Abstract: A safety module for a motor speed control circuit, when speed control circuit has a failure mode in which full power is applied to the motor being driven by the speed control circuit. The safety module has a high pass filter coupled to a variable voltage power output of the speed control circuit, and a threshold member coupled to an output of the high pass filter for passing a signal only if a change in the signal exceeds a predetermined value. A semiconductor short-circuiting switching device is coupled to the threshold device and is also coupled to the power terminals of the motor and to the output of the speed control circuit for shorting out the output of the speed control circuit responsive to an abrupt increase in a signal at the output of the speed control circuit which exceeds the predetermined value at the output of the speed control circuit.

Abstract: A motor-driven power steering control system of a motor vehicle for assisting a driver in manipulating a steering wheel by making use of an assist torque generated by a reversible motor which is operatively coupled to a steering mechanism of the motor vehicle includes an electric reversible motor mechanically coupled to a steering system of the motor vehicle through an electromagnetic clutch, a motor drive circuit, an H-bridge switching driver circuit for driving the electric reversible motor in forward or reverse direction under the control of the motor drive circuit, and a clutch control circuit for controlling the electromagnetic clutch.

Abstract: An apparatus for thermal protection of an electric motor is provided, including a monitoring device for generating a signal representative of the current in a conductor supplying electrical power to the electric motor. A control circuit processes the current signal and utilizes the processed signal and motor thermal parameters, including the thermal resistance and thermal capacitance of the rotor, to generate signals representative of the temperature of at least the rotor. A comparator circuit, which may be part of the control circuit, compares the temperature signals to reference maximum temperature signals and produces a control signal when the temperature signals and reference signals satisfy a predetermined relationship. The control signal may be applied to a contactor to interrupt current to the motor. A method for thermal protection of an electric motor is also provided, including thermal modeling of the rotor temperature.

Abstract: A disconnect switch circuit for disconnecting an under-voltage battery from a hard disk drive connected between a voltage supply line and ground includes a MOSFET device connected between the battery and the voltage supply line, control means responsive to the supply voltage on the voltage supply line for generating a control signal powering the gate of the MOSFET switch. The control signal turns on the MOSFET switch when the supply voltage is in normal condition and turns off the MOSFET switch when the supply voltage drops below an under-voltage limit, thereby beginning head retract in the hard disk drive.

Abstract: A pulse motor control device comprises, as additional component parts, a power-off detecting circuit, and a turning-off circuit. The power-off detecting circuit detects, when a driving switch is turned off, a dropping of a voltage supplied to a driving circuit and outputs a power-off detection signal. The turning-off circuit includes diodes and a control resistor. The diodes are connected respectively to control terminals of all driving transistors of the driving circuit. When the control transistor is turned on in response to the power-off detection signal, voltages of control terminals of the driving transistors are dropped to the ground level through the diodes, thereby turning off the driving transistors.

Abstract: A method and device for distinguishing between partial discharge and electrical noise in high voltage conductors such as in motor and generator stators, power cables, gas insulated switchgear and other equipment where high voltage insulation is subject to deterioration. A series of comparators sets a trigger threshold and a voltage range, set by a computer, whereby pulses falling within the voltage range are sampled at four short intervals and then four longer intervals to produce a general pulse width profile. The voltage range is varied by the computer so that a number of voltage ranges are sampled during each selected portion of an ac cycle. The pulse width of pulses falling within each voltage range is recorded by the computer, and displayed graphically. In a preferred embodiment the device is provided with two channels, for receiving a signal from each end of a partial discharge detector described in U.S. Pat. No. 4,949,001.

Abstract: An efficient fan drive circuit to drive a variable fan used in a power supply of a personal computer system. The fan drive circuit uses a diode to establish the minimum fan speed during operation in the normal temperature range. The bleeder resistor normally coupled between the fan and a negative output voltage is removed and replaced with a current source. The current source also serves to shut down the power supply if the fan is not operating properly or is not installed. A shut down circuit remains to shut down the power supply when excessive temperature occurs, or when the current source detects that the fan is malfunctioning or not installed.

Abstract: An apparatus and method for protecting an induction motor from momentary power loss in a three-phase, alternating current, power supply. The apparatus includes a circuit for detecting when the motor switches from a mode of operation as a motor to a mode of operation as a generator, and a microprocessor connected to the detector to receive the detection of a switch in mode of operation, and for generating a fault disconnect signal in response thereto to initiate disconnecting the motor from the power source. The method includes the steps of detecting when the motor switches from a mode of operation as a motor to a mode of operation as a generator and generating a fault disconnect signal in response thereto to initiate disconnecting the motor from the power source. The apparatus and method provide for robustness of the fault detection data, and for avoiding false detections of momentary power loss.

