Abstract: A motor control for a reciprocating load includes overvoltage suppression. The motor control comprises a variable frequency drive (VFD) operatively connected to a power source for operating a motor to drive the reciprocating load. A sensor determines motor torque. A control unit is connected to the VFD and to the sensor and is adapted to control the VFD in a normal mode to operate the motor at a select reference frequency. The control unit predicts occurrence of a negative motor torque condition based on sensed motor torque and in response to a negative motor torque condition controls the VFD in a negative motor torque mode to operate the motor at a higher frequency than the select reference frequency to prevent the motor from entering a negative slip condition.

Abstract: A control for an induction motor operated by a variable frequency drive (VFD) includes a control unit adapted to control the VFD in a normal mode or a stopping mode. The normal mode comprises controlling the VFD at a select commanded operating frequency to control speed of the induction motor. The stopping mode comprises controlling the VFD at a substantially lower commanded operating frequency to operate the induction motor at a high negative slip condition to rapidly stop rotation of the induction motor.

Abstract: A noise attenuation circuit is disclosed for use in a motor drive system. The motor drive system includes a pulse width modulated inverter providing three phase power output on three phase conductors for driving a motor. The noise attenuation circuit includes a common mode transformer including a common mode choke having a core, with first, second and third choke windings on the core, each connected in series with one of the three phase conductors, and a fourth winding on the core. A three phase iron core transformer creates a neutral point representing common mode voltage. The iron core transformer has three primary windings connected in a wye configuration. A capacitor circuit is connected between the iron core transformer and the three phase conductors to prevent saturation of the iron core transformer during pulsed DC operating conditions. The fourth winding is connected between the neutral point and the DC bus and develops a common mode voltage that is equal and opposite to that existing in the system.

Abstract: A noise attenuation circuit is used in a motor drive system. The motor drive system includes a variable frequency drive having a pulse width modulated inverter converting DC power from a DC bus to three-phase power output on three-phase conductors for driving a motor. The noise attenuation circuit comprises a common-mode transformer including a common mode choke having a core, with first, second and third choke windings on the core, each connected in series with one of the three phase conductors, and a fourth winding on the core. A three-phase iron core transformer creates a neutral point representing common mode voltage. The iron core transformer has three primary windings connected in a "wye" configuration to the three phase conductors.

Abstract: An imaging system for a linear motor that provides information concerning movement of the same along a plurality of directions, with the information concerning motion along any one direction being substantially unaffected by motion of the motor in a differing direction. In this fashion, a plurality of detectors may be mounted onto the rotor of the linear motor to sense movement along a particular direction, with the detector being insensitive to motion of the motor along a differing direction. The system includes a substantially planar surface, such as a platen, having disposed thereon a pattern forming a two dimensional grid-like array.