Drives and Controls Magazine
8.5mm-tall robot crawls through airgaps in motors
Published:  30 November, 2015

ABB has developed a remotely controlled device that crawls in the air-gap between the stator and rotor of large motors or generators to inspect their status, thus cutting downtime, inspection costs and the need to remove the rotor. The 8.5mm-high InSight inspection crawler is fitted with five cameras that provide high-resolution coverage of the whole length of the stator core. The results are recorded for later assessment.

Unlike conventional inspection devices which are restricted to generators with large air gaps, the new device can be used on any large motor or generator with an air-gap of 10mm or more. ABB claims that the device can inspect a machine in just three days, compared to the eight days that would typically be needed if the rotor has to be removed.

The crawler provides a video feed of the stator and rotor core, windings, wedges, stator teeth, air ducts, rotor support blocks and parts of the end-windings. It can be used to spot problems such as broken laminations, burned cores, blocked vent ducts, spark erosion and bulging, or signs of movement at slot exit or in vent ducts.

The crawler is tethered to a control cabinet containing five monitors, and carries on-board LEDs to illuminate the air-gap. It moves on a magnetic roller mechanism and is guided by an operator using a joystick and speed controller, which can also be used to adjust four of the five cameras.

The robot crawler (shown at the bottom of image) is controlled and monitored remotely via five screens

A modular track system can be configured to allow visual inspections of a variety of motors and generators in a fraction of the time of conventional methods. As well as videos, the device captures still images and has a voice-over function that records the inspector’s comments for later reference.

The crawler extends ABB’s Leap service, which assesses the condition of stator winding insulation and estimates its remaining lifetime. During scheduled minor maintenance (when the end covers, but not the rotor, are removed) the crawler can gather data on the stator which can be used to plan future maintenance.