Abstract: An improved timed-off control apparatus and method are provided to prevent excessive cycling of an electrically operated device, such as an air conditioning compressor. The timed-off control apparatus provides a predetermined timed-off period (e.g., five minutes), during which the electrically operated device is constrained to remain in an off state after the device is deactivated by a loss of power. For example, in an air conditioning system, fluctuations in power supply voltage and thermostat switch bounces may result in excessive cycling of the system compressor. By constraining the compressor to remain deactivated for the selected timed-off period, the compressor is protected against excessive cycling. In order to achieve consistent and predictable timed-off periods, a field effect transistor (FET) is used in conjunction with a resistance/capacitance (RC) circuit. When the power supply is interrupted, the FET is turned off state and remains off during the timed-off period.

Abstract: An inverter air conditioner controller includes an ac/dc converter for changing ac power into dc power, a dc/ac inverter for changing dc power into ac power having a desired frequency and a desired voltage to drive a compressor, compressor lock presumption unit for preliminarily determining whether a compressor lock occurs, and frequency increasing unit for increasing an operational frequency to a desired value. When it is presumed that compressor lock occurs, the operational frequency is increased. If the operational current value then reaches an overcurrent detection level, a lock protection unit for activates an overcurrent breaker to stop the compressor.

Abstract: Methods and apparatus for monitoring and controlling the operation of a refrigeration unit in a manner which eliminates the need for circuit breakers and fuses in control circuits which are instrumental in selecting and changing the operational mode of the refrigeration unit. When a need to change to a different operating mode is detected, a controller energizes a control device associated with the different operating mode and quickly determines if the current draw is within an acceptable range. If the current draw is within an acceptable range or window, the controller initiates the requested different operating mode. If the current draw is not within the acceptable range, the controller generates an appropriate alarm and different courses of action are decided upon which depend upon whether the current draw is above or below the limits of the acceptable range, the nature of the requested operating mode, and the desired temperature of a space conditioned by the refrigeration unit.

Abstract: A gas friction pump with rotor and stator, a motor for driving the rotor, and a circuit serving as a power supply to the motor, the circuit having electronic components for representing the current drawn by the motor.

Abstract: An overvoltage protection device for protecting the electrical system of a vehicle against overvoltages, the vehicle having an on-board wiring network connected to an electrical generator and having electrical devices connected thereto, includes a controllable switch for effectively short-circuiting the generator in case of an overvoltage condition. The switch includes a switching transistor connected in parallel to the generator. Evaluation circuitry connected to receive the generator voltage is provided for issuing a first evaluation signal when a predetermined overvoltage threshold is exceeded and for issuing a second evaluation signal when the generator voltage subsequently falls below a predetermined low voltage threshold. A memory is provided for receiving the evaluation signals and for controlling the switching transistor. The memory stores one of the received evaluation signals until receipt of the other evaluation signal.

Abstract: A current control method and apparatus for use in an air conditioning apparatus is disclosed. A total current detection portion is mounted at the AC power supply portion and a peak current detection device is mounted between the conversion portion and the inverter. The total current detection portion detects a maximum current applied to the air conditioning apparatus and the peak current detection portion detects a peak current generated in the inverter. The limitation of the detected total current value is particularly preset in the heating and in the cooling operations. When the detected value surpasses the preset limitation, the inverter motor is stopped.

Abstract: This invention provides an inverter controlled air conditioner capable of employing a rush current preventing relay having a small capacitance, thereby decreasing the cost. An inverter circuit includes a rectifying circuit connected to an AC power supply, a smoothing capacitor connected to the output terminals of the rectifying circuit, and a switching circuit, connected to the two terminals of the capacitor, for outputting a voltage having a predetermined frequency upon performing switching. An auxiliary power supply circuit has a rectifying circuit connected to the AC power supply. A control section drives the switching circuit with an output from the rectifying circuit as the operation voltage. Relay drive circuits for receiving the output from the rectifying circuit as the operation voltage are connected to an electromagnetic contactor and a relay. When the air conditioner is started, the control section energizes the relay for a predetermined period of time t.sub.

Abstract: An air-conditioning apparatus includes a control circuit adapted to detect, from among first to third line voltages of a three-phase AC power supply, the second or third line voltage not synchronizing with a serial signal. The control circuit detects a difference between a phase angle of the detected line voltage and that of the serial signal, compares the difference with set values and determines, by that comparison, whether the three-phase AC power supply is in a positive-phase sequence or in a negative-phase sequence. The operation of a compressor is inhibited when the negative-phase sequence is determined by the control circuit.

