Need help setting up a large lathe (air interlock)

[DanP]

"Hobby" lathe, that's the biggest hobby lathe I have ever seen or imagined!

 

[mcostello]

Depends what Your hobby is!

 

[MachineTom]

You may consider posting on the Practial Machinist board. Folks there a mostly industrial sized tools. Most likely someone can help you there.

 

[Entropy455]

I made a post on Practical Machinist Boards - not one reply. . . .

 

[ignator]

I made a post on Practical Machinist Boards - not one reply. . . .

They are extremely 'sensitive' to post titles. I would ask them again there with something like;
"Axelson-Clearing Model 2516 Air chuck operation question". I see your post there from July. Also ask about a schematic or manual in the post, but describe how your wanting to understand the supply pressure, and any issues about operation. They want very descriptive titles, and machine details so they don't have to ask "20 questions".

 

[ignator]

I made a post on Practical Machinist Boards - not one reply. . . .

Also don't say anything about "HOBBY" they don't play well with us.

 

[Entropy455]

I'm about to pull a permit for my second power panel. I figure I need 300 amperes at 230 volts to adequately power my phase converter (150 ampere breaker for each converter-motor). This will permit me to operate my lathe up to about 30 horsepower (the lathe has a 40 horsepower motor).

If for whatever reason 30 horsepower is not enough - and I honestly can't see that happening, considering the massive cuts required to even draw 10 horsepower - I'll bump the isolation breakers up to 200 amperes each - which will get me an honest 37 horsepower into the cutter. My gut tells me that 30 horsepower will be plenty.

My transformer is 37.5 kVA, which I share with my neighbor. My garage has 350 KCML feeders (185 foot run). My wires are fine, but the transformer may be too small - not for running the lathe, but for starting it. The lights might flicker every time I start the lathe, which will be a no-go for my wife, and for my neighbors. If this happens, I'll pay the power company to replace the 37.5 unit with 50 or 75 kVA transformer.

Before I worry about the air supply, and what it does, I'm going to focus on resolving my power-supply issues first. . . . (i.e. building my phase converter)

 

[Entropy455]

Point taken ignitor - I'll repost my question - more specific & detailed, less the word hobby. . . .

 

[ignator]

I'm about to pull a permit for my second power panel. I figure I need 300 amperes at 230 volts to adequately power my phase converter (150 ampere breaker for each converter-motor). This will permit me to operate my lathe up to about 30 horsepower (the lathe has a 40 horsepower motor).

If for whatever reason 30 horsepower is not enough - and I honestly can't see that happening, considering the massive cuts required to even draw 10 horsepower - I'll bump the isolation breakers up to 200 amperes each - which will get me an honest 37 horsepower into the cutter. My gut tells me that 30 horsepower will be plenty.

My transformer is 37.5 kVA, which I share with my neighbor. My garage has 350 KCML feeders (185 foot run). My wires are fine, but the transformer may be too small - not for running the lathe, but for starting it. The lights might flicker every time I start the lathe, which will be a no-go for my wife, and for my neighbors. If this happens, I'll pay the power company to replace the 37.5 unit with 50 or 75 kVA transformer.

Before I worry about the air supply, and what it does, I'm going to focus on resolving my power-supply issues first. . . . (i.e. building my phase converter)

Should be interesting to hear if inrush current is not a problem. I'm not aware of a VFD that can power a 40HP motor from single phase. I think the issue is they have very good phase loss detectors to protect the input diodes from failure. Someone may have more knowledge with this, as I've never used a VFD greater then 10HP from single phase, to drive 7.5HP motors. But It's clear your going down the RPC route, hope that is fruitful. Unless you're are going to do serious material removal rates, I can't imagine needing more then 5HP of spindle power. I suspect the 40HP just idling uses more then 5HP of power, most of that just inherent losses.
Hope all goes well.

 

[Entropy455]

Inrush current will be the dominant problem. The rule-of-thumb is that the converter should be twice the size of the machine's motor - which is why I'm building an 80 horsepower converter.

