Abstract: An auxiliary rotation-system starter includes a starter motor, a main circuit portion having a main contact portion, an auxiliary circuit portion having a driving coil portion for opening or closing the main contact portion, and a fuse for cutting the current flow to the driving coil portion by fusing at a predetermined temperature. The main circuit portion is connected between the starter motor and a power source. The auxiliary circuit portion is connected in parallel with the main contact portion. The fuse is provided in the auxiliary circuit portion.

Abstract: A circuit protection device includes an overheat protecting circuit connected to a main circuit and capable of being activated so as to shut down the main circuit when operating temperature of the main circuit reaches a predetermined value, and a current limiting circuit connected to the main circuit for preventing current through the main circuit from exceeding a predetermined threshold value. The current limiting circuit is further connected to the overheat protecting circuit and controls activation of the overheat protecting circuit when the current through the main circuit reaches the predetermined threshold value. Therefore, erroneous operation of the circuit protection device due to a shift in component characteristics of the overheat protecting circuit attributed to limitations in fabrication can be avoided.

Abstract: A method for monitoring thermal overload of an electric load element in a motor vehicle containing other electric consumers, which can be switched into a stand-by phase is disclosed. The load element is monitored by a control device using a calculated load temperature parameter. During a first operational phase, a power loss of the load element or a quantity that is essentially proportional thereto is evaluated for calculating the load temperature parameter. During one or more stand-by phases, the control device is switched with essentially no current between the first operational phase and a second operational phase. After the control device is switched on in the second operational phase, at least one quantity, which is characteristic for the moment of switching on, is evaluated for calculating the existing load temperature parameter.

Abstract: A control circuit for a motor including a contactor circuit having a contactor, a first end and a second end, and a snubber circuit connected across the contactor circuit. The snubber circuit includes a first port electrically connected to the first end of the contactor circuit, a second port electrically connected to the second end of the contactor circuit, a first sub-circuit electrically connected to one of the first and second ports, and a second a second sub-circuit electrically connected in series with the first sub-circuit and to the other of the first and second ports. The first sub-circuit includes a resistor and a first non-linear device electrically connected in parallel branches, and the second sub circuit includes an energy storage device and a second non-linear device electrically connected in parallel branches.

Abstract: A system and a method for protecting electric motors and their respective control circuits are described, wherein it is possible to distinguish whether a situation of surge current results from a overload or from a short-circuit on the motor (1). This is achieved by means of a system for protecting an electric motor (1) and its control circuit (2), the motor speed control being carried out by means of a set of switches (Ch), the system comprising a control central (7) capable of measuring the electricity conduction time (Tc) of each of the switches (Ch) and to measure the time (Td) passed between the beginning of conduction of one of the switches (Ch) and the occurrence of a surge current, the central (7) making a comparison of said times (Td, Tc) and being capable of determining whether said surge current results from an overload or a short-circuit of the electric motor (1) or on one of the switches (Ch).

Abstract: A thermal protection apparatus for an AC traction motor including a stator, a rotor, a blower fan and an inverter includes a method and apparatus for predicting the motor temperature assuming that the blower is operational. The method and apparatus also determines an estimated motor temperature by measuring the motor resistance or the rotor slip. The estimated motor temperatures compared to the predicted motor temperature to determine the condition of the motor cooling system.

Abstract: A method and system for operating an electrical system including an electrical machine to predict an incipient fault in the electrical machine. A neutral-to-ground leakage signal representative of current between a neutral point of the machine and an electrical ground is generated and stored in a memory. If the leakage signal exceeds a selected threshold, the electrical system is operated at a reduced power condition to control the current. Temperature criteria of the electrical system at which any moisture that could cause the high leakage current is determined with a temperature sensing system and the temperature is monitored and compared to the selected temperature criteria. The electrical system returns to operations at normal power conditions if the leakage signal returns to within the selected threshold. The leakage current signal information stored in the memory is analyzed to predict an incipient fault in the electrical system.

