Motor assembly for driving a pump or rotary device with a low inductance resistor for a matrix converter

Abstract

A resistor assembly for a motor drive circuit for an electric motor assembly can have a generally circular shape. The resistor assembly includes a resistor with input and output connectors and a pair of conductor elements extending from the input and output connectors. The pair of conductor elements extend adjacent each other along a curved serpentine path so the resistor has a generally circular outer perimeter and a generally circular inner perimeter. The curved serpentine path of the pair of conductor elements allows current to flow through the pair of conductor elements so that magnetic fields generated by the current flow through the pair of conductor elements cancel each other, thereby providing the resistor with low inductance.

What is claimed is: 
     
         1 . An electric motor assembly for driving a rotary machine, the motor assembly comprising:
 an electric motor having an output shaft that extends along a central axis of the electric motor, the electric motor being operable to rotate the output shaft;   a motor frame that houses the electric motor so that the output shaft protrudes from an end of the motor frame;   a first plate having a cavity configured to house motor drive electronics; and   a resistor assembly within the cavity, the resistor assembly comprising:
 a case defining a recess; and 
 a resistor within the case, the resistor comprising an input, an output, and a conductor extending from the input to the output and forming a plurality of nested arcuate paths arranged such that current flows in opposite directions through adjacent segments of the plurality of nested arcuate paths, wherein magnetic fields generated by the current flow cancel each other. 
   
     
     
         2 . The assembly of  claim 1 , wherein an outer wall of the case has a generally circular shape. 
     
     
         3 . The assembly of  claim 2 , wherein the case is removably coupleable to the first plate and further comprises a cutout defined by a pair of walls extending from the outer wall to an end wall proximate a curved inner wall of the case, the input and output configured to extend into the cutout when the resistor is housed in the case. 
     
     
         4 . The assembly of  claim 1 , wherein the resistor forms a generally planar shape. 
     
     
         5 . The assembly of  claim 4 , wherein the conductor of the resistor forms a curved serpentine path. 
     
     
         6 . The assembly of  claim 1 , further comprising a dielectric material disposed over the resistor so that at least a portion of the resistor is disposed between the dielectric material and a base wall of the case, the dielectric material defining a generally planar front surface of the resistor assembly. 
     
     
         7 . The assembly of  claim 1 , further comprising a second plate having an opening configured to receive the output shaft therethrough, the second plate being coupleable about the output shaft proximate to the end of the motor frame between the first plate and the end of the motor frame. 
     
     
         8 . A plate assembly configured for use with an electric motor assembly, the plate assembly comprising:
 a first plate having a cavity that houses motor drive electronics; and   a resistor within the cavity, the resistor comprising an input, an output, and a conductor extending from the input to the output and forming a plurality of nested arcuate paths arranged such that current flows in opposite directions through adjacent segments of the plurality of nested arcuate paths and magnetic fields generated by the current flow cancel each other.   
     
     
         9 . The plate assembly of  claim 8 , further comprising a case detachable from the plate assembly, the case defining a recess configured to receive at least a portion of the resistor therein. 
     
     
         10 . The plate assembly of  claim 8 , wherein the resistor is generally planar. 
     
     
         11 . The plate assembly of  claim 8 , wherein the conductor forms a curved serpentine path. 
     
     
         12 . The plate assembly of  claim 8 , further comprising a dielectric material disposed over the resistor. 
     
     
         13 . The plate assembly of  claim 8  further comprising a second plate having an opening configured to receive a motor output shaft therethrough, the second plate being coupleable about the output shaft proximate to an end of a motor frame between the first plate and the end of the motor frame. 
     
     
         14 . A resistor for a motor drive circuit of an electric motor assembly, the resistor comprising:
 an input;   an output; and   a conductor extending from the input to the output and forming a plurality of nested arcuate paths arranged such that current flows in opposite directions through adjacent segments of the plurality of nested arcuate paths and magnetic fields generated by the current flow cancel each other.   
     
     
         15 . The resistor of  claim 14 , wherein the conductor is formed in a curved serpentine path. 
     
     
         16 . The resistor of  claim 14 , wherein the conductor forms a generally planar shape. 
     
     
         17 . The resistor of  claim 14 , further comprising a case having a generally annular shape with a curved outer wall, a curved inner wall that defines a central opening of the case, and a base wall, a recess defined by and between the curved inner wall, the curved outer wall and the base wall, wherein the conductor is configured to be disposed in the recess between the curved inner wall and curved outer wall of the case. 
     
     
         18 . The resistor of  claim 17 , wherein the case further comprises a cutout defined by a pair of walls extending from the curved outer wall to an end wall proximate the curved inner wall, the input and output configured to extend into the cutout when the conductor is housed in the recess. 
     
     
         19 . The resistor of  claim 17 , further comprising a dielectric material disposed over the conductor so that at least a portion of the conductor is disposed between the dielectric material and the base wall of the case. 
     
     
         20 . The resistor of  claim 19 , wherein the dielectric material is a ceramic material.