Abstract: A thermally protected heater element is located in an oil sump such that it is normally located beneath the surface of the oil whereby the oil is heated and acts as a heat sink relative to the heater element. If the oil level drops below the heater element, the thermal protection disables the heater element and the compressor whereby the location of the heater element defines the nominal minimum oil level.

Abstract: A method of protecting the compressor motor of a refrigeration system using a multiphase AC power source. The method comprises the steps of monitoring each phase of the power supply to the compressor motor; calculating the average phase for the phases of the AC power supply; determining a maximum phase unbalance deviation from the average phase; determining if a first level of phase unbalance protection is active; setting a system protection level as the first level of phase unbalance protection if the first level is active; setting the system protection level as a second higher level of phase unbalance protection if the first level is not active; and initiating a compressor motor shutdown if the system protection level is exceeded by the maximum unbalanced phase deviation.

Abstract: Apparatus for protecting a compressor operating in a refrigeration device such as a heat pump includes a heater for maintaining lubricating oil contained in a crankcase of the compressor at a preselected temperature that will prevent the oil from absorbing any refrigerant. A control circuit is connected to an alternating current source of electrical power for controlling the operation of the compressor. The control circuit includes a thyristor having a blocking state and a conducting state. If the heater fails to operate, the thyristor will be disposed in the blocking state thereby preventing the compressor from operating. The control circuit also includes a trigger for changing the thyristor from the blocking state to the conducting state, and a full wave bridge or rectifier for converting the voltage drop across the thyristor from an alternating current voltage to a direct current voltage.

Abstract: A method, and apparatus, for protecting a compressor motor in a refrigeration system from overload comprising the steps of setting a first overload trip point; setting a second overload trip point; comparing the first trip point setting with the second trip point setting; and shutting down the compressor motor if the first trip point setting is not substantially equal to the second trip point setting.

Abstract: A protective time delay delay circuit delays energization to an electric load until a predetermined time has elapsed from a previous deenergization. A transistor has its emitter connected to an ac conductor and has its base coupled to an RC timing circuit. The collector is connected to the gate of a triac whose current electrodes are coupled to the thermostat conductor and to a load device. A small resistor and a zener can be connected to the transistor to provide brownout protection. A temperature sensitive resistor can be included to increase or decrease the lockout period as a function of temperature. This resistor can be remotely mounted in thermal proximity to the load to be protected. A thermistor placed in parallel to latching capacitor can provide thermal overload protection.

Abstract: A memory stores, in advance, at least a first V/F pattern corresponding to an air conditioning load and having reference voltage and frequency characteristics, and a second V/F pattern having voltage and frequency characteristics lower than those of the first V/F pattern in a starting region of a variable-capacity compressor for driving a refrigeration cycle. A detector detects an over current supplied to an inverter for driving the compressor. A controller stops the compressor through the inverter when the detector detects the over current, and restarts or holds the compressor through the inverter in accordance with the detection count of the over current. The compressor is restarted with the first V/F pattern from the memory when the detection count is smaller than a first predetermined count, and when the detection count reaches a second predetermined count larger than the first predetermined count.

Abstract: An air-conditioner comprises a refrigerating circuit having a compressor, a condenser, an expansion device and an evaporator which are connected by suitable refrigerant conduits. An electric current path for making a current flow through the compressor includes an AC power source, to which a current transformer is coupled, and an output of the current transformer is converted into a DC voltage which is then given as a (+) input of a comparator. A reference voltage is given to a (-) input of the comparator. When the DC voltage exceeds the reference voltage of the comparator, the high level is outputted from the comparator. When the high-level output from the comparator persists for three seconds, the compressor is stopped forcedly and a three-minute timer is turned on. After a lapse of three minutes, the flow of the current through the current path of the compressor is resumed. Thereby, a lightly locked state is removed.

Abstract: In a variable speed air conditioning system driven by an electronically commutated DC motor, the large DC capacitor associated with the compressor motor drive discharges to the normally AC powered compressor oil sump heater upon the loss of AC power to the system.

