Schematic of overcurrent relay (late 70's) - delay function, how ?

Hi.

Have a schematic of an overcurrent relay - I know the original drawing is from 1979 so I assume the age of the unit is from the 70's.

I have seen the unit being tested so I know it's function by mechanical drums/counter, sso it seems that the component is controlling speed or delay of the mechanical wheels.

I know there are members in here that have being around for longer time than myselv, so had being nice if anybody recognise the symbol. I also upload the full schematic for the relay so you see where it's located.

Just a little disclaimer : It may be symbols that is exclusely used in Europe/Scandinavia - that I don't know. The schematic doesn't contain name/model of the unit - for that I have to see it by myself (way out in no-mans-land).

I'd guess it's a mechanical "flag" indicator, either a bistable solenoid or split field controlled visual marker that shows the device has tripped.

It operates from the DC supply P2 - N2 and is fed power either at the right side, from the "tripped" indicator relay, or the left from the mechanical overload reset button.

The actual overload sense devices are the I r-s-t and K r-s-t ones, the rest of the circuit is indication from those. The only possible delay in tripping would be thermal or hydraulic in the overloads.

The tripped indicator relay does have an R-C delay, possibly just for noise or interference suppression - it runs from the I r-s-t trips, which seem to need manual reset via the R button.


There is a type of DC motor that has a centre-tapped series field. The centre tap connects to one brush and the other brush and field ends are the external connections. The motor runs one direction or the other depending on which field terminal is powered.

That type would fit in with the operation of that device.

[I had some old aircraft servos that used that three wire system, also Lionel model train motors with wound fields work like that.]

>google<
They appear to actually be called "split field" motors:

**broken link removed**

I agree looks a bit like a dashpot relay.
If you just want to protect a motor use a thermal relay.

Thanks a lot for your inputs. Espechially since you introduce me for english terms I haven't heard of before. So I read up on dashpot relay and yes, I agree that the eqipment probably contains one or more of these.

Just a little question in adition. The b9 switch purpose is to switch between normal operation "D", in-between position "N" and test-mode "P", so that the device can be tested without disconnect parts of the facility. What is the actual english term for that kind of switch?

b9 Three position switch - centre off.
Some can also be spring return to centre off, either left or right side. The other side maintained.
Max.