Electric motor
A noise suppression circuit uses a chip type ferrite bead as a major component of the noise suppression circuit. A motor using this circuit and the compact arrangement of the noise suppression circuit within the layout of an end cap of the motor is also disclosed. The preferred embodiment avoids soldering of the ferrite bead during assembly of the motor.
1. An electric motor comprising:
a permanent magnet stator;
a wound rotor including a shaft, a rotor core fixed to the shaft so as to confront the stator, a commutator, and a plurality of windings wound on the rotor core and terminated on the commutator;
motor terminals for connecting the motor to a source of electrical power;
brush gear including at least two brushes for electrically connecting the windings to the motor terminals; and
a noise suppression circuit for reducing the EMI emissions from the motor,
wherein the noise suppression circuit includes a ferrite bead component in series between one of the motor terminals and one of the brushes,
wherein the ferrite bead has two bead terminals, and said one of the motor terminals has a terminal contact portion which makes electrical contact with one of the bead terminals,
the terminal contact portion extends about an edge of the ferrite bead and faces an end and a surface of the ferrite bead.
2. An electric motor comprising:
a permanent magnet stator;
a wound rotor including a shaft, a rotor core fixed to the shaft so as to confront the stator, a commutator, and a plurality of windings wound on the rotor core and terminated on the commutator;
motor terminals for connecting the motor to a source of electrical power;
brush gear including at least two brushes for electrically connecting the windings to the motor terminals; and
a noise suppression circuit for reducing the EMI emissions from the motor,
wherein the noise suppression circuit includes a ferrite bead component in series between one of the motor terminals and one of the brushes,
wherein the ferrite bead has two bead terminals, and said one of the brushes is connected to the ferrite bead by a brush link, and the brush link has a link contact portion which makes electrical contact with one of the bead terminals, and
the link contact portion extends about an edge of the ferrite bead and faces an end and a surface of the ferrite bead.
3. The motor of claim 2 , wherein said one of the motor terminals has a terminal contact portion which makes electrical contact with the other of the bead terminals, and the terminal contact portion extends about another edge of the ferrite bead and faces another end and a surface of the ferrite bead.
4. An electric motor comprising:
a permanent magnet stator;
a wound rotor including a shaft, a rotor core fixed to the shaft so as to confront the stator, a commutator, and a plurality of windings wound on the rotor core and terminated on the commutator;
motor terminals for connecting the motor to a source of electrical power;
brush gear including at least two brushes for electrically connecting the windings to the motor terminals; and
a noise suppression circuit for reducing the EMI emissions from the motor,
wherein the noise suppression circuit includes a first ferrite bead component in series between a first motor terminal and a first brush, and a second ferrite bead component connected in series between the second motor terminal and the second brush, the first and second ferrite beads being chip type ferrite beads;
wherein the motor has an end cap which supports the motor terminals and the brush gear, and the ferrite beads are fitted to pockets formed in the end cap;
wherein the pocket has a resiliently deformable front wall which is resiently deformed by the ferrite bead and urges the ferrite bead towards a back wall of the pocket; and
wherein each front wall has a ridge at each side portion, the ridges bearing on the respective ferrite bead at end portions thereof.
5. The motor of claim 4 , wherein each ferrite bead has two bead terminals forming caps on each end of the chip, and each motor terminal has a terminal contact portion which makes electrical contact with a first one of the bead terminals.
6. The motor of claim 5 , wherein each of the brushes is connected to a respective one of the ferrite beads by a brush link, and each brush link has a link contact portion which makes electrical contact with a second one of the bead terminals.
7. An electric motor comprising:
a permanent magnet stator;
a wound rotor including a shaft, a rotor core fixed to the shaft so as to confront the stator, a commutator, and a plurality of windings wound on the rotor core and terminated on the commutator;
motor terminals for connecting the motor to a source of electrical power;
brush gear including at least two brushes for electrically connecting the windings to the motor terminals; and
a noise suppression circuit for reducing the EMI emissions from the motor,
wherein the noise suppression circuit includes a first ferrite bead component in series between a first motor terminal and a first brush, and a second ferrite bead component connected in series between the second motor terminal and the second brush, the first and second ferrite beads are chip type ferrite beads;
wherein the motor has an end cap which supports the motor terminals and the brush gear, and the ferrite beads are fitted to pockets formed in the end cap;
wherein each ferrite bead has two bead terminals forming caps on each end of the chip, and each motor terminal has a terminal contact portion which makes electrical contact with a first one of the bead terminals;
wherein each of the brushes is connected to a respective one of the ferrite beads by a brush link, and each brush link has a link contact portion which makes electrical contact with a second one of the bead terminals;
wherein in each pocket, at least one of the terminal contact portion and the link contact portion has a projection which projects above the ferrite bead to retain the ferrite bead within the pocket.
8. The motor of claim 7 , wherein each terminal contact portion and each link contact portion has a projection which projects above the respective ferrite bead to retain the ferrite bead within the respective pocket.
9. The motor of claim 8 , wherein in each pocket, one of the terminal contact portion and the link contact portion has a resiliently deformable finger bearing against an end of the ferrite bead and pressing the ferrite bead into contact with the other of the terminal contact portion and the link contact portion.
10. The motor of claim 7 , wherein the terminal contact portions extend about an edge of the ferrite bead and face an end and a surface of the respective ferrite bead.
11. The motor of claim 7 , wherein the link contact portions extend about an edge of the ferrite bead and face an end and a surface of the respective ferrite bead.
12. The motor of claim 7 , wherein the pocket has a resiliently deformable front wall which is resiently deformed by the ferrite bead and urges the ferrite bead towards a back wall of the pocket.
13. The motor of claim 7 , wherein the noise suppression circuit further includes a capacitor connected between the motor terminals.
14. The motor of claim 7 , wherein each ferrite bead is electrically connected between the motor terminal and brush by a releasable mechanical connection.