relays for B+

[Don[_4_]]

Will this relay work to switch 500 DCv .5 amps? I can't find 500v
relays under big buck prices.

tyco/P&B K10P-11A15-120

http://www.mouser.com/ProductDetail/Tyco-Electronics/K10P-11A15-120/?
qs=iO7mgM19OaZKj751FOt%252b%252bQ%3d%3d

Thanks,
Don

[Trevor Wilson[_3_]]

Don wrote:
> Will this relay work to switch 500 DCv .5 amps? I can't find 500v
> relays under big buck prices.
>
> tyco/P&B K10P-11A15-120
>
> http://www.mouser.com/ProductDetail/Tyco-Electronics/K10P-11A15-120/?
> qs=iO7mgM19OaZKj751FOt%252b%252bQ%3d%3d
>

**The rating on the relay is 30 Volts DC, so you can bet that it won't work.
High Voltage DC relays are expensive beasts. Either spend the money or find
another way.


--
Trevor Wilson
www.rageaudio.com.au

[Patrick Turner]

On Jul 7, 2:41*am, Don > wrote:
> Will this relay work to switch 500 DCv .5 amps? I can't find 500v
> relays under big buck prices.
>
> tyco/P&B K10P-11A15-120
>
> http://www.mouser.com/ProductDetail/Tyco-Electronics/K10P-11A15-120/?
> qs=iO7mgM19OaZKj751FOt%252b%252bQ%3d%3d
>
> Thanks,
> Don

Using a relay to switch a 500Vdc rail on or off can lead to prologned
arcing between the contacts if they don't open to be a wide distance,
and fTHERE ew idtanceand 5

[Patrick Turner]

On Jul 7, 2:41*am, Don > wrote:
> Will this relay work to switch 500 DCv .5 amps? I can't find 500v
> relays under big buck prices.
>
> tyco/P&B K10P-11A15-120
>
> http://www.mouser.com/ProductDetail/Tyco-Electronics/K10P-11A15-120/?
> qs=iO7mgM19OaZKj751FOt%252b%252bQ%3d%3d
>
> Thanks,
> Don

Trying to switch a 500Vdc amp rail with a relay can lead to prolonged
arcing between contacts if they don't open wide enough. Few relays I
have ever seen do this unless they are very bulky industrial types.
Using a relay rated for 30Vdc is madness. That same relay might be OK
for 110Vac. However, there are applications where I have wanted to
discharge the +500Vdc B+ caps in an amp very quickly to make an
umbilical cable plug pin voltage go to safe levels within 0.5 seconds.
So I have used a two pole relay meant for 240V mains with both relays
in series and biased at 250Vdc, with 0.1uF x 630Vdc rated caps across
the contacts and with series resistance of 470 ohms at 20W rating
which will take the maximum current of about 1A for a short time when
the caps are discharged.

Even the simplest thing you may want to do with 500Vdc needs careful
analysis and thought or else you'll end up with smoke and regrets. If
there is a choke involved in the 500Vdc rail, it makes matters worse
to design around it, and a suitable diode, say IN5408 may need to be
placed across the choke to prevent back EMF causing voltage across the
relay to go very high when contacts oen and DC flow is interupted. So
you need to know what you are doing. Its usually better to try to
always switch the AC transformer winding producing the 500Vdc. There
are also ways of using an SCR to perform switching instad of a relay.
About 16 years ago I made a bench top PSU capable of 600Vdc at 100mA,
and it has an over current protection circuit with SCR in series with
500Vdc, and the gate control circuit works from a board powered by a
12Vdc supply biased at the Vdc rail, and it includes a relay to switch
the gate signal and turn a red lamp on to tell me when I've gone over
current. I can reset it just by turning off the ac on/off switch. Its
very primitive as most things I made back in 1994 were, but its never
failed, and saved me from smoke and expensive repairs during many
tests of tube gear and finding out the basics myself as you should be
doing.

Patrick Turner.

