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Contactors/Relays

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  Contactors/Relays David Lesher <wb8foz@panix.com> - 2017-10-14 18:16 +0000
    Re: Contactors/Relays legg <legg@nospam.magma.ca> - 2017-10-14 15:38 -0400
      Re: Contactors/Relays David Lesher <wb8foz@panix.com> - 2017-10-18 22:32 +0000
        Re: Contactors/Relays legg <legg@nospam.magma.ca> - 2017-10-18 23:11 -0400
          Re: Contactors/Relays David Lesher <wb8foz@panix.com> - 2017-10-19 06:11 +0000
            Re: Contactors/Relays legg <legg@nospam.magma.ca> - 2017-10-19 15:02 -0400
              Re: Contactors/Relays rickman <gnuarm@gmail.com> - 2017-10-19 18:48 -0400
                Re: Contactors/Relays legg <legg@nospam.magma.ca> - 2017-10-19 23:02 -0400
                  Re: Contactors/Relays rickman <gnuarm@gmail.com> - 2017-10-20 00:49 -0400
                    Re: Contactors/Relays legg <legg@nospam.magma.ca> - 2017-10-20 12:03 -0400
                      Re: Contactors/Relays rickman <gnuarm@gmail.com> - 2017-10-20 13:17 -0400
                        Re: Contactors/Relays legg <legg@nospam.magma.ca> - 2017-10-21 09:52 -0400
                          Re: Contactors/Relays Michael A Terrell <mike.terrell@earthlink.net> - 2017-10-21 12:23 -0400
                            Re: Contactors/Relays legg <legg@nospam.magma.ca> - 2017-10-21 13:00 -0400
                              Re: Contactors/Relays Michael A Terrell <mike.terrell@earthlink.net> - 2017-10-21 19:23 -0400
                                Re: Contactors/Relays legg <legg@nospam.magma.ca> - 2017-10-22 09:24 -0400
                                  Re: Contactors/Relays David Lesher <wb8foz@panix.com> - 2017-10-22 18:59 +0000
                        Re: Contactors/Relays David Lesher <wb8foz@panix.com> - 2017-10-22 06:25 +0000
                      Re: Contactors/Relays David Lesher <wb8foz@panix.com> - 2017-10-26 05:00 +0000
                        Re: Contactors/Relays legg <legg@nospam.magma.ca> - 2017-10-29 13:23 -0400
                          Re: Contactors/Relays Michael A Terrell <mike.terrell@earthlink.net> - 2017-10-30 16:04 -0400
                          Re: Contactors/Relays David Lesher <wb8foz@panix.com> - 2017-11-03 06:07 +0000
        Re: Contactors/Relays upsidedown@downunder.com - 2017-10-19 13:00 +0300
          Re: Contactors/Relays David Lesher <wb8foz@panix.com> - 2017-10-22 06:23 +0000
          Re: Contactors/Relays David Lesher <wb8foz@panix.com> - 2017-10-26 05:04 +0000
    Re: Contactors/Relays legg <legg@nospam.magma.ca> - 2017-10-14 15:52 -0400
      Re: Contactors/Relays David Lesher <wb8foz@panix.com> - 2017-10-19 06:03 +0000
    Re: Contactors/Relays legg <legg@nospam.magma.ca> - 2017-10-14 16:20 -0400
      Re: Contactors/Relays David Lesher <wb8foz@panix.com> - 2017-10-19 06:04 +0000
        Re: Contactors/Relays rickman <gnuarm@gmail.com> - 2017-10-19 03:49 -0400
          Re: Contactors/Relays David Lesher <wb8foz@panix.com> - 2017-10-22 06:18 +0000
            Re: Contactors/Relays rickman <gnuarm@gmail.com> - 2017-10-22 03:57 -0400
    Re: Contactors/Relays edward.ming.lee@gmail.com - 2017-10-14 14:15 -0700
      Re: Contactors/Relays David Lesher <wb8foz@panix.com> - 2017-10-15 03:36 +0000
        Re: Contactors/Relays M Philbrook <jamie_ka1lpa@charter.net> - 2017-10-15 12:07 -0400
          Re: Contactors/Relays mpm <mpmillard@aol.com> - 2017-10-15 09:19 -0700
            Re: Contactors/Relays David Lesher <wb8foz@panix.com> - 2017-10-19 06:10 +0000
          Re: Contactors/Relays David Lesher <wb8foz@panix.com> - 2017-10-19 06:08 +0000
        Re: Contactors/Relays edward.ming.lee@gmail.com - 2017-10-16 08:48 -0700
      Re: Contactors/Relays David Lesher <wb8foz@panix.com> - 2017-10-19 06:06 +0000
    Re: Contactors/Relays Hul Tytus <ht@panix.com> - 2017-10-14 21:20 +0000
      Re: Contactors/Relays David Lesher <wb8foz@panix.com> - 2017-10-19 06:07 +0000
        Re: Contactors/Relays legg <legg@nospam.magma.ca> - 2017-10-19 23:11 -0400
    Re: Contactors/Relays John Larkin <jjlarkin@highlandtechnology.com> - 2017-10-14 16:43 -0700
    Re: Contactors/Relays upsidedown@downunder.com - 2017-10-15 10:20 +0300
    Re: Contactors/Relays Neon John <no@never.com> - 2017-10-15 09:49 -0400