Abstract: In a protection circuit for a plurality of fans, an element is associated with each fan. The impedance or the current value of the element indicates the operation condition of the fan. For example, the impedance or the current value may be low if the fan is operative or functioning normally, and high when the fan is inoperative or functioning abnormally. The elements are arranged in parallel between two conductive lines. A detection circuit determines the total impedance or current value between the two lines. If the total impedance or current is not within a predetermined range which indicates that all fans are operating normally, at least one of the fans functions abnormally. The number of lines required to convey the operation status of the fans to the detection circuit is only two and does not depend on the number of fans involved.

Abstract: A fully protected H-bridge for a d-c motor consists of two high side MOSFETs and a control and logic IC on a first conductive heat sink all within a first package and two discrete low side MOSFETs. The entire bridge is controlled by the IC. Shoot thru protection is provided for each leg, and a PMW soft start sequence is provided through the control of the low side MOSFETs, programed by an external, chargeable RC circuit. Input signals to the high side MOSFETs select the operation modes. Protective circuits are provided for short circuit current and over current conditions. Sleep mode and braking/non braking control is also provided.

Abstract: When an operation switch of a motor control circuit is switched on or when the operation switch and an automatic operation switch are simultaneously switched on, a switching device is switched on to energize a relay winding and a contact in the relay is switched to drive a motor. When an overcurrent is passed to a current detecting resistor and a temperature rise in the current detecting resistor is detected by the temperature dependent resistor and/or when a rise in a voltage across terminals of the current detecting resistor is detected by an overvoltage detecting circuit, the switching device is switched off via the bias circuit to thereby stop the driving of the motor.

Abstract: This invention includes a circuit that approximates the thermal behavior of a fuse or other electronic device that is coupled in series with the circuit. In one preferred embodiment, the circuit protects a fuse coupled in series with a rechargeable battery from clearing during soft short conditions. Thus, when the instantaneous current is temporarily above the current rating of the fuse, yet the root mean squared current is below the current rating of the fuse, the circuit works to estimate the heating of the fuse element and limit the current to a root mean squared value that is less than the current rating of the fuse. One embodiment includes a programmable comparator that actuates a counter which, in turn, increments to estimate heating of the element when the current exceeds a predetermined threshold.

Abstract: Electronic equipment can be operated in an enclosure wherein the electronic equipment is powered by a DC power source including a rectifier that receives an AC power signal and a battery that provides backup when the AC power signal is interrupted. For example, a DC power signal generated by the DC power source and a temperature in the enclosure for the electronic equipment can be monitored. The DC power signal can be blocked from the electronic equipment in the enclosure when the DC power signal is less than a low voltage threshold for the battery or when the temperature in the enclosure is outside a range of first high and low temperature thresholds for operation of the electronic equipment. The DC power signal can be provided to the electronic equipment in the enclosure when the DC power signal is above the low voltage threshold for the battery and when the temperature in the enclosure is within the range of the first high and low temperature thresholds for operation of the electronic equipment.

Abstract: A thermal management system for a portable battery powered electronic device, and particularly, a portable battery powered ultrasound device, which controls the temperature of the device such that the external surface temperature satisfies medical safety regulatory requirements, and such that the heat generated by the device does not reduce battery life, reduce component life, decrease reliability of the device, or cause device shutdown because of overheating. A thermal management system monitors the respective temperatures of various system components, and, based on the monitored temperatures, performs control to cool the ultrasound system, maintaining the external surface temperature below the safety regulated temperatures and ensuring reliability of system components.

Abstract: A start-up switch 50 for an electric motor 1 comprises a resistive element (54) which is so constituted as to be connectable to an electric current path (15) and which has such a characteristic that its resistance value increases by the heat generated by electric current that flows through the electric current path (15) and a thermostatic switch (60) which is connected in series with the resistive element (54). The thermostatic switch (60) has an actuation member (60) which is responsive to temperature so that upon reaching a preselected temperature, said member moves from a closed current path position to an open current path position. The thermostatic switch (60) is positioned to be in direct heat transfer relationship with the resistive element (54) so that the member will (66) rise in temperature as the resistive element (54) rises in temperature.

