We had an existing installation with a failed VFD Drive. The failure was attributed to short cycling surges from the power company during intermittent outages. The surges damaged the main control printed circuit board and rendered the drive out of service except for the bypass mode.

Allen-Bradley Express F II

After an evaluation of the existing components and the control scheme used, we decided we had adequate room to retrofit a new drive in the existing enclosure. This became even more practical when we found out the original drive is obsolete and just the main circuit board had a replacement cost of $3,000.00 if you could find one. Unfortunately we would also have had to replace the main circuit board to determine if other failed components existed. The goal was to give the owner a new drive for a cost substantially less than the repair of the existing obsolete unit. Our goal was for an installed cost of under $3,000.00, the cost of just the replacement main PCB.

Below is the exposed failed circuit boards and power modules.

Having adequate room and clearances, we were able to use the existing contactor, power breaker, and other components for the new drive. In the below picture the new drive is mounted and being wired into the existing system.

New drive installed with an extension cable for mounting the keypad on the enclosure door.

New drive installed and operational. The goal was achieved and a new drive was retrofitted into an existing installation with substantial savings to the owner. The complete installation for this 10HP unit was under $3000.00. We made sure we installed an anti-short cycle time delay relay on the drive contactor so on/off cycles would not reach the drive except after a given time delay(1-8 minutes). These new drives default to an OFF state when there is a power interruption. Per the customers request and needs, we were able to modify the drive parameters so the drive would automatically come back on to the preset RPM(Hertz) and go right back to pumping once power was restored. No operator intervention necessary.