Re: [CAD_CAM_EDM_DRO] loking for help with power supply for rutex drives...

keith wrote:

>i want to build or buy a power supply for rutex drives. i want to
>use three of them to power three 3/4 hp micro 100 dc brush servo
>motors on my old knee mill.
>
>i'm not sure which drive are best fitted to my motors, but i'm
>leaning towards the R90H (200V/40A). there are two other sizes
>available that i can use if i can find the right power supply for
>them. R990H2 (200V/10A) or R990H (100V/20A)
>
>

Your motor has a 5.8 A rating, but calculating back from the peak torque,
it seems that the peak current rating is 26 A. 150 Lb-In is a LOT of
torque. I think using a 20 A drive, limiting you to 115 In-Lb, or
1840 Oz-In, will do quite well. In fact, you don't even want to use
the full rating of a 20 A Rutex drive with these motors, or you are
likely to break something, like the ballnuts!

>if i'm to build one,i need help to select the appropriate components,
>as i am a machinist, and not an engineer. can anyone reccomend which
>components i would need and where to find them? what va rating for
>the transformer? what type of rectifier? what kind of capacitor or
>filter? any schematics for this?
>
>or can anyone possibly reccomend where i can buy a power supply?...
>just got the motors, can't wait to get this up and running!
>
>my motor info is as follows:
>Nema 42 Face mount with 5/8" output shaft
>
>
>>120 Volt Nominal Terminal Voltage Rating
>>Torque constant: 5.75 Lb-In/Amp
>>Cont Torque Rating: 34 Lb-In
>>Peak Torque: 150 Lb-In
>>Weight: 14 lbs
>>It is rated for up to 120 Volts, 5.8 amps.
>>The motor's back-emf constant is 68.6 Volts/kRPM...so,
>>The motor will run 15 RPM for every volt you give it.
>>For example, on a 48 volt supply, you could expect 700 RPM for a no-
>>
>>
>load
>

What screws will you be using? The original Acme, or are you putting in
ballscrews? What thread pitch? With a 5 TPI screw direct driven at
700 RPM, you'd get 140 IPM - not too bad. You certainly don't need a belt
reduction with this motor! But, you probably need a bit more than 48 V
to get good performance, and have a margin for the drive.

I think a Gecko 320 drive would work fine for this application, but the
Rutex
100V 20A drive would also work well. You could also go for the 200V 20A
drive, but there is no need to go much over 100 V with this setup,
unless you
feel 600 IPM rapids are what you have to have. Note that the Bridgeport
ways
are just not designed for these speeds, and you'd BETTER have ballscrews or
your Acme screws and nuts will be shot in weeks!

As for power supply, a 20 - 30 A supply should be sufficient, as long as the
capacitor bank is adequate. So, you need a transformer with a 20-30 A
rating at roughly 70 V AC. This will produce about 100 V DC.
You need a 30 A bridge rectifier. Another way to set this up is a
center-tapped 140 V winding, and use two 50 A rectifiers on heat sinks.
it is also possible to set up a "step-down" transformer in the 240:240
configuration, but run it from 120 V and you get 120 V center-tapped,
which will give you about 84 V DC, which should work pretty well.
About 100,000 uF of computer-grade capacitors should do for the
filter, but that is a rough number, you can make use of what is available.

Jon