Abstract: A process for controlling the speed of an electric motor. A reference value of motor temperature is provided and directed to a summing junction. The actual temperature of the motor is sensed and also directed to the summing junction. The two values are summed and employed as a reference of motor current. This reference is directed to a second summing junction while the value of actual motor current is sensed. The actual value is also directed to the second junction. These last two values are summed at the second junction to provide a reference for adjusting motor speed.

Abstract: A thermal model of an electric apparatus such as a transformer or motor, from which signals can be obtained representing temperatures of the conductors and of the adjacent core material, includes storing first and second values, respectively, representing conductor temperature and core material temperature. The magnitude of the current(s) in the apparatus is sensed and a digital signal representative thereof is added to the first value to represent heat generated in the conductors. Values are determined for both heat transferred from the conductors and heat transferred into the apparatus core based on the difference in the first and second values. The value representing heat transferred from the conductor is subtracted from the first value to give a new first value and the value representing heat transferred to the core is added to the second value.

Abstract: An arrangement for cooling an electric rotating machine such as an alternator of an automotive vehicle by means of a fan which is intermittently driven in accordance with the cooling requirements of the electric rotating machine. A heat source is associated with the electric rotating machine which is representative of the degree of heating of the rotating machine. The heat source may be the radiator of the rectifier diodes of the alternator. A heat sensitive means in the form of a spring of "memory alloy" controls the coupling/uncoupling with respect to the shaft of the rotating machine of the fan which is mounted free for rotation coaxially of the shaft of the machine. The heat sensitive means is in heat exchange relation with the heat source. The spring, for example, operates a lever which activates a control rod passing through the hollow shaft to control the coupling or clutching of the fan with respect to the rotating shaft.

Abstract: A generalized real-time thermal model of an induction motor produces values indicative of the transient and steady state temperature condition of the motor. Each of these values is compared with respective predetermined limits and power to the motor is removed when any value exceeds its respective limit in order to prevent damage to the motor.

Abstract: A variable speed drive for an AC motor has features to reduce the speed of the motor if excess temperature is encountered in the variable speed drive system. The system has a rectifier that converts AC supply voltage into DC voltage on the positive and negative rails. Frequency switches switch the DC voltage to power conductors in a sequence and at a rate to determine the selected frequency. The frequency switches are controlled by a DC demand voltage. A temperature sensor provides an electrical response corresponding to the temperature in the system. The temperature response is compared to a reference voltage, and if it exceeds the reference voltage, the comparator provides an output that draws down the demand voltage by a value corresponding to the difference. Lowering the demand voltage lowers the speed of the motor to allow the system to cool under reduced load conditions.

Abstract: An apparatus for predicting the remaining useful life of a motor uses the temperature and past history of the motor to determine the amount of insulation degradation for its prediction. The remaining useful life projection is provided at a display and may be used to trip the circuit breakers supplying power to the motor when projected life is shorter than the expected life or may be used to issue a warning that the rate of motor degradation exceeds the rate necessary to achieve the expected life for the motor.Motor protection is provided by tripping the circuit breakers supplying power to the motor before the actual temperature of the motor windings exceeds the temperature at which catastrophic and irreversible insulation failure would occur while not tripping the breakers for momentary transients.

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: Apparatus and method for protecting a squirrel cage induction motor against excessive temperatures which can occur in the rotor, provides a thermal model of the rotor. The thermal model has three regions A, B and C representing the starting portion of the rotor conductor, and the rotor core. The rotor is frequency sensitive and currents of higher frequency induced in the conductors tend to be in region A, and currents of lower frequency tend to be in region B. Equipment connected to the stator winding determines values for the positive and negative sequence components of the supply for the fundamental frequency and preferably also for the second and third harmonics present, and provides signals representing these values. Heat calculation circuitry receives the values for all the positive and negative sequence components and a signal representing speed, determines the currents that would be induced in regions A, B and C, and derives equivalent currents which would produce the same heat.

Abstract: A protective control system is provided for stopping an engine-driven pump when a fault condition such as low oil level, low oil pressure or high temperature occurs in the engine. The protective control system includes an electric battery, a solenoid valve regulating fuel (or air) flow to the engine and energizable from the battery, an electronic circuit energizable from the battery for controlling the solenoid valve, and fault-sensing switches for controlling the electronic circuit and shutting off the fuel supply to stop the engine upon occurrence of a fault. The electronic circuit includes a solid state voltage regulator device connected between the battery and the solenoid valve, and this device includes an adjustment terminal which is biased to control the power supply to the solenoid valve. The electronic circuit further includes a transistor which controls the bias on the adjustment terminal and the transistor, in turn, is responsive to operation of any one of the fault-responsive switches.

