Low on power!

landm1 · Apr 7, 2010

Hello,

Still kicking the tires on used machines and as usual I am not going to come up with the name plate power required on the average year 2000 and newer horizontal.
Also, as usual, we will get nowhere near the maximum horsepower available, currently we run all of our mazaks, lathes and mills, at 50% rapids, don't make a lot of money but I very rarely replace parts and hoses let alone the power bill, most runs are under 200 parts.
Some of our machines are near 120 amps required on the nameplate and they are on 100 amp breakers, never triped a breaker. One problem we did have with one machine, we bought new QT 15 in 95', it would trip a 100 amp when you turned on the machine, went to a 125 amp slow blow, never had a problem.
So most of the machines are rated at 150-200 amps, I was hoping to run on a 125 amp breaker, what is the worst possible outcome? The reason for this is we are running our shop off 3 200 amp panels, every nameplate power required would exceed most of that so I would like to keep the "weak link" on the inside panels. Our power supply runs at about 208 volts and we are in a 10 year old industrial building with top notch electrical setup, less my setup!
I am sure most of you are in the same boat, let me hear the worst of it!

LandM-1

Ox · Apr 7, 2010

My shop was set-up on trippple 200's for about 10 yrs. What a pain!

I picked up a 600A 600V fusible disconnect and ran a new mast. Then pulled off of that as required. SO much better set-up now! All machines are on slow blo fuses now. Before we were taxing the breakers to max and they would get weak and need replaced.

Not sure what the question was, but maybe that has some input for you. ???

------------

Think Snow Eh!
Ox

cnctoolcat · Apr 7, 2010

Damn Japanese way overate maximum current draw for cnc machines, imo.

Mazak's spec plate assumes every motor and electrical device on the machine would be maxed-out on amp draw at the same time, plus a safety factor on top of all that. Impossible.

It's amazing you were tripping a 100 amp breaker when turning on a QT15. I have 2 QT15's running off of just 1, 100 amp breaker...never been a problem. These lathes might draw 30 amps or so when running normal.

You are like me, machines run at reduced rapids. You can reduce the max rapids in the machine parameters, then you can keep your rapid overide at the normal 100%. Look in your electrical manual for the correct parameters. Sometimes it's a giveaway: RFX would be rapid feed X.

I even have the spindle accel/decel rates slowed on all my Mazaks. Makes it a lot easier on the spindle drives, the spindle motor, and the related mechanicals. Cycle time difference is null.

Greg

Captdave · Apr 7, 2010

I'm with Greg on slowing down the acel/decel parameters, I run a RPC on a Qt-8 and it dropped the amp draw from 70 to 30 with no appreciable increase in cycle times. I’m sure that it would make a significant difference in larger machines. Only draw back I have found is if I use a compression tap holder is to program a shallower depth to compensate for slower deceleration.

fpworks · Apr 7, 2010

One of my machines is supposed to be on a 150 amp circuit breaker. Unfortunately, our building has the low end "home" grade boxes, so the largest three phase breaker I can run is a 100 amp.

I paid an electrical engineer to come validate it for the county inspector. He monitored the loads on the machine for a solid month and said that a 50 amp breaker would be adequate for the loads I was pulling. I ran some big parts that month that had the machine standing on 80% spindle loads.

I also run 50% rapids. 100% rapids on a 2000+ ipm machine is needlessly violent and doesn't give you hardly anything on cycle time.

My biggest current draws are the air compressor and the air conditioning...machines aren't so bad.

landm1 · Apr 7, 2010

Low power!

Hello,

Great Mazak feedback. The QT 15 that was tripping the 100 amp was that way as brand new. I was always thinking it was something in the transformer loading up for a micro second, we had plenty of people look at it but the draw was so short nothing could detect it.
What I am really looking for is to confirm that if all the stars line up all that is going to happen is it is going to trip and degrade the breaker.

Thanks for the input!

LandM-1

Perry Harrington · Apr 7, 2010

FWIW, I just completed wiring on one of my machines yesterday. My Hardinge CHNC-1 has "FLA 50" on the back, that's what you are supposed to go off when wiring it. I put in a 60A breaker and 6ga wire to handle it. The slo-blo fuses inside at the disconnect are rated for 25A. The machine has a 7.5/10HP spindle, so 25A is closer to reality.

Buuut...I used to run this machine on a 20A breaker with 12ga wire. When the spindle would ramp up for CSS cutting the flourescent light would dim in unison with the spindle ramping, so obviously 12ga wasn't quite right for the machine. These machines have pretty fast accel/decel rates, so the 6ga and 50A is really what you want for peak performance.

