Building a smarter air compressor-- my Champion Project compressor

Hohn

Hohn

Joined
Jul 29, 2005
Messages
3,476
Location
Diesel Central, Indiana
In later 2024 I was perusing the Marketplace and stumbled across an ad that caught my eye: "Industrial air compressors, $200 each"

Scrolling through a couple, the distinctive green Champion caught my eye. I knew they are highly regarded so I beat feet to go check it out after work. I figured if only the pump was good and the tank and motor were junk it was still worth the asking price. (The R15b pump alone is over $2000). And even if the pump needed a little work, you can get every part needed for a full rebuild with little effort. I bought the compressor and made a call to buddy who has the trailer and some well-trained helpers.

1783533642843.webp



At home, I had a chance to survey what I had:

R15b pump, free spinning, very clean oil, appears in perfect working order.
3 Ph Baldor 4 pole motor, unknown condition
Belts worn
Lots of grime and evidence of leakage
Automatic tank drain
Oil level warning system

So I dive in and start disassembly and cleaning.
1783533909164.webp


About a gallon of mineral spirits later, we have this:

1783533944378.webp




So begins the process of testing for function.

Most important is probably the motor since they are by far the most likely failure on a compressor.

1783534041700.webp



Motor shop connects it to 3ph power and it jumps to life instantly! Gobs of torque and almost no play in the bearings at all. They said the motor is in great condition, just give it a hit of grease in each zerk and put it to work.

Pump inspection appears to be OK, but there's not much I can do to truly inspect it. If I took it apart, I'd be foolish to put the old parts back in, so I'm calling the pump good based on how good it feels barring over and how clean the oil is. The only "Restoration" the pump needs was some fresh premium HPL recip-life oil and a bit of cleaning.

The final piece was assessing the tank. With an automatic drain installed, you'd think a tank would be in good shape, but the auto drain setup in these is sort of wonky and not reliable (it's often removed).

I plumbed the big compressor to my recently completed shop air piping and used my small 120V compressor to pressurize it. The check valve was leaking, but after replacing that the big tank is tight like a tiger. The tank is solid.

(image removed - MOD)


So after part time attention over two years, the Champion now has:
Good Tank✅
Good Motor✅
Good pump✅
Auto Tank Drain removed ✅
No more oil monitor puking oil✅
Brand new BX65 belts✅

Which means it's time to conquer the final hurdle: running it on 3ph power at home.
 
Last edited by a moderator:
Hohn said:
In later 2024 I was perusing the Marketplace and stumbled across an ad that caught my eye: "Industrial air compressors, $200 each"

Scrolling through a couple, the distinctive green Champion caught my eye. I knew they are highly regarded so I beat feet to go check it out after work. I figured if only the pump was good and the tank and motor were junk it was still worth the asking price. (The R15b pump alone is over $2000). And even if the pump needed a little work, you can get every part needed for a full rebuild with little effort. I bought the compressor and made a call to buddy who has the trailer and some well-trained helpers.

View attachment 346936


At home, I had a chance to survey what I had:

R15b pump, free spinning, very clean oil, appears in perfect working order.
3 Ph Baldor 4 pole motor, unknown condition
Belts worn
Lots of grime and evidence of leakage
Automatic tank drain
Oil level warning system

So I dive in and start disassembly and cleaning.
View attachment 346937

About a gallon of mineral spirits later, we have this:

View attachment 346938



So begins the process of testing for function.

Most important is probably the motor since they are by far the most likely failure on a compressor.

View attachment 346939


Motor shop connects it to 3ph power and it jumps to life instantly! Gobs of torque and almost no play in the bearings at all. They said the motor is in great condition, just give it a hit of grease in each zerk and put it to work.

Pump inspection appears to be OK, but there's not much I can do to truly inspect it. If I took it apart, I'd be foolish to put the old parts back in, so I'm calling the pump good based on how good it feels barring over and how clean the oil is. The only "Restoration" the pump needs was some fresh premium HPL recip-life oil and a bit of cleaning.

The final piece was assessing the tank. With an automatic drain installed, you'd think a tank would be in good shape, but the auto drain setup in these is sort of wonky and not reliable (it's often removed).

