power supply switching...

S

server

Guest
I\'m thinking about a big new box, with three universal-input power
supplies in the back. The customer wants a power switch on the front.

I guess I can just run the AC through the switch. But that\'s big ugly,
maybe noisy wiring, and such switches tend to fail from inrush surge.

Surge might be fixed with an NTC current limiter.

I could switch the input AC with a big relay in the back. But where
would I get the power to do that? I\'d need a power relay whose coil
operates from 100 to 240 volts.

Or switch the DC supply outputs with some mosfets.

Digikey has some small universal-input DC supplies, 12 or 24 VDC out,
for around $10. One of those could power the relay or the mosfet
circuit.

There would probably be a real power switch on the AC inlet/filter
brick; this would be a \"soft\" power switch.

Do modern PFC-corrected power supplies have big input current surges?
Gotta find out.

Any suggestions?



--

John Larkin Highland Technology, Inc

Science teaches us to doubt.

Claude Bernard
 
On Thu, 03 Sep 2020 09:44:39 -0700, jlarkin@highlandsniptechnology.com
wrote:

I\'m thinking about a big new box, with three universal-input power
supplies in the back. The customer wants a power switch on the front.

I guess I can just run the AC through the switch. But that\'s big ugly,
maybe noisy wiring, and such switches tend to fail from inrush surge.

Surge might be fixed with an NTC current limiter.

I could switch the input AC with a big relay in the back. But where
would I get the power to do that? I\'d need a power relay whose coil
operates from 100 to 240 volts.

Or switch the DC supply outputs with some mosfets.

Digikey has some small universal-input DC supplies, 12 or 24 VDC out,
for around $10. One of those could power the relay or the mosfet
circuit.

There would probably be a real power switch on the AC inlet/filter
brick; this would be a \"soft\" power switch.

Do modern PFC-corrected power supplies have big input current surges?
Gotta find out.

Any suggestions?
Click to expand...

The MeanWell LRS-200 series specs a 60 amp typ inrush current. Times
three power supplies.

The PFC front-end is a boost converter. The AC line initially sees a
bridge, a smallish inductor, and a big cap.





--

John Larkin Highland Technology, Inc

Science teaches us to doubt.

Claude Bernard
 
On 2020/09/03 9:44 a.m., jlarkin@highlandsniptechnology.com wrote:
I\'m thinking about a big new box, with three universal-input power
supplies in the back. The customer wants a power switch on the front.

I guess I can just run the AC through the switch. But that\'s big ugly,
maybe noisy wiring, and such switches tend to fail from inrush surge.

Surge might be fixed with an NTC current limiter.

I could switch the input AC with a big relay in the back. But where
would I get the power to do that? I\'d need a power relay whose coil
operates from 100 to 240 volts.

Or switch the DC supply outputs with some mosfets.

Digikey has some small universal-input DC supplies, 12 or 24 VDC out,
for around $10. One of those could power the relay or the mosfet
circuit.

There would probably be a real power switch on the AC inlet/filter
brick; this would be a \"soft\" power switch.

Do modern PFC-corrected power supplies have big input current surges?
Gotta find out.

Any suggestions?
Click to expand...

Don\'t over-design this! The customer wants a power switch? Give them one
that handles sufficient current to do the job, then +50 to +100% over.

Fluke 9010As had a solution for the power switch (noise, electrical
safety, etc.) up front - they used a long push rod that worked the
push-on/push-off switch buried in the power supply box at the back of
the test gear.

Won\'t something like that help you with UL approval as well?

KISS

John ;-#)#
 
On Thu, 3 Sep 2020 10:24:54 -0700, John Robertson <spam@flippers.com>
wrote:

On 2020/09/03 9:44 a.m., jlarkin@highlandsniptechnology.com wrote:


I\'m thinking about a big new box, with three universal-input power
supplies in the back. The customer wants a power switch on the front.

I guess I can just run the AC through the switch. But that\'s big ugly,
maybe noisy wiring, and such switches tend to fail from inrush surge.

Surge might be fixed with an NTC current limiter.

I could switch the input AC with a big relay in the back. But where
would I get the power to do that? I\'d need a power relay whose coil
operates from 100 to 240 volts.

Or switch the DC supply outputs with some mosfets.

