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: The safety circuit of the present invention is connected to a drive control circuit for applying driving signals to a plurality of switching devices connected to respective stator coils of the brushless D.C. motor at a predetermined timing, and sequentially supplying a driving current to each phase of the stator cells. The safety circuit is adapted to simultaneously detect the driving signals and generate a cut-off signal for cutting off the driving current supplied to each of the stator coils in the event that the driving signals are simultaneously applied to the switching devices in controlling a driving operation of the brushless D.C. motor.

Abstract: Protection of induction motors and generators is provided to allow rapid reclosure of the power supply or fast transfer from one power supply to an alternate supply. A switching sequence is disclosed in which motor stator windings are short circuited immediately following interruption of the supply voltage. Said short circuit quickly discharges to a safe value the energy stored in the rotor of the induction machine, allowing the short circuit to be removed and safe reconnection to the power supply to be accomplished without further delay.

Abstract: Motor control circuits having solid-state switching elements are commonly used on industrial vehicles such as lift trucks. A short circuit condition in the motor circuit can cause catastrophic failure of the semiconductor switching element. The instant invention detects such a short circuit condition and modifies the motor control signals supplied by a chopper circuit to a switching element. The apparatus includes a trigger circuit for receiving the motor control signals and sensing a voltage across the motor produced in response to electrical power delivered from a power supply.

Abstract: A protection circuit for the power transistor of an automotive motor control circuit. The protection circuit comprises a protection transistor, a resistor, and a Zener diode. The emitter-collector circuit of the protection transistor is connected in series with the resistor across the primary conduction path of the power transistor, with the resistor connected across the conduction control terminals of the power transistor. The Zener diode is connected in series with the emitter-base circuit of the protection transistor across the motor, with the Zener diode poled to oppose current flow through the emitter-base circuit. Transient inductive voltage generated across the motor upon removal of an externally applied control signal exceeds the reverse breakdown threshold of the Zener diode and biases the protection transistor conductive.

Abstract: A pre-expander for polymer beads is disclosed which includes a pre-expansion chamber having an agitator therein. The agitator is driven by an electric motor. The power requirements of the motor are monitored to determine the resistance which the beads are offering to motion of the agitator. The resistance to motion increases as the beads expand. Pre-expansion is stopped when the resistance offered by the beads results in a predetermined power requirement.

Abstract: A brushless DC fan with a winding supply circuit having an internal voltage regulator can afford current limiting and thermal protection and provide various desired fan speeds without alteration of the basic fan circuit, the windings, or other manufacturing items. A voltage setting circuit element can set fan speed externally and can be used to establish various fan speeds. An internal voltage establishing circuit element sets the maximum speed. The regulator replaces the fan's protective thermistor to shut down the voltage to the windings when locked rotor occurs. Bringing out a lead for the purpose of connecting a speed controlling resistor, thermistor, or active programming means to the internal circuitry enables the fan's end user to alter operation as needed.

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: A H-switch circuit is disclosed for rotationally driving a DC motor in a forward or reverse direction. The H-switch circuit comprises overcurrent-detecting circuits for four output transistors, which are respectively provided in order to detect the output transistor having an overcurrent, a circuit for generating an output signal upon detecting an overcurrent an integrating circuit controlled to be in a charge or discharge state according to the output signal representative of an overcurrent condition, and a circuit for turning off the output transistors when the integrating circuit is in the charge state and setting the integrating circuit to a discharge state. The charge and discharge operations of the integrating circuit are intermittently repeated until the overcurrent condition of the output transistor ends.

Abstract: The rotor of a brushless synchronous machine, such as an alternator exciter machine, includes a field winding and a rectifier for applying full wave rectified power to the field winding. To protect the rectifier from excessive inverse voltages when such voltages are induced in the field winding, for example during motor starting, alternator paralleling, etc., the present invention employs an excessive voltage sensor and a triggerable bypass circuit for bypassing such excessive inverse voltage from the rectifier when the sensor senses such excessive inverse voltage. The sensor preferably includes a solid state relay capable of assuming either of two output conditions, depending on the magnitude, and with a prescribed input circuit, the polarity, as well, of a voltage induced in the field winding.