Abstract: An electric motor unit with continuous current containing a connection plate and a card that carries electronics for the control of the motor. The card also contains electronics to monitor the current in order to detect the blockage of the motor's rotor and electronics to control the power supply of the motor. The card and/or the plate carries devices to sense temperature. The electronics to control the power supply are linked to the device(s) sensing temperature, as well as to the electronics monitoring the current. The control electronics cuts off the power supply of the motor when blockage of the motor's rotor is detected and a temperature measured by at least one of the devices reaches a high threshold value and reestablishes the power supply of the motor when the temperature is at or below a low threshold value.

Abstract: An improvement in a starting system for an electric motor, which drives a hermetic compressor of refrigeration and comprises a main winding (1), and an auxiliary winding (2), which are energized by an electric current source (3), through a hermetic terminal (40) affixed to the outside of the compressor shell, the auxiliary winding (2) having a terminal connected to the electric current source (3) through a starting device (10) mounted inside the compressor shell and in series with a fusible element (20) to be opened when submitted to an electric current, in order to definitively interrupt the energization of the auxiliary winding (2) by means of the starting device (10), said hermetic terminal (40) being designed to receive an external starting device (50), in order to promote the selective connection between said other terminal of the auxiliary winding (2) and the electric current source (3) upon the definitive opening of the circuit defined by the fusible element (20) and the starting device (10).

Abstract: An integrated circuit including one or more power devices, and circuitry which reliably (and independently) shuts down each power device that is detected to be in an undesired operating condition (e.g., one or both of an overcurrent condition and an overvoltage condition) that causes a thermal fault, but which does not shut down any power device that is not in such undesired operating condition. In typical implementations in which the integrated circuit has multiple power devices and an overvoltage detection circuit for each power device, the integrated circuit includes a thermal fault detection circuit and logic circuitry which receives the output of the thermal fault detection circuit and each overvoltage detection circuit. The logic circuitry generates signals which shut down appropriate ones of the power devices in response to the thermal fault detection and overvoltage detection signals it receives.

Abstract: A sensor for facilitating the measurement of temperature and magnetic field is described. The sensor comprises an optical cable having a distal end encompassed in a sheath of giant magnetoresistive material. Temperature changes alter the spectrum emissivity of the giant magnetoresistive material. Magnetic field changes alter the spectrum changes that occur from distorting the optical fiber that occur when the giant magnetoresistive material distorts the optical fiber.

Abstract: A protective device against excessive currents occurring in an electric circuit between a voltage source and a load mounted downstream of said device, comprising a first triggering component with high current sensitivity and adapted to be triggered, rapidly, but reversibly, in case of excessive current in the circuit, and a second triggering component, mounted in parallel with the first, capable of bearing a temporary voltage higher than the power supply voltage, when the first component is triggered, and of being triggered rapidly and reversibly thereafter. The triggering component are preferably conductive polymer components. Also, a triac switch comprising such a protective device mounted upstream of the triac and a third component is mounted on the triac trigger.

Abstract: A motor driving control device that achieves as high as possible phase coil energization level while preventing thermal destruction of the power switching element by using precise thermal detection of a portion of the power switching element inside a switching module of the control device. An electric power loss Lt at the switching element is used for calculating a saturation temperature Tjgoal. On the basis of the saturation temperature, Tjgoal, and a time constant &tgr; of temperature rise, an instant junction temperature Tjnow is calculated. A difference Error between the instant junction temperature Tjnow and an upper temperature limit value Tjmax is calculated. In a motor locked condition, a coefficient Kt is calculated for the target torque, the target torque being equal to the required torque multiplied by Kt. Kt is based on the Error for calculating the target torque. If Error is greater than or equal to a predetermined value, K3, Kt is set to be 1, even if Kt is in excess of 1.

Abstract: A vehicle electric assist steering system (10) includes a switching circuit (56) for providing electrical power to an electric motor (52) of the vehicle steering system. The switching circuit (56) has a temperature condition. A temperature sensor (69) is coupled with the switching circuit (56) for providing an output signal (71) having a value indicative of the temperature condition of the switching circuit (56). A stall detector (70) is responsive to the output signal (71). The stall detector (70) is operable to reduce power to the electric motor to different level during a stall condition based on the sensed temperature condition of the switching circuit (56).

