Hi Folks

I've got a problem with over voltage surges taking out a switch mode PSU. I
don't know a lot about electronics but looking at catalogues VDR/Varistors
look like they could be my friend. Basically I'm looking for a simple way
of blowing the inline 5a fuse if the input voltage goes over 240V AC.

Cost is also an issue here. Anyone got any suggestions on what I should use
?

--
Colin Birch
http://www.railscans.co.uk

Colin Birch wrote:

Hi Folks

I've got a problem with over voltage surges taking out a switch mode PSU.
I don't know a lot about electronics but looking at catalogues
VDR/Varistors look like they could be my friend. Basically I'm looking for
a simple way of blowing the inline 5a fuse if the input voltage goes over
240V AC.

Cost is also an issue here. Anyone got any suggestions on what I should
use ?

You might take a look at transzorbs:
http://www.vishay.com/diodes/protect...sd/trans-zorb/

Good Luck!
Rich

"Colin Birch" wrote in message
.. .
Hi Folks

I've got a problem with over voltage surges taking out a switch mode PSU.
I
don't know a lot about electronics but looking at catalogues VDR/Varistors
look like they could be my friend. Basically I'm looking for a simple way
of blowing the inline 5a fuse if the input voltage goes over 240V AC.

Cost is also an issue here. Anyone got any suggestions on what I should
use

This might help;

http://en.wikipedia.org/wiki/Surge_protector

As you can see there are various options, the MOV (basically a VDR) is still
common in comercial appliances but each transient event takes a little bit
out of the device.

The more you have distributed around your mains supply wiring, the better
they work and longer they last, there are various protected socket strips on
sale, there are also single socket MOV units that the plug piggybacks onto
in the wall socket and even blank MOV protection modules - you plug them
into a spare wall socket but they have no socket holes in the top, these are
claimed to protect a ring-main as part of the house wiring.

As RG says; there are more modern devices like Tranzorbs, these are more
likely to fail S/C and blow the fuse. The MOVs quietly absorb and dissipate
the spike as heat - they also fail quietly at end of life by disintegrating
so you don't know you've lost protection - but if you have a lot of them
distributed around the wiring it takes a major event like near lightening
strike for this to happen.

All in all - less time running around replacing fuses.


?

--
Colin Birch
http://www.railscans.co.uk

On Wed, 30 Nov 2011 21:36:54 -0000, "Ian Field"
wrote:


"Colin Birch" wrote in message
. ..
Hi Folks

I've got a problem with over voltage surges taking out a switch mode PSU.
I
don't know a lot about electronics but looking at catalogues VDR/Varistors
look like they could be my friend. Basically I'm looking for a simple way
of blowing the inline 5a fuse if the input voltage goes over 240V AC.

Cost is also an issue here. Anyone got any suggestions on what I should
use

This might help;

http://en.wikipedia.org/wiki/Surge_protector

As you can see there are various options, the MOV (basically a VDR) is still
common in comercial appliances but each transient event takes a little bit
out of the device.

The more you have distributed around your mains supply wiring, the better
they work and longer they last, there are various protected socket strips on
sale, there are also single socket MOV units that the plug piggybacks onto
in the wall socket and even blank MOV protection modules - you plug them
into a spare wall socket but they have no socket holes in the top, these are
claimed to protect a ring-main as part of the house wiring.

As RG says; there are more modern devices like Tranzorbs, these are more
likely to fail S/C and blow the fuse. The MOVs quietly absorb and dissipate
the spike as heat - they also fail quietly at end of life by disintegrating
so you don't know you've lost protection - but if you have a lot of them
distributed around the wiring it takes a major event like near lightening
strike for this to happen.

All in all - less time running around replacing fuses.

---
What is it you don't understand about: "Basically I'm looking for a
simple way of blowing the inline 5a fuse if the input voltage goes
over 240V AC." ?

And by the way, MOV's don't generally fail gracefully, they generate a
fireball when they die.

--
JF

On Wed, 30 Nov 2011 21:36:54 -0000, "Ian Field"
wrote:


"Colin Birch" wrote in message
. ..
Hi Folks

I've got a problem with over voltage surges taking out a switch mode PSU.
I
don't know a lot about electronics but looking at catalogues VDR/Varistors
look like they could be my friend. Basically I'm looking for a simple way
of blowing the inline 5a fuse if the input voltage goes over 240V AC.

Cost is also an issue here. Anyone got any suggestions on what I should
use

This might help;

http://en.wikipedia.org/wiki/Surge_protector

As you can see there are various options, the MOV (basically a VDR) is still
common in comercial appliances but each transient event takes a little bit
out of the device.