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 washing machine control circuits of the type in which a semiconductor controlled rectifier SCR is arranged in series with the motor M in order to control the speed of the motor, a short circuit fault of the SCR can result in damage to the machine.A bistable device BD is reset at each zero crossing of the applied mains voltage and is set in each half cycle only if the voltage across the SCR reaches a level which cannot be reached if the SCR is short-circuited. A logic circuit LOG detects any non-setting of the bistable device for three or more consecutive half cycles of the same or alternating polarity and responds thereto by disconnecting the supply to the motor (contact R1).

Abstract: A microprocessor control motor starter is utilized in which the microprocessor measures the status of AC input signals which are coupled thereto by way of an isolating electro-optical device. The electro-optical device provides a square wave output signal. Thirty-six samples are made to determine if the output signal is at a digital "1" level or a digital "0" level. If more than 18 digital "1's" are found, that is an indication that the device has failed and a trip operation is initiated by the microprocessor. If less than 18 but greater than some arbitrarily chosen small number such as 6 is found, that is an indication that the switch empowering the optoelectrical device is in a closed but valid disposition. If a number less than 6 is found, that is an indication that the switch is in the open disposition. If the device is failed, the microprocessor will trip the motor.

Abstract: A microprocessor control motor starter is utilized in which a capacitor-backed random access memory is utilized to store certain critical data about the status of a motor so that if the power supply voltage temporarily drops below a certain value the critical information will not be lost. The microprocessor which controls the motor attempts to reinitialize itself as in the case long term power outage. A subroutine is provided which determines whether the motor can immediately be placed in the state it was in before the power outage occurred, or whether an automatic restart may take place, or whether the motor must be operator restarted manually.

Abstract: An apparatus for detecting and indicating the motion of electric motors includes a voltage sensing module which can be connected to the power terminals of any known type of electric motor and a display module. In the primary embodiment of the invention the voltage sensing module senses the applied or self-generated voltages present between the motor windings, and when no voltage is present, the display module provides an output which may be an electrical signal, or a visual, tactile or audible display. The apparatus is inherently reliable and fail-safe. A failure of components within the apparatus causes a display module output indicative that the motor is running when in fact it is stationary.

Abstract: Electric motor starter circuits for operating motors which cannot be restarted under load, but which maintain sufficient momentum during merely momentary interruptions of AC power to continue normal operation upon power restoration. Conventional motor starter circuits drop the motor off line, even in the event of momentary interruptions. The starters disclosed herein prevent unintended and unnecessary equipment down time as a result of AC motor starters dropping out during mere momentary power interruptions through the provision of a delayed drop out circuit including a DC voltage storage capacitor connected to the coil of the motor starter relay subsequent to the initiation of normal AC energization. In one embodiment, actual motor rotation is sensed to determine when to allow the motor starter relay to drop out.

Abstract: An adjustable-frequency three phase motor control system (2, CSI, M) is provided with a spike voltage clamp (SVC) to control the magnitude of voltage spikes generated during commutation of the current source inverter (CSI) thereby to protect the low voltage power devices (12a-c, 14a-c, SCRl-6) from damage. This spike voltage clamp comprises a rectifier bridge (32) connected to the output terminals (01, 02, 03) of the inverter (3) a storage capacitor (C) connected across the rectifier bridge output terminals, and a spike voltage dissipating resistor (Ra, Rb) and a gate turn-off thyristor (GTO) connected in series across the capacitor. A clamp control circuit (CC) precharges the storage capacitor and senses an increasing voltage thereon in response to voltage spikes across the motor terminals and gates the thyristor (GTO) to allow the resistor to dissipate a portion of the energy of the voltage spikes thereby limiting the magnitude of the voltage spikes.