Digikey has some small universal-input DC supplies, 12 or 24 VDC out,
for around $10. One of those could power the relay or the mosfet
circuit.

There would probably be a real power switch on the AC inlet/filter
brick; this would be a \"soft\" power switch.

Do modern PFC-corrected power supplies have big input current surges?
Gotta find out.

Any suggestions?




Don\'t over-design this! The customer wants a power switch? Give them one
that handles sufficient current to do the job, then +50 to +100% over.
Click to expand...

The inrush could get close to 200 amps.


Fluke 9010As had a solution for the power switch (noise, electrical
safety, etc.) up front - they used a long push rod that worked the
push-on/push-off switch buried in the power supply box at the back of
the test gear.

Won\'t something like that help you with UL approval as well?

KISS

John ;-#)#
Click to expand...

These people probably don\'t care about UL, but we may as well try to
stay within the UL/CE rules. A \"soft\" power switch would help some
there. A pushrod might be helpful, but we still need a switch. Maybe
DC switching after the power supplies, with giant mosfets, is the way
to go... if it doesn\'t get out of hand.



--

John Larkin Highland Technology, Inc

Science teaches us to doubt.

Claude Bernard
 
On a sunny day (Thu, 03 Sep 2020 09:51:07 -0700) it happened
jlarkin@highlandsniptechnology.com wrote in
<lf72lf106d4t0jnkm5jp4liiuh8pl9pk3k@4ax.com>:

The MeanWell LRS-200 series specs a 60 amp typ inrush current. Times
three power supplies.

The PFC front-end is a boost converter. The AC line initially sees a
bridge, a smallish inductor, and a big cap.
Click to expand...

Would a big triac work as power switch?
Drive it with some DC from a small supply that is powered by the power switch
Is that legal?
Over here you may need a real switch in the power line.
So maybe 2 switches, one big one to cut the mains,
and a push button thing or touch screen or whatever for on off.
No noise no sparks.
?
 
On 09/03/20 17:44, jlarkin@highlandsniptechnology.com wrote:
I\'m thinking about a big new box, with three universal-input power
supplies in the back. The customer wants a power switch on the front.

I guess I can just run the AC through the switch. But that\'s big ugly,
maybe noisy wiring, and such switches tend to fail from inrush surge.

Surge might be fixed with an NTC current limiter.

I could switch the input AC with a big relay in the back. But where
would I get the power to do that? I\'d need a power relay whose coil
operates from 100 to 240 volts.

Or switch the DC supply outputs with some mosfets.

Digikey has some small universal-input DC supplies, 12 or 24 VDC out,
for around $10. One of those could power the relay or the mosfet
circuit.

There would probably be a real power switch on the AC inlet/filter
brick; this would be a \"soft\" power switch.

Do modern PFC-corrected power supplies have big input current surges?
Gotta find out.

Any suggestions?
Click to expand...

Can\'t you do that with a single multi output supply. Might be
cheaper than 3 supplies and whatever added circuit it needs
to fix the surge issue ?.

Have a stack of rechargeable tools and other stuff that needs
to be topped up every so often, 8 or 10 chargers, time switch
for on/off. Solved it by fitting a big 25 amp ind relay from the
timeswitch, Noisy, crude, but gets the job done and no blown
line fuses yet...

Chris
 
On Thu, 03 Sep 2020 19:24:50 +0100, Chris <xxx.syseng.yyy@gfsys.co.uk>
wrote:

On 09/03/20 17:44, jlarkin@highlandsniptechnology.com wrote:


I\'m thinking about a big new box, with three universal-input power
supplies in the back. The customer wants a power switch on the front.

I guess I can just run the AC through the switch. But that\'s big ugly,
maybe noisy wiring, and such switches tend to fail from inrush surge.

Surge might be fixed with an NTC current limiter.

I could switch the input AC with a big relay in the back. But where
would I get the power to do that? I\'d need a power relay whose coil
operates from 100 to 240 volts.

Or switch the DC supply outputs with some mosfets.

Digikey has some small universal-input DC supplies, 12 or 24 VDC out,
for around $10. One of those could power the relay or the mosfet
circuit.

There would probably be a real power switch on the AC inlet/filter
brick; this would be a \"soft\" power switch.

