AC detection delay for electrical equipments

[qwertyqwq]

Hi,

The company that im working for is designs electrical panels for our costumers. One of our customers having trouble on some kind of turn on delay. Here are the details;

There is a K1 contactor(Schneider LC1D25) in the electrical panel which is powerful 3 phase contactor for directly 3ph induction motor control. The K1 contactors situation depends on 2 long wired sensor switch. Each sensor is approximately 5meters far away from the electrical panels. Those sensor switches also works with 230Vac voltage and they are basically switch acting devices. They arent include any electronic parts inside or any other slow behavior parts.
There is also a RELAY on the right side of the schematic. This relay is for dry contact output for costumer fault signal monitoring. This relay is a miniature relay from schneider RSB2A080P7 type and it sense the unexpected turn on behaviour at the sensors via K1's NC contacts. Now problem begins...

Here i m sharing a example circuit of exact system part.

when system energized with 230vac supply, (even LONG SENSOR 1 and 2 shorts )tiny little amount of time delay accurse to activate the K1 contactor. this amount of time delay is enough to activate the RELAY . so the costumer PLC detects faults on the LONG SENSOR 1 or 2 . Although I told them to generate some delay on the PLC side for get rid of false fault signals but they are no capable of do that or they dont know how to do . So they are asking for easy alternative solutions.

As known one of the solution is using turn on delay timer device. But i thought maybe using a high voltage capacitor or resistor etc across the RELAY coil would help to slow down the fast activation. What do you think ?

Thank you.

 

[AnalogKid]

Because everything in the panel is running on AC, and simple R-C delay network will not work.

What will work is putting an AC-powered delay-on timer relay in the place of K1, and use its contacts to drive the K1 coil. Others on this forum with more industrial control panel experience can fill in in the details.

ak

 

[rjenkinsgb]

A better approach would be to use the on delay timer to directly replace the fault relay.

That keeps the K1 circuit as simple as possible.

Or, add an activation delay in the PLC that monitors the relay, if that is what the monitoring connects to??

That would generally be advisable on any fault monitoring input that is not extremely time critical, to avoid noise, glitches or race conditions such as this from causing false alarms.

 

[AnalogKid]

A better approach would be to use the on delay timer to directly replace the fault relay.

That doesn't prevent brief false energizing of the contactor:

when system energized with 230vac supply, (even LONG SENSOR 1 and 2 shorts )tiny little amount of time delay accurse to activate the K1 contactor.

I think he means a tiny amount of time *occurs* to activate the contactor.

ak

 

[Diver300]

This might do what you want.

When the circuit turns on, nothing happens until K1 operates. When K1 does operate, R1 turns on, and the NO contact of R1 keeps R1 on until the power is lost.

When either sensor turns off, the NC contact of K1 turns on R2, which has volt-free alarm contacts as before.

The downside is that the sensors have to have worked at the same time, since the last power cut, for an alarm to be raised.

 

[AnalogKid]

Again, I don't think that prevents K1 from operating very briefly due to false operation of the sensors at power-on.

ak

 

[rjenkinsgb]

when system energized with 230vac supply, (even LONG SENSOR 1 and 2 shorts )tiny little amount of time delay accurse to activate the K1 contactor. this amount of time delay is enough to activate the RELAY . so the costumer PLC detects faults on the LONG SENSOR 1 or 2 .

The relay is a fault detector, and should only energise if the power is applied to the whole circuit, but K1 does not energise.

The problem the OP describes is that the contactor K1 is relatively slow to operate.
So, between power being applied and K1 actually energising to disconnect the fault relay, the much faster relay briefly activates and flags a fault condition when there is not actually one.

It is a "Race condition" problem with different parts of the circuit having different operating delays.

A genuine fault would be if eg. power is applied but K1 has not activated with a couple of hundred milliseconds.

An on-delay timer in place of the relay would prevent the brief false error state occurring.

 

[Diver300]

Again, I don't think that prevents K1 from operating very briefly due to false operation of the sensors at power-on.

ak

As long as the NO and NC contacts of K1 don't operate at the same time, and there is no bouncing of the armature, then there shouldn't be any energisation of the output.

 

[qwertyqwq]

The relay is a fault detector, and should only energise if the power is applied to the whole circuit, but K1 does not energise.

The problem the OP describes is that the contactor K1 is relatively slow to operate.
So, between power being applied and K1 actually energising to disconnect the fault relay, the much faster relay briefly activates and flags a fault condition when there is not actually one.

It is a "Race condition" problem with different parts of the circuit having different operating delays.

A genuine fault would be if eg. power is applied but K1 has not activated with a couple of hundred milliseconds.

An on-delay timer in place of the relay would prevent the brief false error state occurring.

We decided to use timer relay.

Thank you.