Enabling through a solid state relay
- robertspark
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17 Jun 2022 04:12 #245298
by robertspark
Replied by robertspark on topic Enabling through a solid state relay
I had a look at the amp manual and the voltage was listed as 24v-220v DC
the use of the capacitor had me as no point with a smps
hence presumed it was just a bridge diode pack and a very big cap bank
the use of the capacitor had me as no point with a smps
hence presumed it was just a bridge diode pack and a very big cap bank
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17 Jun 2022 08:26 - 17 Jun 2022 08:30 #245307
by robertspark
Replied by robertspark on topic Enabling through a solid state relay
I have not had success using smps with CNC / stepper drives.
I've only attempted to use one once and it would squeal sometimes.
I suspect that it was the back EMF under deceleration. it was nothing fancy just a 36v smps. the stepper drives were not very good either they were tb6600 drives and it was when I first started with CNC.
I suspect with a smps you may need some sort of voltage clamp such as a MOV
www.mornsun-power.com/html/news-detail/blog-posts/308.html
problem with movs is they are not really designed for regular use to clamp over voltage conditions such as back emf.
I do use smps but only for my control voltages 5v 12v and 24v.
I use toroidal transfomers 45v and 55v AC 450w and 800w rated.
I also use drives that are designed to take AC (leadshine am882H / DMA882S) so I don't worry about bridge rectifiers and more importantly capacitors with low ESR and long life cycles and high capacitance ratings as they are built into the drives.
if I were to build another big machine, then I'd probably try to get mains voltage rated drives..... as it simplifies things further, which is how my lathe servo spindle drive works.
appreciate that the cost increases but it simplifies wiring and components.
I would not use a smps for a motor / motor drive again and would never recommend it to anyone.
I've only attempted to use one once and it would squeal sometimes.
I suspect that it was the back EMF under deceleration. it was nothing fancy just a 36v smps. the stepper drives were not very good either they were tb6600 drives and it was when I first started with CNC.
I suspect with a smps you may need some sort of voltage clamp such as a MOV
www.mornsun-power.com/html/news-detail/blog-posts/308.html
problem with movs is they are not really designed for regular use to clamp over voltage conditions such as back emf.
I do use smps but only for my control voltages 5v 12v and 24v.
I use toroidal transfomers 45v and 55v AC 450w and 800w rated.
I also use drives that are designed to take AC (leadshine am882H / DMA882S) so I don't worry about bridge rectifiers and more importantly capacitors with low ESR and long life cycles and high capacitance ratings as they are built into the drives.
if I were to build another big machine, then I'd probably try to get mains voltage rated drives..... as it simplifies things further, which is how my lathe servo spindle drive works.
appreciate that the cost increases but it simplifies wiring and components.
I would not use a smps for a motor / motor drive again and would never recommend it to anyone.
Last edit: 17 Jun 2022 08:30 by robertspark.
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- tommylight
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17 Jun 2022 14:02 #245323
by tommylight
Replied by tommylight on topic Enabling through a solid state relay
Sometimes, a lot !I've only attempted to use one once and it would squeal sometimes.
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17 Jun 2022 16:25 #245333
by Kylizer
Replied by Kylizer on topic Enabling through a solid state relay
Ok so I was wrong when I said capacitor and it is indeed "bridge diode pack and a very big cap bank" Thanks everyone for the info to. Im diving into it all before I make a next move.
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18 Jun 2022 00:35 #245367
by andypugh
Replied by andypugh on topic Enabling through a solid state relay
On my lathe the servo drives feed back the bus voltage (Mesa 8i20) so what I do is:
1) Have an resistor and normally-closed (mechanical) relay in the PSU that discharges the caps when the input power goes off. You can do this with just a resistor, but it ends up getting pretty big and hot if you want to discharge the cap in seconds rather than minutes.
2) I initially charge the caps through a resistor. When HAL sees the bus voltage get to near full voltage I then enable motion and energise an SSR that bypasses the resistor. Hal will also refuse to _open_ the crowbar circuit if the caps are still charged. But I have rather forgotten how that bit works. But you don't want to open a relay that is passing a lot of DC current, in general.
1) Have an resistor and normally-closed (mechanical) relay in the PSU that discharges the caps when the input power goes off. You can do this with just a resistor, but it ends up getting pretty big and hot if you want to discharge the cap in seconds rather than minutes.
2) I initially charge the caps through a resistor. When HAL sees the bus voltage get to near full voltage I then enable motion and energise an SSR that bypasses the resistor. Hal will also refuse to _open_ the crowbar circuit if the caps are still charged. But I have rather forgotten how that bit works. But you don't want to open a relay that is passing a lot of DC current, in general.
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20 Jun 2022 17:41 #245490
by Kylizer
Replied by Kylizer on topic Enabling through a solid state relay
Is the capacitor used for when the motors start up to help keep the system from lagging down?
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21 Jun 2022 23:32 #245569
by andypugh
Replied by andypugh on topic Enabling through a solid state relay
It is there so that the DC voltage stays near nominal during the low parts of the AC input cycle. It smooths the rectified AC power.Is the capacitor used for when the motors start up to help keep the system from lagging down?
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