Mechanical delay.

[itsmoked]

Long ago I saw one of these but now that I could actually use one....nada

I want to prevent someone from starting a motor more often than every 15 minutes.(EVER!)

I have electronic timing so I can start a 15 minute timer that prevents hitting start again until it times out. But you get the clever/stupid operator who figures out that if power is lost the timer resets. Then they just crank off the disconnect and then back on, and away they go with a 30 second cycle.

I have seen mechanical bellows(?)types that essentially cock with the initial turn on then take x minutes, regardless of the power situation, to re-close.

Anyone have a lead, or know what these are called? Or have an effective alternate solution? Google bombed for me.

Keith Cress
Flamin Systems, Inc.-

http://www.flaminsystems.com

 

[jraef]

Hi Keith,
What you saw was a "pneumatic time delay relay" (aka pneumatic timer). You are correct in that they will work regardless of the electrical power condition. What you would want is an Off Delay version with NCTC (Normally Closed Timed to Close) contacts plus a set of NO instantaneous contacts. The NCTC contacts will change state immediately when the coil in energized, but will after the coil is de-enerized they will remain in that condition until the bellows lets all the air out.

The first time you give a start command, the command signal passes through the NCTC contacts to the timer coil, which also then seals itself in through the NO instantaneous contacts which were in parallel to the NCTC, which then also feeds the remaining desired control circuit. Once the run command is removed (ahead of this timer circuit), the coil drops out and of course the NO instantaneous contacts will open, but the NCTC contacts will remain open until the bellows allows it to re-close, which prevents the circuit from being re-energized.

Just so you know though, some electronic Off-Delay timers use retentive memory (through a super cap usually) and will maintain their condition regardless of power status as well, effectively duplicating the action of a pneumatic timer. In the electronic timer world, it will be referred to as "Off Delay Without Auxiliary Voltage"

 

[waross]

Hi Keith
Everyone used to make them. Square D, GE, Allen Bradley, Westinghouse, Cutler Hammer, Telemechanique.
The Cadillac was Agastat. They had a dial calibrated in seconds or minutes. This feature saved a lot of time on startups. The others had numbers that did not corelate with time. You may spend 10 minutes or more setting a 2 minute delay on most of the other timers.
Respectfully

 

[itsmoked]

Thanks a million you two! Agastat!! That's the name I recall now. No wonder googling was hopeless.

I am going to take a run at the electronic ones because... I'm an electronics type of guy!

Keith Cress
Flamin Systems, Inc.-

http://www.flaminsystems.com

 

[jraef]

Agastats are still available (albeit for a hefty price), they have just been bought out by Tyco. You're right though Bill, the 7000 Series is the Cadillac of pneumatic timers.

http://relays.tycoelectronics.com/datasheets/7000.pdf

By the way Keith, had your user not bought that el-cheap-o soft starter, this lockout function would have been a simple programmable setting. Not bad for you though, assuming of course you can get paid to provide the solution in external logic!

 

[itsmoked]

Yeah sheesh. It gets even better.. He's having a deadbeat client buy all the stuff as a way to get some overdue money from him. [flush]

But to-wit, how would a classy SS hold that time thru a power cycle? Or would it just look at its internal temperature and keep itself thermally locked out, since that is the crux of the matter anyway?

Keith Cress
Flamin Systems, Inc.-

http://www.flaminsystems.com

 

[itsmoked]

I found one for only.. $300!!
Yow, they are pricey aren't they.

It looks like you could stop a train with one though.

Keith Cress
Flamin Systems, Inc.-

http://www.flaminsystems.com

 

[ScottyUK]

Wow - $300! ABB make these timers, as do Schneider under the Telemecanique brand, Moeller, A-B. They are commodity items in the UK. They are about £30, and mount on top of a small contactor or large control relay so figure on about £50 - £60 all in. RS are expensive but you get delivery next day - a wholesaler should knock 20 - 30% out of the RS price.

Take a look the later part of the following link:

http://rs

http://www.com/cgi-bin/bv/rswww/sea...feceeldgkidhgh.0&cacheID=uknetscape&Nr=avl:uk

----------------------------------

Sometimes I only open my mouth to swap feet...

 

[LionelHutz]

Keith,

Some soft-starters will just save the present lockout time values when they are turned off and return to the same lockout time when powered back on. Other soft-starter have a built-in time clock and they can re-calculate what the lockout time should be when powered on. I guess there could be one out there that has a supercap and just keeps timing that I don't know of too.

I think AB has a true electronic one - try 700-HRQ maybe.

