I am trying to hold in some square D ice cube relays (in a momentary contact circuit that control solenoids) so that they don't drop out in a power failure. I used an inexpensive APC UPS, but these units have a transfer rate of 6 to 8 milliseconds (fine for a computer power supply) and they wouldn't hold. Does anyone know from experience whether a 2-4 ms transfer rate will do me any good or will I need to go to an online unit?
UPS Transfer Times and Relays
- Thread starter jckenner
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Re: UPS Transfer Times and Relays
Any chance you can use 24V dc relays? The capoacitors in the 24V power supply should buffer any short outage the UPS gives. In addition, the current through a relay won't drop to zero instantly. The magnetic field around the coil has to collapse, and that takes some time.
To be honest, I don't know how an AC relay works. The alternating current should pull the contacts in and then push them away. I suspect that AC relays have a built in diode to convert the AC to DC. Can anyone confirm this?
Steve
Any chance you can use 24V dc relays? The capoacitors in the 24V power supply should buffer any short outage the UPS gives. In addition, the current through a relay won't drop to zero instantly. The magnetic field around the coil has to collapse, and that takes some time.
To be honest, I don't know how an AC relay works. The alternating current should pull the contacts in and then push them away. I suspect that AC relays have a built in diode to convert the AC to DC. Can anyone confirm this?
Steve
- Location
- Lockport, IL
- Occupation
- Retired Electrical Engineer
Re: UPS Transfer Times and Relays
Can you replace the relays with the Time Delay on Drop Out (TDDO) style? I do not know if Square D makes them in the "ice cube" size, but it may be worth a look.
Can you replace the relays with the Time Delay on Drop Out (TDDO) style? I do not know if Square D makes them in the "ice cube" size, but it may be worth a look.
Re: UPS Transfer Times and Relays
Such a fast transfer must be done in phase, that is the normal and emergency sources must be in phase, or magical things can happen.
You weren't that specific but trying to put two and two together, I am assuming that you are looking to ride through a momentary power outage from a normal source. It looks as if you're looking for a time delay normal to emergency (TDNE) feature. If so, you may consider a time delay relay that is time delay off. These relays often are adjustable in the range of .1 sec to 120 sec for example. They will not change contacts until the time delay setting has timed out. If the power is restored before the time out the relay does not transfer.
Such a fast transfer must be done in phase, that is the normal and emergency sources must be in phase, or magical things can happen.
You weren't that specific but trying to put two and two together, I am assuming that you are looking to ride through a momentary power outage from a normal source. It looks as if you're looking for a time delay normal to emergency (TDNE) feature. If so, you may consider a time delay relay that is time delay off. These relays often are adjustable in the range of .1 sec to 120 sec for example. They will not change contacts until the time delay setting has timed out. If the power is restored before the time out the relay does not transfer.
charlie tuna
Senior Member
- Location
- Florida
Re: UPS Transfer Times and Relays
the device you need is manufactured by "agastat".
the device you need is manufactured by "agastat".
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