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#481403 — Contactors/Relays

I have futilely been seeking 100A 3ph NC/Form B relays/contactors.
It seems they are all stashed in the "unicorn eggs" box, sigh.

So a second design approach involves dual coil relays. The
flavor I seek has one larger coil to close the relay, and a
second, much lower power holding coil to keep it closed.  Of
course, I'm not finding them either. The ones I unearth are
"close coil, open coil" flavor.

Anyone seen such?

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#481409

On Sat, 14 Oct 2017 18:16:57 +0000 (UTC), David Lesher
<wb8foz@panix.com> wrote:

>I have futilely been seeking 100A 3ph NC/Form B relays/contactors.
>It seems they are all stashed in the "unicorn eggs" box, sigh.
>
>So a second design approach involves dual coil relays. The
>flavor I seek has one larger coil to close the relay, and a
>second, much lower power holding coil to keep it closed.  Of
>course, I'm not finding them either. The ones I unearth are
>"close coil, open coil" flavor.
>
>Anyone seen such?

Are you still insisting on DIN rail mounting?

RL

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#482021

legg <legg@nospam.magma.ca> writes:


>Are you still insisting on DIN rail mounting?

No, but that's the least important aspect.... not finding any mounting type...

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#482073

On Wed, 18 Oct 2017 22:32:46 +0000 (UTC), David Lesher
<wb8foz@panix.com> wrote:

>legg <legg@nospam.magma.ca> writes:
>
>
>>Are you still insisting on DIN rail mounting?
>
>No, but that's the least important aspect.... not finding any mounting type...

This 'fail closed' issue may be a misconception. What mode of failure
are you anticipating this to cover? 

If there is energy available on either terminal of the open contacts,
it should be harnessed to develope the required switch circuit state.
If there is no power on either terminal, then its state doesn't
matter.

RL

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#482092

legg <legg@nospam.magma.ca> writes:


>This 'fail closed' issue may be a misconception. What mode of failure
>are you anticipating this to cover? 

Nope, it's what's needed....
Control power drops, relay contacts close.


-- 
A host is a host from coast to coast.................wb8foz@nrk.com
& no one will talk to a host that's close..........................
Unless the host (that isn't close).........................pob 1433
is busy, hung or dead....................................20915-1433

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#482167

On Thu, 19 Oct 2017 06:11:58 +0000 (UTC), David Lesher
<wb8foz@panix.com> wrote:

>legg <legg@nospam.magma.ca> writes:
>
>
>>This 'fail closed' issue may be a misconception. What mode of failure
>>are you anticipating this to cover? 
>
>Nope, it's what's needed....
>Control power drops, relay contacts close.

Where does control power come from?
I'd expect use a power fail signal to do it's business during a
hold-up time period.

If there is only control power, then there's nothing to control, so
the normal state, in that condition, should be your 'fail-safe'
default.

RL

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#482188

legg wrote on 10/19/2017 3:02 PM:
> On Thu, 19 Oct 2017 06:11:58 +0000 (UTC), David Lesher
> <wb8foz@panix.com> wrote:
>
>> legg <legg@nospam.magma.ca> writes:
>>
>>
>>> This 'fail closed' issue may be a misconception. What mode of failure
>>> are you anticipating this to cover?
>>
>> Nope, it's what's needed....
>> Control power drops, relay contacts close.
>
> Where does control power come from?
> I'd expect use a power fail signal to do it's business during a
> hold-up time period.
>
> If there is only control power, then there's nothing to control, so
> the normal state, in that condition, should be your 'fail-safe'
> default.

Are you suggesting the relay needs to be powered from the contacts and it 
needs to *remember* the state it was last in when control power fails? 
Seems simpler to just power the coil from the control side and use a NC 
relay.  No small part of the use of relays comes from the isolation. 
Powering the relay from the load side means you have to start all over again 
with an isolation barrier.

