Bench mains supply - another attempt


 

Hi guys,
Some of you might remember that I'm trying to set up a mains AC supply
separate from my wall mains, because I can't risk blowing the fuse.
The idea was to use an UPS for devices that might create a short, and
if the DUT shorted then the idea was the UPS would just shut down, no
harm done.

I've conferred with the APC help line. Here's what they said:

1. when the UPS output gets shorted, overload protection kicks in, and
after the short is cleared the UPS can be reset and is ready to go
2. doing this repeatedly is not something the UPS is meant to do, and
they say it might damage the UPS.

I recognize (2) is just defensive thinking, and was wondering if
anyone had any experience or insight into how the overload protection
works.

Asked whether adding a fuse to the output of the UPS would work, they
weren't able to say if that would help at all. What do you guys think?

Here are the UPSes that I'm currently considering:

racks:
APC Smart UPS SU2200RMI3U - €320 - huge, full-depth 3U rack, from an older line
APC Smart UPS SUA1500RMI2U - €405 - still big, but a third the size,
half-depth 2U
APC Smart UPS SU1400RMI2U - €290 - half-depth 2U
APC Smart UPS SC 1500i 2U - €259 - half-depth 2U, looks ancient

desktop:
APC Smart UPS SUA1500I - €275, tiny

I would appreciate any help.

Cheers,
Damian


chris hayes <chris.hayes60@...>
 

Hi Damian
Apologies if you have already considered this: put an 500Watt halogen bulb in the supply line while testing an unknown load. These have a 10 ohm cold resistance (240 Volt versions), (presumably 5 ohms in USA) If the load becomes shorted it merely puts the light on.
ChrisH


 

Hi Chris,

On Sat, Nov 2, 2013 at 10:06 AM, chris hayes
<chris.hayes60@...> wrote:
Hi Damian
Apologies if you have already considered this: put an 500Watt halogen bulb in the supply line while testing an unknown load. These have a 10 ohm cold resistance (240 Volt versions), (presumably 5 ohms in USA) If the load becomes shorted it merely puts the light on.
ChrisH
Yeah, but it's difficult to find a 1000W light bulb (I have some
high-power equipment I need to test) on the one hand and on the other
hand as the load goes up the voltage drops, so for higher loads it's
less than perfect. I could make up the voltage with a Variac but
that's getting complicated.

Cheers,
D.


stefan_trethan
 

You can find halogen bulbs up to 2000W easily in Germany, I can supply
mail order sources.

Any DIY store will have 500W halogen lights for under 10eur, including
the bulb, buy two and parallel.

Complicated? And the UPS thing isn't?


If you are prepared to spend a few hundred bucks on a UPS you might as
well go double or nothing and get a used AC source, which gives you so
much more value for money.

I just wouldn't want to be on the other side of a UPS with unknown
control loop response and unknown output behaviour that was never
designed for this purpose.

ST

On Sat, Nov 2, 2013 at 10:39 AM, cheater00 . <cheater00@...> wrote:
Hi Chris,

On Sat, Nov 2, 2013 at 10:06 AM, chris hayes
<chris.hayes60@...> wrote:
Hi Damian
Apologies if you have already considered this: put an 500Watt halogen bulb in the supply line while testing an unknown load. These have a 10 ohm cold resistance (240 Volt versions), (presumably 5 ohms in USA) If the load becomes shorted it merely puts the light on.
ChrisH
Yeah, but it's difficult to find a 1000W light bulb (I have some
high-power equipment I need to test) on the one hand and on the other
hand as the load goes up the voltage drops, so for higher loads it's
less than perfect. I could make up the voltage with a Variac but
that's getting complicated.

Cheers,
D.


------------------------------------

Yahoo Groups Links



Don Black <donald_black@...>
 

You can get projector lamps up to 1000 watt, I bet you'd find some cheap NOS on eBay. Just the old dim bulb trick on steroids.

Don Black.

