Star Delta Motor....No Timer?

[chrisreisinger79]

I am currently building a new control panel to replace the outdated one for a large two speed cooling fan. The fan has a Low Speed Contactor, a High Speed Contactor, and a Star Contactor operating in conjuction with the high speed contactor. The contactors are wired as you would typically find for Star/Delta High Speed. However, there is currently no timer to disengage the Star Contactor. So...during the entire High Speed operation, both the Star and High Contactor remain engaged. What could the possible reason for this be?

 

[Jraef]

It's a 2 speed 1 winding motor. The circuit looks like a wye-delta starting scheme to the untrained eye but it's different. If you look at it in this drawing, they show one contactor as if it is 5 pole, but that doesn't exist, so it's done with two contactors that close together.

 

[chrisreisinger79]

You are correct, it is a two-speed single winding motor. But the contactors are currently wired as follows:



Is this accomplishing the same thing?

 

[Jraef]

You are correct, it is a two-speed single winding motor. But the contactors are currently wired as follows:

View attachment 18047

Is this accomplishing the same thing?

Yes. There are several different versions of 2S1W motor, Constant Torque, Constant HP, or Variable Torque, the windings are slightly different.