Abstract: In a motor control unit adapted to control each switching element of each switching arm and control the current sent to a motor, the temperature sensing diodes 19a˜19c are arranged near the switching elements and a constant current circuit 18 is connected to the temperature sensing diode. An overheat prevention means is also provided to recognize the switching element temperature by detecting a forward voltage value of the diode and to place the switching element in an OFF-state when the switching element is judged to be in an overheat condition based on the recognized temperature of the switching element.

Abstract: A semiconductor switch is installed in a power supply line of a motor, and photocouplers, which constitute a switching control circuit for turning on and off the semiconductor switch, are series-connected between a constant-voltage source and the output ends of a comparator of a starting circuit and a comparator of a trip circuit. An overload at the time of starting the motor is detected by a current transformer, and the semiconductor switch is activated so as to readily cut off the motor driving current.

Abstract: A combination circuit breaker/motor starter includes a circuit breaker trip unit having a microprocessor and at least one removably connectable contactor or other functional module. The functional module is encoded with an identifier, such that the microprocessor can determine the type of functional module and appropriate configuration parameters, such as trip times, for the particular application of the functional module. Power is supplied continuously to the trip unit during motor overload or short circuit conditions.

Abstract: A motor start switch includes a temperature responsive resistor element and a cutout switch electrically connected in series with a start winding of an electric motor. The cutout switch is in thermal contact with the temperature responsive resistor element so that heat from the temperature responsive resistor element is transferred to a bimetal element in the cutout switch, causing the bimetal element to open the switch. Heat from a motor overload protector provides heat to maintain the bimetal element in an open position. As heat to operate the temperature responsive resistor element is obtained from existing circuit elements, the efficiency rating of the motor is unaffected.

Abstract: A method and apparatus are provided for disconnecting a starting winding of a single-phase motor during startup. The method includes the steps of disposing a heater element of a thermal switch in series with a main winding of the single-phase motor and disposing a set of contacts of the thermal switch in series with the starting winding of the single-phase motor.

Abstract: A hermetic electric compressor includes a motor unit having a stator coil and a compressor unit driven by the motor unit for compressing refrigerant gas. A temperature sensor is provided at the stator coil for monitoring a temperature of the stator coil. A control unit is further provided to control a rotational frequency or speed of the motor unit via the stator coil depending on the monitored temperature of the stator coil. The temperature sensor and the control unit are connected via a shielded cable or a twisted pair. The shielded cable or the twisted pair may be grounded via a capacitor. Further, a thermostat may also be provided at the stator coil and connected in series to the temperature sensor.

Abstract: A device for protecting a braking resistor for locomotives supplied with AC power obtained by chopping the DC voltage from the power grid comprising at least one pack of resistive components of the resistor which has at least one reference resistive component which is made of a different material than the other resistive components of the pack but is suitable to react thermally in the same manner as the other resistive components of the pack when it is crossed by the same current, and a control circuit which is associated with the pack of resistive components and is suitable to detect their temperature by detecting the variations in the electrical characteristics of the reference resistive component.

Abstract: Embodiments of a combination motor starting device and protector module including a motor start winding cut-out switch for an electric motor are described. In the one embodiment, the motor protector includes a heater element and a bimetallic protector switch, electrically connected in series and configured to be coupled between a power source and the motor windings. The bimetallic protector switch includes a stationary contact, a movable contact, and a bimetal element, responsive to current flow through the protector, controls movements of the movable contact. The heater element is positioned in heat transfer relationship with the protector bimetal element. The motor starting device, in one form, is a positive temperature coefficient resistor (PTCR) element configured to be connected in circuit with the motor start winding. A bimetallic cut-out switch is connected in series with the PTCR.

