# Re-Wriring Old Machines with Two Motors with Two VFDs



## HMF (Nov 27, 2010)

JEP wired up a Reid automatic surface grinder with two VFD's - one for the spindle motor and one for the table motor. He removed the large old control box in the process.






Here is a before and after of the control box. On the left was the on-off switch. A cable came down from the table reversing switch and a power feed to the table motor went through the little round opening to the motor on the other side of the machine. JEP kept the cable from the reversing switch (after figuring which of the wires did the switching and then wired them to phone wire (in the little new box) which he then ran through the round opening to the table motor VFD on the other side of the machine, discarding the old power feed in the process.

He could have put the little new box over the round hole but he ran it to the front of the machine so he could put a start or stop switch there if he chooses later. You can see the outline of the old box.

He mounted the VFD's to the column of the grinder - in this pic they are clamped in place with G-clamps.






This view shows how he ran the various cables. The box under the table motor VFD has a switched socket for the sump motor and an unswitched socket for other uses. Note the phone wire running up to the VFD and the motor feed running from the VFD down to the motor.







"Inside the little new box"
The table reversing switch had 5 wires. With a tester he found which two wires tripped for forward and reverse to a third wire - the common. The other two wires (black and white taped off) are dead. You can see the three control wires simply spliced to three of the wires of a standard 4 wire phone cable. The fourth (black) unused wire he could wire for an emergency off (uses the same common wire).


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