The more you have distributed around your mains supply wiring, the better
they work and longer they last, there are various protected socket strips on
sale, there are also single socket MOV units that the plug piggybacks onto
in the wall socket and even blank MOV protection modules - you plug them
into a spare wall socket but they have no socket holes in the top, these are
claimed to protect a ring-main as part of the house wiring.

---
None of that nebulous crap seems to be what the OP's looking for,
which is a way to keep surges from toasting his PSU when they go above
240V RMS.
---

As RG says; there are more modern devices like Tranzorbs, these are more
likely to fail S/C and blow the fuse.

---
Trying to use Rich to further your own agenda by putting words in his
mouth and supplying disinformation is ingenuous.

If you have some data which proves that Zeners configured as
surge-stoppers are somehow inferior to MOV's, I'd like to see it.

--
JF

John Fields wrote:

If you have some data which proves that Zeners configured as
surge-stoppers are somehow inferior to MOV's, I'd like to see it.

The only actual evidence I have is entirely anecdotal - I was once
working at an outfit that made various high voltage power supplies, and
they used MOVs all over the place for arc protection. One day, Transzorbs
showed up in some trade mag; we tried some and the muckety-mucks decided
to replace _ALL_ of the MOVs with Transzorbs because they made MOVs look
like two-leaded turds.

Hope This Helps!
Rich

On Wed, 30 Nov 2011 19:12:43 -0600, John Fields
wrote:

On Wed, 30 Nov 2011 21:36:54 -0000, "Ian Field"
wrote:


"Colin Birch" wrote in message
...
Hi Folks

I've got a problem with over voltage surges taking out a switch mode PSU.
I
don't know a lot about electronics but looking at catalogues VDR/Varistors
look like they could be my friend. Basically I'm looking for a simple way
of blowing the inline 5a fuse if the input voltage goes over 240V AC.

Cost is also an issue here. Anyone got any suggestions on what I should
use

This might help;

http://en.wikipedia.org/wiki/Surge_protector

As you can see there are various options, the MOV (basically a VDR) is still
common in comercial appliances but each transient event takes a little bit
out of the device.

The more you have distributed around your mains supply wiring, the better
they work and longer they last, there are various protected socket strips on
sale, there are also single socket MOV units that the plug piggybacks onto
in the wall socket and even blank MOV protection modules - you plug them
into a spare wall socket but they have no socket holes in the top, these are
claimed to protect a ring-main as part of the house wiring.

---
None of that nebulous crap seems to be what the OP's looking for,
which is a way to keep surges from toasting his PSU when they go above
240V RMS.
---

As RG says; there are more modern devices like Tranzorbs, these are more
likely to fail S/C and blow the fuse.

---
Trying to use Rich to further your own agenda by putting words in his
mouth and supplying disinformation is ingenuous.

If you have some data which proves that Zeners configured as
surge-stoppers are somehow inferior to MOV's, I'd like to see it.

Ian Field seems to be vying for the special award for village idiot of
the year.

...Jim Thompson
--
| James E.Thompson, CTO | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona 85048 Skype: Contacts Only | |
| Voice480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |

I love to cook with wine. Sometimes I even put it in the food.

"Rich Grise" wrote in message
...
John Fields wrote:

If you have some data which proves that Zeners configured as
surge-stoppers are somehow inferior to MOV's, I'd like to see it.

The only actual evidence I have is entirely anecdotal - I was once
working at an outfit that made various high voltage power supplies, and
they used MOVs all over the place for arc protection. One day, Transzorbs
showed up in some trade mag; we tried some and the muckety-mucks decided
to replace _ALL_ of the MOVs with Transzorbs because they made MOVs look
like two-leaded turds.

Hope This Helps!
Rich


I use a lot of MOVs because they appear frequently as salvageable items in
scrap equipment, no doubt I'll start using tranzorbs once I start finding
them.

On Thu, 1 Dec 2011 14:24:07 -0000, "Ian Field"
wrote:


"Rich Grise" wrote in message
...
John Fields wrote:

If you have some data which proves that Zeners configured as
surge-stoppers are somehow inferior to MOV's, I'd like to see it.

The only actual evidence I have is entirely anecdotal - I was once
working at an outfit that made various high voltage power supplies, and
they used MOVs all over the place for arc protection. One day, Transzorbs
showed up in some trade mag; we tried some and the muckety-mucks decided
to replace _ALL_ of the MOVs with Transzorbs because they made MOVs look
like two-leaded turds.

Hope This Helps!
Rich


I use a lot of MOVs because they appear frequently as salvageable items in
scrap equipment,

---
A _lot_ of MOVs?

Idiotic, but understandable, since you don't seem to understand that
MOVs culled from trashed equipment are, more than likely, damaged
goods.

