Really Slow Compressors?

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Rol diy

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Yep I know you can get 110v to 220v vdf...
Tend to be expensive... but you also will have a hard time running a 3 hp on 110v.

90% yeah... that I didn't know... good to know.
 

tbone1004

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Yep I know you can get 110v to 220v vdf...
Tend to be expensive... but you also will have a hard time running a 3 hp on 110v.

90% yeah... that I didn't know... good to know.

they're pretty cheap, under $300. You can't run 3hp on a normal 110v outlet which is why they don't really make VFD's that do voltage conversion above 1.5hp since that is the limit on a 15a circuit. You MIGHT be able to squeak a 3hp motor on a 20a circuit, but not when you factor in the losses from the VFD doing phase and voltage conversion. Anything bigger than that is going to be 230v in. The way I see it with VFD's though is that they are close enough in price to a motor starter, that you are far better off getting a 3p motor which is more efficient and longer lasting than a 1p motor *and often cheaper*, and then spending a negligible amount of extra money on the VFD where you can control starting and stopping, as well as fine tune the speeds as needed vs. just buying the motor starter. For a normal 5hp compressor, a soft starter is going to be about $350, where the VFD is $550. Not a lot of extra money given how much more versatile the VFD is and not only that, the soft stop really helps in motor and compressor wear as well.

On the 90%, that was a typeo, it's typically around 80% IIRC. Some of the oiled compressor guru's may be able to comment, but it has to be around 80% since the European equivalent motors running on 50hz run around 83% the speed of their American cousins running on 60hz, but they don't like to go much slower than that.
If you put a VFD on a Rix, also remember that you are only going to be able to go down to about 20% of the rated RPM of the motor or you'll have cooling issues with it and they get pretty angry, so any slower than 20% of rated nameplate will have to be done with pulley changes or using a slower motor RPM *which is more expensive, so do what you can with pulleys before trying to go to higher pole motors
 

Open Ocean Diver

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they're pretty cheap, under $300. You can't run 3hp on a normal 110v outlet which is why they don't really make VFD's that do voltage conversion above 1.5hp since that is the limit on a 15a circuit. You MIGHT be able to squeak a 3hp motor on a 20a circuit, but not when you factor in the losses from the VFD doing phase and voltage conversion. Anything bigger than that is going to be 230v in. The way I see it with VFD's though is that they are close enough in price to a motor starter, that you are far better off getting a 3p motor which is more efficient and longer lasting than a 1p motor *and often cheaper*, and then spending a negligible amount of extra money on the VFD where you can control starting and stopping, as well as fine tune the speeds as needed vs. just buying the motor starter. For a normal 5hp compressor, a soft starter is going to be about $350, where the VFD is $550. Not a lot of extra money given how much more versatile the VFD is and not only that, the soft stop really helps in motor and compressor wear as well.

On the 90%, that was a typeo, it's typically around 80% IIRC. Some of the oiled compressor guru's may be able to comment, but it has to be around 80% since the European equivalent motors running on 50hz run around 83% the speed of their American cousins running on 60hz, but they don't like to go much slower than that.
If you put a VFD on a Rix, also remember that you are only going to be able to go down to about 20% of the rated RPM of the motor or you'll have cooling issues with it and they get pretty angry, so any slower than 20% of rated nameplate will have to be done with pulley changes or using a slower motor RPM *which is more expensive, so do what you can with pulleys before trying to go to higher pole motors
Hi tbone, can you please send me a link for the VFD? I’m very interested in a VFD that can produce 3phase 220 volts from 115. Thanks
 

Rol diy

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I have used a 220v 1 phase transformer to 575v 1phase. Then input it into a 575v vdf using only single phase instead of 3 phase.
To get 575v 3 phase output.
You should derate the vdf abit. But it works well. And don't need a roto phaser.
Have a drill press with a real goofy motor and was no good way to covert it to single phase. Now it works great and got tons of speed control.
The price of vdf have dropped like crazy.
You can get Chinese ones for like 130$ for 3 hp... but I wouldn't try pushing them to hard... always get one hp higher if you can.
16242442086255389562109547922609.jpg
16242443149846531274771079375926.jpg

My travel compressor.
interchangeable gas to electric... with my 110v 220v adapter
 

Open Ocean Diver

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I’ve done that, also have run them from DC. I think we usually double the HP, so for 3 we would use a 5 or 7.5 HP. I’ve never seen a VFD that will run from 115 and produce 220 without a transformer.
 

tbone1004

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These are the 1.5hp's, you can change the filters for different hp ratings
1.5hp vfd | 1.5 horsepower variable frequency drive

Allen Bradley and all of the big boy VFD manufacturers also make them up to 1.5hp.

@Rol diy the 575v motor likely came out of a textile mill, fun fact and are definitely not dual voltage motors.
 

Open Ocean Diver

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These are the 1.5hp's, you can change the filters for different hp ratings
1.5hp vfd | 1.5 horsepower variable frequency drive

Allen Bradley and all of the big boy VFD manufacturers also make them up to 1.5hp.

@Rol diy the 575v motor likely came out of a textile mill, fun fact and are definitely not dual voltage motors.
Oh ya I’m familiar with those. I miss understood I thought you found a drive that will run on 115 and produce 220 3phase.

I use a rotary phase converter and a transformer In my shop to test and repair VFD’s.
 

Rol diy

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115v 1phase input to 220v 3 phase output.
Is that what you are looking for??

Yes they make that.
They are nice. you do not need any type of phaser.

I also have used 1phase 220v input to 380v 3 phase output. And used it on my 600v 3phase lathe motor... I know the hp will be less but it works great... plus fwd and rev are all built into the vdf!!!!
 

tbone1004

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Oh ya I’m familiar with those. I miss understood I thought you found a drive that will run on 115 and produce 220 3phase.

I use a rotary phase converter and a transformer In my shop to test and repair VFD’s.

They do, that's what I'm using on my Rix compressors as well as my Masterline booster
 

Open Ocean Diver

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We installed this on a pump at an asphalt plant. Not sure how they boost the output voltage.

upload_2021-6-23_9-11-34.jpeg
 

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