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An electric power steering drive system provided with a motor with its torque pulsation reduced, and a controller characterized by excellent manufacturability. The stator core of a motor is composed of an annular back core and a plurality of teeth created separately from the back core and secured on

An electric power steering drive system provided with a motor with its torque pulsation reduced, and a controller characterized by excellent manufacturability. The stator core of a motor is composed of an annular back core and a plurality of teeth created separately from the back core and secured on the inner periphery of the back core. An 8-pole/9-slot, 10-pole/9-slot or 10-pole/12-slot relationship is found between the number of the magnets of a rotor (number of poles) and the number of slots. The diameter of the stator coil is 1.0 mm or more. A motor controller comprises a power module, a conductor module and a control module. The terminal of the power module and the bus bar of the conductor module are connected by welding, whereas the terminal of the power module and terminal of the control module are connected by soldering.

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What is claimed is: 1. An electric power steering system comprising: a motor for electric power steering; and a controller generating alternating current for driving said motor; said motor for electric power steering comprising: a stator equipped with a stator coil; and a rotor supported rotatably

What is claimed is: 1. An electric power steering system comprising: a motor for electric power steering; and a controller generating alternating current for driving said motor; said motor for electric power steering comprising: a stator equipped with a stator coil; and a rotor supported rotatably inside said stator; said stator being equipped with a stator coil wherein the stator core is split, and the stator core is integrally constructed thereafter; said rotor comprising: a rotor core; and a plurality of magnets secured on the surface of said rotor core; wherein said magnets whose stator side is curved and whose polarity reverses alternately in the circumferential direction are magnetized in the axial direction; said motor for electric power steering further comprising: a connection board on the side of the stator for supplying alternating current to the stator coil; said controller incorporating: a power module equipped with a semiconductor switching device; a conductor module; and a control module; inside the case; said control module supplying said power module with the control signal for generating the control signal for controlling said semiconductor switching device and driving the motor for electric power steering; said power module containing a semiconductor switching device, and generating 3-phase alternating current for driving said motor in conformity to said control signal; said conductor module comprising: a bottom formed of resin; a plate-formed conductor provided on said bottom; a relay; and a capacitor; wherein said plate-formed conductor forms a circuit for sending 3-phase alternating current to be supplied to the motor for electric power steering; wherein said conductor module is secured onto one side of the case interior in such a way that the bottom thereof will be located at the upper position; said power module is arranged on the other side of the case interior; and said power module and plate-formed conductor of the conductor module are electrically connected; wherein a chamber is formed between the bottom of the case and the bottom of the conductor module arranged in such a way that the bottom thereof will be located at the upper position; and said relay and capacitor are arranged in the chamber; wherein a hole is provided on the bottom of said conductor module arranged in such a way that the bottom thereof will be located at the upper position; said relay and capacitor terminals protrude from the hole; and said protruding terminals and plate-formed conductor are connected by welding; and wherein the alternating current generated by the power module is supplied to the stator coil through the connection board for the motor for electric power steering. 2. The electric power steering system described in claim 1 wherein welded connection between said power module and conductor module is accomplished by connecting a plurality of wires by wire bonding. 3. A controller for electric power steering wherein a power module containing a semiconductor switching device, a conductor module and a control module are arranged in a case; wherein said control module controls the semiconductor switching device of the power module and supplies said power module with the control signal for generating the 3-phase alternating current to drive the motor for electric power steering; wherein said power module contains a semiconductor switching device, and generates 3-phase alternating current for driving said motor in conformity to said control signal; said conductor module comprising: a bottom formed of resin; a plate-formed conductor provided on said bottom; a filter; and a capacitor; wherein said plate-formed conductor forms a circuit for sending 3-phase alternating current to be supplied to the motor for electric power steering; wherein said conductor module is secured onto one side of the case interior in such a way that the bottom thereof will be located at the upper position, said power module is arranged on the other side of the case interior, and said power module and plate-formed conductor of the conductor module are electrically connected; wherein a chamber is formed between the bottom of the case and the bottom of the conductor module arranged in such a way that the bottom thereof will be located at the upper position, and said filter and capacitor are arranged in the chamber; wherein a hole is provided on the bottom of said conductor module arranged in such a way that the bottom thereof will be located at the upper position, said filter and capacitor terminals protrude from the hole, and said protruding terminals and plate-formed conductor are connected by welding; and wherein said control module is mounted on said power module, and said power module and control module are connected by soldering. 4. A controller for electric power steering wherein a power module containing a semiconductor switching device, a conductor module and a control module are arranged in a case; wherein said control module controls the semiconductor switching device of the power module and supplies said power module with the control signal for generating the 3-phase alternating current to drive the motor for electric power steering; wherein said power module contains a semiconductor switching device, and generates 3-phase alternating current for driving said motor in conformity to said control signal; wherein said conductor module contains a longitudinal structural member formed of resin, a bottom, a plate-formed conductor arranged on said bottom, a relay and a capacitor; and the plate-formed conductor constitutes an electric circuit for sending 3-phase alternating current to be supplied to the motor for electric power steering; wherein said conductor module is secured onto one side of the case interior in such a way that the bottom thereof will be located at the upper position, a chamber is formed between the bottom of the case and the bottom of the conductor module arranged in such a way that the bottom thereof will be located at the upper position, and said relay and capacitor are arranged in the chamber; wherein a hole is provided on the bottom of said conductor module arranged in such a way that the bottom thereof will be located at the upper position, said filter and capacitor terminals protrude upwardly from the hole, part of the plate-formed conductor is bent upward, and the upward bent part of the plate-formed conductor, and the protruding terminals of said filter and said capacitor are electrically connected; wherein said power module is arranged in the chamber arranged between the conductor module of the case interior and the other side of the case interior; wherein said power module and the plate-formed conductor of the conductor module are electrically connected through wire bonding; wherein said control module is mounted on said power module, and said power module and control module are connected by soldering; and wherein a connector for supplying the motor for electric power steering with 3-phase alternating current is arranged on the side of said case on the conductor module side.