On 02-Nov-13 8:39 PM, cheater00 . wrote:
 

Hi Chris,

On Sat, Nov 2, 2013 at 10:06 AM, chris hayes
wrote:
> Hi Damian
> Apologies if you have already considered this: put an 500Watt halogen bulb in the supply line while testing an unknown load. These have a 10 ohm cold resistance (240 Volt versions), (presumably 5 ohms in USA) If the load becomes shorted it merely puts the light on.
> ChrisH

Yeah, but it's difficult to find a 1000W light bulb (I have some
high-power equipment I need to test) on the one hand and on the other
hand as the load goes up the voltage drops, so for higher loads it's
less than perfect. I could make up the voltage with a Variac but
that's getting complicated.

Cheers,
D.



Don Black <donald_black@...>
 

Something like this . Set eBay search for cheapest first to get past all the new TV projector replacements and you'll find the NOS 16mm movie and 35mm slide projector lamps. You might even find an old slide projector you can get the lamp housing off that will have the socket and physical protection ready made. These are now rapidly becoming obsolete and you might pick one up at a garage sale, etc.

Don Black.

On 02-Nov-13 9:56 PM, Don Black wrote:
 

You can get projector lamps up to 1000 watt, I bet you'd find some cheap NOS on eBay. Just the old dim bulb trick on steroids.

Don Black.

On 02-Nov-13 8:39 PM, cheater00 . wrote:
 

Hi Chris,

On Sat, Nov 2, 2013 at 10:06 AM, chris hayes
wrote:
> Hi Damian
> Apologies if you have already considered this: put an 500Watt halogen bulb in the supply line while testing an unknown load. These have a 10 ohm cold resistance (240 Volt versions), (presumably 5 ohms in USA) If the load becomes shorted it merely puts the light on.
> ChrisH

Yeah, but it's difficult to find a 1000W light bulb (I have some
high-power equipment I need to test) on the one hand and on the other
hand as the load goes up the voltage drops, so for higher loads it's
less than perfect. I could make up the voltage with a Variac but
that's getting complicated.

Cheers,
D.




 

Stefan,

On Sat, Nov 2, 2013 at 11:52 AM, Stefan Trethan <stefan_trethan@...> wrote:
You can find halogen bulbs up to 2000W easily in Germany, I can supply
mail order sources.
If you could - that would be great.

Any DIY store will have 500W halogen lights for under 10eur, including
the bulb, buy two and parallel.

Complicated? And the UPS thing isn't?


If you are prepared to spend a few hundred bucks on a UPS you might as
well go double or nothing and get a used AC source, which gives you so
much more value for money.

I just wouldn't want to be on the other side of a UPS with unknown
control loop response and unknown output behaviour that was never
designed for this purpose.

ST
How would the AC source be used in this scenario? Can you recommend
some example units?

Cheers,
Damian


stefan_trethan
 

This is where I bought a bunch of incandescent bulbs before the sale
of some types was banned:
<http://www.leuchtstark.de/Leuchtmittel/HALOGENLAMPEN/mlight/Halogen-Stab/mlight-Halogenstab.html>

This would be a typical AC source:
<http://www.ebay.com/itm/AC-POWER-SOURCE-/281193312449?pt=LH_DefaultDomain_2&hash=item41786d70c1>
The advantage is that they have adjustable voltage and frequency,
overload protection, and are meant to deal with unknown loads.
And no batteries to deal with.

ST

On Sat, Nov 2, 2013 at 12:23 PM, cheater00 . <cheater00@...> wrote:
Stefan,

On Sat, Nov 2, 2013 at 11:52 AM, Stefan Trethan <stefan_trethan@...> wrote:
You can find halogen bulbs up to 2000W easily in Germany, I can supply
mail order sources.
If you could - that would be great.

Any DIY store will have 500W halogen lights for under 10eur, including
the bulb, buy two and parallel.

Complicated? And the UPS thing isn't?


