Relay needed for new project with 600V DC rating.

[Geoff C]

I need to switch a double pole relay at 600 V DC at about 1
amp resistive load. The only relays I have been able to find
so far are reed relays- voltage rating OK but stretching with
current rating, and larger DC contacters- too expensive and
power hungry. Would prefer a coil power <5 watt and lifetime
of 200,000 operations.
The application is a switching special discharge lamp with 600
V strike voltage. Cannot use a transistor because circuit is
dual function and no ground reference exists and would like to
use as many current parts as possible.

 

[Trevor Wilson]

I need to switch a double pole relay at 600 V DC at about 1
amp resistive load. The only relays I have been able to find
so far are reed relays- voltage rating OK but stretching with
current rating, and larger DC contacters- too expensive and
power hungry. Would prefer a coil power <5 watt and lifetime
of 200,000 operations.
The application is a switching special discharge lamp with 600
V strike voltage. Cannot use a transistor because circuit is
dual function and no ground reference exists and would like to
use as many current parts as possible.

**I reckon you're probably screwed. I don't know of any relays which have
such a high DC Voltage rating. Furthermore, I don't know of any discharge
lamps which exhibit a resistive load and no back EMF effects. That does not
suggest that they do not exist, however. Can you switch an AC supply at some
point? Much easier to do, with a TRIAC.

 

[Geoff C]

**I reckon you're probably screwed. I don't know of any relays which have
such a high DC Voltage rating. Furthermore, I don't know of any discharge
lamps which exhibit a resistive load and no back EMF effects. That does not
suggest that they do not exist, however. Can you switch an AC supply at some
point? Much easier to do, with a TRIAC.

The reeds have the rating but I'm worried about contact life.
There are minimal back EMF effects in these lamps since they
have negligible inductance/capacitance or any other energy
storage mechanism and the minimal leakage inductance should be
able to be handled with a snubber. The lamps do have negative
resistance regions in there operating range. The lamps are low
pressure neon and are modulated with on-off pulsing.

 

[Phil Allison]

I need to switch a double pole relay at 600 V DC at about 1
amp resistive load. The only relays I have been able to find
so far are reed relays- voltage rating OK but stretching with
current rating, and larger DC contacters- too expensive and
power hungry. Would prefer a coil power <5 watt and lifetime
of 200,000 operations.
The application is a switching special discharge lamp with 600
V strike voltage. Cannot use a transistor because circuit is
dual function and no ground reference exists and would like to
use as many current parts as possible.

** Farnell have a high voltage reed relay (expensive) rated at the sort of
voltage and current figures you are talking, but in single pole though.

BEWARE: Any pair of metal contacts opening under 1 amp and with 600
volts DC available is GOING to arc and burn - so expect short life.

Switching the AC supply is *vastly* preferable and probably the only
way to get 200,000 operations is to use a triac.



................ Phil

 

[John Robertson]

I can see where switching the AC might be a problem as this is a DC
lamp. Switching the AC could work if there is no filter cap on the DC,
otherwise your inrush current on the diodes would probably shorten
their life substantially.

Could SCRs be used instead of diodes on the DC supply? At half wave
you would only be looking at around 600PIV and those are not too many
arms and legs in cost. Much easier to turn on and off, crossing zero
detection etc...

John :-#)#

** Farnell have a high voltage reed relay (expensive) rated at the sort of
voltage and current figures you are talking, but in single pole though.

BEWARE: Any pair of metal contacts opening under 1 amp and with 600
volts DC available is GOING to arc and burn - so expect short life.

Switching the AC supply is *vastly* preferable and probably the only
way to get 200,000 operations is to use a triac.



............... Phil

(Please post followups or tech enquires to the newsgroup)
John's Jukes Ltd. 2343 Main St., Vancouver, BC, Canada V5T 3C9
Call (604)872-5757 or Fax 872-2010 (Pinballs, Jukes, Video Games)
www.flippers.com
"Old pinballers never die, they just flip out."

