Air gap measuring apparatus

An air gap measuring apparatus for measuring width of an air gap formed between a rotator rotatably supported about an axis and a stator fixedly set up at an outer periphery of the rotator in a rotating electrical machine, the apparatus comprising:

• an insertion section that has a first flat plate section, and a second flat plate section which is disposed parallel to the first flat plate section with a space and which is movable toward and away from the first flat plate section, the insertion section being configured to be inserted into the air gap;
• gap adjusting means that is disposed inside the insertion section, and drives the second flat plate section such that the second flat plate section moves away from the first flat plate section, until an outer surface of the first flat plate section and an outer surface of the second flat plate section abuts on the outer periphery of the rotator and an inner periphery of the stator;
• an operating section that is attached to the gap adjusting means, extends to outside of the insertion section, and operates the gap adjusting means;
• an elastic body that has an end that follows the first flat plate section, and other end that follows the second flat plate section, such that strain is formed due to movement of the second flat plate section away from the first flat plate section;
• a strain gage that is adhered on a surface of the elastic body, and outputs electrical signals corresponding to the strain of the elastic body, the strain being formed due to movement of the second flat plate section away from the first flat plate section;
• and
• calculating means that is connected to the strain gage, and calculates distance between the first flat plate section and the second flat plate section based on the electrical signals from the strain gage.