Striatech DVR motor for PM's 2-3 HP lathes 1236,1236T,1340GT.. etc

[JimDawson]

Ya know... the power savings is starting to look like a pretty big deal... I just got my new electric rate for our local aggregation program... it's going from .0495 to .0979... my per kWh just nearly doubled .

Might be a good excuse to go with a servo motor. They only use enough power to keep the RPM constant at the current torque requirement.

Example: My CNC lathe spindle idling at around 600 RPM runs about 2.4% of the rated power input, then goes up from there as needed when cutting. Where my mill, equipped with a standard 3 phase motor/VFD runs about 60% rated power input when idling at around 600 RPM. The difference is in the way the motors work. Bottom line is that a standard 3 phase motor is not as efficient in a variable speed/torque application as a servo motor, but probably more efficient in a properly sized fixed speed/torque application.

 

[Ischgl99]

I can pick up locally from PM and just my impression from the 2 emails with Eisen and many with PM... PM has better support.. not worth saving just a couple hundred.

Now I remember you mentioning that earlier, yes, definitely easier to run over and pick it up. Then you can oogle what they have for your next purchase

Ya know... the power savings is starting to look like a pretty big deal... I just got my new electric rate for our local aggregation program... it's going from .0495 to .0979... my per kWh just nearly doubled .

Is that your total rate? Supply and delivery? Here in CT, our supply charge is $0.12 and the delivery charge is $0.13 per kwh. At $0.25/kwh, every bit of savings helps.

 

[mksj]

I'll likely just leave it in high range.. that's 205 to 1800 RPM in the "A" pulley setup.

One thing that did cross my mind was I could change the pulley sizes... if for some odd reason I need a slightly different motor pulley to spindle/gear box pulley setup.... but that's pretty limited in how much you will affect it.

As I mentioned, if you flip the "stock" motor pulley you split the speed range, i.e. low speed pulley is ~2.2:1 and high speed pulley is approximately 1:1, flip the motor pulley going from the larger motor pulley to the larger headstock pulley you now have ~1.6:1. Add a VFD and run it from 30-90 Hz you have the full speed range.

Single phase motors are not very power efficient, a 3 phase motor in the 84-90% efficiency, Striatech gives no numbers but they are not comparing it to a VFD driven motor, you will probably break even in power savings after 100 years... Your power is cheap, in San Diego the off peak rates (i.e. when you are working and not home) is around $0.30 KWH and in the evening it moves up to $0.70, and then they start stacking fee hikes if you are burning more than a 100W bulb, let alone run a large motor. I am running a 9.6 KW solar system, my excess power (4 MWH) generation this year they give me back $0.03 KWH, which basically covers all the fees and taxes they pass through.

 

[skcncx]

Is that your total rate? Supply and delivery? Here in CT, our supply charge is $0.12 and the delivery charge is $0.13 per kwh. At $0.25/kwh, every bit of savings helps.

$0.0495 is just the per/kWh supply portion. My last bill for using 1,650 kWh was $201. $80 was just for supply, $120 for delivery and various fees.

My bill doesn't show me what the per/kWh delivery rate is, but even if it was a flat fee, my next bill at .for same usage will jump from $201 to $280... since the $80 portion of supply cost is nearly doubling.

I have just had a very good rate lately.

 

[Ischgl99]

$0.0495 is just the per/kWh supply portion. My last bill for using 1,650 kWh was $201. $80 was just for supply, $120 for delivery and various fees.

My bill doesn't show me what the per/kWh delivery rate is, but even if it was a flat fee, my next bill at .for same usage will jump from $201 to $280... since the $80 portion of supply cost is nearly doubling.

I have just had a very good rate lately.

Ok, so it looks like your delivery charge is about $0.073 per kwh. Even with your supply doubling, your electricity rate is lower then probably everyone in the Northeast, but still enough that it’s worth considering efficiency.

 

[Ischgl99]

Your power is cheap, in San Diego the off peak rates (i.e. when you are working and not home) is around $0.30 KWH and in the evening it moves up to $0.70, and then they start stacking fee hikes if you are burning more than a 100W bulb, let alone run a large motor.

Ouch! I am really happy we are not variable rate here in CT, that would certainly push a lot more people to use solar. But, as more people use solar, the delivery portion of the electricity bill needs to be paid by a smaller number of people and will keep going up.

 

[skcncx]

Single phase motors are not very power efficient, a 3 phase motor in the 84-90% efficiency, Striatech gives no numbers but they are not comparing it to a VFD driven motor, you will probably break even in power savings after 100 years...

Right, I imagine they are comparing to a standard AC, single phase motor.

Thanks for all the input! I have levelled up my knowledge on a lot of things with everyone's advice. If for nothing else, I appreciate the discussion and learning.

With that, I ended up putting my order in and deposit for the single phase PM-1236T. Arrives mid October (barring delays of course). 3 phase was not until next year. I guess if I really think it was a bad decision I can see if I can change the order and just wait the extra 4-6 months.

I have to start somewhere and for my skill level, any motor will get me going. This is a big upgrade over my Atlas 618 with a sewing machine motor (BLDC) and that fact I was considering their PM-1228 version the PM-1236T is a big step up from my original plan. Personally, I wish they would give you a BLDC motor option for this or pre-wired with the VFD 3 phase they sell. Can't say it's logical, but I would wait longer for the 3 phase if it was turn key.

