Improved Motor Inspection Without Removing Rotor

Phil Black - PII Editor 01/12/2015

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Robot gives visual inspection of the stator and rotor core and winding through the air gap without a rotor thread out

A miniature robot fitted with five cameras is being used to crawl in the air gap between the stator and rotor of large motors or generators to visually inspect their status, thereby reducing downtime, inspection costs and the need to withdraw the rotor.

Called the ABB InSight, the 8.5 mm high robotic inspection crawler is tethered to a control cabinet that features two large and three small monitors. A joystick and speed controller is used to navigate the crawler – which uses a magnetic roller mechanism – around the air gap and to adjust four of the five cameras. On board LEDs illuminate the journey, while a microprocessor, accelerometers, RS485 communication and video multiplexing provides a video feed of the stator and rotor core, winding, wedges, stator teeth, air ducts, rotor support blocks and parts of the end windings.

A modular track can be reconfigured to provide in-situ visual inspections for a wide variety of motors and generators in a fraction of the time of conventional methods. Unlike conventional inspection devices, which are restricted to turbo/hydro generators with very large air gaps, ABB InSight can be used on all large motors and generators which have an air gap of 10 mm or more.

Typical savings using ABB InSight are shown in the table below.

Inspection activity	With rotor threaded out	With ABB InSight	Savings
Total outage (days)	8	3	5

The crawler is an extension of the ABB LEAP service which helps to assess the condition of the stator winding’s insulation and estimates its remaining lifetime. Furthermore, ABB InSight is an extension of ABB’s maintenance plan. During scheduled minor maintenance (when only the end covers are removed but rotor is not pulled) ABB InSight helps provide more in-depth information on the stator. This data can be utilised to plan future maintenance activities and support decision making on the time and scope of major maintenance, when the rotor is removed.

ABB InSight provides 100 percent uniform, high-resolution coverage of the entire length of the stator core, with coverage recorded for later, in-depth assessment and expert evaluation when required. The device captures still images and has a voice-over feature that records the inspector’s comments for later use.

This provides a faster, more accurate way to inspect the machines in depth by taking a closer look at broken laminations, core burns, blocked vent ducts, effects of spark erosion and bulging or signs of movement at slot exit or in vent ducts.