I bought the CNC retrofit package from Ajax Cnc. I'll be using my old servos and xmfr. The xmfr is a three phase device and the Fanuc system used three seperate servo amps with power supplied from the xmfr. The new servo amp has only one power input. So how can the three windings from the xmfr be combined into one? It seems to me that they need to be in phase but I don't know how to check and would like to avoid letting out any magic smoke. Thanks, ERS
If the servo amps want a DC input, and want a single one for the three axes, I would suggest that you combine the transformer windings using a three-phase bridge rectifier (six diodes), with one side of the three secondaries connected together as a common, and the other side of the three connected as three-phase input to the bridge. (You're connecting the windings in 'Y' (wye) in this way.) Another option would be to connect them in Delta, but you'll have to be sure not to reverse one of the windings, or you will draw too much current and burn something out.
They *can't* be in phase from a three phase transformer. The best you can do is shoot for either a Delta or a Wye connection, depending on which gives you a more reasonable rectified voltage for the servo amps. (The first trick is to find out what voltage is needed to power the servo amps, and then what voltage is available from each winding. It may be that you *can't* get the needed voltage from any reasonable wiring with that transformer.
There is a *lot* of magic smoke in a big three-phase transformer.
My servo amps happen to take single phase 115V in to each amp, and each amp contains a proper power supply (and all the heat sinks needed).
Good Luck, DoN.
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