If you are prepared to spend a few hundred bucks on a UPS you might as
well go double or nothing and get a used AC source, which gives you so
much more value for money.

I just wouldn't want to be on the other side of a UPS with unknown
control loop response and unknown output behaviour that was never
designed for this purpose.

ST
How would the AC source be used in this scenario? Can you recommend
some example units?

Cheers,
Damian


------------------------------------

Yahoo Groups Links



 

Stefan,

On Sat, Nov 2, 2013 at 12:54 PM, Stefan Trethan <stefan_trethan@...> wrote:
This is where I bought a bunch of incandescent bulbs before the sale
of some types was banned:
<http://www.leuchtstark.de/Leuchtmittel/HALOGENLAMPEN/mlight/Halogen-Stab/mlight-Halogenstab.html>

This would be a typical AC source:
<http://www.ebay.com/itm/AC-POWER-SOURCE-/281193312449?pt=LH_DefaultDomain_2&hash=item41786d70c1>
The advantage is that they have adjustable voltage and frequency,
overload protection, and are meant to deal with unknown loads.
And no batteries to deal with.

ST
Thanks for the links. The AC power source looks interesting. I might
go with that instead - I didn't realize that those could handle shorts
and other messed up loads. Do you know the right technical term in
German? Searching for "wechselstromquelle" and "stromquelle", the
closest thing to lab equipment was a power supply for an incubator..

Thanks,
Damian


 

A fuse or circuit breaker is not going to act any faster than the overload
protection in a good UPS or inverter. I would be worried about the UPS or
inverter burning out to save a fuse.

I know how the UPS overload protection *could* work but whether APC implemented
a robust design is anybody's guess. An inverter based on a current mode output
switching regulator design for instance would have cycle-by-cycle current
limiting and be practically indestructible.

I doubt APC or anybody else is going to be very helpful.

An easy solution may be to add a standard low current (5 amps?) AC circuit
breaker inline with one outlet. In the event of overload, it should trip before
your main circuit breaker.

On Sat, 2 Nov 2013 09:16:59 +0100, you wrote:

Hi guys,
Some of you might remember that I'm trying to set up a mains AC supply
separate from my wall mains, because I can't risk blowing the fuse.
The idea was to use an UPS for devices that might create a short, and
if the DUT shorted then the idea was the UPS would just shut down, no
harm done.

I've conferred with the APC help line. Here's what they said:

1. when the UPS output gets shorted, overload protection kicks in, and
after the short is cleared the UPS can be reset and is ready to go
2. doing this repeatedly is not something the UPS is meant to do, and
they say it might damage the UPS.

I recognize (2) is just defensive thinking, and was wondering if
anyone had any experience or insight into how the overload protection
works.

Asked whether adding a fuse to the output of the UPS would work, they
weren't able to say if that would help at all. What do you guys think?

Here are the UPSes that I'm currently considering:

racks:
APC Smart UPS SU2200RMI3U - €320 - huge, full-depth 3U rack, from an older line
APC Smart UPS SUA1500RMI2U - €405 - still big, but a third the size,
half-depth 2U
APC Smart UPS SU1400RMI2U - €290 - half-depth 2U
APC Smart UPS SC 1500i 2U - €259 - half-depth 2U, looks ancient

desktop:
APC Smart UPS SUA1500I - €275, tiny

I would appreciate any help.

Cheers,
Damian


------------------------------------

Yahoo Groups Links



 

 I use a 500W bulb when testing unknown items, and even during the repair process, until I am certain that all is OK to plug into regular AC.


Even though your application is different, it is certainly the solution I would use.


About APC - I was one of the very first APC dealers in Israel in the 1990's, and was very satisfied with them, until 2006, when I noticed a severe drop in quality and reliability. I always opened the cases, to see what was really on the PCBs.


They also became VERY RF-noisy, unacceptable in my environment.


I had a customer engineer come out to my lab to have it out with him, and I was not satisfied with his evasive answers.