Do modern PFC-corrected power supplies have big input current surges?
Gotta find out.

Any suggestions?




Can\'t you do that with a single multi output supply. Might be
cheaper than 3 supplies and whatever added circuit it needs
to fix the surge issue ?.
Click to expand...

The MeanWell LRS-200s are crazy cheap, around $30 each, and the
triples cost $250 or so. Don\'t know why.


Have a stack of rechargeable tools and other stuff that needs
to be topped up every so often, 8 or 10 chargers, time switch
for on/off. Solved it by fitting a big 25 amp ind relay from the
timeswitch, Noisy, crude, but gets the job done and no blown
line fuses yet...
Click to expand...

Some giant relay is a possibility, but I need to get the coil voltage
from somewhere. AC line voltage could be 120 or 240.
 
On Thu, 03 Sep 2020 10:37:58 -0700, jlarkin@highlandsniptechnology.com
wrote:

On Thu, 3 Sep 2020 10:24:54 -0700, John Robertson <spam@flippers.com
wrote:

On 2020/09/03 9:44 a.m., jlarkin@highlandsniptechnology.com wrote:


I\'m thinking about a big new box, with three universal-input power
supplies in the back. The customer wants a power switch on the front.

I guess I can just run the AC through the switch. But that\'s big ugly,
maybe noisy wiring, and such switches tend to fail from inrush surge.

Surge might be fixed with an NTC current limiter.

I could switch the input AC with a big relay in the back. But where
would I get the power to do that? I\'d need a power relay whose coil
operates from 100 to 240 volts.

Or switch the DC supply outputs with some mosfets.

Digikey has some small universal-input DC supplies, 12 or 24 VDC out,
for around $10. One of those could power the relay or the mosfet
circuit.

There would probably be a real power switch on the AC inlet/filter
brick; this would be a \"soft\" power switch.

Do modern PFC-corrected power supplies have big input current surges?
Gotta find out.

Any suggestions?




Don\'t over-design this! The customer wants a power switch? Give them one
that handles sufficient current to do the job, then +50 to +100% over.

The inrush could get close to 200 amps.
Click to expand...

You have to consider also the house wiring and house fuses.

If you use separate relays for each PSU, you could delay the turn on
for some of the PSUs, limiting the peak current to a manageable level.

n the US, if you have split phase (2 x 120 V) you could reduce the
current, but this requires a two pole relay.

If the issue is only relay contact rating (and not house fuses), just
get a three phase relay, so each contact has to handle only 60 A peak.
In the US, if 120/208 V three phase happens to be available, you could
run each PSU from own phase.

Of course, in the rest of the world a 1x230 V or 230/400 V three phase
could also be used with the same relay and only select between one and
three phases.
 
On Thu, 03 Sep 2020 22:46:41 +0300, upsidedown@downunder.com wrote:

On Thu, 03 Sep 2020 10:37:58 -0700, jlarkin@highlandsniptechnology.com
wrote:

On Thu, 3 Sep 2020 10:24:54 -0700, John Robertson <spam@flippers.com
wrote:

On 2020/09/03 9:44 a.m., jlarkin@highlandsniptechnology.com wrote:


I\'m thinking about a big new box, with three universal-input power
supplies in the back. The customer wants a power switch on the front.

I guess I can just run the AC through the switch. But that\'s big ugly,
maybe noisy wiring, and such switches tend to fail from inrush surge.

Surge might be fixed with an NTC current limiter.

I could switch the input AC with a big relay in the back. But where
would I get the power to do that? I\'d need a power relay whose coil
operates from 100 to 240 volts.

Or switch the DC supply outputs with some mosfets.

Digikey has some small universal-input DC supplies, 12 or 24 VDC out,
for around $10. One of those could power the relay or the mosfet
circuit.

There would probably be a real power switch on the AC inlet/filter
brick; this would be a \"soft\" power switch.

Do modern PFC-corrected power supplies have big input current surges?
Gotta find out.

Any suggestions?




Don\'t over-design this! The customer wants a power switch? Give them one
that handles sufficient current to do the job, then +50 to +100% over.

The inrush could get close to 200 amps.

You have to consider also the house wiring and house fuses.

