Servicing technique keeps DC motors and drives standardised

The company utilises a set of specialist tools, including a magnetising cabinet, as well as intellectual property built up over decades in the drives industry, in applying the new technique.

Often the settings on DC drives attached to motors that have been serviced or re-wound are incorrect because the magnets in the DC permanent-magnet motor have been allowed to degrade. The standard philosophy within the rewind industry is to remove the armature and replace it with a keeper to stop the magnets degrading. However, older magnets, and the material used to manufacture some newer magnets, will degrade while the armature is being removed and the keeper is being put in its place. The same applies when the armature is put back in after repair or servicing. The result is increased RPM and lost torque, which may mean the motor draws more current, costs more money to run, and creates a greater environmental impact.

Without the CPA process, an in-house engineer has to re-set the DC drive to cope with the changes to the motor. As a result, all the DC drive/motor systems in the plant eventually become unique and cease to be interchangeable. The only answer is to demagnetise the motor before repairing it and then remagnetise it to the correct level afterwards, as CP Automation does. The company derives the calculation for this from the speed and EMF (electro-motive force) settings on the name plate of the motor.

Tony Young, a director of CP Automation, comments: "Plant managers want to swap equipment around in the event of a breakdown or maintenance issue. However, they often find that the DC drives attached to permanent-magnet motors on different production lines have different settings - making it hard to interchange things easily. Our solution means that that the settings will be exactly as specified on the name plate, meaning they can be swapped around easily."