-- 

Rick C

Viewed the eclipse at Wintercrest Farms,
on the centerline of totality since 1998

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#482232

On Thu, 19 Oct 2017 18:48:50 -0400, rickman <gnuarm@gmail.com> wrote:

>legg wrote on 10/19/2017 3:02 PM:
>> On Thu, 19 Oct 2017 06:11:58 +0000 (UTC), David Lesher
>> <wb8foz@panix.com> wrote:
>>
>>> legg <legg@nospam.magma.ca> writes:
>>>
>>>
>>>> This 'fail closed' issue may be a misconception. What mode of failure
>>>> are you anticipating this to cover?
>>>
>>> Nope, it's what's needed....
>>> Control power drops, relay contacts close.
>>
>> Where does control power come from?
>> I'd expect use a power fail signal to do it's business during a
>> hold-up time period.
>>
>> If there is only control power, then there's nothing to control, so
>> the normal state, in that condition, should be your 'fail-safe'
>> default.
>
>Are you suggesting the relay needs to be powered from the contacts and it 
>needs to *remember* the state it was last in when control power fails? 
>Seems simpler to just power the coil from the control side and use a NC 
>relay.  No small part of the use of relays comes from the isolation. 
>Powering the relay from the load side means you have to start all over again 
>with an isolation barrier.

There's no memory involved. This is the designer's decision. If it is
important that the contacts be in a certain configuration under
certain conditions, then it's the designer's responsibility to provide
circuitry that's smart enough to enforce it.

Intentionally configuring a lower power electronic control circuit
that can't function, always, when the higher-powered controlled
electrical quantity is present doesn't make sense.

RL

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#482235

legg wrote on 10/19/2017 11:02 PM:
> On Thu, 19 Oct 2017 18:48:50 -0400, rickman <gnuarm@gmail.com> wrote:
>
>> legg wrote on 10/19/2017 3:02 PM:
>>> On Thu, 19 Oct 2017 06:11:58 +0000 (UTC), David Lesher
>>> <wb8foz@panix.com> wrote:
>>>
>>>> legg <legg@nospam.magma.ca> writes:
>>>>
>>>>
>>>>> This 'fail closed' issue may be a misconception. What mode of failure
>>>>> are you anticipating this to cover?
>>>>
>>>> Nope, it's what's needed....
>>>> Control power drops, relay contacts close.
>>>
>>> Where does control power come from?
>>> I'd expect use a power fail signal to do it's business during a
>>> hold-up time period.
>>>
>>> If there is only control power, then there's nothing to control, so
>>> the normal state, in that condition, should be your 'fail-safe'
>>> default.
>>
>> Are you suggesting the relay needs to be powered from the contacts and it
>> needs to *remember* the state it was last in when control power fails?
>> Seems simpler to just power the coil from the control side and use a NC
>> relay.  No small part of the use of relays comes from the isolation.
>> Powering the relay from the load side means you have to start all over again
>> with an isolation barrier.
>
> There's no memory involved. This is the designer's decision. If it is
> important that the contacts be in a certain configuration under
> certain conditions, then it's the designer's responsibility to provide
> circuitry that's smart enough to enforce it.
>
> Intentionally configuring a lower power electronic control circuit
> that can't function, always, when the higher-powered controlled
> electrical quantity is present doesn't make sense.

So all designed equipment has to be 100% reliable?  How about since the 
requirement is to have the contacts closed when the controlling circuitry 
isn't powered to be implemented by a relay with normally closed contacts?

I don't get what your problem with this is.  The controlling system will be 
built to run from whatever power is deemed appropriate.  Your assertion that 
it *must* be powered by the load is without basis.  You are aware that the 
controlling circuit might be doing other things.  YOU seem to be unaware 
that there may be a larger system involved.