Abstract: A self-diagnosing apparatus for a brushless motor which has a voltage detection circuit for detecting drive current to the brushless motor, and for outputting voltage at one of different levels corresponding to a short circuit condition, an open circuit condition and other conditions. When the output of the voltage detection circuit is at a high (H) level, a short circuit condition is determined, whereas when that output is at a low (L) level, an open circuit condition is determined. When the output of the voltage detection circuit is at a level intermediate between "H" and "L" levels, and simultaneously when the output voltage does not pulsate, a motor lock condition is determined.

Abstract: A method of operating a brushless motor having a stationary assembly with at least two different energizable windings for producing spaced apart magnetic fields in time sequence, and a rotor adapted to rotate in response to the magnetic fields. The method includes the steps of simulating rotor position in accordance with the back emf condition of at least one winding, energizing a selected one of the windings in accordance with the simulated rotor position, sensing an underspeed condition when the motor speed is less than a minimum value for a length of time, and preventing energization of any of the windings when the motor speed is less than the minimum value for the length of time. An electrically commutated motor controller apparatus controls and speed of a variable speed motor compressor driven by an electrically commutated motor. A controller circuit includes a circuit for producing feedback signals representative of a back emf of the motor.

Abstract: A protective electronic relay is disclosed of the type which includes a feed source with a one-phase transformer, rectifying bridge, filter condenser and voltage regulator. Pickups are provided where one-phase signals are generated, connected to some diodes, connected to some capacitors and to a zener diode for the purpose of obtaining rectified, filtered and limited signals with a voltage level proportional to the line intensity of the protected motor. A multiple microswitch connected to some resistors permits presetting of the voltage level and nominal triggering intensity of a relay. An R-C network that can be timed in various scales comprised of resistors a capacitor and another multiple microswitch allows adjustment of the triggering time constant and is applied to that voltage level at the non-inverting input of an operational amplifier whose inverting input is at a reference voltage.

Abstract: Disclosed is a motor drive device with tacho-generator that can be configured as a back-up motor. This device is designed for the driving of a movable element. It comprises an electrical rotor motor with supply coil, associated with a tachometrical sensor inducing an electrical current in at least one electrical coil, a regulator circuit controlling the speed and the position of the electrical motor as a function of the servo signal delivered by said electrical coil and applied to the supply coil. This device further comprises means to continue the driving of the movable element in the event of the malfunctioning of the electrical motor or of its electrical supply. These means to continue the driving of the movable element are constituted by a failure detection circuit which, in the event of failure, activates switching means to connect the electrical coil of the tachometrical sensor to an electrical supply source. Application: improvement of the safety of a motor drive mechanism.

Abstract: A starter motor energized through a relay is protected from low voltages by a circuit which senses low voltages and turns off the motor relay via a transistor switch. A generator voltage sensing circuit also turns off the relay via the same switch when a generator voltage threshold is reached. For operation over a wide system voltage range, the coil of the relay is protected against high voltages by a chopper circuit which operates the transistor switch at a duty cycle of 100% at low voltages across the coil and lower duty cycles at high voltages. For a 12 volt relay the average current at higher voltages is maintained at a value approximating that obtained at a steady state 12 volts.

Abstract: The present invention provides a drive and control circuit for a single phase, brushless DC motor. The drive and control circuit includes an integrated circuit having a maximum rated voltage lower than the maximum net voltage of the overall circuit. Internal transistors in the integrated circuit are used to drive the emitters of two external power transistors which are connected to the windings of the DC motor. In this manner, a relatively inexpensive integrated circuit can be used to drive and control a DC motor having a much higher operating voltage.

Abstract: A control arrangement for electrical motors and motor vehicles includes measures which fulfill the requirements with respect to short circuits, protection against polarity reversal, load-dump protection, blocking against defective operation, reduced complexity, direct drivability from a computer unit, reduced disturbance spectrum and reduced inherent loss.

Abstract: An electronic safety circuit for a portable gas heater includes a transformer and half wave rectifier connected in parallel with a fan motor for charging a capacitor, and a solid state switching circuit, which may be either a pair of cascaded transistors, an SCR, or a Darlington switch, for applying a reverse polarity voltage across the solenoid of a solenoid operated gas valve to immediately turn off the gas valve in the event of loss of power to the combustion fan motor. The electronic safety circuit may be conveniently mounted on a PC board and enclosed in the combustion fan motor.