Abstract: A compressor controller of a refrigerating device comprises a power supply voltage detecting device, a voltage comparing device, and a compressor driving device. When the temperature in a compartment of the refrigerating device rises and the compressor is required to be driven to cool the compartment, the power supply voltage detecting device detects the voltage of the power supply which feeds power to the compressor. The voltage comparing device compares the power supply voltage with a reference voltage. When the power supply voltage is no lower than the reference voltage, the compressor driving device starts the compressor. The compressor controller also includes a compressor starting condition detecting device, a compressor halting device, and a voltage compensating device. The compressor starting condition detecting device detects the starting condition of the compressor by detecting the voltage or the current which is fed to the compressor by the power supply.

Abstract: A motor protector includes a case having an open end, a terminal plate secured to the case and having a pair of fixed contacts, a disc-shaped bimetal supported in the case and having a pair of movable contacts engaged with and disengaged from the fixed contacts respectively, a temperature-sensitive switch disposed so as to close the open end of the case and sensing the temperature of a sensed object to be turned on when the temperature thereof reaches a predetermined value, and a heater disposed in the vicinity of the bimetal and connected in series to the temperature-sensitive switch.

Abstract: A microwave oven and a refrigerator are combined in a single cabinet and share line power supplied to the cabinet. Door interlocks and a manually settable time are provided for disconnecting electrical supply to the compressor of the refrigerator during operation of the magnetron of the microwave oven. The circuitry provided ensures that electrical supply is reconnected to the compressor upon expiration of the timer setting, even if the door of the oven is incidentally left open after use.

Abstract: An electronic control for regulating the operation of a two-speed motor in a heat transfer system such as a heat pump or air conditioner. The control receives high and low demand signals from a thermostat and a motor unit operates at high and low speeds in response to, respectively, high and low speed signals. The control includes an initial timer, high and low speed operators, and a speed change delay. The initial timer detects the occurrence of a demand signal from the thermostat, counts a predetermined period of time, and responsively issues an initial timing completion signal. The high and low speed operators detect the timing completion signal as well as either a high or low thermostat demand signal. One of the operators then responsively issues either a high or low speed signal to the motor unit. The motor unit accordingly operates at a high or low speed. The speed change delay detects the change in a thermostat demand signal from a high to a low state or a low to a high state.

Abstract: A hermetic box contains a motor and a self reset type protector which interrupts the supply of electric power to the motor when an abnormally heated condition takes place in the hermetic box and automatically supplies again the electric power when the abnormally heated condition ceases. The motor is energized by an inverter having AC output terminals connected to the motor outside of the hermetic box. A current detector which detects that no current is flowing into the motor is provided on the output side of the inverter outside for a hermetic box.

Abstract: An advanced latching circuit (14) is used for latching a compressor (16) to a power source (18). The circuit includes the solenoid (32) of a compressor relay. A first set of contacts (28) of the compressor relay, a capacitor (34) and a resistor (36) are connected in parallel with each other and in series with the solenoid (32). Power supplied to the latching circuit (14) with the capacitor discharged energizes the solenoid (32) and latches the circuit. The opening of the latching circuit (14) by a safety switch (38, 40) deenergizes the solenoid to disconnect the compressor from its power source and charges the capacitor (34). The solenoid cannot be reenergized to reactivate the compressor until service personnel remedy the heat pump malfunction and interrupt power to the latching circuit (14).

Abstract: A high dielectric constant capacitor comprising a thin film deposited on a substrate, the thin film being composed of a mixture of a tantalum oxide and a titanium oxide wherein the ratio of Ti to Ta is in the range from 0.1 to 4 atomic percent.

Abstract: Calibrated methods and systems for protecting refrigerant motor/compressors against overload and loss of refrigerant conditions, independent of compressor and system size, while avoiding the need for a plurality of sensors. The disclosed methods and systems are generic in the sense that they may be employed in a variety of different air conditioner or heat pump models of different sizes and capacities, without being specifically tailored for a particular model, although a factory calibration adjustment is required. The disclosed methods and systems sense loading on the compressor motor, and make control decisions based thereon. A permanent compressor motor reference loading is established when the refrigeration system has a known correct refrigerant charge and the motor/compressor has a known load. This is typically accomplished in the factory after a predetermined stabilization interval has elapsed following initial start up of the motor/compressor.

