Contactors/Relays

Are you still insisting on DIN rail mounting?

RL

Add your own solenoid.

RL

RL

David - are the "close coil, open coil" relays the type that are opened by a pulse on one coil and closed by a pulse on the other?

Hul

AC relays and contactors do that automatically. The seated inductance is much higher than the open inductance, so the coil current drops when the relay is fully closed.

Have you looked at companies making star/delta soft starter relays ?

You might find some relays with NC or switch over contacts.

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

Or pay someone to turn it for us....

-- A host is a host from coast to snipped-for-privacy@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

NO not NC main contacts.

-- A host is a host from coast to snipped-for-privacy@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

Yes....

-- A host is a host from coast to snipped-for-privacy@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

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

-- A host is a host from coast to snipped-for-privacy@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

Now I'm confused. Above you said if control power drops the relay contacts should close. Here you say they should be NO. Those two things are not compatible.

Do you have room for three separate relays each with a single NC contact ?

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

legg wrote on 10/19/2017 3:02 PM:

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

That is the usual function of the physical component of an electronically controlled transfer switch, partly due to the power requirement of the movement.. The auxilliary signal contacts can provide information on the operating state and may also be used directly to energize or disable the appropriate coil.

RL

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.