I estimate I'll draw 7.6 horsepower worth of electricity at idle, costing me 68 cents per hour at idle - and that's just to run the converter.

I'll take & post pictures of the phase converter construction process. I'll also post pictures of my design schematic. My experience is that rotary phase converters work very well. With an 1800 rpm fully-enclosed motor - if you select quality contactors and quality capacitors for the controls (and remember to grease the motor bearings once per year), a rotatory phase converter should run 60,000 hours before maintenance is required (essentially lasting forever).

 

[ignator]

Inrush current will be the dominant problem. The rule-of-thumb is that the converter should be twice the size of the machine's motor - which is why I'm building an 80 horsepower converter.

I estimate I'll draw 7.6 horsepower worth of electricity at idle, costing me 68 cents per hour at idle - and that's just to run the converter.

I'll take & post pictures of the phase converter construction process. I'll also post pictures of my design schematic. My experience is that rotary phase converters work very well. With an 1800 rpm fully-enclosed motor - if you select quality contactors and quality capacitors for the controls (and remember to grease the motor bearings once per year), a rotatory phase converter should run 60,000 hours before maintenance is required (essentially lasting forever).

Seems your well informed.
I started my shop out with a RPC I made from a 5HP 3600RPM motor. Worked OK, but very noisy in my 8x30 shop space. It also was a TEFC motor. I got it surplus, where it had been rebuilt at one time with new ball bearings, but whomever did this, did not remove the shield from the zerk side of the bearing. Pumped the bell housing full of grease.

But I don't have anything like a 40HP motor to spin.

 

[Entropy455]

There are three advantages of using an 1800 rpm motor for building a phase converter.

(1) they spin slow (compared to 3600 rpm) which means extended bearing life, and less audible noise during operation (fan, hum, etc)
(2) HP for HP, they have higher rotating inertia (more moving mass) than 3600 rpm motors, which provides an extra kick when starting other loads
(3) an 1800 rpm motor has appreciably more copper - which means lower impedance, which means extra kick when starting other loads
Downside is the extra copper drives the cost of the motor up.

To reduce operating noise, always use rubber isolation mounts (i.e. thick rubber sheets/sections) between the converter motor and the converter frame/chassis. Just make sure both the motor, frame, and lathe are properly grounded.

The new solid state drives are pretty trick, but expensive. A 40 horsepower unit is WAY outside of what I'm willing to spend.

I was contemplating mounting a 3-71 Detroit diesel on the other side of the shop wall, and drive the lathe directly at 1800 rpm via pto/belts (replacing the 40 hp lathe motor with a simple belt-driven jackshaft). However I cannot stand the idea of having to start a combustion engine to run my lathe. Starting a phase converter is somewhat of an irritation in itself, but at least I don't have to feed it diesel, change its oil, or keep its battery charged. . .

3 phase power ends about 2 miles down the road. It would cost well over 100 grand to bring it to my house. Maybe if I win the lotto. . .? Until then, rotary converters are the ticket - especially when constructed from scratch to keep costs down.

 

[ignator]

There are three advantages of using an 1800 rpm motor for building a phase converter.

(1) they spin slow (compared to 3600 rpm) which means extended bearing life, and less audible noise during operation (fan, hum, etc)
(2) HP for HP, they have higher rotating inertia (more moving mass) than 3600 rpm motors, which provides an extra kick when starting other loads
(3) an 1800 rpm motor has appreciably more copper - which means lower impedance, which means extra kick when starting other loads
Downside is the extra copper drives the cost of the motor up.

To reduce operating noise, always use rubber isolation mounts (i.e. thick rubber sheets/sections) between the converter motor and the converter frame/chassis. Just make sure both the motor, frame, and lathe are properly grounded.

The new solid state drives are pretty trick, but expensive. A 40 horsepower unit is WAY outside of what I'm willing to spend.