Abstract: A molded submersible well motor comprises a hollow cylindrical frame 4 formed of resinous molding material into which a stator assembly having stator cores 2 and coils 15 is molded. End brackets 10, 11 also formed of resinous molding material are detachably secured to opposite ends of said frame to close the openings thereof. A surge absorber unit 6 is molded into the frame, and a starting switch 14 for said motor is molded into end bracket 10.

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 pulse control circuit for a d.c. series motor having an armature and two oppositely-wound field windings, comprises a contactor in series with the motor, two main thyristors each connected in series with the armature and a respective one of the field windings, means for controlling the mark-to-space ratio of conduction of each thyristor, one or other of the main thyristors being brought into operation in dependence upon the desired direction of drive of the armature, means for sensing failure of commutation of the main thyristor, and means for causing opening of the contactor in response to such sensing. The control circuit includes means for firing the other main thyristor immediately commutation failure is sensed, thereby to limit the net field flux and motor torque in the period during which the contactor is opening.

Abstract: Circuit interrupter switchgear including a drawout unit mounted within an enclosure and operable between engaged and disengaged positions by means of a drive means having a two-way position actuated drive clutch. The position actuated drive clutch has an engaging means that is responsive to a sensing means for selectively engaging and disengaging a torque source with the drive means according to predetermined positions of the drawout unit.

Abstract: An electrically surge protected motor having a submersible housing (10) can be manufactured and tested for insulation weaknesses by first assembling the motor components in the housing (10) without completing a path to ground therethrough. Then the windings (11, 12) of the motor may be subjected to a voltage surge greater than the voltage magnitude at which the motor is to be surge protected. After completion of the test, a path to ground through an impedance device (17) which establishes the voltage magnitude at which the motor is to be protected may be completed. Several alternative grounding devices (23, 24, 25, 26 or 28) may be provided externally of the housing (10).

Abstract: Apparatus for use with an environmentally controlled electronic system to prevent damage by supply line voltage reduction in which an air conditioning motor is connected across the supply line to the electronic system, a device is connected in the supply line upstream of the motor connection for sensing power flow in a direction away from the electronic system when the supply line voltage is reduced and the motor operates as a generator, and a switch is interposed in the supply line between the motor connection and power supply which opens in response to reversed power flow to direct power from the motor operating as a generator to the electronic system.

Abstract: This is concerned with a sensing control for a vacuum cleaner to sense the speed of the beater brush so that when it becomes clogged or jammed and tends to slow down, the control will automatically disconnect all power from the drive motor to thereby protect both the motor and any drive belts that are used. Some aspects are usable with either a canister or an upright vacuum cleaner and some are specifically concerned with an upright unit.

Abstract: A protective circuit is provided for a brushless excitation system using a rotating rectifier assembly to supply field excitation to a synchronous generator. A thyristor is connected across the generator field winding and made conductive when the field winding voltage exceeds a preset level to shunt the field winding and protect the rectifier diodes against high reverse voltages.

Abstract: A diesel electric locomotive has a dynamic braking system including a plurality of traction motors connected across dynamic braking grids. Air blowers for cooling the grids have motors which are connected across the grids. The failure of any motor is detected by monitoring the voltage across the motor with respect to a reference potential. The reference potential is developed in a bridge arrangement wherein the bridge imbalance is detected by a current sensor or by a reference potential generated in another motor circuit where another current sensor is used to detect a variance from the reference value. A circuit responsive to failure signals but voltage isolated from the traction motor circuits actuates an indicator as well as a relay for diminishing or terminating the dynamic braking function.

Abstract: A circuit for protecting single phase induction motors of the type having a start winding connected in series with a start/run capacitor. The circuit contains a resistance bridge wherein the motor start winding forms one leg thereof. A d.c. signal is applied to the input terminals of the bridge. A filter is connected to the output terminals of the bridge so that a relatively ripple free d.c. output signal from the bridge can be applied to the positive input terminal of a d.c. comparator, the negative terminal of which is connected to d.c. reference ground. A reference resistor in a leg of the bridge adjacent the start winding is selected so that the bridge is unbalanced to present a positive d.c. signal to a terminal of the comparator so long as the resistance value of the start winding is less than the value of the reference resistor.

