Dashpot Operation 1

[EEtheEE]

Hello,

Does anyone have any links that describe/illustrate the operation of a dashpot? My limited knowledge is that it is a "bucket" having a paddle submerged in oil (or other medium). As current passes through the device, the oil heats up and begins to flow through an oriface in the paddle. If enough heat is generated by the current (over current situation), oil flow will cause the paddle to move and the unit will trip.

Am I missing anything?

Thanks for the help in advance.

Erich

 

[byrdj]

are you thinking about a mechinical time delayed relay.

he dashpot is an oil filled cylinder with a small hole in the piston.

when the relay is reset, coil deenegrized, contacts open, the piston will be at one end. when the coil is energized, it first starts to force the piston to the other end. It takes time for the oil to be forced through the small hole from one side to the other. It may take a minute for the piston to travel enough to let the contacts make. thus a one minute time delay to make contacts after the coil was energived

 

[dpc]

These were used for protective relays as well as trip units on low voltage power circuit breakers (GE's version was the EC).

You might check with GE - last I knew they were still selling the EC-2 trip units for use on dc breaker applications.

These things are nice for a historical collection, but I wouldn't want any in service on my system.

 

[EEtheEE]

Thanks to both of you. We have a couple pieces of LV switchgear equipment that still uses this technology. We are in the process of changing them out and was interested in how the trip worked.

 

[Zogzog]

I have bins full of those in our shop. I would estimate they have about a 80% failure rate based on hundereds of primary injection tests.

EEtheEE we can upgrade those for you with any type of trip unit you desire, however, we recommend AC PRO units.

http://www.epowerplus.com

 

[EEtheEE]

Thanks Zogzog, but we have already purchased the replacement units and are currently scheduling the work.

 

[jraef]

be careful by the way. Some of the older dash pot relays used PCB laden oil.