[NT]

On Jul 7, 2:27*am, Patrick Turner > wrote:
> On Jul 7, 2:41*am, Don > wrote:
>
> > Will this relay work to switch 500 DCv .5 amps? I can't find 500v
> > relays under big buck prices.
>
> > tyco/P&B K10P-11A15-120
>
> >http://www.mouser.com/ProductDetail/Tyco-Electronics/K10P-11A15-120/?
> > qs=iO7mgM19OaZKj751FOt%252b%252bQ%3d%3d
>
> > Thanks,
> > Don
>
> Trying to switch a 500Vdc amp rail with a relay can lead to prolonged
> arcing between contacts if they don't open wide enough. Few relays I
> have ever seen do this unless they are very bulky industrial types.
> Using a relay rated for 30Vdc is madness. That same relay might be OK
> for 110Vac. However, there are applications where I have wanted to
> discharge the +500Vdc B+ caps in an amp very quickly to make an
> umbilical cable plug pin voltage go to safe levels within 0.5 seconds.
> So I have used a two pole relay meant for 240V mains with both relays
> in series and biased at 250Vdc, with 0.1uF x 630Vdc rated caps across
> the contacts and with series resistance of 470 ohms at 20W rating
> which will take the maximum current of about 1A for a short time when
> the caps are discharged.
>
> Even the simplest thing you may want to do with 500Vdc needs careful
> analysis and thought or else you'll end up with smoke and regrets. If
> there is a choke involved in the 500Vdc rail, it makes matters worse
> to design around it, and a suitable diode, say IN5408 may need to be
> placed across the choke to prevent back EMF causing voltage across the
> relay to go very high when contacts oen and DC flow is interupted. So
> you need to know what you are doing. Its usually better to try to
> always switch the AC transformer winding producing the 500Vdc. There
> are also ways of using an SCR to perform switching instad of a relay.
> About 16 years ago I made a bench top PSU capable of 600Vdc at 100mA,
> and it has an over current protection circuit with SCR in series with
> 500Vdc, and the gate control circuit works from a board powered by a
> 12Vdc supply biased at the Vdc rail, and it includes a relay to switch
> the gate signal and turn a red lamp on to tell me when I've gone over
> current. I can reset it just by turning off the ac on/off switch. Its
> very primitive as most things I made back in 1994 were, but its never
> failed, and saved me from smoke and expensive repairs during many
> tests of tube gear and finding out the basics myself as you should be
> doing.
>
> Patrick Turner.

With a suitable CR snubber across the relay's switch contacts, the
relay is no longer switching the 500v.


NT

[Phil Allison[_3_]]

"Nutcase Troll"


With a suitable CR snubber across the relay's switch contacts, the
relay is no longer switching the 500v.


** Care to nominate values that will work reliably ?

This will be fun..........


..... Phil

[Phil Allison[_3_]]

"Patrick Turner"

Even the simplest thing you may want to do with 500Vdc needs careful
analysis and thought or else you'll end up with smoke and regrets. If
there is a choke involved in the 500Vdc rail, it makes matters worse
to design around it, and a suitable diode, say IN5408 may need to be
placed across the choke to prevent back EMF causing voltage across the
relay to go very high when contacts oen and DC flow is interupted.


** Putting a diode across filter choke defeats the choke's operation.



...... Phil

[[email protected]]

On Jul 7, 11:15*pm, "Phil Allison" > wrote:
> "Patrick Turner"
>
> Even the simplest thing you may want to do with 500Vdc needs careful
> analysis and thought or else you'll end up with smoke and regrets. If
> there is a choke involved in the 500Vdc rail, it makes matters worse
> to design around it, and a suitable diode, say IN5408 may need to be
> placed across the choke to prevent back EMF causing voltage across the
> relay to go very high when contacts oen and DC flow is interupted.
>
> ** Putting a diode across filter choke defeats the choke's operation.
>
> ..... *Phil

He must have meant a ' coil ' instead of choke . The diode solution is
quite common in relays .

[Patrick Turner]

On Jul 8, 3:58*pm, wrote:
> On Jul 7, 11:15*pm, "Phil Allison" > wrote:
>
> > "Patrick Turner"
>
> > Even the simplest thing you may want to do with 500Vdc needs careful
> > analysis and thought or else you'll end up with smoke and regrets. If
> > there is a choke involved in the 500Vdc rail, it makes matters worse
> > to design around it, and a suitable diode, say IN5408 may need to be
> > placed across the choke to prevent back EMF causing voltage across the
> > relay to go very high when contacts oen and DC flow is interupted.
>
> > ** Putting a diode across filter choke defeats the choke's operation.
>
> > ..... *Phil
>
> He must have meant a ' coil ' instead of choke . The diode solution is
> quite common in relays .