 

[Geoff C]

I can see where switching the AC might be a problem as this is a DC
lamp. Switching the AC could work if there is no filter cap on the DC,
otherwise your inrush current on the diodes would probably shorten
their life substantially.

Could SCRs be used instead of diodes on the DC supply? At half wave
you would only be looking at around 600PIV and those are not too many
arms and legs in cost. Much easier to turn on and off, crossing zero
detection etc...

John :-#)#



(Please post followups or tech enquires to the newsgroup)
John's Jukes Ltd. 2343 Main St., Vancouver, BC, Canada V5T 3C9

The lamp is connected in the collector circuit of a NPN
transistor, which forms part of a closed loop current sink.
This current sink is includes an opamp as control element, the
input to which is an arbitrary, well sort of square wave
generated by a uP card. So AC control is totally out. The
frequency is less than 500Hz. Looks like a reed relay with an
active snubber may be the way to go.

 

[Phil Allison]

I can see where switching the AC might be a problem as this is a DC
lamp.

** Do you have DC mains where you are ??

Switching the AC could work if there is no filter cap on the DC,

** Switching the AC works - billions of 240 volt switches prove it.

otherwise your inrush current on the diodes would probably shorten
their life substantially.

** The magnetic surge is worse.

Could SCRs be used instead of diodes on the DC supply?

** Fun making them turn off when you want to.

At half wave
you would only be looking at around 600PIV and those are not too many
arms and legs in cost. Much easier to turn on and off, crossing zero
detection etc...

** When does a DC voltage zero cross ?

If you remove gate drive - an SCR will go off at the next zero
automatically



........... Phil

 

[Brian Goldsmith]

I need to switch a double pole relay at 600 V DC at about 1
amp resistive load. The only relays I have been able to find
so far are reed relays- voltage rating OK but stretching with
current rating,


****I would have the gravest reservations about using any reed relay at
600 Volt DC!
I would have reservations about using anything that was not designed
specifically for that particular voltage.


Brian Goldsmith.

 

[Unbeliever]

I need to switch a double pole relay at 600 V DC at about 1
amp resistive load. The only relays I have been able to find
so far are reed relays- voltage rating OK but stretching with
current rating, and larger DC contacters- too expensive and
power hungry. Would prefer a coil power <5 watt and lifetime
of 200,000 operations.
The application is a switching special discharge lamp with 600
V strike voltage. Cannot use a transistor because circuit is
dual function and no ground reference exists and would like to
use as many current parts as possible.

Geoff,
You might look at GTO's (Gate Turn Off SCRs). Another possibility is a
DC (optically coupled FET output) solid state relay. I've used 500V ones
from NAIS & Crydom, don't know if they have 600 volters. You might choose
to make your own using a photocoupler or even a reed to switch a HV fet on
and off.

That being said, Farnell have an Erg brand 8kV, 3A relay (not at the same
time, it's rated at 50W). This might do the job if you ensure 0V (or low
volts) across it for a few ms at turn off, if you don't need instant turn
off of you lamp (HC? D2?). Beware of arcing during contact bounce at turn
on, though.

HTH
Alf
[email protected]
www.micromagic.net.au

 

[Mike Harding]

You might look at GTO's (Gate Turn Off SCRs). Another possibility is a
DC (optically coupled FET output) solid state relay. I've used 500V ones
from NAIS & Crydom, don't know if they have 600 volters. You might choose
to make your own using a photocoupler or even a reed to switch a HV fet on
and off.

Are mercury relays still available? Don't recall their
specs. but I suspect one of those may do the job, or
am I showing my age?

Mike Harding

 

[Mike Harding]

You might look at GTO's (Gate Turn Off SCRs). Another possibility is a
DC (optically coupled FET output) solid state relay. I've used 500V ones
from NAIS & Crydom, don't know if they have 600 volters. You might choose
to make your own using a photocoupler or even a reed to switch a HV fet on
and off.

Are mercury relays still available? Don't recall their
specs. but I suspect one of those may do the job, or
am I showing my age?

Mike Harding