Since then I never sold another new APC product.

However, I still service the old APC's - especially the heavy Metal-cased SU's, and after a recap, they go right back into service, good for another 20+ years.

So, if you want APC, buy a used one - pre-2005, replace the batteries, and be prepared for a recap, all at a fraction of the price of a newer inferior unit. 


I moved to Gamatronic - Israeli-designed and Taiwan-built, and those are built like a brick, super-reliable, and super RF-quiet. Available world-wide, so you should have no problems sourcing them.


Menahem Yachad

Israel




---In tekscopes@..., <cheater00@...> wrote:

Stefan,

On Sat, Nov 2, 2013 at 12:54 PM, Stefan Trethan <stefan_trethan@...> wrote:
> This is where I bought a bunch of incandescent bulbs before the sale
> of some types was banned:
> <http://www.leuchtstark.de/Leuchtmittel/HALOGENLAMPEN/mlight/Halogen-Stab/mlight-Halogenstab.html>
>
> This would be a typical AC source:
> <http://www.ebay.com/itm/AC-POWER-SOURCE-/281193312449?pt=LH_DefaultDomain_2&hash=item41786d70c1>
> The advantage is that they have adjustable voltage and frequency,
> overload protection, and are meant to deal with unknown loads.
> And no batteries to deal with.
>
> ST

Thanks for the links. The AC power source looks interesting. I might
go with that instead - I didn't realize that those could handle shorts
and other messed up loads. Do you know the right technical term in
German? Searching for "wechselstromquelle" and "stromquelle", the
closest thing to lab equipment was a power supply for an incubator..

Thanks,
Damian


chris hayes <chris.hayes60@...>
 

Hi Damian
 
$8.42 for a twin pack: Free shipping to home by UnbeatableSale.com
 
Feit Electric BPQ500T3/CL/RS/2 500-Watt Clear Rough Service Halogen, 2 Pack
 
Much cheaper over here in the uk
 


 

Menahem,

On 2 Nov 2013 18:17, <yachadm@...> wrote:
>
>
>
>  I use a 500W bulb when testing unknown items, and even during the repair process, until I am certain that all is OK to plug into regular AC.
>
>
> Even though your application is different, it is certainly the solution I would use.
>
>
> About APC - I was one of the very first APC dealers in Israel in the 1990's, and was very satisfied with them, until 2006, when I noticed a severe drop in quality and reliability. I always opened the cases, to see what was really on the PCBs.
>
>
> They also became VERY RF-noisy, unacceptable in my environment.
>
>
> I had a customer engineer come out to my lab to have it out with him, and I was not satisfied with his evasive answers.
>
>
> Since then I never sold another new APC product.
>
> However, I still service the old APC's - especially the heavy Metal-cased SU's, and after a recap, they go right back into service, good for another 20+ years.
>
> So, if you want APC, buy a used one - pre-2005, replace the batteries, and be prepared for a recap, all at a fraction of the price of a newer inferior unit. 
>
>
> I moved to Gamatronic - Israeli-designed and Taiwan-built, and those are built like a brick, super-reliable, and super RF-quiet. Available world-wide, so you should have no problems sourcing them.
>
>
> Menahem Yachad
>
> Israel

Any insights on how the overload protection in SU or SUA series is done? Do you have schematics?

D.


Peter Gottlieb <hpnpilot@...>
 

I've been traveling on business and also really busy... let me look again and see what I can find.

On 11/2/2013 1:56 PM, cheater00 . wrote:

Menahem,
On 2 Nov 2013 18:17, <yachadm@... <mailto:yachadm@...>> wrote:



I use a 500W bulb when testing unknown items, and even during the repair
process, until I am certain that all is OK to plug into regular AC.


Even though your application is different, it is certainly the solution I
would use.


About APC - I was one of the very first APC dealers in Israel in the 1990's,
and was very satisfied with them, until 2006, when I noticed a severe drop in quality and reliability. I always opened the cases, to see what was really on the PCBs.