Do you know how to test an MOV in order to determine whether it's in
spec or not?
---

no doubt I'll start using tranzorbs once I start finding them.

---
More to the point, the question is, "Will you recognize a transorb
once your eyes land on it", and will you know how to apply it?

--
JF

On Thu, 01 Dec 2011 18:22:28 -0600, John Fields
wrote:

On Thu, 1 Dec 2011 14:24:07 -0000, "Ian Field"
wrote:


"Rich Grise" wrote in message
...
John Fields wrote:

If you have some data which proves that Zeners configured as
surge-stoppers are somehow inferior to MOV's, I'd like to see it.

The only actual evidence I have is entirely anecdotal - I was once
working at an outfit that made various high voltage power supplies, and
they used MOVs all over the place for arc protection. One day, Transzorbs
showed up in some trade mag; we tried some and the muckety-mucks decided
to replace _ALL_ of the MOVs with Transzorbs because they made MOVs look
like two-leaded turds.

Hope This Helps!
Rich


I use a lot of MOVs because they appear frequently as salvageable items in
scrap equipment,

---
A _lot_ of MOVs?

Idiotic, but understandable, since you don't seem to understand that
MOVs culled from trashed equipment are, more than likely, damaged
goods.

Do you know how to test an MOV in order to determine whether it's in
spec or not?
---

no doubt I'll start using tranzorbs once I start finding them.

---
More to the point, the question is, "Will you recognize a transorb
once your eyes land on it", and will you know how to apply it?

Once I looked up a Sturmey Archer "dynamo", I relegated Ian to the
dunce corner... along with JL. At least JL should have known the
idiocy of Ian's scheme... particularly given JL's statements about
voltage limiting... he really had no clue ;-)

...Jim Thompson
--
| James E.Thompson, CTO | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona 85048 Skype: Contacts Only | |
| Voice480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |

I love to cook with wine. Sometimes I even put it in the food.

On Sat, 03 Dec 2011 07:28:06 -0800, Fred Abse
wrote:

On Thu, 01 Dec 2011 17:28:41 -0700, Jim Thompson wrote:

Once I looked up a Sturmey Archer "dynamo"

In 1936 terms, the multipole ring magnet in those things was quite cutting
edge technology. They must have used an ingenious magnetizing machine.

Certainly. But Ian, with Larkin's blessing, purposes to get something
for nothing.

...Jim Thompson
--
| James E.Thompson, CTO | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona 85048 Skype: Contacts Only | |
| Voice480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |

I love to cook with wine. Sometimes I even put it in the food.

"Fred Abse" wrote in message
news
On Thu, 01 Dec 2011 17:28:41 -0700, Jim Thompson wrote:

Once I looked up a Sturmey Archer "dynamo"

In 1936 terms, the multipole ring magnet in those things was quite cutting
edge technology. They must have used an ingenious magnetizing machine.

How did posts from my thread get in the OVP thread?

Not to worry though - apparently the 20 pole magnet ring is either cast or
sintered from the type of alnico that depolarises instantly if you remove
the keeper, apparently if you take out the armature for mere seconds the
dynamo is scrap, its also stated that the alnico slowly but surely loses
magnetism over time even if not interfered with.

It crossed my mind to dump a high voltage capacitor into the armature
winding (making sure the poles are aligned) but I don't have a surplus of
armatures to risk destroying the windings.

Hi folks and thanks for the replies. I'm still looking for a bit of basic
info though. I'm confused by the two terms Max AC voltage rating and
Clamping voltage. If the switch mode psu is running off 240V and I want to
limit the input voltage to 250/260V do I need a maximum AC voltage rating
of 260V or a clamping voltage of 260V? Seems a bit confusing for a novice
:-( Also when wiring them in circuit they go live to neutral but do I also
need them live to earth?

--
Colin Birch
http://www.railscans.co.uk

"Colin Birch" wrote in message
.. .
Hi folks and thanks for the replies. I'm still looking for a bit of basic
info though. I'm confused by the two terms Max AC voltage rating and
Clamping voltage. If the switch mode psu is running off 240V and I want to
limit the input voltage to 250/260V do I need a maximum AC voltage rating
of 260V or a clamping voltage of 260V? Seems a bit confusing for a novice


One of the manufacturers makes life easy by selling 275VRMS MOVs for 240V
mains use, I've found 1100V MOVs in some Nokia monitors.

The more current technology; transorbs might be the way to go, but since
they're more likely to fail S/C you should aim for the highest voltage your
equipment can comfortably survive.

Your first port of call should be the datasheet/appnote area of a
manufacturer's website - ISTR Littlefuse make surge protectors and have at
least acceptable tech info.