Power distribution questions
22 Nov 2023 05:05 #286209
by djdelorie
Power distribution questions was created by djdelorie
I've gotten to the part in my custom cnc build (Avid 5x10) where I'm pondering an official power wiring. So far I've been running each component off various extension cords but I finally added a dedicated 50 amp circuit just for the cnc machine. My internals are:
30 amps 240v for the spindle (draws 22 max)
20 amps 240v for the servos (draws 8 max)
a few amps of 120v for logic and PC (draws 3-4)
which means I'll have at least three breakers in the box, as well as some way of turning everything on and off. I'd prefer the "latching" type of on/off so if we lose power it doesn't come to life again unexpectedly.
The questions are:
One big contactor then break out to breakers, or break out to breakers then 3 small contactors?
Contactors or SSRs? If SSRs, do you need to open both hots for 240V rails? Those two just go to power supplies.
I figure a latching setup of some sort for the logic rail; should the spindle and servo rails be controllable from linuxcnc or is that useless? Otherwise, I could tie those coils to the logic power to just slave them.
Or... separate latching on/off switches (buttons) for each rail, and turn them all on/off manually?
Lastly... rail mount or bolt to the panel?
Thanks!
DJ
30 amps 240v for the spindle (draws 22 max)
20 amps 240v for the servos (draws 8 max)
a few amps of 120v for logic and PC (draws 3-4)
which means I'll have at least three breakers in the box, as well as some way of turning everything on and off. I'd prefer the "latching" type of on/off so if we lose power it doesn't come to life again unexpectedly.
The questions are:
One big contactor then break out to breakers, or break out to breakers then 3 small contactors?
Contactors or SSRs? If SSRs, do you need to open both hots for 240V rails? Those two just go to power supplies.
I figure a latching setup of some sort for the logic rail; should the spindle and servo rails be controllable from linuxcnc or is that useless? Otherwise, I could tie those coils to the logic power to just slave them.
Or... separate latching on/off switches (buttons) for each rail, and turn them all on/off manually?
Lastly... rail mount or bolt to the panel?
Thanks!
DJ
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22 Nov 2023 11:49 #286221
by andypugh
Replied by andypugh on topic Power distribution questions
Maybe separate the circuits into those that should turn off on e-stop and those that should remain on.
My lathe is wired with the PC/controller power supply[1] direct from the input manual power switch. This, in conjunction with the physical e-stop chain, controls the main power breaker. [2]. There is a GPIO input that detecs when the e-stop chain is physically broken that also drives the LinuxCNC e-stop input.
If the PC is in standby I can press a button on the panel which boots the PC. When LinuxCNC is taken out of e-stop and powered-on the main contactor is closed ans servo / spindle amp are powered up.
I have a bit more logic in HAL to sequence a soft start to keep my wall-box breakers from tripping, and to disable motion until the amps are ready. This is rather simplified by the fact that my amps report-back bus voltage on smart-serial.
[1] I chose a PC that can take 24V DC power input. So I also have a permanent 24V supply.
[2] The main power breaker is a contactor with a 24V coil. The coil is actuated by an SSR which is controlled by LinuxCNC, with the 24V wring looping round the e-stop chain.
My lathe is wired with the PC/controller power supply[1] direct from the input manual power switch. This, in conjunction with the physical e-stop chain, controls the main power breaker. [2]. There is a GPIO input that detecs when the e-stop chain is physically broken that also drives the LinuxCNC e-stop input.
If the PC is in standby I can press a button on the panel which boots the PC. When LinuxCNC is taken out of e-stop and powered-on the main contactor is closed ans servo / spindle amp are powered up.
I have a bit more logic in HAL to sequence a soft start to keep my wall-box breakers from tripping, and to disable motion until the amps are ready. This is rather simplified by the fact that my amps report-back bus voltage on smart-serial.
[1] I chose a PC that can take 24V DC power input. So I also have a permanent 24V supply.
[2] The main power breaker is a contactor with a 24V coil. The coil is actuated by an SSR which is controlled by LinuxCNC, with the 24V wring looping round the e-stop chain.