Abstract: The voltage that occurs across the run capacitor of a permanently split capacitor type motor when the motor is in operation is quite high compared to the voltage that is present if the motor is stalled. These different voltage conditions are sensed through the use of a voltage pickoff to control an optical type isolation circuit which in turn controls a switch means to energize a fault indicator.

Abstract: A solid state electronic circuit for protecting a single phase induction motor against excessive loading by comparing motor start winding voltage with motor source voltage is disclosed, wherein the circuit automatically removes the motor from its driving source upon the occurrence of such excessive loading. An additional feature includes comparing start winding voltage with source voltage to remove the motor from its driving source upon the occurrence of excessive start winding voltage and corresponding excessive high motor speed. A motor starting circuit to permit the start winding voltage to rise to its normal running level and a time delay restarting circuit to permit the motor to automatically restart after elapse of a selected lock out period following removal of the motor from the source due to insufficient or excessive loading is also provided.

Abstract: A circuit for detecting whether, or not, a three-phase load is correctly connected to a three-phase supply employs an inductance, capacitor and resistor connected in the three branches of the load circuit so as to generate a single phase output signal when connected to the supply, to voltage of the signal depending upon the connection to the supply. The circuit requires only three wires and not connected to a ground, or neutral. The output signal controls a reversing switch to ensure that the load is always automatically connected correctly; in a preferred form only one of the voltages is sufficient to light a source of radiant energy to activate a sensor to energize the reversing switch.

Abstract: A low voltage protection circuit for an air conditioner compressor which employs a series of diodes to control the application of an a.c. source potential to the resistive heater element of a conventional thermally responsive switch. The diode circuit maintains the heater element directly across the source potential at all times when the thermally responsive switch is open, but only during alternate half-cycles of the source potential when the thermally responsive switch is closed to thereby protect the compressor against potentially damaging low voltage conditions while reducing the power consumed by the heater element during periods of normal source voltage level.

Abstract: The disclosed Leonard type elevator system comprises a reversible converter for controllably driving a DC motor, and an AC voltage detector and a DC voltage detector connected to the AC and DC sides of the converter respectively for detecting the voltages developed on the respective sides of the converter. When a difference in detected voltage between the two detectors exceeds a predetermined magnitude due to a decrease in the AC source voltage, a comparator produces an output serving to disconnect the DC motor from the converter. Also the comparator may produce such an output when the converter receives regenerative power from the DC motor.

Abstract: An electrical device is connected to the magnetic starter of an electrical motor to protect the motor windings from a loss of power on one or more input lines of a three phase power source. The device includes two transformers each being connected across two input lines and having one input line in common with each other. The transformer secondaries are each connected in a relay circuit so that a voltage on the secondary of each transformer above a predetermined value will actuate the relay in its respective circuit. The contacts of both relays are connected in series with each other and with the magnetic starter of the electrical motor so as to actuate the magnetic starter when both relays are closed. When the voltage on any of the three input lines drops substantially below a normal operating level, one or both of these relays will open, immediately turning off the magnetic starter and shutting down the motor to prevent damage to the motor windings.

Abstract: This invention relates to the protection of power transistors in an H configuration power amplifier which drives a D.C. motor. When the amplifier is switched off, it may be possible for the base terminals of the transistors to be turned "on" which results in the transistors conducting. If two series transistors conduct, the resulting short circuit may damage or destroy the transistors. This invention provides an easy and economical apparatus for protecting the transistors in the power amplifier by grounding the base input terminals of the power transistors during all times when the transistors are switched "off.