Abstract: The winding temperature of an asynchronous motor is determined for control as regards overheating, in that a value representing the prevailing motor resistance is calculated on the basis of the amplitude of the voltage (2) impressed on the motor, the amplitude of the motor current (1), the phase angle (8) between the voltage and the current, as well as the slip (3), derived from overtones in the current flowing in the input lines to the motor. The resistance value is converted (15) to a corresponding temperature value which is used for updating a winding temperature value produced in parallel on the basis of the difference between the dissipated power and the cooling loss power, when the slip lies within predetermined limits.

Abstract: A protection device and circuit for a fluid pump or the like including a motor control relay MS for actuating relay contacts MS-1, MS-2, MS-3 that control the communication of power to a drive motor 10a, and a manual reset motor protection device 24 that deenergizes the control relay in response to sensed malfunctions. The motor protection device comprises a manual reset motor protector 40 having switch contacts 42 connected in series with the motor control relay and a tripping coil 44 which, when energized, opens the switch contacts. A current shunt path 46 including serially connected pump assembly mounted sensors 48, 50, normally shunts current around the tripping coil and is interrupted in the event of a sensed malfunction, causing the energization of the tripping coil which opens the switch contacts and deenergizes the drive motor. The switch contacts must be manually reclosed to reactivate the pump assembly.

Abstract: A thermoswitch is physically located on a portion of the current supply connector between the current source and the exciter winding of the starter motor. The portion, constructed as a simple strip with flaps holding the thermostat, influences the temperature-dependent control portion of the thermoswitch according to heating in the armature, field winding, and brushes of the starter motor. The thermoswitch turns OFF the starter system by interrupting current supply to the kick-in starter relay.

Abstract: An electronic control system to automatically determine the validity of an apparent overheating signal from an overheat monitor of a gas-cooled dynamoelectric machine and reduce machine load or indicate a monitor malfunction. Upon receipt of an apparent overheat signal by the control system, filtration of the monitored cooling gas is automatically initiated to remove pyrolysates released into the gas by overheated elements within the machine. A normal monitor response is thereby effected, provided the overheat signal is valid. If filtration of the monitored cooling gas fails to elicit a normal response within a preselected time period a monitor malfunction is indicated. The control system initiates a scheduled reduction in machine load either subsequent to validation of overheating or as verification is initiated, and if a valid indication of overloading persists, trips the excitation and remaining load from the machine.

Abstract: Disclosed is an overload protective circuit for an electric motor which is adaped to monitor and track motor temperature as a function of an operating parameter, namely armature current. The motor's armature current is sensed and converted to a multi-bit digital signal which is used to address a programmable read only memory (PROM) which has been pre-programmed with discrete digital values of temperature for a plurality of armature currents for the motor being protected. The digital address signal for the armature motor current is periodically updated at a relatively rapid rate and depending upon the armature current sensed, multi-bit temperature values are outputted from the PROM to a digital latch which operates a relatively slower rate to output another address back to the PROM so as to predict what the temperature will be at the next time increment based on the present current value and the present temperature.

Abstract: A protective disconnect to prevent overheating of electrical apparatus is described. The device consists of a cutting member accepting a conductor and capable, upon closure, of severing said conductor. The cutting member is surrounded by a thermoconstrictive material which, upon being subjected to heat at a certain temperature, actuates said member.

Abstract: A flux sensor is provided for measuring magnetic flux in laminated cores, and especially for measuring the axial flux in the end regions of the stator cores of large generators. The sensor comprises a flat, multi-turn coil of fine wire enclosed in an insulating enclosure which includes a pressure-supporting member of greater thickness than the coil. The sensor is thin enough to be placed between the laminations of a generator core and the high clamping pressure is carried by the pressure-supporting member which protects the coil. The leads are flat conductors brought out between the laminations to the periphery of the core. Such a sensor can remain permanently embedded in the core since it does not effect the core structure.

Abstract: An indication is derived of the thermal properties of a constant load motor during acceleration and deceleration periods without actually monitoring thermal properties of the motor. The motor is accelerated and/or decelerated in response to command pulses so there is a rotational speed change during the acceleration and deceleration periods. In respnse to the command pulses, the charge on a capacitive means is changed so the charge change is proportional to (1) the change of the motor rotation speed during the periods and (2) the reciprocal of the periods. In response to the charge change there is derived an indication of the thermal properties as a function of the electrical, thermal and mechanical characteristics of the motor.