-- 

Rick C

Viewed the eclipse at Wintercrest Farms,
on the centerline of totality since 1998

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#482257

On Fri, 20 Oct 2017 00:49:08 -0400, rickman <gnuarm@gmail.com> wrote:

>legg wrote on 10/19/2017 11:02 PM:
>> On Thu, 19 Oct 2017 18:48:50 -0400, rickman <gnuarm@gmail.com> wrote:
>>
>>> legg wrote on 10/19/2017 3:02 PM:
>>>> On Thu, 19 Oct 2017 06:11:58 +0000 (UTC), David Lesher
>>>> <wb8foz@panix.com> wrote:
>>>>
>>>>> legg <legg@nospam.magma.ca> writes:
>>>>>
>>>>>
>>>>>> This 'fail closed' issue may be a misconception. What mode of failure
>>>>>> are you anticipating this to cover?
>>>>>
>>>>> Nope, it's what's needed....
>>>>> Control power drops, relay contacts close.
>>>>
>>>> Where does control power come from?
>>>> I'd expect use a power fail signal to do it's business during a
>>>> hold-up time period.
>>>>
>>>> If there is only control power, then there's nothing to control, so
>>>> the normal state, in that condition, should be your 'fail-safe'
>>>> default.
>>>
>>> Are you suggesting the relay needs to be powered from the contacts and it
>>> needs to *remember* the state it was last in when control power fails?
>>> Seems simpler to just power the coil from the control side and use a NC
>>> relay.  No small part of the use of relays comes from the isolation.
>>> Powering the relay from the load side means you have to start all over again
>>> with an isolation barrier.
>>
>> There's no memory involved. This is the designer's decision. If it is
>> important that the contacts be in a certain configuration under
>> certain conditions, then it's the designer's responsibility to provide
>> circuitry that's smart enough to enforce it.
>>
>> Intentionally configuring a lower power electronic control circuit
>> that can't function, always, when the higher-powered controlled
>> electrical quantity is present doesn't make sense.
>
>So all designed equipment has to be 100% reliable?  How about since the 
>requirement is to have the contacts closed when the controlling circuitry 
>isn't powered to be implemented by a relay with normally closed contacts?
>
>I don't get what your problem with this is.  The controlling system will be 
>built to run from whatever power is deemed appropriate.  Your assertion that 
>it *must* be powered by the load is without basis.  You are aware that the 
>controlling circuit might be doing other things.  YOU seem to be unaware 
>that there may be a larger system involved.

This isn't reliability, it's functionality.

About the only power control circuits I can think of that could use
normally closed power contact is a circuit breaker (fuse function) or
motor starter (who's on first function).
Both of these are motivated by the controlled source of power or it's
physical effect, and the latter isn't really affecting the source, so
much as it is signalling the load.

For signal level applications, potential damage to the switch itself,
or the effects of normal power flow on the switch's ability to
function are not usually a consideration.

I've worked on the development of an ultrafast multiphase transfer
switch, with hybrid semiconductor/mechanical brush contacts, and it's
automatic/manual control interface. At a certain power levels, you
have to enforce your own 'fail safe' environment. Gravity, leaf
springs or permanent magnets just don't cut it.

Isn't the apparent rarity of the requested hardware sufficient
indication that the OP might be barking up the wrong tree?

RL

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#482267

legg wrote on 10/20/2017 12:03 PM:
> On Fri, 20 Oct 2017 00:49:08 -0400, rickman <gnuarm@gmail.com> wrote:
>
>> legg wrote on 10/19/2017 11:02 PM:
>>> On Thu, 19 Oct 2017 18:48:50 -0400, rickman <gnuarm@gmail.com> wrote:
>>>
>>>> legg wrote on 10/19/2017 3:02 PM:
>>>>> On Thu, 19 Oct 2017 06:11:58 +0000 (UTC), David Lesher
>>>>> <wb8foz@panix.com> wrote:
>>>>>
>>>>>> legg <legg@nospam.magma.ca> writes:
>>>>>>
>>>>>>
>>>>>>> This 'fail closed' issue may be a misconception. What mode of failure
>>>>>>> are you anticipating this to cover?
>>>>>>
>>>>>> Nope, it's what's needed....
>>>>>> Control power drops, relay contacts close.
>>>>>
>>>>> Where does control power come from?
>>>>> I'd expect use a power fail signal to do it's business during a
>>>>> hold-up time period.
>>>>>
>>>>> If there is only control power, then there's nothing to control, so
>>>>> the normal state, in that condition, should be your 'fail-safe'
>>>>> default.
>>>>
>>>> Are you suggesting the relay needs to be powered from the contacts and it
>>>> needs to *remember* the state it was last in when control power fails?
>>>> Seems simpler to just power the coil from the control side and use a NC
>>>> relay.  No small part of the use of relays comes from the isolation.
>>>> Powering the relay from the load side means you have to start all over again
>>>> with an isolation barrier.
>>>
>>> There's no memory involved. This is the designer's decision. If it is
>>> important that the contacts be in a certain configuration under
>>> certain conditions, then it's the designer's responsibility to provide
>>> circuitry that's smart enough to enforce it.
>>>
>>> Intentionally configuring a lower power electronic control circuit
>>> that can't function, always, when the higher-powered controlled
>>> electrical quantity is present doesn't make sense.
>>
>> So all designed equipment has to be 100% reliable?  How about since the
>> requirement is to have the contacts closed when the controlling circuitry
>> isn't powered to be implemented by a relay with normally closed contacts?
>>
>> I don't get what your problem with this is.  The controlling system will be
>> built to run from whatever power is deemed appropriate.  Your assertion that
>> it *must* be powered by the load is without basis.  You are aware that the
>> controlling circuit might be doing other things.  YOU seem to be unaware
>> that there may be a larger system involved.
>
> This isn't reliability, it's functionality.
>
> About the only power control circuits I can think of that could use
> normally closed power contact is a circuit breaker (fuse function) or
> motor starter (who's on first function).
> Both of these are motivated by the controlled source of power or it's
> physical effect, and the latter isn't really affecting the source, so
> much as it is signalling the load.
>
> For signal level applications, potential damage to the switch itself,
> or the effects of normal power flow on the switch's ability to
> function are not usually a consideration.
>
> I've worked on the development of an ultrafast multiphase transfer
> switch, with hybrid semiconductor/mechanical brush contacts, and it's
> automatic/manual control interface. At a certain power levels, you
> have to enforce your own 'fail safe' environment. Gravity, leaf
> springs or permanent magnets just don't cut it.
>
> Isn't the apparent rarity of the requested hardware sufficient
> indication that the OP might be barking up the wrong tree?