I plumbed the big compressor to my recently completed shop air piping and used my small 120V compressor to pressurize it. The check valve was leaking, but after replacing that the big tank is tight like a tiger. The tank is solid.

(image removed - MOD)


So after part time attention over two years, the Champion now has:
Good Tank✅
Good Motor✅
Good pump✅
Auto Tank Drain removed ✅
No more oil monitor puking oil✅
Brand new BX65 belts✅

Which means it's time to conquer the final hurdle: running it on 3ph power at home.
Click to expand...
You want to run a 3 phase motor at home?
Make sure the motor is wired for 208/240 and get a single phase 240v input VFD.
 
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There are a couple way to power three phase motors at home:

1) Rotary Phase Converter (RPC)
2) Variable Frequency Drive (VFD)
3) DPS-- Digital Phase shifter

The rotary phase converter is the best way to make an entire shop full of 3 phase motors happy. But for a single motor, it's way too expensive to be worthwhile.

The DPS gets ruled out pretty fast when you see that the virtual 3rd phase is basically carrying no load (3a or less on that leg) and its essentially running as two phase once the motor is started. Ruled this out as penny wise, pound foolish.


Which leaves the Variable Frequency Drive as the intriguing last option. They are cost effective and enable all kinds of cool control options. Because they are inverter based, all three phases are balanced and the motor has full power and runs cool.

Many VFDs are from mysterious companies of no support, while the other extreme of industrial grade units is often quite a bit more expensive than a new motor. I found a middle of the road option from Automation Direct. Taiwanese made, USA-based support, company in business a long time with a real history. (buy VFDs off Amazon at your peril).

While it's triple the price of a Vevor-grade unit, it also has some advanced PLC function built in. This will be relevant later. And it's still cheaper than replacing the motor with single phase.


Before pulling the trigger on the VFD, I finalized a control strategy based on what this VFD will support. The strategy not only involves a traditional pressure switch (145/175), but a pressure tranducers (Dwyer Omega PX119, 4-20ma output, 200psi).


This is where the "smarter" comes in.... advanced control.
 
The particular VFD I've settled on has some fairly sophisticated PLC controls within in, making a separate PLC largely unnecessary. So now that the VFD is providing the ability to change motor speed and vary the output based on air pressure, what do we do with that?

PID control is a popular option. This would essentially speed up and slow down the motor as needed to maintain a fairly constant pressure. If you had a tire shop or such with significant and constant air demand, this would probably be a good way to produce little to no motor starts other than the initial one in the morning. As air demand slowed, the compressor would spin down to some minimum speed to lower output and run longer and slower (and usually, cooler).

But as home gamer and single user of air, my air demand is very erratic, with extremes from steady 20-30 SCFM for minutes at a time (die grinder, cutoffs, carbon arc gouge), or just quick pops of the needle scaler between weld passes to remove slag and peen the pass or the Roloc touch ups to remove paint or rust, or a couple bolts with the impact or air ratchet.

Because of my erratic duty cycle, a PID control on the compressor would have a lot of motor starts. Even with a really sophisticated soft start, more starts is worse than fewer.


But starting for its own sake isn't the reason we care about frequent starts. HEAT is why we care about frequent starts. This is where we have to consider the ODP nature of this particular Baldor motor. One of the selling points of VFDs is that you can slow motors down to run them cooler. But an ODP motor-- unlike a TEFC-- does not run cooler when you slow it down because you are also slowing down the airflow that cools it.

Moreover, slowing down the ODP motor in a recip compressor application doesn't make it much quieter (it's mostly lower pitch, not lower volume), it doesn't improve efficiency, and it doesn't run the motor cooler.


So slowing the compressor down--while safe within limits--doesn't really improve anything for the compressor's life. Leaving it at 60hz means it runs coolest once shut down and heat soaking.

But, can we speed the motor up and get more air when needed? YES WE CAN!

This is where this particular compressor is well-suited to a "high output" mode. The Champion R15b pump has a rated speed range from 400-1050 rpm. As configured by Champion, but 5hp model runs the pump at 710 rpm at 60hz. The higher pump speeds are the realm of the larger 7.5hp model compressor.

But of course, that 7.5hp motor is nowhere near 7.5hp or actual load for most of the pressure range of the compressor. Indeed, at lower pressures of 100-120psi, the 7.5hp compressor is probably loaded its motor to only 5hp or so. You see where we're going with this, right?