Abstract: A three phase motor is constructed with each of the three phase windings thereof split in half so that the motor may be selectively connected for energization from either a relatively high or relatively low source. Motor protectors are provided in the form of a three pole automatic resetting overload relay means and two thermostatic switches. The heaters for the individual poles of the overload relay means are connected in series with a half section of the individual phase windings and do not have to be changed when either high or low voltage energization is selected for the motor. The thermostatic switches are embedded in two of the other three winding sections but electrically insulated from the motor winding. The control contact means of the overload relay means and the thermostatic switches are connected in series with the energizing coil of the electromagnet for the contact through which the motor is connected to its energizing source.

Abstract: An SCR is connected across one of three line contacts which couple the power lines to the windings of an a.c. motor. When the line contacts are opened to shut down the motor, heating current is applied to one of the motor windings through the SCR to raise its temperature above the ambient dew point. The SCR is fired every cycle of the line current and the firing angle is controlled in response to a command signal to provide the proper amount of heating current in the motor winding. The command signal is generated by summing a preselected reference signal with a negative feedback signal which is indicative of the amount of motor heating.

Abstract: An electrical insulating pocket receptacle for securing a sensing element within electrical windings of a motor includes a sheet-like flexible material having a body support portion supporting a pocket within which the element is located and having four tabs projecting from the body support portion. The tabs on the opposite side of the pocket are located within the winding and hold the pocket in place within the winding with an exposed open end for insertion and removal of the element. A wire holding tab is secured to one of the support tabs and is folded upon itself and secured against the coil end turns by the end tie cords. A third locking tab is pulled down over the spade of the sensing element to securely hold the sensing element in place. A fourth tab may be used to fold over the pocket to additionally insulate the sensing element from the windings of the motor in which the insulating pocket receptacle is inserted.

Abstract: A prime mover has a stationary assembly with a generally annular grouping of winding end turns extending therefrom, and a structural member of the prime mover is spaced from the winding end turn grouping. An overload protector device is disposed in abutting engagement with a part of the winding end turn grouping, and means is associated with both the stationary assembly and the overload protector device and arranged in biasing engagement with the structural member for positioning the overload protector device in the abutting engagement thereof with the part of the winding end turn grouping.A method of assembling a device with the prime mover is also disclosed.

Abstract: A plastic coil bobbin has a recess with the precise dimensions of a thermal fuse. On one side, the recess is open so that, as the coil is wound on the bobbin, successive layers of coil wire form a wall-like surface closing that open side. As the fuse is press fit into the recess, it is also forced into intimate contact against the wall of wire. Thus, the only material between the fuse and wire is a thin plastic shell forming the fuse housing. Since the fuse rating takes this wall thickness into account, there is effectively no thermal insulation between the coils and the fuse. Accordingly, under overheating conditions, the fuse opens a circuit when there is overheating and before a fire can start.

Abstract: Apparatus for mounting a thermal overload protector to the compressor motor of a hermetically sealed compressor unit. The apparatus includes an arcuate bracket which follows the radial curvature of the stator laminations and which is mounted to the stator end face by bolts simultaneously used to secure the laminations in place. A hollow protector holder made of insulating material is received by a sliding snap-fit on an upstanding plateau in the bracket and is held against rotation therein, the inside of the holder being specifically contoured to receive and hold an overload protector of preselected shell geometry.

Abstract: A motor is electrically coupled to a power source through a motor starter. The motor starter is selectively operated by a relay to connect and disconnect the power source to the motor. A counter is set whenever a select motor temperature condition exceeds a predetermined level to provide an indication of the number of motor starts. The relay is operated to cause the motor starter to disconnect the power source from the motor whenever the motor fails to run continuously during a given time period following a predetermined number of starts.

Abstract: Apparatus for protecting the armature of an electric motor against excessive temperatures comprises a resiliently compressible and expansible pad in the armature circuit and composed of thermally sensitive, non-conductive material containing a plurality of conductive particles engageable with one another when the pad is in a compressed condition to establish a conductive path through the pad. The pad normally is maintained in a compressed, conductive condition by resilient force applying means which is of such resilience as to permit expansion of the pad in response to an increase in its temperature and render the pad non-conductive.