They also became VERY RF-noisy, unacceptable in my environment.


I had a customer engineer come out to my lab to have it out with him, and I
was not satisfied with his evasive answers.


Since then I never sold another new APC product.

However, I still service the old APC's - especially the heavy Metal-cased
SU's, and after a recap, they go right back into service, good for another 20+ years.

So, if you want APC, buy a used one - pre-2005, replace the batteries, and
be prepared for a recap, all at a fraction of the price of a newer inferior unit.


I moved to Gamatronic - Israeli-designed and Taiwan-built, and those are
built like a brick, super-reliable, and super RF-quiet. Available world-wide, so you should have no problems sourcing them.


Menahem Yachad

Israel
Any insights on how the overload protection in SU or SUA series is done? Do you have schematics?

D.


Ed Breya
 

I would suggest just putting a bunch of commonly available lamps - such as the 500W halogen work light ones - in parallel, rather than huge, exotic lamps, to make whatever size is needed. The work lights and lamp bulbs are available almost everywhere. Sometimes it's cheaper to buy a whole fixture with the bulb included, than the separate replacement bulbs - then you get the socket too, which is needed anyway. Another option if you have enough junk laser printers available, is to use the fuser lamps from them - typically around 750-1000W. They have nice ceramic mounts, but are kind of long, so trickier to mount and cool within a piece of equipment.


 

On Sat, 2 Nov 2013 10:39:10 +0100, you wrote:

Hi Chris,

On Sat, Nov 2, 2013 at 10:06 AM, chris hayes
<chris.hayes60@...> wrote:
Hi Damian
Apologies if you have already considered this: put an 500Watt halogen bulb in the supply line while testing an unknown load. These have a 10 ohm cold resistance (240 Volt versions), (presumably 5 ohms in USA) If the load becomes shorted it merely puts the light on.
ChrisH
Yeah, but it's difficult to find a 1000W light bulb (I have some
high-power equipment I need to test) on the one hand and on the other
hand as the load goes up the voltage drops, so for higher loads it's
less than perfect. I could make up the voltage with a Variac but
that's getting complicated.

Cheers,
D.
There is no reason you could not use multiple bulbs in parallel but if the total
bulb wattage is high enough, then an equipment short is going to trip the
circuit breaker anyway.

How large is the apartment circuit breaker? The simple thing to do might be to
just build an outlet extension that has its own small (5 amp?) short delay
circuit breaker which under overload conditions should trip before the main
circuit breaker. I had something similar on my old workbench and it did indeed
trip before the 15 or 20 amp outlet circuit breaker.


tubesnthings@aol.com <tubesnthings@...>
 

Nice, Ed!
Think I'll incorporate that into the variable AC source I've been collection panel meters for - am a sucker for large face bakelite amp meters, so there will be a few of those, for good measure, along with fuses for multiple ranges, digital volt meter and bypass switch for the variac…etc…maybe some blinking lights? Just kidding.
Better get to building it before feature-creep gets the better of this project.
But, with a couple of metered GR units at my disposal I have limited motivation to get off the dime…
Bernd Schroder

Sent from my Verizon Wireless Droid


-----Original message-----
From: edbreya@...
To:
TekScopes@...
Sent:
Sat, Nov 2, 2013 18:24:38 GMT+00:00
Subject:
RE: Re: [TekScopes] Re: Bench mains supply - another attempt

 

I would suggest just putting a bunch of commonly available lamps - such as the 500W halogen work light ones - in parallel, rather than huge, exotic lamps, to make whatever size is needed. The work lights and lamp bulbs are available almost everywhere. Sometimes it's cheaper to buy a whole fixture with the bulb included, than the separate replacement bulbs - then you get the socket too, which is needed anyway. Another option if you have enough junk laser printers available, is to use the fuser lamps from them - typically around 750-1000W. They have nice ceramic mounts, but are kind of long, so trickier to mount and cool within a piece of equipment.