This is all that's on my order at the moment, DRO to be added. I'll keep a few cutters and inserts from my atlas 618 , but may opt for PM's 5/8 master turning set or a set from AR Warner.... there are endless options.
• PM-1236T 12″X36″ ULTRA PRECISION LATHE
• Wedge Quick Change Tool Post Set, BXA Size
• Micrometer Carriage Stop
• 1/8-5/8 Ultra Precision Keyless Drill Chuck MT3
• MT-3 Slim Body Live Center


Also, I talked to PM's tech support just to effectively go over exactly the advice given here on single vs 3 phase and of course 3 phase is preferred for all the discussed reasons, finer RPM control, braking, slow start etc. He did mention some have reported the single phase has some harmonic affect and can show up in the material being turned, you can see it but don't feel it. He also mentioned that he was of the understanding that the 3 phase motor was likely a higher quality motor and overall longer lasting (that is mainly because of how 3 phase motors are designed) vs single phase motors with more components to likely fail.

 

[skcncx]

Still need gears for torque multiplication.

Not to beat a dead horse... that makes sense... but then then PM-1228 doesn't have a gear box, just low/high pulley range and the rest is just the 2 HP variable speed BLDC motor.... so, maybe that works for smaller class lathes... but the PM-1236T single or 3 phase is only 2 HP as well, not like it needs more HP.

If it was me ordering a new lathe I’d go with 3 phase even if I just used a static converter to start.

Yea, too bad they are 4+ months longer than the single phase... I guess in the long run, that's not that long. Though PM does have one OEM PM-1236T 3 phase motor on the shelf to sell.. but it's $399.. I ended up ordering the single phase version since it's coming mid October... but at least I know what $$ I'm up against *if* I do the full motor swap to 3 phase w/VFD and all it entails.

As others have mentioned... there aren't many, if any, motor options for this lathe, sounds like space constraints being the biggest.... maybe if you hang the motor off the back more you would have more options if not trying to fit it in the space already given.

 

[matthewsx]

Not to beat a dead horse... that makes sense... but then then PM-1228 doesn't have a gear box, just low/high pulley range and the rest is just the 2 HP variable speed BLDC motor.... so, maybe that works for smaller class lathes... but the PM-1236T single or 3 phase is only 2 HP as well, not like it needs more HP.


Yea, too bad they are 4+ months longer than the single phase... I guess in the long run, that's not that long. Though PM does have one OEM PM-1236T 3 phase motor on the shelf to sell.. but it's $399.. I ended up ordering the single phase version since it's coming mid October... but at least I know what $$ I'm up against *if* I do the full motor swap to 3 phase w/VFD and all it entails.

As others have mentioned... there aren't many, if any, motor options for this lathe, sounds like space constraints being the biggest.... maybe if you hang the motor off the back more you would have more options if not trying to fit it in the space already given.

Torque is different from HP, and the 1228 at 490 lbs is in a different class than the 1236-T at 850lbs. I'm sure both are fine lathes but I'd expect the 1236-T to be able to take a much bigger cut than the 1228. The old saying "HP sells cars but torque wins races" applies here, both my lathes have back gears and it definitely makes a difference beyond just slowing down the spindle.

If they have the 3 phase motor in stock you might as well get it now, no telling if it will be available when you need it.

One other thing to consider, a longer wait gives you more chance to find a deal on a good used lathe. I've seen that happen many times to forum members.

John

 

[skcncx]

Torque is different from HP, and the 1228 at 490 lbs is in a different class than the 1236-T at 850lbs. I'm sure both are fine lathes but I'd expect the 1236-T to be able to take a much bigger cut than the 1228. The old saying "HP sells cars but torque wins races" applies here, both my lathes have back gears and it definitely makes a difference beyond just slowing down the spindle.

Yea, there's a lot to this... one number doesn't tell all... I guess it's like my 6.5 HP shop vac on 110v.... it only get's that fake HP number because how fast it can spin the motor (in a vacuum tube, test lab).

If they have the 3 phase motor in stock you might as well get it now, no telling if it will be available when you need it.

It's crossing my mind. My original budget went from $6K... now it's nearly at 10K for a PM-1236T with added accessories and DRO. I'm hoping for a while I'm satisfied with the single phase motor.. I have to imagine for the next year or so, it will be good enough. I don't think I'll regret going from the PM-1228 to the PM-1236T.

I'm also thinking about what $$ I want to hold back for a nicer 3 jaw chuck or 4 jaw chuck... to start the included economy 3 jaw chuck is all I'll have.

One other thing to consider, a longer wait gives you more chance to find a deal on a good used lathe. I've seen that happen many times to forum members.

Been looking each day the last few months to see what comes up... so far, older stuff that all needs a complete reconditioning for the size I want. The challenge is if I "wait and see..." and nothing comes available in 5 months, it's not like the PM machines will be available then. It'll likely just be get in line again for another 4-5 months wait. At least that's the current state of supply and existing orders. Certainly paying a premium to buy new. My anxiousness to have something sooner is certainly at play.