FIELD OF THE INVENTION
The invention relates to an instrument carrier and a method for inspection of a dynamoelectric machine including a stator and a rotor, the rotor being disposed in an approximately circularly cylindrical manner relative to a main axis, being rotatable about the main axis and leaving a gap (being usually referred to as an "air gap" irrespective of a gas atmosphere present in the machine and of an installed cooling system) in a recess of the stator being approximately circularly cylindrical relative to the main axis, and appropriate means, that is to say optical, acoustic and/or mechanical instruments as well as lamps, grippers and the like, being inserted into the gap between the stator and the rotor in order to carry out the inspection.
Ensuring the trouble-free operation of a dynamoelectric machine, in particular a large dynamoelectric machine, for example a turbo-driven generator, and the timely detection of an incipient malfunction of such a machine, require regular inspections repeated at intervals of a few months to a few years, with it always being necessary to undertake manifold examinations and tests. A possible test in that regard is the visual inspection of the appropriately accessible surfaces of the components of the machine, in particular the surfaces of the stator and the rotor. Further possible tests include examination of the components by means of ultrasound in accordance with various methods, and tests of the magnetizability of the ferromagnetic components present in any dynamoelectric machine, for example tests of yokes composed of laminations stacked one upon the other in the stators. In order to perform such tests, it is possible, for example, to determine and evaluate the influence on the yoke of weak and locally limited magnetic fields. Mention must also be made of mechanical tests, in particular strength tests and crack detections. Not the least is the desire for possibilities of being able to recover relatively small parts from the machine, for example loosened screws and the like.
Conventional methods for the inspection of dynamoelectric machines each require removal of the rotor, which is extremely time consuming and expensive, particularly in large dynamoelectric machines having an electric power output and power consumption that are typically greater than 50 MVA. In order to be able to dispense with such expensive dismantling work, a device is known which permits an instrument platform to be drawn through the gap between the stator and the rotor in a large dynamoelectric machine and which runs along guide rails or guide cables that are led through the gap from one end of the large machine to the other. However, on the basis of the conventional dimensions of larger dynamoelectric machines, the instrument platform can neither be kept free from vibrations nor be positioned with special accuracy. Moreover, the instrument platform can tilt in the gap and jam, after which it would not be possible to recover it without considerable risk to the inspected machine and hardly without the extremely expensive removal of the rotor from the stator. The use of that device is therefore very problematical.
U.S. Pat. No. 4,255,762 discloses a device for inspecting tubes, in which a probe having an optical inspection system on a support arm is introduced into the tube to be inspected. Such a device can be used in dynamoelectric machines only by accepting disadvantages, because on the basis of the conventional dimensions of the gap to be inspected it is hardly possible for the necessary support arms to be used in a vibration free manner and avoiding collisions with the stators or rotors.
The inspection of a dynamo electric machine in a gap between a stator and a rotor emerges in addition to a corresponding device from U.S. Pat. No. 4,889,000. In that case, a sliding device resembling a rail and reaching into the gap is mounted on the rotor and can move around the rotor on chains. Seated on the rail is an instrument carrier which can travel through the gap and carries various means for carrying out inspections. In that device it is problematical that special grooves are necessary on the yoke for holding and guiding the instrument carrier, and for fixing the rail on the rotor.