Or maybe you just don't understand his application?

-- 

Rick C

Viewed the eclipse at Wintercrest Farms,
on the centerline of totality since 1998

[toc] | [prev] | [next] | [standalone]

#482363

On Fri, 20 Oct 2017 13:17:32 -0400, rickman <gnuarm@gmail.com> wrote:

>legg wrote on 10/20/2017 12:03 PM:
>> On Fri, 20 Oct 2017 00:49:08 -0400, rickman <gnuarm@gmail.com> wrote:
>>
>>> legg wrote on 10/19/2017 11:02 PM:
>>>> On Thu, 19 Oct 2017 18:48:50 -0400, rickman <gnuarm@gmail.com> wrote:
>>>>
>>>>> legg wrote on 10/19/2017 3:02 PM:
>>>>>> On Thu, 19 Oct 2017 06:11:58 +0000 (UTC), David Lesher
>>>>>> <wb8foz@panix.com> wrote:
>>>>>>
>>>>>>> legg <legg@nospam.magma.ca> writes:
>>>>>>>
>>>>>>>
>>>>>>>> This 'fail closed' issue may be a misconception. What mode of failure
>>>>>>>> are you anticipating this to cover?
>>>>>>>
>>>>>>> Nope, it's what's needed....
>>>>>>> Control power drops, relay contacts close.
>>>>>>
>>>>>> Where does control power come from?
>>>>>> I'd expect use a power fail signal to do it's business during a
>>>>>> hold-up time period.
>>>>>>
>>>>>> If there is only control power, then there's nothing to control, so
>>>>>> the normal state, in that condition, should be your 'fail-safe'
>>>>>> default.
>>>>>
>>>>> Are you suggesting the relay needs to be powered from the contacts and it
>>>>> needs to *remember* the state it was last in when control power fails?
>>>>> Seems simpler to just power the coil from the control side and use a NC
>>>>> relay.  No small part of the use of relays comes from the isolation.
>>>>> Powering the relay from the load side means you have to start all over again
>>>>> with an isolation barrier.
>>>>
>>>> There's no memory involved. This is the designer's decision. If it is
>>>> important that the contacts be in a certain configuration under
>>>> certain conditions, then it's the designer's responsibility to provide
>>>> circuitry that's smart enough to enforce it.
>>>>
>>>> Intentionally configuring a lower power electronic control circuit
>>>> that can't function, always, when the higher-powered controlled
>>>> electrical quantity is present doesn't make sense.
>>>
>>> So all designed equipment has to be 100% reliable?  How about since the
>>> requirement is to have the contacts closed when the controlling circuitry
>>> isn't powered to be implemented by a relay with normally closed contacts?
>>>
>>> I don't get what your problem with this is.  The controlling system will be
>>> built to run from whatever power is deemed appropriate.  Your assertion that
>>> it *must* be powered by the load is without basis.  You are aware that the
>>> controlling circuit might be doing other things.  YOU seem to be unaware
>>> that there may be a larger system involved.
>>
>> This isn't reliability, it's functionality.
>>
>> About the only power control circuits I can think of that could use
>> normally closed power contact is a circuit breaker (fuse function) or
>> motor starter (who's on first function).
>> Both of these are motivated by the controlled source of power or it's
>> physical effect, and the latter isn't really affecting the source, so
>> much as it is signalling the load.
>>
>> For signal level applications, potential damage to the switch itself,
>> or the effects of normal power flow on the switch's ability to
>> function are not usually a consideration.
>>
>> I've worked on the development of an ultrafast multiphase transfer
>> switch, with hybrid semiconductor/mechanical brush contacts, and it's
>> automatic/manual control interface. At a certain power levels, you
>> have to enforce your own 'fail safe' environment. Gravity, leaf
>> springs or permanent magnets just don't cut it.
>>
>> Isn't the apparent rarity of the requested hardware sufficient
>> indication that the OP might be barking up the wrong tree?
>
>Or maybe you just don't understand his application?