By using the VFD to speed up the pump at lower pressures, we can get significantly more air output (rivaling the 7.5hp models) from a standard 5hp motor.

A standard induction motor on a VFD operates at constant power above its rated frequency and at constant torque below its rated frequency. So at 80-85hz, we've traded roughly 40% more speed for roughly 40% less torque ability. But this is also 40% more air.

But at low pressures, we can still spin the pump with only 60% of the motor torque. This allows us to fill the tank at low pressures with 40% less time. This a pretty massive performance increase.

So, how high can we carry the pressure at this higher speed?
 
Hohn said:
There are a couple way to power three phase motors at home:

1) Rotary Phase Converter (RPC)
2) Variable Frequency Drive (VFD)
3) DPS-- Digital Phase shifter

The rotary phase converter is the best way to make an entire shop full of 3 phase motors happy. But for a single motor, it's way too expensive to be worthwhile.

The DPS gets ruled out pretty fast when you see that the virtual 3rd phase is basically carrying no load (3a or less on that leg) and its essentially running as two phase once the motor is started. Ruled this out as penny wise, pound foolish.


Which leaves the Variable Frequency Drive as the intriguing last option. They are cost effective and enable all kinds of cool control options. Because they are inverter based, all three phases are balanced and the motor has full power and runs cool.

Many VFDs are from mysterious companies of no support, while the other extreme of industrial grade units is often quite a bit more expensive than a new motor. I found a middle of the road option from Automation Direct. Taiwanese made, USA-based support, company in business a long time with a real history. (buy VFDs off Amazon at your peril).

While it's triple the price of a Vevor-grade unit, it also has some advanced PLC function built in. This will be relevant later. And it's still cheaper than replacing the motor with single phase.


Before pulling the trigger on the VFD, I finalized a control strategy based on what this VFD will support. The strategy not only involves a traditional pressure switch (145/175), but a pressure tranducers (Dwyer Omega PX119, 4-20ma output, 200psi).


This is where the "smarter" comes in.... advanced control.
Click to expand...
You can get used top name brand VFDs off ebay for good prices.
If that's still to expensive put a big 4 pole single phase motor on there with appropriate pulley and belt.
 
Running the pump faster produces more air, for sure. But it turns out that two-stage compressor pumps, by virtue of their efficiency at higher pressure ratios, don't have a huge increase in motor load as a result of discharge pressure.

This is confirmed by the Champion specs for the difference compressor models that use this pump. The 175psi ratings that use a 5hp motor run the pump at 734 rpm, while the 125psi ratings run the pump only modestly faster at 800rpm. This yields a rated output bump from 17.2SCFM to 19.1 SCFM.

By contrast, the 7.5 compressors with the same pump will run it at 990 rpm for both pressure ratings. Obviously Champion could run the pump slightly faster within their own 1050rpm limit for a 125psi rating, but chooses not to do so.


The upshot here is the lower pressure doesn't provide the chance to drastically speed up the motor. SO the "40% more air" is only true at very low pressures-- 40psi or less roughly. Which is still quite useful because it turns out that the slowest part of filling the tank is the first few moments at very low pressure.

However, there's still a useful and significant increase in air at line pressures that are useful (100psi) or more. This increase is on the order of 10% within CHampion's own estimations of motor load appropriateness.

But here's the thing-- the VFD puts YOU in charge of determining how hard you will run the motor. Let's say that champion decided that 13a motor load against the 14a FLA rating was as hard as they wanted to push it. After all, it's an industrial produce designed for 24/7/365 usage and long life. But maybe as a home hobbyist you want to trade some life you may not need for performance you want. Maybe you look at that 14a FLA and the 1.15 SF and decide that 15a is an acceptable max load, or even 16a using all that SF.


So in the final analysis, here's about how much more performance we get from running constant power on the motor staying entirely within the margin the Champion puts on the Baldor:

1783598532629.webp





And if we decided take the motor to FLA and perhaps into SF with an additional 10% nominal load:
1783598718018.webp




The final analyis suggest that a 5hp industrial compressor in home-shop usage on a VFD might be capable of effectively delivering 7.5hp compressor performance at pressure of 100psi or less.

