This DC shunt motor has been returned for a scheduled overhaul and remedial works to fit thermal protection. The motor is 15 years old and has been held as a spare for the in-service DC motor which is still in operation after 25 years. The application justifies holding a spare motor due to the very high cost of lost production.
The motor drives a gearbox within a complex hoisting mechanism. A crane may have several different motors for hoist, gantry, trolley and boom. The characteristics of the DC shunt motor is particularly suited to the high starting torque and speed range needed for these applications.
As part of the equipment upgrade, a new modern DC drive is being installed which will have the facility to connect to the motor’s new thermal devices.
These were retrofitted onto the shunt and interpole coils with the leads terminated in the connection box.
After testing with the new drive, the motor will be put into full service as a replacement to the older unit which is currently operating.