Quite likely.....

But then, I didn't get to be where I am today by (insert trumpism
here)!

RL

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#482376

legg wrote:
> On Fri, 20 Oct 2017 13:17:32 -0400, rickman <gnuarm@gmail.com> wrote:
>
>> legg wrote on 10/20/2017 12:03 PM:
>>> On Fri, 20 Oct 2017 00:49:08 -0400, rickman <gnuarm@gmail.com> wrote:
>>>
>>>> legg wrote on 10/19/2017 11:02 PM:
>>>>> On Thu, 19 Oct 2017 18:48:50 -0400, rickman <gnuarm@gmail.com> wrote:
>>>>>
>>>>>> legg wrote on 10/19/2017 3:02 PM:
>>>>>>> On Thu, 19 Oct 2017 06:11:58 +0000 (UTC), David Lesher
>>>>>>> <wb8foz@panix.com> wrote:
>>>>>>>
>>>>>>>> legg <legg@nospam.magma.ca> writes:
>>>>>>>>
>>>>>>>>
>>>>>>>>> This 'fail closed' issue may be a misconception. What mode of failure
>>>>>>>>> are you anticipating this to cover?
>>>>>>>>
>>>>>>>> Nope, it's what's needed....
>>>>>>>> Control power drops, relay contacts close.
>>>>>>>
>>>>>>> Where does control power come from?
>>>>>>> I'd expect use a power fail signal to do it's business during a
>>>>>>> hold-up time period.
>>>>>>>
>>>>>>> If there is only control power, then there's nothing to control, so
>>>>>>> the normal state, in that condition, should be your 'fail-safe'
>>>>>>> default.
>>>>>>
>>>>>> Are you suggesting the relay needs to be powered from the contacts and it
>>>>>> needs to *remember* the state it was last in when control power fails?
>>>>>> Seems simpler to just power the coil from the control side and use a NC
>>>>>> relay.  No small part of the use of relays comes from the isolation.
>>>>>> Powering the relay from the load side means you have to start all over again
>>>>>> with an isolation barrier.
>>>>>
>>>>> There's no memory involved. This is the designer's decision. If it is
>>>>> important that the contacts be in a certain configuration under
>>>>> certain conditions, then it's the designer's responsibility to provide
>>>>> circuitry that's smart enough to enforce it.
>>>>>
>>>>> Intentionally configuring a lower power electronic control circuit
>>>>> that can't function, always, when the higher-powered controlled
>>>>> electrical quantity is present doesn't make sense.
>>>>
>>>> So all designed equipment has to be 100% reliable?  How about since the
>>>> requirement is to have the contacts closed when the controlling circuitry
>>>> isn't powered to be implemented by a relay with normally closed contacts?
>>>>
>>>> I don't get what your problem with this is.  The controlling system will be
>>>> built to run from whatever power is deemed appropriate.  Your assertion that
>>>> it *must* be powered by the load is without basis.  You are aware that the
>>>> controlling circuit might be doing other things.  YOU seem to be unaware
>>>> that there may be a larger system involved.
>>>
>>> This isn't reliability, it's functionality.
>>>
>>> About the only power control circuits I can think of that could use
>>> normally closed power contact is a circuit breaker (fuse function) or
>>> motor starter (who's on first function).
>>> Both of these are motivated by the controlled source of power or it's
>>> physical effect, and the latter isn't really affecting the source, so
>>> much as it is signalling the load.
>>>
>>> For signal level applications, potential damage to the switch itself,
>>> or the effects of normal power flow on the switch's ability to
>>> function are not usually a consideration.
>>>
>>> I've worked on the development of an ultrafast multiphase transfer
>>> switch, with hybrid semiconductor/mechanical brush contacts, and it's
>>> automatic/manual control interface. At a certain power levels, you
>>> have to enforce your own 'fail safe' environment. Gravity, leaf
>>> springs or permanent magnets just don't cut it.
>>>
>>> Isn't the apparent rarity of the requested hardware sufficient
>>> indication that the OP might be barking up the wrong tree?
>>
>> Or maybe you just don't understand his application?
>
> Quite likely.....
>
> But then, I didn't get to be where I am today by (insert trumpism
> here)!


