1. Home
  2. Electronics Repair
  3. Dual-purpose 3-phase motor?

Dual-purpose 3-phase motor?

In my business I come across old German equipment with 3-phase induction motors that are connected in Y-configuration to start and within a few seconds switched to delta for running. This is done, I'm told, to lessen the inrush current at switch-on.

Typically the motors have 3 independently-wound windings with 6 connections, both ends of each winding are brought out to the terminal block.

I'd like to understand a little more about why this works. Is it as simple as the fact that between 2 supply phase connections in the Y configuration there are 2 windings and in delta there's only 1? (The Y configuration's common point is not connected to ground or neutral.)

Thanks,

--
Al, the usual
Reply to
Usual Suspect
Loading thread data ...

You have it, except that there is a phase angle between the windings, so they do not share the total voltage as if they were two independent inductors. Instead of the volts per turn dropping by half, it drops by a factor of 1/square root of 3.

formatting link

Reply to
John Popelish

Thanks, John. Much clearer now. Good reference.

--
Al, the usual
Reply to
Usual Suspect

ElectronDepot website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.