Abstract: An apparatus for protecting a synchronous machine from a field overvoltage is disclosed. The apparatus comprises a field excitation control circuit which is impressed with the armature voltage of the synchronous machine so as to provide a DC power supply for producing a DC output to excite the field winding of the synchronous machine, a first discharge circuit which is adapted to discharge the stored energy of the field winding when the synchronous machine is to be tripped under predetermined conditions, and a second discharge circuit for reducing the field voltage by allowing a field current to flow therethrough in response to generation of an overvoltage whose absolute value is higher than a predetermined level, across the field winding.

Abstract: A method and apparatus for detecting and correcting the occurrence of flashover in a direct current electric motor. The polarity and magnitude of voltage on the field winding of the motor is continuously monitored. Detection of a sudden reversal of the polarity of the field voltage accompanied by a rapid increase in magnitude results in the generation of a flashover signal. The flashover signal is coupled to power controlling elements regulating power supplied to the motor and is effective to force removal of power from the motor. In a preferred embodiment the apparatus is disclosed in a two-motor system with two field windings serially connected such that the field voltage monitoring is accomplished on a differential basis.

Abstract: Apparatus for generating minimally delayed closing instructions for turbine valves of turbo-generator sets in the event of power system short circuits wherein major faults resulting in a drop in the system voltage are detected and act upon the valve means controlling the fluid flow to the turbine in such manner that a rapid closure of the valve means prevents the turbo-generator from falling out of step in the case of a sustained fault condition. A provisional valve-closing signal is produced upon a predetermined drop in the system voltage but this is cancelled in the event that the ensuing acceleration of the turbo-generator set does not increase to a predetermined level within two revolutions of the set.

Abstract: A protection circuit is provided which incorporates a reed relay whose contacts form the circuit breaker of an electrical appliance. The winding of the reed relay is supplied with a rectified alternating current derived from a current transformer coupled to the supply line to the appliance. In order to avoid periods of zero current in the winding, the winding is also supplied with a rectified alternating current from a source which is out of phase with that supplying the supply line. Failure of the current on the line will cause the contacts to open. Preferably the relay has a set of self latching contacts to prevent re-energization of the winding once de-energized. A manually operable reset switch is provided in series with the self latching contacts.

Abstract: A motor protector for three-phase electric motors includes two independent sensing transformers for simultaneously sensing the voltage across two phases of a three-phase power supply to detect failures in all of the power lines including either the primary or secondary side of a line transformer. A first relay is actuated by the electric power sensed across the one phase and a second relay is actuated by the electric power sensed across said other phase through a set of contacts of the first relay for disconnecting the second sensing transformer from the power supply when there is a failure that results in a reduction in voltage in the one phase to prevent production of feedback voltages through the phase windings of a line transformer. For a wye-delta line transformer configuration the one phase is a high leg and the other phase is the low leg.

Abstract: Apparatus for overvoltage protection of the field winding of a synchronous dynamoelectric machine. A protective spark gap device is electrically connected in parallel across the field winding of the machine and is designed to weld itself into a short-circuit when the voltage across the field winding increases to an unacceptable value. The weldable spark gap provides a positive indication of problems in the field circuit and at the same time protects the field circuit from damage from continued operation. The protective spark gap is not self-restoring and therefore must be removed and replaced before operation is resumed.

Abstract: Circuitry for rapidly switching off the power to a universal motor upon sensing of overloading of the motor. Sudden motor overloading results in rapid speed reduction that is detected by measuring the voltage drop across the motor armature. The circuitry detects this drop and removes a gating signal to a triac switch in series with the motor to remove the power to the motor within one cycle of the applied AC.

Abstract: In a protection circuit for a device such as a motor, the unused half or a dedicated half of an AC signal on the secondary of an isolation transformer is sensed to disconnect the AC line from the device if the line voltage is abnormal, such as being too low. Conveniently the protection circuit is employed in a complete motor protection system which may include a thermal protection circuit, a low oil pressure protection circuit, and/or a time delay circuit to prevent start-up too soon after shut-down.