    What happens when that 100A 3P NC contactor fails from an open coil, 
or a loose wire?

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#482379

On Sat, 21 Oct 2017 12:23:32 -0400, Michael A Terrell
<mike.terrell@earthlink.net> wrote:

>legg wrote:
>> On Fri, 20 Oct 2017 13:17:32 -0400, rickman <gnuarm@gmail.com> wrote:
>>
>>> legg wrote on 10/20/2017 12:03 PM:
>>>> On Fri, 20 Oct 2017 00:49:08 -0400, rickman <gnuarm@gmail.com> wrote:
>>>>
>>>>> legg wrote on 10/19/2017 11:02 PM:
>>>>>> On Thu, 19 Oct 2017 18:48:50 -0400, rickman <gnuarm@gmail.com> wrote:
>>>>>>
>>>>>>> legg wrote on 10/19/2017 3:02 PM:
>>>>>>>> On Thu, 19 Oct 2017 06:11:58 +0000 (UTC), David Lesher
>>>>>>>> <wb8foz@panix.com> wrote:
>>>>>>>>
>>>>>>>>> legg <legg@nospam.magma.ca> writes:
>>>>>>>>>
>>>>>>>>>
>>>>>>>>>> This 'fail closed' issue may be a misconception. What mode of failure
>>>>>>>>>> are you anticipating this to cover?
>>>>>>>>>
>>>>>>>>> Nope, it's what's needed....
>>>>>>>>> Control power drops, relay contacts close.
>>>>>>>>
>>>>>>>> Where does control power come from?
>>>>>>>> I'd expect use a power fail signal to do it's business during a
>>>>>>>> hold-up time period.
>>>>>>>>
>>>>>>>> If there is only control power, then there's nothing to control, so
>>>>>>>> the normal state, in that condition, should be your 'fail-safe'
>>>>>>>> default.
>>>>>>>
>>>>>>> Are you suggesting the relay needs to be powered from the contacts and it
>>>>>>> needs to *remember* the state it was last in when control power fails?
>>>>>>> Seems simpler to just power the coil from the control side and use a NC
>>>>>>> relay.  No small part of the use of relays comes from the isolation.
>>>>>>> Powering the relay from the load side means you have to start all over again
>>>>>>> with an isolation barrier.
>>>>>>
>>>>>> There's no memory involved. This is the designer's decision. If it is
>>>>>> important that the contacts be in a certain configuration under
>>>>>> certain conditions, then it's the designer's responsibility to provide
>>>>>> circuitry that's smart enough to enforce it.
>>>>>>
>>>>>> Intentionally configuring a lower power electronic control circuit
>>>>>> that can't function, always, when the higher-powered controlled
>>>>>> electrical quantity is present doesn't make sense.
>>>>>
>>>>> So all designed equipment has to be 100% reliable?  How about since the
>>>>> requirement is to have the contacts closed when the controlling circuitry
>>>>> isn't powered to be implemented by a relay with normally closed contacts?
>>>>>
>>>>> I don't get what your problem with this is.  The controlling system will be
>>>>> built to run from whatever power is deemed appropriate.  Your assertion that
>>>>> it *must* be powered by the load is without basis.  You are aware that the
>>>>> controlling circuit might be doing other things.  YOU seem to be unaware
>>>>> that there may be a larger system involved.
>>>>
>>>> This isn't reliability, it's functionality.
>>>>
>>>> About the only power control circuits I can think of that could use
>>>> normally closed power contact is a circuit breaker (fuse function) or
>>>> motor starter (who's on first function).
>>>> Both of these are motivated by the controlled source of power or it's
>>>> physical effect, and the latter isn't really affecting the source, so
>>>> much as it is signalling the load.
>>>>
>>>> For signal level applications, potential damage to the switch itself,
>>>> or the effects of normal power flow on the switch's ability to
>>>> function are not usually a consideration.
>>>>
>>>> I've worked on the development of an ultrafast multiphase transfer
>>>> switch, with hybrid semiconductor/mechanical brush contacts, and it's
>>>> automatic/manual control interface. At a certain power levels, you
>>>> have to enforce your own 'fail safe' environment. Gravity, leaf
>>>> springs or permanent magnets just don't cut it.
>>>>
>>>> Isn't the apparent rarity of the requested hardware sufficient
>>>> indication that the OP might be barking up the wrong tree?
>>>
>>> Or maybe you just don't understand his application?
>>
>> Quite likely.....
>>
>> But then, I didn't get to be where I am today by (insert trumpism
>> here)!
>
>
>    What happens when that 100A 3P NC contactor fails from an open coil, 
>or a loose wire?
>
>
OP wants NC as result of loss of control, which an open coil
represents.

