PSU design

[Ross77]

Hi All
I'm looking to build a new PSU for my Nova mill as the old one has just expired. I want to allow capacity for a 4th axis which will be the next project.

I can't decide on the correct Voltage and Current, but with 4 axis and max driver voltage as 50V I was aiming at 45V and 10amp.

Basic calc's are indicating a 500VA transformer which seems a bit large for this little mill. so my question is:

1. Is 45V too much for this little mill any way?
2. Would I be better using 30V and a 300VA transformer
3. Are there any standard designs with rectifier type and capacitor values?

[Clive S]

Ross check your email:

[Ross77]

Thanks to Clive I'm just about there but struggling on the Capacitor selection The transformer is 300VA and its giving 40VDC (after the rectifier) so 7.5A max

If I follow the online designs and aim for 5% ripple at max current then I need A 37,500uf Cap which is quite expensive and much larger than my other PSU's. 10% ripple is better @ 18,750uf but not sure if 4V ripple is acceptable.?

Assuming that it wont be running flat out and the working current is likely to be 5amps then the ripple with 18.750uf would be better than 10%

Given that most of the ready made ones use a much lower values I can only assume that they have high ripple voltage and it doesn't matter. Am I over thinking this And anything over 10,000uf will be ok?

[Neale]

Ripple is not a problem - the stepper drivers are happy with quite a wide range of input voltages, even varying during the mains cycle. Just follow the guidelines on this forum and don't worry about formal calculations designed for more sensitive environments.