Putting a diode across a relay coil to allow current to flow in
opposite direction to normal coil DC stops a back emf rising when coil
current cuts off so that SS devices powering the coil don't cop
excessive voltage which exceeds their V rating.

Putting a diode across a filter choke in C+L filter in PSU does the
same thing. But the diode would be a complete nuisance if the voltage
drop across choke winding resistance was low and Vac across choke was
high. But where Vac at choke input was say 1Vrms, and choke output Vac
was say 0.01Vrms, or negligible, and where Vdc drop was say 10Vdc,
then Vout would not rise above Vin and diode would never conduct
unless someone rapidly switched off the current in the choke at its
output, when choke Vo would try to rise hugely. I recall enduring the
failures of some high voltage power transistors in a regulated power
supply because of this phenomena and I then used a couple of 6AS7G
instead of the BU208 I'd tried to use.
http://www.datasheetcatalog.com/datasheets_pdf/B/U/2/0/BU208.shtml

When farnarkling with 500Vdc B+ PSUs, there's a long list of horrible
things one has to learn about to avoid smoke.

Not much is in old textbooks about simple solid state stuff dealing
with PSUs for tubes. So each time a puff of smoke happens, you are
forced to discover what should have been written in the text books.

Patrick Turner.

[mick]

On Wed, 06 Jul 2011 12:41:18 -0400, Don wrote:

> Will this relay work to switch 500 DCv .5 amps? I can't find 500v relays
> under big buck prices.
>
> tyco/P&B K10P-11A15-120
>
> http://www.mouser.com/ProductDetail/Tyco-Electronics/K10P-11A15-120/?
> qs=iO7mgM19OaZKj751FOt%252b%252bQ%3d%3d
>
> Thanks,
> Don


Switching DC is totally dependant on the size of the air gap of the
contacts. A single break contact will generally switch less voltage than
a double break contact. You can usually just about get twice the DC
rating of a single contact by putting 2 in series, but not always. On
some relays you can even manage 3 contacts in series but the law of
diminishing returns kicks in and you won't get 3 times the DC rating. The
best you can usually get is to use a small 4-pole contactor (about 4kW
rated). These are usually 600vAC/400vDC rated double-break contacts. For
your application you would need 2 contacts in series.

The problem is that DC will produce an arc as the contact opens. The arc
will try to maintain for as long as possible. Some high power DC relays/
contactors use electro or permanent magnets to pull the arc sideways, at
right angles to the contact face, so that it becomes stretched and more
easily broken by the air gap.

Note that the breaking capacity at DC bears no relation to the insulation
breakdown voltage or the contact's carrying or making capacity. Just
because a relay will withstand 500vDC and will make it satisfactorily, it
won't necessarily break it. Reed relays often fall into this group. They
will carry, say 3A at 500vDC, but will only break 0.5mA of DC or 0.5A of
AC.

Always try to switch AC rather than DC. It is easier and far kinder to
the contacts!


--
Mick (Working in a M$-free zone!)
Web: http://www.nascom.info
Filtering everything posted from googlegroups to kill spam.

[Don Pearce[_3_]]

On Wed, 06 Jul 2011 12:41:18 -0400, Don >
wrote:

>Will this relay work to switch 500 DCv .5 amps? I can't find 500v
>relays under big buck prices.
>
>tyco/P&B K10P-11A15-120
>
>http://www.mouser.com/ProductDetail/Tyco-Electronics/K10P-11A15-120/?
>qs=iO7mgM19OaZKj751FOt%252b%252bQ%3d%3d
>
>Thanks,
>Don

Only B+? Marshall guitar amps have a standby switch that kills the
entire HT. It is a dual pole single throw operating on both halves of
the mains transformer secondary. It is very reliable.

d

[Jan Jongejan, PE1SBG]

Don wrote:

> Will this relay work to switch 500 DCv .5 amps? I can't find 500v
> relays under big buck prices.
>
> tyco/P&B K10P-11A15-120
>
> http://www.mouser.com/ProductDetail/Tyco-Electronics/K10P-11A15-120/?
> qs=iO7mgM19OaZKj751FOt%252b%252bQ%3d%3d
>
> Thanks,
> Don

Search for a vacuumrelais. They are made for schwitching kilovolts.

Greetings,
Jan