Eaton Corporation

Michael R Scharnick

Jerome Kenneth Hastings

James E Hansen

Thomas A Wilsdon

Gary Mayer

Gunars Briedis

A switching filter is disclosed for discriminating false control signals from actual control signals. The switching filter is particularly useful on a high impedance input, such as that of a motor controller. The filter is designed to compensate for capacitive, inductive, and/or resistive coupling between extended control lines that are run in parallel with other power lines. A low impedance is switched into the otherwise high impedance control line input for a brief instant to dissipate and phase shift false control signals to prevent the controller from interpreting the false signals as actual control signals. The filter includes a first resistor connectable to sense a presence of a possible false control signal, and a second resistor, having much lower resistance than the first resistor, connected in a path between the control line input and circuit common. A switch is provided in series with the second resistor to open and close the path between the control line input and circuit common in response to the possible false control signal. A timer is activated by a presence of a possible false control signal on the first resistor and activates the switch to provide a low shunting resistance across the control line to common for the brief period. The low shunting resistance not only dissipates the amplitude of any false signals, but also phase shifts the signals such that the controller cannot recognize multiple, successive false signals as a true control signal.

Switching filter producing a low impedance control input on a high

A contactor has an armature, a pull-in coil and a holding coil. When the system is energized through a first switch such as a thermostat, the low current holding coil is energized in preparation for holding the armature pulled in after the pull-in coil is energized and the armature has finished its power stroke. A solid-state switching device and the pull-in coil are connected in series between both terminals of a power source. A control circuit causes the solid-state switching device to be conductive the instant power is supplied to the circuit through the first switch. One embodiment of the control circuit is based on logic gates. RC circuits associated with the gates keep the solid-state switching device and pull-in coil conducting long enough for the armature to pull-in. After the solid-state switching device turns on, the transistor is controlled to turn off, deenergizing the pull-in coil while the holding coil holds the armature in until the first switch opens and power input is discontinued. Another embodiment, based on a programmable timer, delivers current pulses to the pull-in coil at uniform periodicity until the armature is pulled in. After the armature is pulled in, pulse signals are shunted from the solid-state switching device so it turns off, and current pulses through the pull-in coil are discontinued, while the holding coil holds the armature in pulled-in condition until the first switch is opened.

Electronic control for 3-wire DC coils

An overload control circuit and method of operation for protecting a three-phase motor from damage due to overload includes monitors reading the load on each phase of the motor and circuitry for combining the three separate phase signals into a single combined load signal which triggers the overload circuit. The gain on the combined load signal and the overload trip delay time may be calibrated and monitored by an external meter to provide for accurate and inexpensive calibration to accommodate specific operating characteristics of the motor being monitored. The circuit provides visual readouts of the mode of operation, including: (1) operating mode; (2) overload onset; (3) shut down initiated; and (4) delay to restart.

Growing community of inventors

Brookfield, WI, United States of America

Michael R Scharnick