Abstract: Gradual starting of an electric motor is provided by increasing the voltage applied to the motor. A reduced voltage starter controls the application of a voltage derived from a line voltage to a motor by using a voltage ramp acceleration control circuit comprising, means for generating a ramp voltage having a predetermined rate of rise, means for controlling the voltage applied to the motor in response to the ramp voltage, means for sensing that the motor is running at substantially full speed, and means responsive to the means for sensing that the motor is running at substantially full speed for increasing the predetermined rate of rise of the ramp voltage, whereby under conditions where the motor is running at substantially full speed before the voltage applied to the motor reaches the line voltage, then the voltage applied to the motor will rise at the increased predetermined rate of rise of the ramp voltage.

Abstract: This disclosure depicts a novel abort cycle timer circuit for use with an AC source of electrical power and for operating electrical controls for machinery. The circuit provides a substantially DC voltage and current, first and second relays with normally open and normally closed contacts and a timing abort circuit. Opening a first of two switches causes the second of the two relays to energize after a time delay. Opening both switches causes the second relay to deenergize after a predetermined time. The novel circuit has improved immunity to electrical and magnetic noise.

Abstract: A solid state overload relay protective apparatus for electric motors which includes not only the overload feature, but the additional features of underload and single phase protection. Small current transformers for sensing the current flow in each phase of the motor are utilized, like those found in the ground fault sensing art because a current-to-voltage converter circuit reflects a short circuit back to the secondary of the transformers. The signal from the current transformers which is proportional to the sensed current in the motor is fed through the converter, a scaling and summing amplifier adjustable for a wide range of motor full load currents, an ideal diode peak detector, a time integrator amplifier, to one input of a comparator circuit having a trip reference voltage signal at another input. The comparator provides an output signal to a transistorized trip level circuit that deenergizes a coil of an overload relay opening its contacts and interrupting power to the motor.

Abstract: An anti-telegraph circuit for locking out the circuit controlling the flow of direct current in a coil winding of an electromagnetically operated switching device, such as a contactor, from an alternating current source whenever improper control voltages are present which would cause repeated operations of the armature picking up and falling out of its sealed position.

Abstract: A self-powered solid state overload relay circuit having current transformers energized by conductors supplying current to a multiphase alternating current motor. The transformers have secondary windings connected to charge a capacitor with a voltage indicative of the magnitude of the maximum current in the motor windings. The circuit includes presetable impedance circuits which permit the circuit to be easily programmed to respond to a range of abnormal motor currents in the winding in motors of varying size and service factor ratings, components which are arranged to duplicate the operation of melting alloy and bimetal type overload relays in an automatic or in a trip-free manual reset mode, a light emitting device which visually indicates when the relay is in a tripped state, and components which cause the relay to be insensitive to ambient temperature variations.