Mazak QTN20 power questions
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  1. #1
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    Default Mazak QTN20 power questions

    I've tried searching for the answers to these questions but can't find. Hoping the machining knowledge hive can answer for me. I have purchased a Mazak QTN20 lathe which I plan to power off a PhasePerfect PT030 30 HP phase converter. I figured 30 hp phase converter, 20 hp lathe, no problem. However, after reading the electrical tag, I am a little confused and have some questions (pic attached)
    • Voltage 230/460 -- Is it safe to assume that the voltage range is +/-10%? Is it OK to use 240 volts, or do I need to step down?
    • Spindle HP MAX 20/30. Does this mean 20 hp if using 230v and 30 hp if using 460v?
    • Largest motor 139 amps? I am obviously misunderstanding something, but using the formula P=sqrt(3) x pf x I x V, assuming a power factor of 0.8 result in current being ~47 amps. 20hp = 15kw= 1.73 * 0.8 * 230v * 47amp. I don't understand 3 phase power too well. I am hoping that someone can please explain the huge discrepancy.


    So the real question is: If I limit the spindle acceleration, will I be able to run this machine on my phase converter? What size breaker should I use?

    Thanks
    20191216_143216.jpg

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    Voltage will be fine running off 240 or 480V. Newer ones have a multitap transformer on them that can be set to match incoming voltage, not sure about what will be on your vintage. What year is the machine?

    The second section is referring to the duty cycle. If I'm reading the tag right, the spindle can pull 20 HP for 30 minutes. The continuous running HP is 15.

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    It's a 1995 T-plus. 20 hp for 30 min makes sense...duh

    So, Can I get away with 100 amps peak? That is all my converter will allow.

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    It'll be fine, I run a cnc lathe with the same hp on a 20hp PP, its on the edge of it but works fine.

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    Quote Originally Posted by MiamiCNC View Post
    So the real question is: If I limit the spindle acceleration, will I be able to run this machine on my phase converter? What size breaker should I use?
    I run my entire shop on a white 30 hp Phase Perfect. I feed it with a 200 amp breaker.

    I reduced the acceleration on my Mazak ST30 ATC/MC cnc lathe to limit the draw on the PP and to save me some coin on how much juice the lathe uses. 22kw spindle.

    Because I reduced the spindle accel, I can run my smaller Mazak cnc lathe at the same time and run the 3 phase air compressor as well.

    Biggest things to watch for is to make damn sure the internal transformer on the Mazak is set correctly to 240v incoming voltage if that's what you have. DO NOT assume it was set properly before you got it and just throw power to it. The transformer has different taps to adjust for whatever incoming voltage you have available. The lathe makes the same power running on 200v as it does 480v. The internal transformer changes it into the machine's required 210 volts.

    Second thing is to get the phasing correct. The main spindle VFD should have a phase indicator light lit up if the phasing is correct and the hydraulic pump should build pressure.

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    Yes as others said reduce the acceleration, dont take enormous cuts and you will be fine.

    It is safe to assume I can lower acceleration on all Fanuc Lathes as well? I heard fanuc can be tricky to deal with on some things. Im shopping for a bigger lathe now myself and will be in the same situation. I need the size for the occasional larger job, but wont have the electrical power to run a machine that size at full capacity. Just want to be sure I dont buy a machine that I cant adjust spindle ramp time on.

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    Usually No need to adjust acceleration on a 15-20hp lathe running on a 20-30hp PP converter. But if you have many machines on 1 PP running at same time over the limit, then yes lowering the peak draws will help. I rarely go over 2500rpm with my lathe so no issues, if you ramp up down to 6000 every 2 seconds then that's different... Anyhow, I wouldn't mess with it until after it shows to be an actual problem.

    I do use G97 whenever I can instead of G96 though to keep the ramp up/down to a minimum, except some facing. On some parts that also reduced cycle times.


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