DC Drive Project A recent project involved replacement of 2 DC drives, a 30 HP and a 5 HP. These drives are used on motors powering the main table and right side head respectively of a large vertical boring mill. Projects such as these keep us in the loop on field applications, allowing us to continue to build on many years of experience with relevant and recent projects where what we teach is used in real applications. We feel that staying in the trade is essential for our continued relevance and ability to speak to field personnel regarding the issues they face every day. Classroom trainers that do not maintain their field service and troubleshooting work, as well as the training piece of the trade, often loose touch with life in the real world technicians, operators and mechanics must face every day.

Photos below show the new Drive, existing motor and panel.

Spedester Drive	30 HP DC Motor, probably from the 40's
Vertical Boring Mill Circa 1940's	Existing panel with new drives

Application Overview DC Drive project. A recent project involved replacement of 2 DC drives, a 30 HP and a 5 HP. These drives are used on motors powering the main table and right side head respectively of a large vertical boring mill. This is a challenging project, because of the sheer weight of the rotating table, as well as the age of all motors involved. The large 30 HP DC motor itself further complicates the process, as the customer wanted 12-14 table RPM out of the machine at full rotational speed. The 30 HP DC motor is a 400 rpm base, with 1500 rpm maximum overspeed. We used a fully digital configurable 4 quadrant electronic reversing and braking drive. The drive is a European made drive called Polyspede sold by Drives Warehouse in Dallas, TX. The price was very reasonable. The technical support offered by Drives Warehouse was excellent. We purchase drives from them frequently. For more information about the drives they sell, you may visit their website at: www.driveswarehouse.com. We tuned the drive to achieve about 12.5 to 13 rpm maximum table speed, smooth accel ramp without overcurrent trip and a smooth regen stop without overvoltage trips. The 5 hp drive was used power the motor on the right side head (not shown). We had previously specified, installed and started up the right head drive in 1988. It was an Allen Bradley DC analog drive that performed well for 20 years. The AB drive lost its field supply, with no parts still available to repair it. We were called upon again to specify, install and start up the drive for the right side head.