Method and apparatus for quantitatively evaluating the stator wedge tightness of an electric alternator

摘要

Disclosed is a method for quantitatively evaluating the tightness of the stator wedges of an alternator, which can be reduced to practice without having to remove or dismantle the rotor of the alternator even when the air-gap of the alternator is as small as 10 mm, and which permits to obtain a quantitative evaluation of the compression percentage of the ripple spring holding the wedges in a simple, efficient and reliable manner. This method makes use of a thin flat sensor having one face provided with a recess in which a piston is mounted. This sensor is inserted into the air-gap of the alternator and positioned in front of the stator wedge to be evaluated so that the piston faces this wedge. Thus, a fluid is injected into the sensor to bring the piston to contact and then press against the wedge while the sensor is backed against the rotor. The pressure of the injected fluid which is proportional to the force applied to the ripple spring, is measured together with the displacement of the stator wedge while the pressure is exerted and the so-measured force and displacement are used to determine the tightness of the wedge. The above mentioned measurement of the displacement of the wedge is achieved by measuring the displacement of the piston in its cylinder by means of strain gauge fixed onto resilient blades bearing against the piston. An apparatus for carrying out this method is also disclosed.