Re: [CAD_CAM_EDM_DRO] Re: Motor calculations? Help!

Hmmm as I recall the New transformer I got from the Surplus center was a
120/240 primary and a 120/240 secondary isolation 3KVA transformer. When
rectified and fed into a large 200VDC cap it produced 164 VDC . The motors
on my tree mill are 3/4HP 130VDc motors that ran happily on 164VDc
The transformer was only $129 as I recall. Due to a PID problem with a new
type servo amp I subsequently removed the 200V 40A servo amps ( not rutex)
and replaced them with Gecko drive G320 servo amps and a 80VDC power supply.
The Tree Mill is set up with a 2/1 ratio timing belt drive so I know the
Gecko will run the machine at 96 IPM using Mach2 with 500 CPR encoders.
When I reprogram the new type servo amp with a new PID filter I will
reinstall them with the 3KVA power supply and should get 200 IPM and test my
courage :)
So $129 is not a bad price for that rating transformer
Dan

----- Original Message -----
From: "Jon Elson" <elson@...>
To: <CAD_CAM_EDM_DRO@yahoogroups.com>
Sent: Saturday, March 19, 2005 6:09 AM
Subject: Re: [CAD_CAM_EDM_DRO] Re: Motor calculations? Help!


>
> Lance Hopper wrote:
>
>>Hello,
>> I've been talking to the guy myself trying to help him out. He's
>>already bought 200V 40A Rutex drives as I understand. Now he's
>>trying to figure out the PS.
>>
>>
> Ah, OK, that sounds like the best course.
>
>> The original drives were fed 120 3ph from the secondaries of a
>>2.5kva 3ph transformer as he describes via his electrical schematics.
>>He was trying to see if the stock 3ph transformer (has delta and Y
>>wiring configurations, he has the schematics, maybe he should post)
>>could take ~220 1ph (all he has available) and output ~120 1ph that
>>could be rectified and used for the Rutex drives. I doubted that it
>>would work and be dangerous/stupid to try, but what do I know.
>>
>>
> Is there any way to use a 3ph transformer for 1ph in and 1ph out?
>
> No, it really will not work well on single phase. Where did this thing
> get
> 120 V 3-phase power? That is an extremely odd voltage. 208 and 230 V
> L-L is the most common low-voltage 3-phase supply in the US. Or, is this
> 120 V line-neutral voltage? That would normally be termed 208 V 3-phase,
> as the line-line voltage is how it is usually measured.
>
>> Is there any way to use a 3ph transformer for 1ph in and 1ph out?
>>What if he used a phase converter and ran 220 3ph to the primary,
>>then just ditched one of the 120 3ph legs to get 120 1ph to be
>>rectified/filtered for the Rutex drives? Any safe/smart workarounds
>>on this?
>>
> The best way to go, I think, would be to use a 240:120 V step-down
> transformer
> rated for 2.5 KVA at that voltage. (If you can't find one with that
> exact rating,
> you could use a 480:240 V 5 KVA transformer at half input voltage.)
> With a 240 V output with a center tap, and using 2 diodes, you can get
> 170 V DC, which may be acceptable to the Rutex drives. (I'm being
> cautious
> here, because the Rutex's 200 V rating is apparently the actual rated
> voltage
> of the transistors. So, I don't know if the 200 V Rutex drive can
> actually be
> run off 170 V DC without problems. It is probably best to ask Rutex about
> that. If necessary, one can get tapped autotransformers to adjust the
> voltage down somewhat.
>
> Jon
>
>>
>> Otherwise, he's going to have some $ into some large kva
>>transformers for the X/Y and Z servos.
>>
>>--- In CAD_CAM_EDM_DRO@yahoogroups.com, "cnc_4_me" <cnc4me@g...>
>>wrote:
>>
>>
>>>--- In CAD_CAM_EDM_DRO@yahoogroups.com, Jon Elson <elson@p...>
>>>
>>>
>>wrote:
>>
>>
>>>>cnc_4_me wrote:
>>>>
>>>>
>>>>
>>>>>Jon, I do not see this the same way you do. Don't you think the
>>>>>continuous current rating is more important than the peak
>>>>>
>>>>>
>>current
>>
>>
>>>>>rating? 28 Kg-Cm / 2.44 Kg-Cm/Amp = 11.5 amps, a gecko would
>>>>>
>>>>>
>>>still
>>>
>>>
>>>>>have plenty of reserve. 20 amp limit would still give 49 Kg-Cm.
>>>>>
>>>>>
>>I
>>
>>
>>>>>wish i had one of these motors for my Z axis.
>>>>>
>>>>>
>>>>>
>>>>>
>>>>What's the peak rating for, if you never can get closer than 20%
>>>>
>>>>
>>of
>>
>>
>>>it?
>>>
>>>
>>>>I might be worried that you might not be able to break static
>>>>
>>>>
>>>friction on
>>>
>>>
>>>>the table with 20 A. What is the leadscrew pitch, and is the
>>>>
>>>>
>>screw
>>
>>
>>>directly
>>>
>>>
>>>>driven by the motor, or is there a belt reduction?
>>>>
>>>>What horsepower and spindle taper does the machine have?
>>>>
>>>>Jon
>>>>
>>>>
>>>From what I understand from reading these forums is that any force
>>>much greater than continuous rating isn't to usable, maybe for a
>>>fraction of a second for fast acceleration. Maybe if he adjusts
>>>acceleration so it does not snap your eyeballs it would be ok.
>>>
>>>49 Kg-Cm is about 47 lb-in. Nothing to sneeze at.
>>>
>>>
>>>I guess what I am getting at is I would not try to discourage this
>>>guy and say it will not work. I think it is very likely it will
>>>work with slower acceleration and with 30% less speed on X and Y
>>>because of voltage restrictions with Gecko drives. Rutex would
>>>
>>>
>>give
>>
>>
>>>him full speed and slightly higher acceleration.
>>>
>>>
>>>Wally
>>>
>>>
>>
>>
>>
>>
>>
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> OFF Topic POSTS: General Machining
> If you wish to post on unlimited OT subjects goto:
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> if you have trouble.
> http://www.metalworking.com/news_servers.html
>
> http://groups.yahoo.com/group/jobshophomeshop I consider this to be a
> sister site to the CCED group, as many of the same members are there, for
> OT subjects, that are not allowed on the CCED list.
>
> NOTICE: ALL POSTINGS TO THIS GROUP BECOME PUBLIC DOMAIN BY POSTING THEM.
> DON'T POST IF YOU CAN NOT ACCEPT THIS.....NO EXCEPTIONS........
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> List Mom
> List Owner
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>
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