If you use separate relays for each PSU, you could delay the turn on
for some of the PSUs, limiting the peak current to a manageable level.

n the US, if you have split phase (2 x 120 V) you could reduce the
current, but this requires a two pole relay.

If the issue is only relay contact rating (and not house fuses), just
get a three phase relay, so each contact has to handle only 60 A peak.
In the US, if 120/208 V three phase happens to be available, you could
run each PSU from own phase.

Of course, in the rest of the world a 1x230 V or 230/400 V three phase
could also be used with the same relay and only select between one and
three phases.
Click to expand...

This won\'t be residential, but it could be used anywhere in the world.

Single phase.

I don\'t think that 600 watts of switching power supply will trip an AC
breaker on startup. I\'m confident it would eventually destroy a small
switch or relay.

The bog disk NTC thermistors are intellectually challenging but do
seem to work.
 
On 9/3/20 12:52 PM, John Larkin wrote:
On Thu, 03 Sep 2020 22:46:41 +0300, upsidedown@downunder.com wrote:

On Thu, 03 Sep 2020 10:37:58 -0700, jlarkin@highlandsniptechnology.com
wrote:

On Thu, 3 Sep 2020 10:24:54 -0700, John Robertson <spam@flippers.com
wrote:

On 2020/09/03 9:44 a.m., jlarkin@highlandsniptechnology.com wrote:


I\'m thinking about a big new box, with three universal-input power
supplies in the back. The customer wants a power switch on the front.

I guess I can just run the AC through the switch. But that\'s big ugly,
maybe noisy wiring, and such switches tend to fail from inrush surge.

Surge might be fixed with an NTC current limiter.

I could switch the input AC with a big relay in the back. But where
would I get the power to do that? I\'d need a power relay whose coil
operates from 100 to 240 volts.

Or switch the DC supply outputs with some mosfets.

Digikey has some small universal-input DC supplies, 12 or 24 VDC out,
for around $10. One of those could power the relay or the mosfet
circuit.

There would probably be a real power switch on the AC inlet/filter
brick; this would be a \"soft\" power switch.

Do modern PFC-corrected power supplies have big input current surges?
Gotta find out.

Any suggestions?




Don\'t over-design this! The customer wants a power switch? Give them one
that handles sufficient current to do the job, then +50 to +100% over.

The inrush could get close to 200 amps.

You have to consider also the house wiring and house fuses.

If you use separate relays for each PSU, you could delay the turn on
for some of the PSUs, limiting the peak current to a manageable level.

n the US, if you have split phase (2 x 120 V) you could reduce the
current, but this requires a two pole relay.

If the issue is only relay contact rating (and not house fuses), just
get a three phase relay, so each contact has to handle only 60 A peak.
In the US, if 120/208 V three phase happens to be available, you could
run each PSU from own phase.

Of course, in the rest of the world a 1x230 V or 230/400 V three phase
could also be used with the same relay and only select between one and
three phases.

This won\'t be residential, but it could be used anywhere in the world.

Single phase.

I don\'t think that 600 watts of switching power supply will trip an AC
breaker on startup. I\'m confident it would eventually destroy a small
switch or relay.

The bog disk NTC thermistors are intellectually challenging but do
seem to work.
Click to expand...
Don\'t you miss big old mercury contact relays? :) Tough critters!
 
torsdag den 3. september 2020 kl. 21.35.36 UTC+2 skrev John Larkin:
On Thu, 03 Sep 2020 19:24:50 +0100, Chris <xxx.syseng.yyy@gfsys.co.uk
wrote:

On 09/03/20 17:44, jlarkin@highlandsniptechnology.com wrote:


I\'m thinking about a big new box, with three universal-input power
supplies in the back. The customer wants a power switch on the front.

I guess I can just run the AC through the switch. But that\'s big ugly,
maybe noisy wiring, and such switches tend to fail from inrush surge.

Surge might be fixed with an NTC current limiter.

I could switch the input AC with a big relay in the back. But where
would I get the power to do that? I\'d need a power relay whose coil
operates from 100 to 240 volts.

Or switch the DC supply outputs with some mosfets.

Digikey has some small universal-input DC supplies, 12 or 24 VDC out,
for around $10. One of those could power the relay or the mosfet
circuit.

There would probably be a real power switch on the AC inlet/filter
brick; this would be a \"soft\" power switch.