Abstract: A temperature sensor is located close to each of a plurality of switching elements. Each of the elements opens and closes a current supplying line from a power supply to a three phase SR motor. A generating circuit of a instruction value for the driving current of the motor generates a target value (It) of the driving current so as to achieve a requested power of the motor and an allowable value of the driving current on the basis of the highest temperature sensed by the temperature sensors. The circuit outputs the target value as an instruction value of the driving current when the target value is smaller than the allowable value and outputs the allowable value as an instruction value of the driving current when the target value is greater than the allowable value.

Abstract: In a motor drive apparatus, a motor drive circuit includes an H bridge circuit composed of four field effect transistors or FETs, and resistors each having electrical resistance sufficiently higher than that of each of the FETs which would be presented when the FET has an ON-state trouble. These resistors are connected in parallel to the respective FETs. To perform a ON-state trouble detecting test on the individual FETs, an OFF signal is fed to all the FETs. If all the EFTS are free of the ON-state trouble, electric potential, representing a result of higher potential of a battery being divided by the resistors, appears at two input terminals of an electric motor connected to the motor drive circuit. If two of the FETs, having their drains connected to a higher-potential electrode of the battery, have the ON-state trouble, the higher potential of the battery appears at the two terminals of the electric motor.

Abstract: A vehicle cooling system including a motor control apparatus that controls operation of a system motor when a cooling fan driven by the motor locks due to foreign matter interference or freezing. When motor input current is detected to be overcurrent, the controller limits the current flow. When current flowing to the electric motor is detected to be overcurrent and ambient air temperature is at or above a predetermined temperature, the controller stops energization of the motor. Thus, when the cooling fan freezes and locks, energization of the motor is maintained until ambient air temperature reaches or exceeds the predetermined temperature. Therefore, when the frozen-locked state is eliminated due to a subsequent temperature rise, an ordinary operating state can again be obtained without the controller subsequently detecting surge current, generated as a result of the motor being re-started from a fully stopped state, as overcurrent and therefore incorrectly stopping motor energization.

Abstract: A multi-function protection system (8) for protecting electrical equipment such as a screw compressor motor is shown having a housing (10, 20) mounting current sensing toroids (CT1, CT2, CT3) and associated circuitry as well as associated circuitry for temperature sensing PTC resistors (S1, S2, S3) adapted to be placed in heat conductive relation with respective windings of the motor. The circuitry is connected to an analog-to-digital converter or ADC (U6) which provides a binary coded input to a micro-controller (U5). The micro-controller performs protection sub-routines to control an output switch (Q4) which in turn controls the state of energization of a relay (K1) coupled to the screw compressor motor.

Abstract: A motor protector (1, 1A) for connection in a circuit for supplying electrical power to a motor (36) to be protected includes first (S1), second (S2) and third (S3) switches in a housing member (2, 3). Each switch (S1, S2, S3) uses a snap-acting bimetallic member (8, 11, 13) for opening and closing electrical contacts (4a and 5a, 8a and 8b; 17 and 27; 18 and 30) of the respective switch. The switches (S1, S2, S3) in the housing member (2, 3) are connected as part of the circuit supplying electrical power to the motor (36) being electrically connected in series with one another so that the opening of any one of them will stop the flow of power to the motor (36) to be protected.

Abstract: An overheating protection system for a switching module prevents thermal breakdown of switching devices for passing currents through a load, for example an electric motor, while making it possible for the switching module to provide as much required current to the load as possible. The system comprises a temperature detector for detecting the temperature of a switching module, a temperature estimator for calculating a temperature change rate of a switching device inside the switching module corresponding to a current passed through the load and calculating an estimated value of the internal temperature of the switching module on the basis of the calculated temperature change rate and the detected temperature and a current limiter for on the basis of the estimated value correcting a target current value of a current controller controlling a current passed by the switching device.

Abstract: A secondary thermal overload device is connected to one winding of a motor having a bi-directional rotatable output shaft and is preset at a lower trip temperature than a trip temperature of a primary thermal overload device connected to the motor to deactivate only the one motor winding effecting closing movement of a garage door at a lower motor operating temperature and before the primary thermal overload device trips while enabling the motor winding associated with an opening movement of the garage door to be activated to open the garage door.