ANd since My piping system is very low in pressure drop, a line pressure of 100psi is enough to supply my tools with 90psi of working pressure.

Which means the VFD is basically turning my $200 5hp compressor into a 7.5hp compressor in terms of real world air delivery. It's true that at the full max pressure of 175psi, the 5hp compressor is still just a 5hp compressor. But at lower pressure--in really high demand situations where it counts-- the VFD controls add a very significant amount of real world air capacity.


This, friends, is what I believe to be a "smarter" air compressor.
 
frankbee3 said:
I think the smarter part is that Hohn will never need to purchase another air compressor
Click to expand...
Rand said:
What is smarter about it? I thought maybe some sort of Computer controlled gadget 🤣
Click to expand...

See above, maybe you agree it's smarter than a fixed speed 60hz compressor.

Not only does this give near-7.5hp performance in a 5hp compressor, it makes more efficient usage of the existing single phase power.

The VFD has a maximum current draw of about 42 amps on my 240v single phase line. And realistically it will basically never in even pull this much. But to meet code I need to run 6 AWG wire and accommodate the theoretical max.


If I ran an actual single phase 7.5hp compressor, I'd be facing inrush values up to 90-100a and some brutal reactive power disruption that the power company wouldn't be too thrilled about.

But with my VFD and 5hp setup, the inrush is essentially nonexistent once the caps on the VFD are charged.

So in the end, nearly 7.5hp worth of air for a lot less peak demand and motor wear/tear from the violent starting of a 7.5hp single phase motor.
 
Hohn said:
Running the pump faster produces more air, for sure. But it turns out that two-stage compressor pumps, by virtue of their efficiency at higher pressure ratios, don't have a huge increase in motor load as a result of discharge pressure.

This is confirmed by the Champion specs for the difference compressor models that use this pump. The 175psi ratings that use a 5hp motor run the pump at 734 rpm, while the 125psi ratings run the pump only modestly faster at 800rpm. This yields a rated output bump from 17.2SCFM to 19.1 SCFM.

By contrast, the 7.5 compressors with the same pump will run it at 990 rpm for both pressure ratings. Obviously Champion could run the pump slightly faster within their own 1050rpm limit for a 125psi rating, but chooses not to do so.


The upshot here is the lower pressure doesn't provide the chance to drastically speed up the motor. SO the "40% more air" is only true at very low pressures-- 40psi or less roughly. Which is still quite useful because it turns out that the slowest part of filling the tank is the first few moments at very low pressure.

However, there's still a useful and significant increase in air at line pressures that are useful (100psi) or more. This increase is on the order of 10% within CHampion's own estimations of motor load appropriateness.

But here's the thing-- the VFD puts YOU in charge of determining how hard you will run the motor. Let's say that champion decided that 13a motor load against the 14a FLA rating was as hard as they wanted to push it. After all, it's an industrial produce designed for 24/7/365 usage and long life. But maybe as a home hobbyist you want to trade some life you may not need for performance you want. Maybe you look at that 14a FLA and the 1.15 SF and decide that 15a is an acceptable max load, or even 16a using all that SF.


So in the final analysis, here's about how much more performance we get from running constant power on the motor staying entirely within the margin the Champion puts on the Baldor:

View attachment 347032




And if we decided take the motor to FLA and perhaps into SF with an additional 10% nominal load:
View attachment 347033



The final analyis suggest that a 5hp industrial compressor in home-shop usage on a VFD might be capable of effectively delivering 7.5hp compressor performance at pressure of 100psi or less.

ANd since My piping system is very low in pressure drop, a line pressure of 100psi is enough to supply my tools with 90psi of working pressure.

Which means the VFD is basically turning my $200 5hp compressor into a 7.5hp compressor in terms of real world air delivery. It's true that at the full max pressure of 175psi, the 5hp compressor is still just a 5hp compressor. But at lower pressure--in really high demand situations where it counts-- the VFD controls add a very significant amount of real world air capacity.


This, friends, is what I believe to be a "smarter" air compressor.
Click to expand...
Then do a VFD and compound 2 stage compressor using an unloader valve.
A compound compressor runs as two single stage cylinders below say 60 to 80psi then switches to 2 stage mode above a certain pressure.
I just use single stage compressors as I have no need for more than 125psi with various soft starters.
 
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