Abstract: The motor controller of the present invention includes a power bus, an insulated gate bipolar power transistor and a control circuit. The direct current power bus provided a source and sink of current to be conducted to and from a controller motor. The insulated gate bipolar power transistor selectively conducts transistor current to and from the motor. The control circuit among other things determines power gate timing of the power transistor and the manner in which the insulated gate bipolar transistor conducts and ceases to conduct transistor current to or from the motor.

Abstract: A transient protection circuit for an inverter has a rectifier capable of supplying direct current from an alternating current power source, where protection is provided against a voltage transient in the AC power source. A DC bus is fed by the rectifier. A bus capacitor is connected across the DC bus. Solid state switches are connected to the DC bus for supplying alternating current to a load. The DC bus voltage is sensed. In response to a transient rise in the DC bus voltage, a resistor is connected across the bus capacitor to provide a discharge path, the solid state switches are disconnected from the DC bus, and after the transient dies away from the DC bus, the solid state switches are reconnected to the bus and the discharge resistor is disconnected from across the bus capacitor.

Abstract: The invention is a current regulator having a source of electric current, a switch connected in series with the source of electric current, and a load receiving current through the switch from the source of current. Means are provided for sensing the current through the load, and means responsive to the current through the load turn the switch on and off so that the average current through the load has a predetermined value. A filter smooths out the variations in the current. An inductor and a diode serve as the filter. A gate turn on thyristor (GTO) control electrode serves as the load and the current regulator maintains the control current needed to sustain conduction of the GTO. The current regulator is incorporated in an inverter using GTO devices to generate AC drive current for a motor.

Abstract: An inverter for supplying electric alternating current (AC) to a load from a DC source of electric current has a DC bus. The DC bus has a positive conductor and a negative conductor. A plurality of switches are connected to the DC bus, and each of the switches has a conducting state and a nonconducting state. The switches are connected so that electric current may flow from the DC bus through at least one of the switches into the load. Means are provided for switching each of the switches from the nonconducting state into the conducting state at a predetermined time for each of the switches. Means are provided for switchably connecting the DC bus to the DC source of electric current. Means are provided for switchably shorting the positive conductor of the DC bus to the negative conductor of the DC bus in order to interrupt the current flow through the switches and thereby drive the switches into the nonconducting state.

Abstract: A pulse generating system for providing firing pulses to selectively trigger solid state control devices connected to a three-phase A.C. line system, and more specifically to trigger said devices in selected relation with respect to the phase and frequency of the A.C. line.

Abstract: An adjustable speed pumping system includes a plurality of pumps respectively driven by variable speed A.C. motors each having a power recovery circuit. Each power recovery circuit includes a series connected rectifier bridge, an inductive reactor and an inverter coupled to the secondary winding of the motor which has an A.C. source connected to the primary winding. A fault clearing mechanism is included in each circuit and includes solid state switches in the bridge actuated by a current level sensor coupled to the inverter output. The power recovery circuit also includes current foldback circuitry and secondary gating circuitry coupled to thyristors in the inverter. The power recovery circuits can be connected in parallel with a single motor and the system includes circuitry for sensing the highest amplitude current in the parallel circuits and controlling all circuits with this current.

Abstract: A pre-step timer circuit for pre-advancing the next timer period (control step) in a DC motor controller, such as in a crane-hoist controller. A sensing resistor module is connected from the line side of a contactor coil of a preceding control step to the input of a timer module in series with the accelerating contactor coil in the next control step. This resistor module sensing the previous coil voltage provides a feed-forward path for the sensed voltage signal to pre-time the next timer module. So, if a master switch is left in the previous control step long enough for the next timer module to time out, then the next control step is actuated immediately when the master switch is advanced thereto.

Abstract: A control system for a multiple speed motor includes a motor circuit having a plurality of resistance varying units in series with the field winding and armature of the motor and separate control circuits for each of the resistance varying units. Each control circuit includes an energizable contactor in series with a gating element and a timer for activating the gating element. The control system includes an activating circuit for bypassing the timer when the level of current flow in the motor circuit is below a certain value. The activating circuit includes a comparator for receiving a reference signal and a signal indicating the level of current flow in the motor circuit and produces an output signal when the current flow is below a certain value which is fed to an OR-gate that also receives a signal from the timer to activate the gating element when either signal is present.