical configurations with nameplate RPM from 1500rpm up to 2300rpm. Same pump, just different rated RPM's based on the motor configuration. The Vertecon 4-stage is sold from 1180 up to 1420rpm *admittedly a narrow band*, and the K14 was sold in configurations *and this is from memory so don't shoot me if it's a bit off* from about 950rpm up to 1500rpm. Again, these are all fairly narrow RPM ranges because cooling, splash lubrication, and the oil pump have fairly narrow RPM ranges where they work effectively, but they are out there. For this though, we aren't talking about changing the RPM though, so I don't know why you're harping on that.

I will agree with you that the simplest course of action is to hard start a single phase motor and if your electrical system can handle it then by all means, it's not really going to do a whole lot, but one of my friends was talking about his 5hp compressor and that it starts fine at home but blows breakers when travelling. His shop is wired a bit overkill and can handle the huge inrush current of starting a compressor under full load from 0, but most can't. Most people will try to find pumps that maximize output based on their breakers that are already wired in and the harsh reality is that a 5hp motor rated to pull 20a on a 1p/240v circuit will most likely trip a standard 30a breaker so you need to soft start them. This is very different than looking at industrial applications where you have 3p power already and you also have the infrastructure to handle hard starts. I went down this path after talking to the drives engineer that did all of the work at the mill and what the best course of action was when dealing with the compressor build that I wanted and while it's not the simplest, it's certainly the best especially since it allows full PLC control if you want to head down that path *which I did with temp/pressure measurement on each stage as well as the nitrox stick*

Yes, jumping the motor is simple as is changing the motor starter system in general but the controls need to get the proper voltage as well, that's what I am referring to. The Bauer Junior II is pretty skinny on controls but will require proper control voltage, at minimum the unloader solenoid needs to be powered correctly.

The post I was replying to is mentioning higher and lower speeds, just trying to voice an rational approach and not let a reader think this is advisable.

You are correct that Bauer sells the same pump in a few different speed variations as do many recip manufacturers. Each of those RPMs are run and tested by Bauer so they would be safe to run at, varying the speed on your own is ill advised was my point. It can be done with the proper know how but I figured that was outside the scope of this post.

I do disagree with you on a 5HP motor tripping a properly sized breaker, that's not normal and an indicator that something else is wrong (maybe just the service). In some cases a soft starter is just an easy solution, especially if you travel with it, so I don't think the recommendation is bad, but anyone experiencing this should look for a root cause just top make sure there's no fire danger.

I do agree with PLC your based control approach, especially integrating your nitrox into it, there is a real danger of runaway O2 in the systems I have seen and that can go all kinds of wrong. Did you use rebreather O2 sensors or did you just get an industrial O2 sensor?

 

[BRT]

Please check on that.

I've been installing both since 1987. Soft starts clip the wave so the voltage and current are limited. They still run at 60 hz

 

[BRT]

Reciprocating saws and punch presses are not examples that reflect the type of vibrations we are discussing, surly with you book writing skills, you are aware of this. compressors; screw type are not reciprocating but rotating so not applicable to this discussion (they do benefit from VFDs) and reciprocating compressors, are not meant to run at varying speeds, that's a fact and why most use unloaders and none come with VFDs.

Running at lower speed will not reduce wear, it will increase it, if you look at it from a wear to CF produced. This is because at lower RPM you will have increased slip and lower efficiency. You also won't know when to change the element or you will be changing the element before it is is due on a CF processed basis so filtration cost is up as well. (there are non worthwhile solutions to this but lets keep the approach reasonable ). Also, you forget about oil pressure? I guess that's not so important....

speeding it up will not reduce torque to any real extent, torque load is developed by the pressure on the piston faces and is primarily related to outlet pressure (which still won't affect torque all that much since it is only varies one stage and still needs to meet a minimum pressure) , all that remains relatively constant. So , actually, HP demand increases, torque remains very much the same. You are right it will cause problems, most importantly, you are increasing the heat load so proper cooling will not occur which has nothing to do with pressure and everything to do with mass flow and cooler sizing.

Running one of these compressors at a speed not on the nameplate or varying the speed is dumb and the argument for such operation is nonsensical. A legit book could be written on how this affects the different systems and therefore ill advised. (oil, fan cooling, heat rejection...)

His compressor is 480, its not as simple as you state to convert, there is likely a transformer. not difficult but not just a jumper either.

As far a being able to write a book on harmonics, I am not capable like you are, but I know that a reciprocating compressor can create harmonics and it is best to run nameplate RPM to avoid running in the magic RPM. Please reference a manufacturer that runs a recip at varying speeds, three conditions, the manufacturer is a reputable one, not one from Alibaba, the machine has some commonality (reciprocating) with what we are discussing and the VFD isn't simply used top meet a code and is then run at steady speed. I don't think this is a staunch recipe for destruction but recommending that the operation speed be changed is bad advise in general, recomending it on a thread to a guy who isnt sure how to change phase requirements is piss poor advice.

I don't need to read up on corona effect to understand basic VFD/ motor principals, I did not state the drive would get beat up, it is, as you say, the motor that will take the beating. My statement was that the motor should be a drive rated motor, AND be sized correctly for the application. a 75HP drive rated motor is rarely used on a 75 HP machine, it is more likely a 100HP motor. Due to operational conditions, the windings may need to be sized to handle more amperage than a 75 can handle. This is application specific and if a VFD is being used as a steady state drive with soft start, it is less applicable but it still remains poor practice to simply add a VFD to an existing motor and think it should be fine. In the case of this compressor we are discussing, compressors have higher than typical parasitic loads on startup, I'd imagine that would push the application up a motor size.

Your a nice guy, allowing warrantee claims on VFDs due to incorrect wiring or dumb techs with screw drivers, I should buy drives from you. (I'm serious) My experience has been that VFDs are overall very reliable and warrantee claims just don't happen unless it happens when the unit is very new. Most issues fail from dirt and dust, warrantee claims are finger pointing contests and the customer pays for a new drive (typically, rightfully so) . The big issue with VFDs is that when they break, you can't just go get a starter and fix it that day like a hard start. I'm in NJ so we can get drives repaired locally but equipment is still down for days. VFDs do have their place but they are overused and the cost/ benefit isn't there to justify it's use.

I agree three phase is better in general but adding a VFD or phase converter of some kind negates most of the advantage vs a hard start single phase.

I also agree on your please check on that @PBcatfish needs to call his local drive guy and get some updated soft starters. I have herd of these types of soft starters but never saw one or understand how it could work reliably, maybe they do exist?

If varying speeds on compressors is always bad why do compressor manufacturers do it when they sell the same compressor with a smaller or bigger motor?