Looking for schematic help

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02 May 2023 18:42 #270501 by gardenweazel
Hello all!
I'm in the process of finishing up a new build of mine and am looking for some "schematic proofing" and advice.

I'm attaching a PDF schematic and my KiCAD schematic below.

Can you kindly provide feedback and advice?

Also note that I have a relay that I have labeled with a question mark. I have the relay on hand and am uncertain where to place it in the diagram.

Thanks in advance for your anticipated feedback and know that I appreciate your time.

NOTE: not all connections have been made as of this date. 

Regards,
Andy

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02 May 2023 21:44 #270510 by spumco
Replied by spumco on topic Looking for schematic help
As I've written elsewhere, wiring questions are likely to get you a range of opinions.

Here's my take on your scheme, from a non-expert:
  • You don't need/want the extra relay
  • I suggest putting the contactor between the EMI filter and the 48v PSU and the VFD.  That way your estop circuit and two-button start/stop (well done, btw) will stop all motion - not just the VFD.
  • The 24v PSU will be unswitched by the contactor, leaving power to the logic circuit (required for the contactor coil, of course)
    • Incoming 240VAC -> breaker -> filter -> terminal block (A) -> contactor -> terminal block (B) -> VFD & 48VDC PSUs
    • Incoming 240VAC -> breaker -> filter -> terminal block (A) -> 24VDC PSU
  • Wouldn't hurt to add individual breakers or fuses between the terminal blocks and the components being fed.
    • This increases cost and takes up space (always at a premium), but provides a bit better protection to individual components rather than a single big-a$$ breaker for the whole thing.
  • Check the inrush current for the 48VDC PSU's and VFD.  You might be surprised how big of a 'hit' happens when all three are energized.  If the inrush is too much for your system (or you suspect it may be), you can switch to two contactors (one for VFD, one for PSU's) and use a time-delay relay on one of the contactors to stagger the inrush current.
  • Don't label the 240VAC stuff "120V".  I know... technically each conductor is 120v to earth/neutral, but they're 240v line to line.  Someone else (future you) might get confused, especially if you later add a neutral and a single 120VAC circuit for a pump or light or other accessory.  Just L1 & L2, and make them black per NFPA 79.
Hope that helps.
-R
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02 May 2023 21:50 #270511 by spumco
Replied by spumco on topic Looking for schematic help
Stupid forum editor.  That wasn't supposed to be a winking emoji.  Should have been terminal block "B".
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02 May 2023 23:43 #270526 by andypugh
Replied by andypugh on topic Looking for schematic help

Check the inrush current for the 48VDC PSU's and VFD.  You might be surprised how big of a 'hit' happens when all three are energized.  If the inrush is too much for your system (or you suspect it may be), you can switch to two contactors (one for VFD, one for PSU's) and use a time-delay relay on one of the contactors to stagger the inrush current.


Or switch them in in sequence using HAL.

On my lathe (which has some big smoothing caps) I actually start the servo drive PSU up through a power resistor and then, when the servo drive bus voltage (readable in HAL) reaches 300V I switch in a relay that bypasses the resistor and signal "drive ready" to the system.

This is partly because my workshop is powered via a 30mA RCD, though.

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03 May 2023 02:32 #270533 by spumco
Replied by spumco on topic Looking for schematic help

 On my lathe (which has some big smoothing caps) I actually start the servo drive PSU up through a power resistor and then, when the servo drive bus voltage (readable in HAL) reaches 300V I switch in a relay that bypasses the resistor and signal "drive ready" to the system.

This is partly because my workshop is powered via a 30mA RCD, though.


@Andy

Interesting - I've wondered about that.

I've got some older servo drive with big inrush values, and newer ones that are about the same kw rating but have minimal inrush current.  You think the manufacturers of the newer ones have internal resistors and some switching logic to accomplish what you're doing externally? 

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03 May 2023 06:48 #270541 by Aciera
Replied by Aciera on topic Looking for schematic help
Also, don't label your DC lines with plus and minus voltages (ie not +24V/-24V) because that implies a voltage of 48V between those lines. Instead of -24V use 0V or 24V COM if you need to keep the DC separate. (Note that the standard labeling will differ between the US and other regions)
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03 May 2023 11:40 #270556 by andypugh
Replied by andypugh on topic Looking for schematic help

I've got some older servo drive with big inrush values, and newer ones that are about the same kw rating but have minimal inrush current.  You think the manufacturers of the newer ones have internal resistors and some switching logic to accomplish what you're doing externally? 


The newer ones might be using inrush current limiters, though finding adequately-rated ones is a bit of a challenge which was why I settled on an active system.

en.wikipedia.org/wiki/Inrush_current_limiter

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03 May 2023 18:12 #270581 by gardenweazel
Not sure if this is a bullet item that I need to address?
  • The 24v PSU will be unswitched by the contactor, leaving power to the logic circuit (required for the contactor coil, of course)
    • Incoming 240VAC -> breaker -> filter -> terminal block (A) -> contactor -> terminal block (B) -> VFD & 48VDC PSUs
    • Incoming 240VAC -> breaker -> filter -> terminal block (A) -> 24VDC PSU

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03 May 2023 21:27 #270588 by spumco
Replied by spumco on topic Looking for schematic help

Not sure if this is a bullet item that I need to address?
  • The 24v PSU will be unswitched by the contactor, leaving power to the logic circuit (required for the contactor coil, of course)
    • Incoming 240VAC -> breaker -> filter -> terminal block (A) -> contactor -> terminal block (B) -> VFD & 48VDC PSUs
      • Incoming 240VAC -> breaker -> filter -> terminal block (A) -> 24VDC PSU

Need?  No, but would be helpful.  I'll try to draw you a schematic tonight explaining my suggestion.
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03 May 2023 21:54 #270589 by gardenweazel
Thanks for that offer! 

Take a look at this attachment PDF, I believe this is what you were referring to.

 

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