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22 Nov 2023 12:00 #286222
by andypugh
Replied by andypugh on topic Power distribution questions
Also, I tend to wire my power supplies and servo amps together with
www.neutrik.com/en/products/power
They are more compact than domestic connectors and latch closed.
I use them for 300V DC too (which they are absolutely not rated for, but works as long as you don't disconnect under power)
I also frequently use SpeakCON (www.neutrik.com/en/product/nlt4fxx-bag) for 240V three-phase. They are not intended for this role but I did check with Neutrik and they confirmed that it wasn't a terrible idea. Despite being intended for audio signals the rating is 250V and 30A.
(As an aside, I have also used SpeakCONs to connect the motorised valves of a central heating controller, using two lines for control power and two for the position feedback microswitch)
Note that I have no qualifications in electrics, or electronics, or engineering in general. I merely offer anecdotes about my own machines and points for dicussion rather than advice.
www.neutrik.com/en/products/power
They are more compact than domestic connectors and latch closed.
I use them for 300V DC too (which they are absolutely not rated for, but works as long as you don't disconnect under power)
I also frequently use SpeakCON (www.neutrik.com/en/product/nlt4fxx-bag) for 240V three-phase. They are not intended for this role but I did check with Neutrik and they confirmed that it wasn't a terrible idea. Despite being intended for audio signals the rating is 250V and 30A.
(As an aside, I have also used SpeakCONs to connect the motorised valves of a central heating controller, using two lines for control power and two for the position feedback microswitch)
Note that I have no qualifications in electrics, or electronics, or engineering in general. I merely offer anecdotes about my own machines and points for dicussion rather than advice.
The following user(s) said Thank You: tommylight
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22 Nov 2023 18:58 #286254
by djdelorie
Replied by djdelorie on topic Power distribution questions
So let me guess how that's wired... the physical estop chain provides 24v when "safe". That 24v is used as power, in conjunction with a sinking relay controlled by linuxcnc, to activate the contactors? And linuxcnc monitors that 24v to detect a physical estop?
Or does the 24v estop power the relay which powers the contactor? I'm guessing not, as you wouldn't specify a 24v coil then.
Or does the 24v estop power the relay which powers the contactor? I'm guessing not, as you wouldn't specify a 24v coil then.
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23 Nov 2023 11:33 #286322
by andypugh
Replied by andypugh on topic Power distribution questions
It's been a few years, so I am slightly fuzzy on some of the details.
The contactor coil is controlled through one channel of a 4 relay module,
photos.app.goo.gl/pB5joQ76XqN9YizF8
I don't know any more whether it uses mechanical relays or SSRs (or, now, whether the contactor coil is, in fact, 24V). However given that the other relays are controlling electromagnetic clutches that run at 24V DC I must have either found a DC-switching SSR board, or used a mechanical relay board. Looking back through old emails I suspect it's mechanical relays as the order confirmation email doesn't mention SSRs)
The contactor coil is in series with the two normally-closed e-stop buttons.
I have forgotten exactly how LinuxCNC reads the status of the e-stop/contactors, but it does. I have plenty of 24V IO, and seem to recall adding a snubber to the contactor coil, presumably to protect one of those IO channels against the back-emf when the coil releases.
Looking at the photo, it looks like the PC is actually powered from 12V and I have permanently-on 24V and 12V, and a switched 24V supply.
The contactor coil is controlled through one channel of a 4 relay module,
photos.app.goo.gl/pB5joQ76XqN9YizF8
I don't know any more whether it uses mechanical relays or SSRs (or, now, whether the contactor coil is, in fact, 24V). However given that the other relays are controlling electromagnetic clutches that run at 24V DC I must have either found a DC-switching SSR board, or used a mechanical relay board. Looking back through old emails I suspect it's mechanical relays as the order confirmation email doesn't mention SSRs)
The contactor coil is in series with the two normally-closed e-stop buttons.
I have forgotten exactly how LinuxCNC reads the status of the e-stop/contactors, but it does. I have plenty of 24V IO, and seem to recall adding a snubber to the contactor coil, presumably to protect one of those IO channels against the back-emf when the coil releases.
Looking at the photo, it looks like the PC is actually powered from 12V and I have permanently-on 24V and 12V, and a switched 24V supply.
The following user(s) said Thank You: djdelorie
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