Abstract: Refrigeration system control systems and methods for protecting a refrigerant motor/compressor, for example in an air conditioner, against conditions of excessive loading. The systems and methods of the invention recognize and distinguish between conditions of high operating load and insufficient condenser airflow, and take appropriate action for each. High operating load conditions are responded to by providing a motor/compressor cool-down interval, followed by a restart, so that an air conditioner remains operating at its maximum capacity, consistent with the field conditions. Insufficient condenser airflow conditions are responded to by eventually terminating operation of the motor/compressor until, for example, a service technician is called. Operation is based on a recognition that excessive loading conditions are manifested much sooner when the cause is insufficient condenser airflow than when the cause is a high operating load.

Abstract: A motor protector having a thermostat metal element thermally coupled to an electrical motor in a refrigerator compressor motor system has a heater responsive to motor current thermally coupled to the thermostat metal element and has an improved component arrangement to provide locked rotor and ultimate trip protection for the motor without requiring calibration of the operating temperature for the protector after assembly or after incorporation in the motor system.

Abstract: A trouble detection apparatus for an air conditioner detects overcurrents occurring within a predetermined time period t.sub.2 which is a shortest time period necessary for stabilization of the compressor operation. By counting a number of occurrences of the above-mentioned detections as criteria of actual trouble, the compressor is stopped when the number becomes two or more; thereby unnecessary interruption of operation of the air-conditioner due to electric noise or a simple overload is eliminated.

Abstract: A control system for an electrically driven variable capacity automotive air conditioning system affords the passenger maximum comfort control without overloading an electrically commutated motor compressor drive. Driver selected comfort settings are sequentially overridden to avoid overloading the motor. As motor overload conditions are alleviated the control system gradually returns to the initial driver selected comfort settings.

Abstract: Disclosed are refrigeration system control systems and methods for compressor motor protection and defrost control. The disclosed systems and methods are generic in the sense that they are self-calibrating and so may be employed in a variety of different air conditioner or heat pump models of different sizes and capacities, without being specifically tailored for a particular model. The disclosed systems and methods sense loading on the compressor and evaporator fan motors, preferably by sensing the voltage across the capacitor-run winding of an AC induction motor and normalizing with respect to line voltage. The self-calibrating capability is implemented by taking advantage of the changing loads as a function of time on both the compressor and fan motors during both normal and abnormal operation of a refrigeration system. In overview, a reference value of motor loading is established for each motor at certain times during an ON cycle.

Abstract: In a hermetic compressor there is provided a resilient retainer member adapted to removably secure a thermal overload protector relative to the compressor casing. The overload protector is arranged in a housing which is adapted to engage the upper wall of the casing. The retainer member includes one end portion dimensioned to engage the housing whereby downward pressure on the retainer member secures the overload protector relative to the casing. The overload protector housing is formed to include a pair outwardly projecting leg members. A slot formed on one of the legs aligns with an opening in the other leg are engageable by a tool which is employed to exert an external force on the housing sufficient to allow removal and replacement of the thermal protector housing relative to the retainer member.

Abstract: A temperature controller for an air conditioner including a temperature sensor that provides an output temperature from the air conditioning device, and a temperature rate of change comparison circuit for providing an indication signal that the rate of change from the temperature sensor exceeds a predetermined reference rate of change indicating that the rate of temperature change from the air conditioner is less than a reference cooling rate. The indication signal from the temperature rate of change comparison circuit is input to a disabling means that disables the air conditioning device. In an embodiment, the rate of change comparison circuit is connected to the thermostat for the system to sample the air conditioning temperatures for comparison with the reference cooling rate.

Abstract: A refrigeration system energy controller 10 for controlling the on-Off cycle time of a refrigeration compressor motor 25. A pressure-sensing device 27 senses high and low pressure thresholds in the refrigeration low-side suction line, the high threshold event being converted to a first digital voltage that energizes the refrigeration compressor motor 25, and the low threshold event being converted to a second digital voltage that produces a fixed duration timing signal setting the minimum time duration of the compressor motor 25 on-Off cycle.

Abstract: Electronic circuitry senses over-voltage and under-voltage within narrow threshold limits, and voltage interruption, in the energization circuit of a sensitive load, such as a refrigeration compressor motor load, to protect against overheating damage and burn-out. Setting to a nominal operating line voltage is provided for to obviate readjustment to the threshold voltages of a window comparator utilized to sense over-voltage and under-voltage.

Abstract: In a hermetic compressor there is provided a resilient retainer member adapted to removably secure a terminal receptacle block assembly and a thermal overload protector relative to the compressor casing. The receptacle block assembly is adapted to engage conductor pins of an electrical terminal secured to the upper wall of the casing while the overload protector is adapted to engage the upper wall of the casing. The retainer member includes a first leg portion dimensioned to engage the thermal overload protector and a second leg portion dimensioned to engage the terminal receptacle block whereby downward pressure on the retainer member secures both the overload protector and terminal receptacle block relative to the casing.