RL

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#482403

legg wrote:
 >
> Michael A Terrell wrote:
>>
>>
>>    What happens when that 100A 3P NC contactor fails from an open
>> coil, or a loose wire?
>>
>>
> OP wants NC as result of loss of control, which an open coil
> represents.



    OK, but how does that help? The contactor closes. What is on each 
side of it, when that happens when it's not supposed to? Is a generator 
or inverter connected to a live power line, out of phase?

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#482447

On Sat, 21 Oct 2017 19:23:24 -0400, Michael A Terrell
<mike.terrell@earthlink.net> wrote:

>legg wrote:
> >
>> Michael A Terrell wrote:
>>>
>>>
>>>    What happens when that 100A 3P NC contactor fails from an open
>>> coil, or a loose wire?
>>>
>>>
>> OP wants NC as result of loss of control, which an open coil
>> represents.
>
>
>
>    OK, but how does that help? The contactor closes. What is on each 
>side of it, when that happens when it's not supposed to? Is a generator 
>or inverter connected to a live power line, out of phase?


I've followed this thread and its predecessor pretty closely, but have
yet to see any app info save: 

'240 VAC resistive; we are interupting both sides of a 240V circuit.'
'I need 2 or 3P.'

Of course the question is, what happens if you can not open one or
either of these terminals, when required? That's the 'failed'
condition, and one that is difficult to to comprehend as being 'safe'.

RL

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#482482

legg <legg@nospam.magma.ca> writes:



>I've followed this thread and its predecessor pretty closely,
>but have yet to see any app info save:

>'240 VAC resistive; we are interupting both sides of a 240V   '
>'circuit.  I need 2 or 3P.                                    '

>Of course the question is, what happens if you can not open
>one or either of these terminals, when required? That's the
>'failed' condition, and one that is difficult to to comprehend
>as being 'safe'.

That's because you only know the small part; not the big
picture. You (& others...) assume too much. The bad thing is not
when the downstream is powered, it's when it's not able to be
powered.

Alas, I'm getting convinced that no one makes the hardware I
seek. The closest I've found are several quite pricy 100A+
contactors with 2 poles NO and 2 NC. I guess I spec two
of them for 3 ph. loads.

-- 
A host is a host from coast to coast.................wb8foz@nrk.com
& no one will talk to a host that's close..........................
Unless the host (that isn't close).........................pob 1433
is busy, hung or dead....................................20915-1433

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#482427

rickman <gnuarm@gmail.com> writes:

>> Isn't the apparent rarity of the requested hardware sufficient
>> indication that the OP might be barking up the wrong tree?

>Or maybe you just don't understand his application?

And rickman gets the prize....


-- 
A host is a host from coast to coast.................wb8foz@nrk.com
& no one will talk to a host that's close..........................
Unless the host (that isn't close).........................pob 1433
is busy, hung or dead....................................20915-1433

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#483003

legg <legg@nospam.magma.ca> writes:


>About the only power control circuits I can think of ......

I hope you're not unhappy to learn that there are situations you
didn't think of, and are unlikely to, especially given I've only
given one tiny part of a bigger picture to you.


-- 
A host is a host from coast to coast.................wb8foz@nrk.com
& no one will talk to a host that's close..........................
Unless the host (that isn't close).........................pob 1433
is busy, hung or dead....................................20915-1433

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#483444

On Thu, 26 Oct 2017 05:00:03 +0000 (UTC), David Lesher
<wb8foz@panix.com> wrote:

>legg <legg@nospam.magma.ca> writes:
>
>
>>About the only power control circuits I can think of ......
>
>I hope you're not unhappy to learn that there are situations you
>didn't think of, and are unlikely to, especially given I've only
>given one tiny part of a bigger picture to you.

It would be a pleasure to be enlightened, should you deign to do so.

RL

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