Abstract: There is disclosed a two-wire (series connectable) delay-on-release timer apparatus for air conditioner compressor motors or the like which is connectable in series in one side of the alternating current circuit with a low voltage alternating current source, a thermostat switch with a shunt resistor acting as an anticipator heater and a relay, or other control, for applying power from the power main to an air conditioner compressor or the like. The timer includes a full-wave rectifier circuit with output connected to an adjustable time delay digital timer and also connected to a gated thyristor whereby turning the thyristor on greatly reduces electrical impedance between the input terminals of the rectifier circuit. A digital timer IC is provided with circuit elements for sensing the difference between thermostat switch closed and thermostat switch open conditions.

Abstract: There is disclosed a monitoring apparatus for a multiphase electrical system of very simple and reliable circuit design capable of monitoring such a system and producing fault signals to operate protective relays and for visual indication. A main component of the apparatus is a multiphase, full-wave bridge rectifier circuit having matched voltage dropping input resistors so that the output of the bridge is a low voltage fluctuating DC signal such that neither the semiconductor diode rectifiers of the full-wave bridge or other internal components of the monitoring apparatus are exposed to high power line voltages. Phase unbalance in the apparatus is detected by evaluating the ratio of the peak to trough voltage of the fluctuating DC signal produced by the full-wave bridge.

Abstract: There is disclosed a twist drill particularly adapted for drilling plastics and composite materials having a sharp point angle, typically 85.degree. to 95.degree., and a very low lip relief angle, typically 2.degree. to 3.degree.; the relief surfaces are broad, though not unusually so, and may each subtend an angle of 40.degree. to 60.degree. about the drill longitudinal axis. A two-flute drill is shown, but the structure may be modified to provide three or more flutes. Land width, helix angle, and other attributes of the twist drill are generally similar to most common varieties of twist drills for steel, wood, or other uses in drill presses or hand drills.

Abstract: There is disclosed a polyphase power line adapter for providing polyphase electric power to operate a motor at a speed less than rated speed particularly useful for pump motors and the like where it is undesirable to stop the motor. A bridge of from nine to eighteen thyristors, which is also conventially used in cycloconverters, connects the input terminals to the output terminals. A delta-to-Y transformer arrangement and a wave shaping circuit produces cyclic pulse control signals synchronized with the wave-forms of the respective phases of the polyphase power line input; one such signal is transmitted to a divider circuit with a maximum division factor (always an integer) corresponding to the factor, N, by which the frequency, and hence, motor speed is to be reduced. A plurality of logical "and" circuits each has its inputs connected to receive one output from the divider circuit and cyclic pulse control signals are supplied to another of the inputs.

Abstract: There is disclosed a frequency monitor circuit, for monitoring AC power frequency for example, in which a gate is provided for a stable oscillator and frequency divider circuit which is responsive to the frequency divided monitored signal and a flip-flop circuit to produce a fixed reference period signal equal to a predetermined number of cycles of the oscillator commencing at the beginning of a full cycle of the monitored signal; a two-stage timer which determines the tolerance for the monitored signal frequency and is adjustable is provided with signals from the monitored signal divider circuit and the fixed reference period circuit and arranged so that the end of the reference period or the end of the divided monitored signal cycle, whichever occurs first, will start the timer. Its output latches a pair of flip-flop circuits acting as decoders which are respectively supplied with the state of the frequency divided monitored signal and the fixed reference period signal.

Abstract: There is disclosed an electro-mechanical sequencer to equalize the running time of multiple (typically four) pumps in a common sump at a sewage treatment plant or the like. The sequencer includes a solid state binary counter receiving an input at an all-pumps-off condition. The binary counter operates a pair of multi-pole-double-throw relays. Control signals (typically four) from float valves or other sensing devices to the pump motors are routed through the first relay and then the second relay; one of the relays shifts the connection of its inputs and outputs by one position; the other relay shifts by two positions. Upon successive input signals to the binary counter the relays are changed from no-shift, to one position shift, two position shift, three position shift, and back to no-shift (in four pump systems). Three pump systems return to no-shift after the two position shift.

Abstract: There is disclosed apparatus for detecting phase unbalance in a 3-phase electric power system and initiating protective shutdown for motors or other loads in the system which includes a 3-phase rectifier, a peak voltage measuring circuit, a comparison circuit for comparing each phase maximum with a predetermined proportion of the peak voltage and generating a pulse whenever a phase maximum exceeds the predetermined proportion of the peak voltage, a missing-pulse detection circuit receiving the pulses, a fault circuit producing a fault signal in response to a signal from the missing-pulse circuit, a delay circuit responsive to the fault circuit and a visual indicator and relay for indicating a persistent phase unbalance fault and initiating protective action.

Abstract: Electrical and electronic circuitry offering protection to motors, compressors and the like, from conditions of low energizing voltage or momentary voltage interruptions resulting in excessive mechanical load (locked rotor). When the undesirable condition is present, an internal relay prevents the equipment from being energized - transient conditions being allowed for by means of suitable time delay circuitry. The protection device provides significant improvement in safety and economy by preventing equipment from burning up.