Do modern PFC-corrected power supplies have big input current surges?
Gotta find out.

Any suggestions?




Can\'t you do that with a single multi output supply. Might be
cheaper than 3 supplies and whatever added circuit it needs
to fix the surge issue ?.

The MeanWell LRS-200s are crazy cheap, around $30 each, and the
triples cost $250 or so. Don\'t know why.



Have a stack of rechargeable tools and other stuff that needs
to be topped up every so often, 8 or 10 chargers, time switch
for on/off. Solved it by fitting a big 25 amp ind relay from the
timeswitch, Noisy, crude, but gets the job done and no blown
line fuses yet...


Some giant relay is a possibility, but I need to get the coil voltage
from somewhere. AC line voltage could be 120 or 240.
Click to expand...

use the output from one of the supplies to turn on the rest?
 
On Thu, 03 Sep 2020 12:35:24 -0700, John Larkin wrote:

On Thu, 03 Sep 2020 19:24:50 +0100, Chris <xxx.syseng.yyy@gfsys.co.uk
wrote:

On 09/03/20 17:44, jlarkin@highlandsniptechnology.com wrote:


I\'m thinking about a big new box, with three universal-input power
supplies in the back. The customer wants a power switch on the front.

I guess I can just run the AC through the switch. But that\'s big ugly,
maybe noisy wiring, and such switches tend to fail from inrush surge.

Surge might be fixed with an NTC current limiter.

I could switch the input AC with a big relay in the back. But where
would I get the power to do that? I\'d need a power relay whose coil
operates from 100 to 240 volts.

Or switch the DC supply outputs with some mosfets.

Digikey has some small universal-input DC supplies, 12 or 24 VDC out,
for around $10. One of those could power the relay or the mosfet
circuit.

There would probably be a real power switch on the AC inlet/filter
brick; this would be a \"soft\" power switch.

Do modern PFC-corrected power supplies have big input current surges?
Gotta find out.

Any suggestions?




Can\'t you do that with a single multi output supply. Might be cheaper
than 3 supplies and whatever added circuit it needs to fix the surge
issue ?.

The MeanWell LRS-200s are crazy cheap, around $30 each, and the triples
cost $250 or so. Don\'t know why.



Have a stack of rechargeable tools and other stuff that needs to be
topped up every so often, 8 or 10 chargers, time switch for on/off.
Solved it by fitting a big 25 amp ind relay from the timeswitch, Noisy,
crude, but gets the job done and no blown line fuses yet...


Some giant relay is a possibility, but I need to get the coil voltage
from somewhere. AC line voltage could be 120 or 240.
Click to expand...

The LSR-200 says max inrush of 60A. Find a power relay with a 12 or 24
volt coil and drive the coil via a small step down transformer. That
way you have lv to the front panel switch.



--
Chisolm
Texas-American
 
On Thu, 3 Sep 2020 13:26:04 -0700 (PDT), Lasse Langwadt Christensen
<langwadt@fonz.dk> wrote:

torsdag den 3. september 2020 kl. 21.35.36 UTC+2 skrev John Larkin:
On Thu, 03 Sep 2020 19:24:50 +0100, Chris <xxx.syseng.yyy@gfsys.co.uk
wrote:

On 09/03/20 17:44, jlarkin@highlandsniptechnology.com wrote:


I\'m thinking about a big new box, with three universal-input power
supplies in the back. The customer wants a power switch on the front.

I guess I can just run the AC through the switch. But that\'s big ugly,
maybe noisy wiring, and such switches tend to fail from inrush surge.

Surge might be fixed with an NTC current limiter.

I could switch the input AC with a big relay in the back. But where
would I get the power to do that? I\'d need a power relay whose coil
operates from 100 to 240 volts.

Or switch the DC supply outputs with some mosfets.

Digikey has some small universal-input DC supplies, 12 or 24 VDC out,
for around $10. One of those could power the relay or the mosfet
circuit.

There would probably be a real power switch on the AC inlet/filter
brick; this would be a \"soft\" power switch.

Do modern PFC-corrected power supplies have big input current surges?
Gotta find out.

Any suggestions?




Can\'t you do that with a single multi output supply. Might be
cheaper than 3 supplies and whatever added circuit it needs
to fix the surge issue ?.

