Apparatus and method of rotational alignment of permanent magnet tandem motors for electrical submersible pump

1. A method of connecting in tandem first and second motors of an electrical submersible well pump assembly, each of the first and second motors having a housing, the first and second motors having first and second shafts, respectively, each of the first and second motors having a plurality of rotor sections, each of the rotor sections having a plurality of circumferentially spaced permanent magnets, defining magnetic poles, the second shaft has a splined end with external splines for meshing engagement with internal splines of a coupling connected with the first shaft for rotation in unison, the method comprising:

rotationally aligning the magnetic poles of the first shaft with the magnetic poles of the second shaft; by:

providing a coupling keyway in the coupling that is in a controlled orientation relative to the magnetic poles of the first shaft;

providing a second shaft splined end keyway between the external splines that is in a controlled orientation relative to the magnetic poles of the second shaft;

placing a coupling key in one of the keyways;

manually rotating the second shaft until the coupling keyway is aligned with the second shaft splined end keyway; and

moving the first and second motor toward each other, causing the internal and external splines to fully engage each other and the coupling key to be within both of the keyways; and

securing the housings of the first and second motors together.

2. The method according to claim 1 , wherein the coupling keyway prevents full meshing engagement of the first and second shafts with the internal splines unless the keyways of the first and second shaft and the coupling are aligned with each other.

3. A method of connecting in tandem first and second motors of an electrical submersible well pump assembly, the first motor having a housing, a first shaft, and a plurality of rotor sections with a plurality of circumferentially spaced permanent magnets that define magnetic poles, the second motor having a housing, a second shaft having a splined end with external splines for meshing engagement with internal splines of a coupling connected with the first shaft for rotation in unison and rotationally aligning the magnetic poles, and a plurality of rotor sections with a plurality of circumferentially spaced permanent magnets that define magnetic poles, the method comprising:

providing a protuberance on an exterior of the second shaft adjacent the splined end of the second shaft, the protuberance being in a controlled orientation relative to the magnetic poles of the second shaft;

providing an orientation slot on an end of the coupling, the orientation slot having two edges facing each other and curving from a circumferentially wider dimension at an entrance to a guide slot portion that is in a controlled orientation relative to the rotor keyway of the first shaft;

moving the first and second motors toward each other, causing the protuberance to contact the edges of the orientation slot and rotate the second shaft as the protuberance slides along the orientation slot into the guide slot portion; then

meshing the external splines with the internal splines; then

connecting the housings together.

4. The method of claim 3 , wherein the two edges are parallel within the guide slot portion.

5. The method of claim 3 , wherein the guide slot portion comprises a first guide slot portion, the alignment means comprising a second guide slot portion that is disposed 180 degrees from the first guide slot portion.

6. The method of claim 3 , wherein the internal splines in the coupling are located axially between the guide slot portion and the first shaft, so that the external splines engage the internal splines only after the protuberance enters the guide slot portion.