Shunt contactor

[Arkansas74]

Hello
we have machines that have single motors that have 2 sets of windings 12.5 amp and 25 amp one is low speed extraction other is high speed extraction they have 3 contactors one they are calling a shunt contractor. How does this shut contractor work and what is the purpose? The 1mc3 is the one they are calling a shunt contractor

 

[augie47]

In one speed, 3 of the leads are tied together, or shunted, with power on the other 3 leads through 1 contactor.
when the speed changes, the shunt contactor opens, the 2nd contactor closes and power is put on all 6 leads.

 

[gar]

180428-2150 EDT

Show the logic for controlling the relays.

Unless a special kind of motor I would not think you would want to short windings when the motor was being powered.

More likely the shorted windings are for dynamic breaking with no power applied.

.

 

[Ingenieur]

looks like a wye delta transition starter
not 2 speed per se, but acts as one under load
starts in y with v across 2 coils, reduced torque
transitions to delta full v across each coil
the shunt is the wye config
main closes with wye/shunt
when commanded wye opens and delta closes, usually mech interlocked

https://library.e.abb.com/public/94476d849ecd4352c1257a6b004c1108/ABB SD (1TVS013113P0300) Rev1.pdf

 

[Ingenieur]

showing the 6 leads/3 ph coils makes it clearer
unlike my dwg lol

 

[MTW]

The motor you have is called a Dahlander in Europe or a Consequent pole motor in the USA. They are not very common on US machines any longer, more prevalent on European designed equipment. The nameplate would tell what type you have for sure as there are a few types. But yours is likely a constant HP type, as the amperage is double at the high speed. Most units the speed ratio is 2 to 1.

The windings in the motor are reconnected with the starter contactors to switch from typically a two pole machine to a four pole machine. Halving the number of poles, doubles the speed. When connected as a four pole the synchronous speed is 1800RPM, when connected as a two pole the synchronous speed is 3600RPM. VFD's have replaced the need for them in most applications today, but they still retain the advantage of less power loss than a VFD. Smaller units can also be switched with a drum switch on machine tools or food equipment. The motor can be a six lead type or a twelve lead type. But they are always a single voltage motor, and cannot be changed without rewinding.

Here are some reference links to read more about them.

https://en.wikipedia.org/wiki/Dahlander_pole_changing_motor

http://machineryequipmentonline.com...ole-motorsthree-speed-consequent-pole-motors/

https://stevenengineering.com/pdf/45NEMAMC_8810.pdf

 

[MTW]

A couple motor connection drawings, one US style, one IEC style.

 

[augie47]

It will blow your mimnd first time you encounter one. "Wow! The factory will screwed this up.. that contactor has a dead short"