The MeanWell LRS-200s are crazy cheap, around $30 each, and the
triples cost $250 or so. Don\'t know why.



Have a stack of rechargeable tools and other stuff that needs
to be topped up every so often, 8 or 10 chargers, time switch
for on/off. Solved it by fitting a big 25 amp ind relay from the
timeswitch, Noisy, crude, but gets the job done and no blown
line fuses yet...


Some giant relay is a possibility, but I need to get the coil voltage
from somewhere. AC line voltage could be 120 or 240.

use the output from one of the supplies to turn on the rest?
Click to expand...

The cheap supplies don\'t have a control input.

I could power them all up and add load switches downstream, controlled
by a little switch. These days, most power switches are fake.
 
On Thu, 03 Sep 2020 15:29:16 -0500, Joe Chisolm
<jchisolm6@earthlink.net> wrote:

On Thu, 03 Sep 2020 12:35:24 -0700, John Larkin wrote:

On Thu, 03 Sep 2020 19:24:50 +0100, Chris <xxx.syseng.yyy@gfsys.co.uk
wrote:

On 09/03/20 17:44, jlarkin@highlandsniptechnology.com wrote:


I\'m thinking about a big new box, with three universal-input power
supplies in the back. The customer wants a power switch on the front.

I guess I can just run the AC through the switch. But that\'s big ugly,
maybe noisy wiring, and such switches tend to fail from inrush surge.

Surge might be fixed with an NTC current limiter.

I could switch the input AC with a big relay in the back. But where
would I get the power to do that? I\'d need a power relay whose coil
operates from 100 to 240 volts.

Or switch the DC supply outputs with some mosfets.

Digikey has some small universal-input DC supplies, 12 or 24 VDC out,
for around $10. One of those could power the relay or the mosfet
circuit.

There would probably be a real power switch on the AC inlet/filter
brick; this would be a \"soft\" power switch.

Do modern PFC-corrected power supplies have big input current surges?
Gotta find out.

Any suggestions?




Can\'t you do that with a single multi output supply. Might be cheaper
than 3 supplies and whatever added circuit it needs to fix the surge
issue ?.

The MeanWell LRS-200s are crazy cheap, around $30 each, and the triples
cost $250 or so. Don\'t know why.



Have a stack of rechargeable tools and other stuff that needs to be
topped up every so often, 8 or 10 chargers, time switch for on/off.
Solved it by fitting a big 25 amp ind relay from the timeswitch, Noisy,
crude, but gets the job done and no blown line fuses yet...


Some giant relay is a possibility, but I need to get the coil voltage
from somewhere. AC line voltage could be 120 or 240.

The LSR-200 says max inrush of 60A. Find a power relay with a 12 or 24
volt coil and drive the coil via a small step down transformer. That
way you have lv to the front panel switch.
Click to expand...

3 supplies is 180 amps... typical.

The transformer would have to work from 120-240 VAC.

I can get a universal-input 12VDC supply for around $10.
 
On 09/03/20 20:35, John Larkin wrote:
On Thu, 03 Sep 2020 19:24:50 +0100, Chris<xxx.syseng.yyy@gfsys.co.uk
wrote:

On 09/03/20 17:44, jlarkin@highlandsniptechnology.com wrote:


I\'m thinking about a big new box, with three universal-input power
supplies in the back. The customer wants a power switch on the front.

I guess I can just run the AC through the switch. But that\'s big ugly,
maybe noisy wiring, and such switches tend to fail from inrush surge.

Surge might be fixed with an NTC current limiter.

I could switch the input AC with a big relay in the back. But where
would I get the power to do that? I\'d need a power relay whose coil
operates from 100 to 240 volts.

Or switch the DC supply outputs with some mosfets.

Digikey has some small universal-input DC supplies, 12 or 24 VDC out,
for around $10. One of those could power the relay or the mosfet
circuit.

There would probably be a real power switch on the AC inlet/filter
brick; this would be a \"soft\" power switch.

Do modern PFC-corrected power supplies have big input current surges?
Gotta find out.

Any suggestions?




Can\'t you do that with a single multi output supply. Might be
cheaper than 3 supplies and whatever added circuit it needs
to fix the surge issue ?.