I was contemplating mounting a 3-71 Detroit diesel on the other side of the shop wall, and drive the lathe directly at 1800 rpm via pto/belts (replacing the 40 hp lathe motor with a simple belt-driven jackshaft). However I cannot stand the idea of having to start a combustion engine to run my lathe. Starting a phase converter is somewhat of an irritation in itself, but at least I don't have to feed it diesel, change its oil, or keep its battery charged. . .

3 phase power ends about 2 miles down the road. It would cost well over 100 grand to bring it to my house. Maybe if I win the lotto. . .? Until then, rotary converters are the ticket - especially when constructed from scratch to keep costs down.

The 3600RPM motor presented itself for a very low surplus cost. I wanted a 10HP motor, but there was only one surplus store in town, and induction motors were only seen once by me with the 5HP motors. It was an avionics company, so most surplus was electronics.
I should have mounted it (the RPC) on the other side of the shop wall for noise abatement. Once the big lathe would run on a VFD, it pretty much ended my RPC days. I have replaced every single phase motor in the shop with 3ph, and a dedicated VFD for each. They are commodity items now, but I did get most of them off eBay or Craigs list.
I don't have your 40HP problem. The big advantage is soft start, and the ability to program in the Hz to RPM spindle conversion constant, and have the LED display show spindle RPM where I leave the belt setting fixed.

You aren't doing this shop upgrade as a hack (reading your description), given a pretty big investment in a higher ampacity panel. I assume you have some pretty costly wire runs, along with service entrance connections. And procuring 2 40HP phase generator motors didn't just walk into the shop.
That is a nice looking gantry crane build.
The one thing that my big lathe has is a large through spindle hole. My use is repair parts, and I'm assuming you didn't invest in your big lathe to make miniature models, and will enable some tasks beyond your other lathes (and it's hard to say no when quality iron falls in your lap).

 

[99Norton]

Now that you have bought your motors you could have a look at https://unique3phase.com
Has a good breakdown on pro & cons of different types of systems.

 

[Wizard69]

I'm still not convinced that your really need two 40 HP phase converters to run this lathe. Mostly due to lathes this size having some sort of clutch/break assembly so the motor starts at almost zero load. There might also be a soft start capability within the controller.

In any event you may very well have to ring out the entire control panel and generate an electrical schematic of the electrics to really be able to use the machine. If you haven't done it before this can be a lot of work. It is even worse if none of the wires have readable wire numbers. It isn't impossible just be prepared to chase down lots of wiring. As far as the big contactors go you should have a pair (assuming reversible spindle here) for the main motor, a coolant pump contactor, and possibly a contactor for driving the saddle rapid if any. So three contactors going to motors of some sort. I never worked on this brand of lathe so there are other possibilities like a shift assist motor, but three motor contactors seems about right. There is a remote possibility that the motor starter is far more complicated supporting dual speeds, soft starting or DC braking, if that is the case your controls can be far more complicated.

Considering the era of the machine and the original buyer, you likely have a master control relay (MCR), contactor as part of the E-Stop circuit. There are likely relays connected to air pressure switches. One thing I noticed is that you have the electrical panel backed up to the barns wall, you will grow to regret that. You will want regular access to the panel for maintenance. Beyond that is you need code compliance you will need most likely 4-6 feet of clearance behind the panel ( I forget the exact distance for that voltage and power level). In any event post a picture of the panel it might be possible to identify some of the contactors and other components in the electrical panel.

By the way the more pictures you post the more it looks like you got a machine in excellent condition. Consider yourself lucky.

 

[Entropy455]

The reason I'm using (qty 2) 40 horsepower phase converters, is because a single 40 horsepower converter might not cut it (i.e. unacceptable voltage drop on the generated phases will stall the motor being started). The industry rule-of-thumb for rotary phase converters is 2:1, where the converter is twice the size of the largest motor being started. If the motor being started is heavily loaded (i.e. no spindle clutch on my lathe, or an air compressor, or a conveyer belt, etc) the recommended ratio jumps to 3:1.