Abstract: A refrigeration compressor is disclosed which includes a compressor means, a two phase motor drivingly connected thereto and an associated power supply operative to convert single phase 60 hertz alternating current to two phase controlled frequency alternating current so as to enable the compressor to be operated from conventional single phase power and at any point within a range of speeds commensurate with the loading thereon. The power supply also includes improved filtering means for each of the output phases of the power supply. A line break motor protector is also provided which is particularly well suited for use with two phase motors. Additionally, in order to increase reliability, circuitry is also provided for directly connecting the two phase motor to the single phase power supply in such a manner so as to enable the two phase motor to be operated directly from the single phase supply in the event of failure of the two phase power supply.

Abstract: In an air conditioner separated into an indoor unit and an outdoor unit, a control circuit comprises a three-phase power source connected in common to the indoor and outdoor units, and a signal line led out from two phases of the power source. A contact of an electromagnetic relay energizing a compressor of the air conditioner is connected on the portion of the signal line in the indoor unit in series with a current sensor sensing the current flowing through the signal line, and a contact of a protective relay protecting the compressor is connected on the portion of the signal line in the outdoor unit in series with the electromagnetic relay. A first controller is disposed in the indoor unit for controlling on-off of the relay contact of the electromagnetic relay, and a second controller is disposed in the outdoor unit for energizing the protective relay contact thereby controlling on-off of the compressor.

Abstract: The invention relates to apparatus and an arrangement for starting and protecting an electrically driven motor-compressor unit. A protector switch and a PTC resistor have a common housing with a bore and slot construction adapted for clamping the housing to the external pressure tube of the motor-compressor unit.

Abstract: A method and control system for protecting an electric motor driven compressor in a refrigeration system are disclosed. The refrigeration system operates to satisfy a load placed on the system and the refrigeration system compressor is turned off when the load is satisfied and the refrigeration system is providing excess capacity. When the compressor is turned off due to excess capacity, current flow to the electric motor driving the compressor is sensed and the refrigeration system is shut down if the sensed current flow is abnormal. In this manner, the compressor and the electric motor driving the compressor are protected against restarting under unfavorable operating conditions which could unduly wear the compressor motor and/or the compressor.

Abstract: The compressor motor controller of the present invention includes a hot motor detector adapted to be coupled to a plurality of temperature sensors for detecting an overtemperature condition of the compressor motor. The hot motor detector incorporates logic switching means for generating a motor control signal. A self diagnostic sensor is coupled to the hot motor detector for detecting an electrically shorted condition of the temperature sensors while a low voltage detector is coupled to the hot motor detector for sensing a low line voltage condition. Means are provided for protecting the compressor motor against the undesirable effects of short cycle operation while a lubricating oil pressure detector receives signals from a pressure transducer which are representative of oil pressure.

Abstract: In a hermetic compressor there is provided a resilient retainer member adapted to removably secure a terminal receptacle block assembly and a thermal overload protector relative to the compressor casing. The receptacle block assembly is adapted to engage conductor pins of an electrical terminal secured to the upper wall of the casing while the overload protector is arranged on a substantially flat portion of the upper wall of the casing. The retainer member is arcuately shaped with its downwardly diverging end portions adapted to engage the receptacle block and thermal protector respectively. A downward force on the apex of the retainer member forces its end portions to securely hold the receptacle block in electrical contact with the conductor pins and thermal protector in intimate contact with the upper wall of the compressor casing.

Abstract: The occurrence of a condition indicative of an impending shutdown causes the closing of a switch which completes a circuit powering an indicator and a relay coil. The powering of the relay coil causes the closing of the associated contacts which completes a circuit for powering the relay coil independent of the initial closing of the switch so that the indicator remains powered/lit until manually disabled. The powering of the coil also results in the establishing of a summary fault signal. A timing relay is used to avoid false signals at start up.

Abstract: A motor protector of the type having a snap acting thermostatic element is shown particularly adapted for use with compressor motors in which a conventional three pin header is mounted on the compressor casing to allow electrical energization of the motor. An improved heat transfer path is formed between the windings of the motor and the thermostatic element of the protector by suspending the protector from one of the motor pins in optimum heat conductive relation therewith and thermally separated from the compressor casing and any component mounted on the other two pins.