The MeanWell LRS-200s are crazy cheap, around $30 each, and the
triples cost $250 or so. Don\'t know why.
Click to expand...

I\'ve used Meanwell supplies. They are not bad, but look very
minimalist in terms of circuit design and the pcb\'s on some
are, shall we say, hastily constructed. Nor is there any ovp
protection. Cheap and cheerful and ok for the occasional
project round the lab, but not sure I would be happy selling
a product with them into a professional environment. What
voltages are needed and, for example, would a standard pc psu
get the job done ?. Various form factors, sizes and power
outputs.

I would shop around for a single 3 output psu, but if you
must use 3, why not a add a cheap wall wart style psu to drive
the relay ?. Gives the capability of remote switching as well...

Chris



Have a stack of rechargeable tools and other stuff that needs
to be topped up every so often, 8 or 10 chargers, time switch
for on/off. Solved it by fitting a big 25 amp ind relay from the
timeswitch, Noisy, crude, but gets the job done and no blown
line fuses yet...


Some giant relay is a possibility, but I need to get the coil voltage
from somewhere. AC line voltage could be 120 or 240.
Click to expand...
 
On Thursday, 3 September 2020 17:44:54 UTC+1, jla...@highlandsniptechnology.com wrote:

I\'m thinking about a big new box, with three universal-input power
supplies in the back. The customer wants a power switch on the front.

I guess I can just run the AC through the switch. But that\'s big ugly,
maybe noisy wiring, and such switches tend to fail from inrush surge.

Surge might be fixed with an NTC current limiter.

I could switch the input AC with a big relay in the back. But where
would I get the power to do that? I\'d need a power relay whose coil
operates from 100 to 240 volts.

Or switch the DC supply outputs with some mosfets.

Digikey has some small universal-input DC supplies, 12 or 24 VDC out,
for around $10. One of those could power the relay or the mosfet
circuit.

There would probably be a real power switch on the AC inlet/filter
brick; this would be a \"soft\" power switch.

Do modern PFC-corrected power supplies have big input current surges?
Gotta find out.

Any suggestions?
Click to expand...

A mains switch & NTC is very simple, does the job. Snubber & parallelled poles help a bit. As someone said, a plastic rod could keep mains out of wherever you don\'t like it. Case flexure can make those fun.

240v rated relays generally run fine on 120, some on 100. Testing required. Obviously you need spare pulling capacity else contact pressure is weak. And permitted mains voltages are >240.

A PTC thermistor in series could in principle reduce the i variation, but you\'d be left needing a coil voltage that\'s not off the shelf. Or perhaps a transistorised i limiter, eg a fet that cuts out peaks when 240v is used.

If your market excludes Japan a series cap could make use of the 50/60Hz difference. 240 then drops a bit more than 110 - but again a useless coil voltage is then needed.

Or series PTC R & parallel NTC or Z etc etc.

Or a 2nd relay that switches in a series C when it gets 240.

Or... so many options.


NT
 
torsdag den 3. september 2020 kl. 22.32.31 UTC+2 skrev John Larkin:
On Thu, 3 Sep 2020 13:26:04 -0700 (PDT), Lasse Langwadt Christensen
langwadt@fonz.dk> wrote:

torsdag den 3. september 2020 kl. 21.35.36 UTC+2 skrev John Larkin:
On Thu, 03 Sep 2020 19:24:50 +0100, Chris <xxx.syseng.yyy@gfsys.co.uk
wrote:

On 09/03/20 17:44, jlarkin@highlandsniptechnology.com wrote:


I\'m thinking about a big new box, with three universal-input power
supplies in the back. The customer wants a power switch on the front.

I guess I can just run the AC through the switch. But that\'s big ugly,
maybe noisy wiring, and such switches tend to fail from inrush surge.

Surge might be fixed with an NTC current limiter.

I could switch the input AC with a big relay in the back. But where
would I get the power to do that? I\'d need a power relay whose coil
operates from 100 to 240 volts.

Or switch the DC supply outputs with some mosfets.

Digikey has some small universal-input DC supplies, 12 or 24 VDC out,
for around $10. One of those could power the relay or the mosfet
circuit.

There would probably be a real power switch on the AC inlet/filter
brick; this would be a \"soft\" power switch.

