This page describes my project to replace the motor-generator and DC drive motor in my 1947 Monarch 10ee lathe with a 5hp 3-phase motor and variable-frequency drive.
The MG set developed a bearing problem which caused rapid wear of the generator brushes. One of the brushes eventually bottomed in its holder. By the time I discovered the problem, a two-inch white and blue flame was issuing from the brush and the commutator lands were badly eroded.
I decided to replace the DC motor, MG set and original controls with a 5hp 3-phase motor and a VFD. I think this will suit my requirements, but I suggest that anyone considering a similar endeavor spend some time researching all the available options. A lot of helpful information can be found in the Monarch forum at Practical Machinist.
Now on to the pictures...