 
In a variac unit that I'm building, I've got two halogen sockets that will be arranged by switching to put the lamps in series, separately, in parallel, or bypassed, for series ballast on the output side. One lamp will be 300W, and the other 500W, so it can provide a range of ballast values. A cooling fan will also be turned on whenever the ballast is not bypassed, allowing for the power dissipation in a fairly small section of the unit.
 
Ed
 
---In TekScopes@..., <tekscopes@...> wrote:

Hi Chris,

On Sat, Nov 2, 2013 at 10:06 AM, chris hayes
<chris.hayes60@...> wrote:
> Hi Damian
> Apologies if you have already considered this: put an 500Watt halogen bulb in the supply line while testing an unknown load. These have a 10 ohm cold resistance (240 Volt versions), (presumably 5 ohms in USA) If the load becomes shorted it merely puts the light on.
> ChrisH

Yeah, but it's difficult to find a 1000W light bulb (I have some
high-power equipment I need to test) on the one hand and on the other
hand as the load goes up the voltage drops, so for higher loads it's
less than perfect. I could make up the voltage with a Variac but
that's getting complicated.

Cheers,
D.


vdonisa
 

 What's so special about that fuse?


A low power isolation transformer with sensibly fused output will do the trick.



---In TekScopes@..., <tekscopes@...> wrote:

Hi guys,
Some of you might remember that I'm trying to set up a mains AC supply
separate from my wall mains, because I can't risk blowing the fuse.


Dieter Teuchert
 

A light bulb behaves as a PTC resistor, and as long as it remains dark, voltage drop will be small. At the same time short circuit current will be small, so it's a cheap and durable protection. A standard solution for testing and fixing switched power supplies and the like. For this type of work an insulation transformer is absolutely necessary for safety reasons. I would avoid using a UPS near my bench since they all send some ground noise.



---In TekScopes@..., <tekscopes@...> wrote:

 What's so special about that fuse?


A low power isolation transformer with sensibly fused output will do the trick.



---In TekScopes@..., <tekscopes@...> wrote:

Hi guys,
Some of you might remember that I'm trying to set up a mains AC supply
separate from my wall mains, because I can't risk blowing the fuse.


 

In Israel, which uses the European standard, all sub-circuit breakers (5, 10, 16, 20, 25A)  are available with either 30mA or 300mA ratings. That's the rating (and of course, the speed) at which the CB will trip.


A microwave oven, refrigerator, or treadmill fitness machine, should be plugged into a 300mA outlet, but a Workshop or bedroom outlet should be rated at 30mA. 

The main (100, 200A) house/office breaker is 300mA rated.


But anyway, I still prefer a 500W bulb for this application. It's a great visual confirmation of a problem, and sometimes, when there is a high drain problem (but not a short) in the DUT, the bulb will glow dimly, which no other "device" will show so clearly.


And, no, I don't have any schematics for the APC's - their standard policy is not to divulge, and certainly not to repair older ones. Out-of-warranty? Throw it away, and sell a new one. But as we know, that "ethic" doesn't hold any water with us here.


So, I just did troubleshooting for any particular problem on my table, but never got into the depths of the how's and why's of the overload protection circuit.



---In tekscopes@..., <dieter@...> wrote:

A light bulb behaves as a PTC resistor, and as long as it remains dark, voltage drop will be small. At the same time short circuit current will be small, so it's a cheap and durable protection. A standard solution for testing and fixing switched power supplies and the like. For this type of work an insulation transformer is absolutely necessary for safety reasons. I would avoid using a UPS near my bench since they all send some ground noise.



---In TekScopes@..., <tekscopes@...> wrote:

 What's so special about that fuse?


A low power isolation transformer with sensibly fused output will do the trick.



---In TekScopes@..., <tekscopes@...> wrote:

Hi guys,
Some of you might remember that I'm trying to set up a mains AC supply
separate from my wall mains, because I can't risk blowing the fuse.