Y-Delta starters in elevators

[jraef]

OK, pardon my ignorance, but I just cam across a curiosity that has me baffled. Open transition Y-Delta starters that use only 2 contactors! I don't yet know how they are wired because I have seen them only on a bench, but everyone assures me that they are not 2 out of the usual 3 contactors, they are using only the 2. They are mechanically interlocked so that only one can be closed at a time and one of them has a shorting bar across the top. As I said, I don't yet know the wiring configuration, but for the life of me, I cannot figure out how they are able to do anything useful! Has anyone else ever come across this? Apparently, it is very common in the elevator world.

 

[davidbeach]

How many contact per contactor? Two six-pole contactors would be an easy solution. Two three-pole contactors might be a bit more of a stretch.

 

[Marke]

How about one end of the windings permanently connected to the incoming phases, and the other end of the windings going to two contactors, one to a star point and the other to the incoming phases.

Means there permanently three phase on one end of the windings, but you can still start and stop the motors OK. - saves the cost of one contactor.

Best regards,

Mark Empson

http://www.lmphotonics.com

 

[Walden]

Many years ago, I saw a star/delta starter with only two contactors. The star contactor had normally closed, fully rated contacts on the top with three normally open main contacts underneath. Is this the beast?

 

[jraef]

They are 3 pole, and all of the contacts are normally open.

Marke, that may be it!

 

[jraef]

For anyone interested or for future reference for searchers, Marke was correct. T1,2,3 leads to the motor are permanently connected to the line, the other 3 leads, T4,5,6, are connected to a common point between the Star and Delta contactors.

 

[Marke]

You just can't assume anything can you!!
Classic case of not doing the obvious and to bad about the safety.

Best regards,

Mark Empson

http://www.lmphotonics.com