Abstract: A supply and protection unit for a hermetic compressor of a thermostatically regulated refrigerator comprising an electrically insulating support body (3) adapted to be fixed to the casing of the compressor (P); said support body being provided with cavities (3a, 3b, 3c, 3d and 3e) opening at one of its faces intended to face towards the compressor for slidably and removably inserting therein of a pair of electrical devices (1, 2) and connection means thereof to be supported against the compressor casing, one of said devices being a thermally operated protection switch (1) and the other being a resistor (2) with a positive temperature coefficient.

Abstract: An equipment protector and energy saving apparatus includes transient protection as well as under voltage protection by preventing the reduced voltage from being applied to motors and other apparatuses that may be damaged because of insufficient voltage being applied thereto. Provision is incorporated to protect for momentary low voltage transients and turn-on prevention, if the line voltage should be reduced below a predetermined value. Provision is also made for correcting for a small increase in line voltage which may occur when the operating equipment is removed from the line. A timing device may be incorporated therein in order to remove the protected equipment from the line for predetermined intervals of time.

Abstract: A motor control system includes a motor system having a pole-amplitude-modulated (PAM) motor, a motor breaker, and a speed switch coupled between the motor breaker and the PAM motor. The PAM motor is coupled to a fan in an exhaust duct having a controlled damper for controlling air flow therethrough. A control system step logic sequencer includes means responsive to permissive signals for providing in sequence control signals to the motor breaker and speed switch in response to confirmation signals received from the motor breaker, the speed switch and the PAM motor.

Abstract: A protection device for a vehicle-mounted air conditioner compressor wherein an electric current for engaging the electro-magnetic clutch of the air conditioner compressor is also fed through a PTC ceramic resistor disposed between a starter contact of the ignition switch and a terminal of the electro-magnetic clutch during the starting operation of an engine in addition to an operation of the conventional circuit including a compressor relay and a compressor switch.

Abstract: A refrigerator includes a compressor, a condenser fan, and an evaporator fan simultaneously energized by a temperature control system which includes a thermistor located to sense the average temperature of the cabinet air and a potentiometer manually adjustable to a desired temperature set point. The on or run time of the compressor and fans is controlled by the thermistor sensed temperature with respect to the set point. The duration of the run time is measured by a resettable counter. The off time is adaptively controlled within a predetermined range which minimizes energy consumption while maintaining good temperature control. An off time counter, which is used to determine the duration of the off cycle, is incremented when the measured run time is less than a desired minimum, is decremented when the measured run time is greater than a desired maximum, and maintains the prior off time when the measured run time is within a desired range.

Abstract: An apparatus is disclosed for activating a thermostat for an air conditioning or heating system. The apparatus comprises a control circuit and a controllable switch connected to activate and deactivate the thermostat controlling the air conditioning or heating system. A timing circuit provides a first timing period in which the thermostat is deactivated in addition to providing a second timing period to activate the thermostat. The control also includes a circuit for deactivating the thermostat for a period of time in the event the compressor terminates operation for any reason. An optional occupancy sensor increases the time of deactivation of the thermostat during periods of non-use of the area being air conditioned or heated. The foregoing abstract is merely a resume of one general application, is not a complete discussion of all principles of operation or applications, and is not to be construed as a limitation on the scope of the claimed subject matter.

Abstract: A protection system for a dynamoelectric machine providing a plurality of protective functions comprises a module having as a first function over temperature protection including thermal sensors adapted to be placed in heat transfer relation with the windings of the machine. The sensors which may be connected in series or in parallel are connected to a sensing circuit provided with shorted sensor protection. When connected in parallel a channel is provided for each sensor and is isolated from one another. Other functions include a minimum off delay timer which prevents rapid cycling of the machine.

Abstract: A current sensing circuit that controls a contactor that connects a load to power lines. The circuit provides an initial momentary delay period after energization of the circuit and before operation of the contactor to permit transients and other short duration anomalies to die out. An immediately succeeding second momentary delay period during which the contactor operation cannot be changed, assures that an initial inrush of current to the load will not cause a fault signal to erroneously operate the contactor. When a fault signal does cause the contactor to be operated, the circuit cannot be set back to its intended operation condition until energization of the sensing circuit is manually interrupted and reestablished. During normal operation of the circuit when current on the power lines is within acceptable limits, the circuit is latched in its proper operating mode.