Power Supply help

[dirtdiggler]

Hi Al,

Thanks for your help with this.

Is that number for one motor or 3 motors?

If it's for one motor would you mind telling me what size transformer I would need for 4 motors?

When you say 60% duty, does that mean that the transformer usually runs at 60% duty?

If I use a toroidal transformer could I run a smaller trnasformer, like a 1KVA per axis? I know these transfomers run more effeciently than laminated type transformers but I'm not sure.

-Kirk

[Al_The_Man]

60% duty factor, is a rating based on the assumption that the total rated current will not be in effect for 100% of the time.
For example for all four motors the 100% rating would be 8.6Kva and 5.75 for 60%.
This is for 120vdc using 27,000µfd for 5% ripple.
You might squeek by with a 1Kva for each, but watch the heating effect.
Toroids are a slightly more efficient.
But I would look at using the existing ones first, maybe.
Al.

[dirtdiggler]

Thanks again Al.

I got in touch with Antek and it looks like they have some great options. They suggested a 1KVA or 1.5KVA for each servo. They said a 1Kva power supply for each would work fine but would have less maximum torque compared to the 1.5KVA, but also said you rarely use maximum torque unless the servos is pushing hard. Not sure if it's worth the extra $$ to move up to the 1.5KVA PS version for full torque or not. I'm going to be cutting mostly soft material and occational aluminum bike parts.

-Kirk

[dirtdiggler]

Hi Al,

Okay, I bought 3 of these 1.5 KVA Toroidal power supply's, one for each motor. They are very nice but HUGE.

Do you know if there is any danger in feeding this much power to each servo drive? I know you specified 1.4 KVA for each so I'm wondering if 1.5KVA is going to be too much power?

Motor specs:

Brand PowerTron
RMS Amps: 14.6
Max RPM 6000
Tachometer: 7
Volt See/RAD K.V. ?233
Max Pulse Amps: 58.3
Rated Torque: 30
Max Volts: 146

[Al_The_Man]

Larger KVA is OK, the motors will only draw the power they require.
Al.

[Larken]

Dirtdigger, i'm reading the cncbrain thread (interesting) and saw some of your questions.

The Viper takes Step/direction signals only. It can't run analog or PWM input.

I would suggest get your system running with Mach and a cheap breakout board to get everything working well, then down the road when cncbrain is ready migrate to it. That way you have the bulk of the system tested and running.

[dirtdiggler]

Thanks Larken,

I was wondering about that, thanks for clearing it up. There is another guy who I'm on email with who is using Viper 200's with a CNC Brain but I'm not sure if he has it working or not. Maybe this is why it's not up and running!

I know the Brain has PWM....and if you want Analog out you need to purchase a separate DAC board they sell. With that said do you know if there is a way to use the Brain it with Vipers or does the PWM make this impossible?

I'm really new to all of this so I will take your advice of sticking with a breakout board.


ThX

[Larken]

With that said do you know if there is a way to use the Brain it with Vipers or does the PWM make this impossible?

Thats not a good idea, unless the Brain can monitor motor current load, since the PWM needs to be varied if current load gets high.
The Viper has about 4 factors (including current control) after the PID that trim the PWM duty cycle to protect the drive.

Does the brain not output step/direction ? There is no reason that it shouldn't that has to do with accuracy. If thats the case with only digital PWM output, there is no drive that it can run that i know of. None of gecko's or other stepper drives, no analog servo drives ...??.

[dirtdiggler]

I'm sure it uses step and direction. In the manual it uses Gecko 320 servo drives as an example for setup. I'm lost on the PWM discussion. I'm not sure what it means or if it's even relevant.

If it can connect to Geckos shouldn't it be able to attach to Vipers?

The setup manual can be downloaded here: CNC Brain is ready! 6-axis Double Closed Loop Controller

[Larken]

Ok, so in the manual at section 8.4.1.1 it shows how to connect to step/direction. Thats all you need to drive the Viper.

(Don't worry about the PWM outputs then, they are for older analog drives)

Thats all good, then !!

[dirtdiggler]

Okay,

Now that I have the main power sorted, how many amps do I need to supply to the 12-18 VDC side of the Vipers? I need to supply 3 drives.

Can I use a simple power supply like this one, and splice it in?:

http://cgi.ebay.com/Samsung-Power-Su...3286.m20.l1116

[Larken]

yes, thats plenty to power the control side of 3 drives.