Abstract: Motor protection for air conditioning and refrigeration compressors includes in a first embodiment a cluster block (22) having a seat for a hermetic motor protector (24, 24') and mounting a combination terminal/fusible link (26/26d, 26d') in which the motor protector and combination terminal/fusible link can be exposed to cooling fluid contained in the compressor container and the cluster block is mounted on a lead-through pin (18a) of a header (18) in the container wall. In a second embodiment the cluster block (30) is mounted on all three pins (18a, 18b, 18c) of header (18) with pin connectors received in parallel extending channels (30a, 30b, 30c) of the cluster block. In another embodiment the cluster block (40) is irregular in configuration in order to accommodate available space in certain compressor containers and has a lid (40g) to enclose the motor protector.

Abstract: An apparatus is provided for controlling temperature of a motor by estimation. The temperature apparatus includes an initial setting circuit for setting an initial value of a temperature representative variable .theta., a temperature rise estimating circuit for calculating .theta.+A (where A is an incremental parameter reflecting a temperature rise under driving of the motor) for renewal of .theta. when the motor is driven, a temperature drop estimating circuit for calculating .theta.-.theta./S (where S is decremental parameter reflecting a temperature drop by heat dissipation of the motor) for renewal of .theta. periodically at a predetermined time interval while the temperature control apparatus is operating, and a power supply prevention circuit for preventing power supply to the motor when .theta. becomes no less than .theta.max (which is an upper limit parameter reflecting an upper tolerable limit temperature of the motor) and until .theta. becomes lower than .theta.max.

Abstract: A temperature-compensating overcurrent detection circuit for a DC motor comprising a converter, an integrator and an overcurrent detector. The present invention provides for an overcurrent detection circuit for a DC motor that is adapted compensate for operating temperature of the motor's environment and such compensating detection circuit does not respond with an early forcible operation when the mechanical device is constrained. The overcurrent detection circuit is adapted to permit the motor to carry out its intended operation exactly without having malfunctions due to noise and a temporary overcurrent.

Abstract: The present invention involves control and protection circuit for a compressor motor which includes an inductively activated contactor for controlling the flow of current to the compressor motor. The circuitry of the present invention includes a plurality of current detectors associated with each phase winding of the compressor motor for sensing the current in each phase winding. The sensed currents are combined in a predetermined manner and used to provide protection against an overcurrent condition, single phase operation and light loading condition. Additional detector circuits are also connected to the present control and protection circuit to provide protection against high temperature in the compressor motor windings, high temperature in various component of the compressor motor, and undervoltage in the power supply.

Abstract: A motor starter for an electrical circuit includes separable contacts for switching an electrical current flowing between a power source and a motor; an operating mechanism responsive to a trip signal for opening and closing the separable contacts; a separable contact state detection circuit providing an operating signal having two states corresponding to the open and closed positions of the separable contacts; a current transformer sensing the electrical current flowing between the power source and the motor and providing a sensed current value; and an overload relay generating the trip signal as an I.sup.2 t function of the sensed current value and the two states of the operating signal. The overload relay employs a pair of thermal time constants which closely model the motor under both natural convection and forced air cooling conditions.

Abstract: A highly efficient motor driver circuit of an electronic controller for linear cryogenic coolers operates directly from a variable power supply, such as a battery, without the need for the voltage regulator control circuit of the prior art. Elimination of the prior art voltage regulator ensures a higher efficiency motor driver circuit of the electronic controller. Both open-loop and closed-loop controllers electronically control the motor driver circuit. The open-loop controller protects against temperature sensor failure, and will limit maximum motor power as a function of system ambient temperature. The closed-loop controller regulates the temperature of the cold finger accurately to a preset value, using feedback from a temperature sensor along with a novel pulse-width modulation concept for modifying motor drive waveforms.