This is just my experience.

Joe788 · Apr 8, 2010

fpworks said:
I also run 50% rapids. 100% rapids on a 2000+ ipm machine is needlessly violent and doesn't give you hardly anything on cycle time.

We are running a part right now that uses about 25 tools, and the cycle time is exactly 45 minutes at 50% rapid (makes 6 parts, OP10 on one pallet, OP20 and 30 on another pallet).

Turning the rapid up to 100% reduced the cycle to 44 minutes 15 seconds. :crazy:

We leave it a 50%. :cheers:

Captdave · Apr 8, 2010

If you have a Fluke meter that you can capture minimum and maximum voltage and amps you may consider setting up a test at each box and record what your currently drawing under normal usage for your shop and machines over the course of several days. Additionally, most slow blow breakers/fuses use an inverse time delay for example a rated 100 amp may have several blow rating, 150 amp/.1 sec, 125/.5 sec etc. Most machinery if they ever reach near there peak rated load it is momentary or the result of a malfunction/crash.

Florescent lighting in a shop has always been one of the best subtle indicators of voltage fluxuation occurrences.

SND · Apr 8, 2010

Breakers are apparently only designed to work at 80% of what their nominal number is. So a 100amp would handle a 80amp steady continuous load. But was told going above the 80% can reduce their life. So thats part of the reason for oversizing them by at the minimum 25%

Perry Harrington · Apr 8, 2010

The electrician I consulted in laying out my shop quoted the NEC as saying "try 125% if 100% keeps blowing" that's the basic gist of breaker sizing :crazy:

IAMATT · Apr 8, 2010

Wow we run a 60amp on our QT15's and never had to trip a breaker even when we stall and crash them.

Ox · Apr 8, 2010

Would any of you guys like to qualify your A's with associated V's? :toetap:

------------

Think Snow Eh!
Ox

cnctoolcat · Apr 9, 2010

All my A's are on 240V's here, Ox-man. True 3 phase from the power company...

psychomill · Apr 12, 2010

Quote:
Originally Posted by fpworks
I also run 50% rapids. 100% rapids on a 2000+ ipm machine is needlessly violent and doesn't give you hardly anything on cycle time.

We are running a part right now that uses about 25 tools, and the cycle time is exactly 45 minutes at 50% rapid (makes 6 parts, OP10 on one pallet, OP20 and 30 on another pallet).

Turning the rapid up to 100% reduced the cycle to 44 minutes 15 seconds.

We leave it a 50%.

Rapids have less effect on smaller machines than larger ones. Interesting comment about running 2000ipm + machines at only 50% rapids.... Since I have many programs/tools that run at nearly the same feeds as max rapids, what's to gain here for me? (or lose... however you look at it).

But, the more rotary axes you have, the more tools you have and the more travel you have... slower rapids can and will add time significantly.
... then again, I'm not interested in trying to make a machine last 20 years... Only how much it's going to make me in the next 5 ....

Sorry to hijack.... now, back to your power issues....

doug6949 · Apr 25, 2010

landm1 said:
The QT 15 that was tripping the 100 amp was that way as brand new. I was always thinking it was something in the transformer loading up for a micro second, we had plenty of people look at it but the draw was so short nothing could detect it.
What I am really looking for is to confirm that if all the stars line up all that is going to happen is it is going to trip and degrade the breaker.

You may be correct in suspecting the transformer.

Iron core transformers have a magnetic memory. The inrush current depends in part on where in the alternating current cycle the power is removed and applied. The greater this difference the greater the inrush current.

This is particularly noticeable in older welding machines where the core is very large and often of low grade materials.

If your lathe has a large or poorly designed main transformer then you may get high inrush current. The circuit trip will be random. The usual solution is a larger breaker. The proper solution is a breaker or fuses specifically designed for high inrush current.

landm1 · Apr 25, 2010

Final setup!

Well,

Thanks for the imput. Did the right thing, had my licensed and insured contrtactor install a 200 amp "switch box". I was hopeing to just go with a 200 amp box and use power for other stuff as well. This is a big "on-off" switch with a 200 amp breaker in the main 1600 amp service on the building.
Once I got the Doosan DHP 4000 on the floor, no doubt about it, that thing need 200 amps!
Another consideration that I overlooked with this machine was to be able to utilize it to it's fullest capicity, 2300 i.p.m., 14,000 rpm and some serious torq.
My neighbor that has one of these was right, they did a real nice job on the hoses, it is real "roomy" in the engin room!

LandM-1

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