D
DJ Delorie
Guest
Before I got too far down the rabbit hole... sanity check time 
tl;dr: I want to run servos off nonisolated 160 vdc
background: I\'m updating this: http://www.delorie.com/electronics/bldc/
So the old driver used an external motor power supply (I had a 80VDC
linear but it\'s big and used hard to get parts) and a separate external
15V driver supply (closed box switcher). The servos I\'ve got are
designed to run off 160 VDC and the power chip can certainly handle it,
which lends itself to non-isolated house voltage (with isolation on the
other side of things, of course). I assume this is the target
application for these servos.
In the USA we have 240v center tapped service.
So if I use a simple two diode rectifier, with neutral as 0v, I should
be getting 160V relative to \"everything else\" as neutral is electrically
connected to ground (eventually)
L1 -->|--*-----*--------
L2 -->|--\' |
--- 160 VDC
---
|
N ------------*--------
Since the 15v supply is isolated, it should work just fine with this,
but it occurs to me... I don\'t need isolation here either. However,
finding info on an easy 160v to 15v buck regulator design is difficult,
and often involves custom wound transformers anyway.
the servos have a protective ground on the UVW cable; I assume that goes
to earth ground and not neutral. What, if anything, goes between ground
and neutral here? I\'m thinking EMI.
Debugging live is a no-go, but I\'ve got a 160v isolated DC power supply
on order for such. It\'s variable, and enough for debugging, but not
enough for full power live usage.
Since I need multiple driver boards, I figured I\'d make one \"power unit\"
for the 160VDC that had the diodes, capacitors, EMI, breakers, etc. and
bring DC to the other boards as if it were a vanilla DC power supply.
With the 80v power supply I could use regenerative braking, but that has
drawbacks (a loose connection during hard stopping fried one of my
boards). I suppose I\'ll need overvoltage protection and a way to \"dump\"
excess, or math how much capacitance I\'ll need - then math inrush
protection.
so... any of the above may be based on invalid assumptions. I may be
missing an obvious better solution. There\'s a non-zero chance of high
voltage sparks and magic smoke events. It may be a stupid idea in
general, and I should just get the giant switching power supply. I
should buy someone else\'s solution instead because reasons.
I could also use pointers to reference designs and known-goods if anyone
has done something similar.
Discuss
Thanks!
DJ
tl;dr: I want to run servos off nonisolated 160 vdc
background: I\'m updating this: http://www.delorie.com/electronics/bldc/
So the old driver used an external motor power supply (I had a 80VDC
linear but it\'s big and used hard to get parts) and a separate external
15V driver supply (closed box switcher). The servos I\'ve got are
designed to run off 160 VDC and the power chip can certainly handle it,
which lends itself to non-isolated house voltage (with isolation on the
other side of things, of course). I assume this is the target
application for these servos.
In the USA we have 240v center tapped service.
So if I use a simple two diode rectifier, with neutral as 0v, I should
be getting 160V relative to \"everything else\" as neutral is electrically
connected to ground (eventually)
L1 -->|--*-----*--------
L2 -->|--\' |
--- 160 VDC
---
|
N ------------*--------
Since the 15v supply is isolated, it should work just fine with this,
but it occurs to me... I don\'t need isolation here either. However,
finding info on an easy 160v to 15v buck regulator design is difficult,
and often involves custom wound transformers anyway.
the servos have a protective ground on the UVW cable; I assume that goes
to earth ground and not neutral. What, if anything, goes between ground
and neutral here? I\'m thinking EMI.
Debugging live is a no-go, but I\'ve got a 160v isolated DC power supply
on order for such. It\'s variable, and enough for debugging, but not
enough for full power live usage.
Since I need multiple driver boards, I figured I\'d make one \"power unit\"
for the 160VDC that had the diodes, capacitors, EMI, breakers, etc. and
bring DC to the other boards as if it were a vanilla DC power supply.
With the 80v power supply I could use regenerative braking, but that has
drawbacks (a loose connection during hard stopping fried one of my
boards). I suppose I\'ll need overvoltage protection and a way to \"dump\"
excess, or math how much capacitance I\'ll need - then math inrush
protection.
so... any of the above may be based on invalid assumptions. I may be
missing an obvious better solution. There\'s a non-zero chance of high
voltage sparks and magic smoke events. It may be a stupid idea in
general, and I should just get the giant switching power supply. I
should buy someone else\'s solution instead because reasons.
I could also use pointers to reference designs and known-goods if anyone
has done something similar.
Discuss
Thanks!
DJ