For lathe positioning within the shop -

I've got (qty 4) 12-ton equipment skates and a pair of bottle jacks that I purchased specifically for moving this lathe around. I'm contemplating moving the ​

lathe to the center of the shop, and moving my milling machines along the wall. Another option would be to move my car-lift towards the front of the shop, and move the lathe further back along the wall. I haven't decided yet. . . .

I recently discovered that high current contactors are very expensive. The contactors I need for building my large phase converter cost about 500 bucks each - and I need three of them. . . . My 10 horsepower converter parts were cheap in comparison.

 

[ignator]

I recently discovered that high current contactors are very expensive. The contactors I need for building my large phase converter cost about 500 bucks each - and I need three of them. . . . My 10 horsepower converter parts were cheap in comparison.

Entropy, I'm curious what your contactor specs are.
For 40HP@240v, looks like 30Kw contact rating.
Ebay has 3 used contactors @ $70 ea;
https://www.ebay.com/itm/ABB-EH-110...=item285e0e818b:g:3ysAAOSwyARbLai6:rk:13:pf:0
Some brand new from China $21 each;
https://www.ebay.com/itm/CJX2-9511-...h=item3d44406e74:g:phQAAOSwcp1Zjlpl:rk:1:pf:0

I bet new name brand is very pricey.

 

[Entropy455]

The converter contactors must be rated for a single-phase horsepower equivalent - which is a little over two-times the 3 phase current rating. A

contactor for starting one 40 horsepower converter should be about 250 amperes. It wouldn't hurt to go a bit larger, because the bank of capacitors wired in parallel with each motor are a very low impedance dead-short during startup (further compounding the surge-current problem). A 250 amp contactor is the absolute minimum I need, and even then - it's on borrowed time.

www.elecdirect.com has some nice 3-pole 265 amp contactors for 450 bucks (plus 60 bucks for the control-coil). For extended life, I'd rather have the 330 amp unit, but it's 572 dollars (plus coil). . . . ! This particular brand is from India, and it seems to be the best value that I've found thus far.

I am very hesitant to purchase used contactors (I'm not saying that I wont). It's just that sometimes electrical equipment is taken out of service because it's old and worn out - and not every used-contactor salesman is honorable. . . .​

 

[Entropy455]

Here's two pictures of my phase converter motors. These set me back 600 dollars (after tax) for the pair. Ten identical motors went up for sale at once, sold as surplus by Boeing. They look almost new - with exception of aircraft factory mystery dust (pictures are as-received). The paint on the sheaves is hardly worn. I'm assuming they were lightly used ventilation fan motors. The motors are 16 inches in diameter, and weigh about 650 pounds each. These are 1800 rpm, 40 horsepower, 230/460 volt 3-phase.

I'm going to build a frame to mount the motors in a stacked configuration - to save floorspace. I'm also going to cut the motor shafts off, to minimize exposed moving parts.

 

[ignator]

Those motors are a pretty good deal, I've always wanted to stop into their surplus store. The company I worked for was a major avionics supplier to them.

I think you can get what you want from eBay new in name brand contactors. They may be shipped off shore (China where we exported all our IP too).

Here is a 250amp, that you can get multiples of Schneider electric $104;
https://www.ebay.com/itm/Schneider-...692880?hash=item3d61cae8d0:g:ZfkAAOSwx3NZZYpi

Here is a 330amp Telemecanique $350;
https://www.ebay.com/itm/Telemecani...=item260944b4ad:g:6DQAAOSwtytZpsmn:rk:37:pf:0

$300
https://www.ebay.com/itm/TC-SHAMROC...IAAOSwEaBaA0kI:rk:100:pf:0&LH_ItemCondition=3

I did a quick search, and for only new, as I agree, you don't know what damage the contacts have from previous life.
But you probably ordered these already. So my post is probably just noise.