Abstract: An electrical load, such as a motor, has a first and a second terminal element for supplying electricity to the load. The second terminal element is directly connected to the load whereas the first terminal element together with a further terminal element forms a clamping socket for a switching device. The further terminal element is electrically connected to the load. When the switching device is inserted into the seat, the first terminal element is connected to the load in series with the further terminal element via the switching device.

Abstract: An arrangement for driving a power control element of a drive unit of a motor vehicle is proposed and the arrangement has a full-bridge output stage. A direct-current motor is arranged in the bridge diagonal and the current through the direct-current motor is limited to at least one preadjusted value in that the clocked drive signals are interrupted when the preadjusted value is exceeded.

Abstract: A starter comprising a contactor with an overcurrent relay provides an appropriate cooling interval for each of multiple classes of a load, such as a motor. An analog equivalent of a digital I.sup.2 t value calculated by a microcomputer in the overload relay is maintained by an external capacitor. When the microcomputer loses power following a trip, the capacitor discharges through a resistor at a rate selected to mimic cooling of the associated class of the load. Restart of the load is prevented until the appropriate interval, represented by the time required for the voltage on the capacitor to decay to a common reset value, has expired. The capacitor is charged to a voltage proportional to the I.sup.2 t trip value for the particular class of the load, which for all classes is below the forward drop of the clamping diodes on the microcomputer inputs to prevent discontinuities in the timing.

Abstract: A thin PTC device that includes a layer of PTC material sandwiched between a pair of metal plates is provided with an increased effective thickness by outwardly extending flanges on at least one of the metal plates. This allows a close fit of the PTC device in a pocket that otherwise would be too large for holding the PTC device properly.

Abstract: This disclosure provides a motor control system and method that is preferably applied to cargo power drive units. Power is supplied to a motor having one or more windings and a thermocouple that is embedded in the motor windings. The thermocouple provides an electronic signal from which both motor temperature and rate of temperature change are derived. A motor control circuit uses these values to determine if a jam condition has occurred (as represented by improper temperature rise) or whether critical overheating is occurring. If so, the motor control circuit causes a power switch to disconnect power from one or more PDUs in the subject bank of PDUs. Power is temporarily disabled, until a cargo operator releases a joy stick control to a neutral position and then attempts to use it again.

Abstract: Apparatus for electrically coupling a motor to a power source and providing overload protection to the motor includes a controller having a programmable module for periodically computing data indicative of motor temperature based upon motor current. The controller supplies an output signal based at least upon the computed motor temperature data. A contactor, responsive to the controller output signal, deenergizes the motor whenever any last-computed motor temperature data reaches or exceeds a threshold temperature. The last-computed motor temperature data is stored in a memory prior to the motor being deenergized. A signal from a timer circuit indicative of elapsed time after the motor is deenergized, together with the stored motor temperature data, enable the programmable module to compute fresh date indicative of motor temperature subsequent to the motor being deenergized.

Abstract: An overload relay, and an overload relay control circuit power source are disclosed herein. The overload relay includes an electronic trip circuit, a contactor such as a three-phase contactor, a current transformer associated with each power conductor coupled to the contactor, and a transformer associated with the contactor. The current transformers are coupled to the control circuit which controls the supply of power to the solenoid of the contactor based upon the level of current flowing in the power conductors connected to the contactor. The solenoid of the contactor is connected to at least one power conductor and maintains the contacts closed when the solenoid is energized. The transformer is magnetically coupled to the windings of the solenoid and produces the power required by the control circuit when the solenoid is energized and the contacts of the contactor are closed.

Abstract: A self-configuring photoelectric control circuit for controlling operation of a load based on ambient light. The photocontrol circuit comprises a photocell responsive to ambient light, a heating resistor connected to the photocell, a bimetallic element in proximity to the heating resistor and movable in response to generation of heat from the heating resistor. A switch is operated by the bimetallic element and is connected between an input connected to a power source and an output connected to the load. A series resistor is connected to the heating resistor and a shunt is connected across the series resistor to provide a current bypass around the series resistor for operation with a low voltage power source, for instance 120 volts. The shunt is maintained in a flexed condition to form the bypass and a connection of the shunt across the series resistor is formed of a meltable material.