 

[jraef]

Yes, Real Time Clocks (with battery backups or super caps) in soft starters are increasingly more common now on higher end versions and other electronic motor protection devices. They need them anyway for maintaining an Overload status condition in any Solid State Overload protection scheme. Still, there are those that don't even do that, meaning you can reset the OL by cycling power too. That's always something to watch out for. I did an industry study on SSOLs about 6 years ago and found that over 1/2 of the ones on the market did not have any kind of "retentive thermal memory". That may have changed by now, a few lawsuits over cooked motors would have a tendency to wake manufacturers up to the issue.

The problem you will find with the lower cost pneumatic timer attachments for control relays mentioned by ScottyUK is that they don't usually have a clear time value on the dial adjustment like those Agastats do. They have a range printed on the front and a tapered indicator on the screwdriver adjustment dial, but getting an accurate setting is a trial and error procedure as waross mentioned earlier. You may want to consider it anyway if price is an issue. After all, you are probably only going to set it once.

 

[dpc]

Agastat timers are very nice. We used to use them by the bushel-full for all timing functions back before PLCs.

 

[itsmoked]

I have found a truck load of different "OFF DELAY" relays. Annoyingly I've also spent hours trying to devine their actual operation from generally clueless data sheets. Some tout "true" off delay. Most have very short delay periods, no doubt due to the draining energy storage aspects. 600 seconds seems about the limit for a 'true' OFF Delay unit.

These same units also have a nasty requirement of a minimum ON period for the delay period to be valid. No doubt this is the time required to actually charge the energy storage device/s. Typical is about 1 second some need 2 seconds.

The ole Agastat needs 50ms for hours of delay! This means a guy poking a "start" button will supply the necessary 'charge time'.

I do like the Agastat's nice setting and superb data sheet.

Advantage: Fast and accurate so I can test and debug with a 10s cycle then confidently set the 15 minute period.

Disadvantage: Idiots can easily devine the function and crank the knob. When the motor or SS fries they can also quickly re-adjust it before whining about 'a problem'.

I would use the Agastat, and to hell with the $$, if you guys can assuage my fears or suggest a solution with respect to the Disadvantage.

Keith Cress
Flamin Systems, Inc.-

http://www.flaminsystems.com

 

[dpc]

Keith,

They used to have a "tamper-proof" cover option that might at least slow down the evil-doers a little.

I believe they also have a little NEMA 1 enclosure that hides the whole thing.

 

[jraef]

Keith, the cheap trick is a little dab of Torque Seal (the pink laquer used for bolt heads) at the base of the time dial going across to the body of the timer so that if they move the dial after you set it, it breaks the daub of paint and you know it. It doesn't stop Bubba from tweaking the timer and frying the soft starter, but it absolves you of culpability. You can usually get a little tube of it at the automotive store.

http://www.hi-line.com/chemicals-torqueseal/203

I've also used lipstick in a pinch, but it's a little easier to clean off and replace (although hopefully Bubba doesn't carry any with him!).

 

[itsmoked]

That's what I was thinking.. I'll do that!
Thanks people.

Happy 4th.

Keith Cress
Flamin Systems, Inc.-

http://www.flaminsystems.com

 

[OperaHouse]

R-K Elctronics

http://www.rke.com

has a COB series true off delay timer with an internal super cap that has an adjustable delay from a half minute to 60 minutes. Don't think it is that expensive, but it does have that uncalibrated dial you have to fiddle with.

 

[itsmoked]

Thanks Opera.

Interesting company.

Their data sheet is clear.

The price is exactly 1/2 of an Agastat.

The minimum ON time is 7 seconds! Ouch.

Keith Cress
Flamin Systems, Inc.-

http://www.flaminsystems.com

 

[waross]

Hi Keith;
I had my head inside a new 70kv class SF6 breaker today. I thought of you when I saw on the relay rail, a Telemecanique relay with a pneumatic timing head added.
Respectfully

 

[OperaHouse]

With it being a true independent off delay, there has to be enough time to charge the capacitor. Unless there is a separate pin to supply power, that should be common problem with other relays of this type. That detail may be hidden in the specs for first power up.

 

[jraef]

That's the simplistic beauty of pneumatic timers such as the Agastat. The "charge time" is just the time it takes to squeeze the bellows, so it's the same as the coil pull-in time. The old argument of a mechanical device being less accurate and/or reliable than an electronic is somewhat true, but that is why the Agastats are so expensive; highly accurate and repeatable for an electro-mechanical device.

That's also why they continue to survive as a product when most of their competitors have fallen away; that and the fact that the contacts on the Agastat are rated for 600VAC, where most other timers are rated 250VAC/DC max. It allows the Agastats to be used in full voltage circuits such as large contactor coils or even small motor operated valves.

PS: For those who are curious as to why I know so much about Agastats (aside from being a user years ago), my ex-employer was in the hunt for buying that division of AMF when they were being divested, and I was assigned to evaluate the viability of that product in the marketplace. We lost out to the big bucks at Tyco.