Do modern PFC-corrected power supplies have big input current surges?
Gotta find out.

Any suggestions?




Can\'t you do that with a single multi output supply. Might be
cheaper than 3 supplies and whatever added circuit it needs
to fix the surge issue ?.

The MeanWell LRS-200s are crazy cheap, around $30 each, and the
triples cost $250 or so. Don\'t know why.



Have a stack of rechargeable tools and other stuff that needs
to be topped up every so often, 8 or 10 chargers, time switch
for on/off. Solved it by fitting a big 25 amp ind relay from the
timeswitch, Noisy, crude, but gets the job done and no blown
line fuses yet...


Some giant relay is a possibility, but I need to get the coil voltage
from somewhere. AC line voltage could be 120 or 240.

use the output from one of the supplies to turn on the rest?





The cheap supplies don\'t have a control input.
Click to expand...

switch for first supply, the supply turns on relay to power other supplies
switch only has to handle inrush of one supply, and the relay voltage is fixed
maybe use a second pole on relay to bypass inrush limiter on first supply
 
On 2020-09-03 13:37, jlarkin@highlandsniptechnology.com wrote:
On Thu, 3 Sep 2020 10:24:54 -0700, John Robertson <spam@flippers.com
wrote:

On 2020/09/03 9:44 a.m., jlarkin@highlandsniptechnology.com wrote:


I\'m thinking about a big new box, with three universal-input power
supplies in the back. The customer wants a power switch on the front.

I guess I can just run the AC through the switch. But that\'s big ugly,
maybe noisy wiring, and such switches tend to fail from inrush surge.

Surge might be fixed with an NTC current limiter.

I could switch the input AC with a big relay in the back. But where
would I get the power to do that? I\'d need a power relay whose coil
operates from 100 to 240 volts.

Or switch the DC supply outputs with some mosfets.

Digikey has some small universal-input DC supplies, 12 or 24 VDC out,
for around $10. One of those could power the relay or the mosfet
circuit.

There would probably be a real power switch on the AC inlet/filter
brick; this would be a \"soft\" power switch.

Do modern PFC-corrected power supplies have big input current surges?
Gotta find out.

Any suggestions?




Don\'t over-design this! The customer wants a power switch? Give them one
that handles sufficient current to do the job, then +50 to +100% over.

The inrush could get close to 200 amps.



Fluke 9010As had a solution for the power switch (noise, electrical
safety, etc.) up front - they used a long push rod that worked the
push-on/push-off switch buried in the power supply box at the back of
the test gear.

Won\'t something like that help you with UL approval as well?

KISS

John ;-#)#

These people probably don\'t care about UL, but we may as well try to
stay within the UL/CE rules. A \"soft\" power switch would help some
there. A pushrod might be helpful, but we still need a switch. Maybe
DC switching after the power supplies, with giant mosfets, is the way
to go... if it doesn\'t get out of hand.
Click to expand...

The canonical approach is a switch feeding a wirewound resistor that is
shunted by a relay.

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC / Hobbs ElectroOptics
Optics, Electro-optics, Photonics, Analog Electronics
Briarcliff Manor NY 10510

http://electrooptical.net
http://hobbs-eo.com
 
On Thursday, September 3, 2020 at 9:44:54 AM UTC-7, jla...@highlandsniptechnology.com wrote:
I\'m thinking about a big new box, with three universal-input power
supplies in the back. The customer wants a power switch on the front.
Click to expand...

So, instead of \'switch\' have standby power and a logic pushbutton to ON/OFF
the heavy power parts. They mass-produce this for PCs, in a variety of
form factors and ratings.
 
On 03/09/2020 18:24, John Robertson wrote:

<snip>
Fluke 9010As had a solution for the power switch (noise, electrical
safety, etc.) up front - they used a long push rod that worked the
push-on/push-off switch buried in the power supply box at the back of
the test gear.

Won\'t something like that help you with UL approval as well?

KISS

John ;-#)#
Click to expand...

Rotary switch actuator on front panel, plastic rod, magnet, reed
switches. Need inrush current limiting.

Or use relay or contactor manually operated by cam or pushrod from front
panel actuator, maybe use the coil for latching?

--
Cheers
Clive
 
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