Abstract: A device for limiting the maximum and/or minimum speed of universal series- or compound-type electric motors. The device includes a first impedance element for limiting the maximum speed of the motor under light load (high speed) conditions to a predetermined value, and a second impedance element for limiting the minimum speed of the motor under high load (low speed) conditions. The limited maximum and minimum speeds of the motor give it operating characteristics which are similar to a shunt motor.

Abstract: A control system for an electric motor includes a detector associated with a regenerated power absorbing circuit for monitoring operation of the regenerated power absorbing circuit for detecting an abnormal condition thereof. The control circuit is responsive to detection of abnormality in the regenerated power absorbing circuit for controlling operation of an inverter in a fail-safe mode.

Abstract: An RC controller includes a circuitboard with a circuit for variably coupling power from a battery to the drive motor of a radio controlled model. The circuit includes braking componentry that produces a low resistance path in parallel with the motor in order to brake the motor under operator control. The braking componentry includes a flyback diode and a semiconductor device connected across the terminals of the drive motor. The flyback diode may be a separate component or a part of the semiconductor device. According to a major aspect of the invention, a fuse is provided in series with the flyback diode to protect it against damage in the event the battery is connected backwards. The fuse is placed to protect the flyback diode without introducing an undesired voltage drop between the battery and the drive motor. Various fuse placements are disclosed. Instead of a separate fuse, one embodiment includes an unfused flyback diode that doubles as a fuse.

Abstract: A controller includes a circuitboard with a circuit for variably coupling power from a battery to the drive motor of a radio controlled model. The circuit has positive and negative input terminals for connection to the battery and an output port for connection to the motor. The circuit also includes braking componentry that produces a low resistance path in parallel with the motor in order to brake the motor under operator control, and the circuit includes a fuse in series with the braking componentry for protecting it from damage in the event the input terminals are connected to the battery with the polarity reversed. An inventive fuse is disclosed that may be used with the controller or elsewhere. The fuse includes a conductive element of predetermined current rating and first and second connectors connected to the conductive element that are configured to plug onto first and second terminal posts with interference fits so that any component fatigue is substantially restricted to the fuse.

Abstract: A single phase, capacitor start electric motor is shown in which energization of the auxiliary winding is controlled by a triac. The triac is protected from excessive voltages caused by the vector sum of capacitor, line and induced voltages which can occur at turn-off of the triac. The triac is protected in several embodiments by a gated semiconductor switch serially connected to a current limiting or discharge resistor, both being coupled across the triac. The semiconductor switch has a voltage breakdown device connected in its gate circuit. When voltage across the triac exceeds a selected level the gated semiconductor is turned on thereby drawing sufficient current momentarily to limit the voltage across the triac to a safe level and allowing the capacitor to discharge its voltage through the auxiliary winding circuit. In another embodiment a stack of high voltage bilateral triggering devices is placed across the triac.

Abstract: A motor driver interface (MDI) circuit for an H-bridge electric motor drive apparatus is responsive to an enable signal to turn off all switching transistors in a not enabled mode and turn on the upper bridge transistors in an enabled mode and includes large resistors, sufficiently large to prevent motor activation therethrough, from the motor terminals to the power supply terminals to establish a bias voltage in the not enabled mode. Fault detection apparatus compares the voltages at the motor terminals with a first reference voltage apparatus in the not enabled mode and a second reference voltage apparatus in the enabled mode in response to the enable signal.

Abstract: A shunt element and a voltage detection circuit are connected in parallel across the armature of a universal series motor. At relatively light loads on the motor, the armature speed increases, thereby increasing the back e.m.f. of the armature. The voltage detection circuit causes the shunt element to conduct, and a shunt current flows through the field of the motor, thereby increasing the field and limiting the speed of the motor. Various embodiments are disclosed.

Abstract: An arrangement for detecting winding shorts in a rotor winding of an electrical machine having a drive shaft with a drive end directly connected to ground and a measuring element provided at the non-drive end of the drive shaft for recording the shaft voltage between the machine shaft and ground. The voltage measuring element produces an output corresponding to the shaft voltage, which is applied to an analysis unit. The analysis unit evaluates the even or fractional harmonic content of the shaft voltage and outputs an alarm signal in the event that the even or fractional harmonic content exceeds a predetermined value.

Abstract: A circuit for protecting electronic equipment such as computers, laser printers, fax machines, and the like from damage due to electrical transients associated with a temporary power interruption is connectable between a source of A.C. power and the electronic equipment. The circuit disconnects the equipment from the power source during a temporary power outage and maintains the equipment disconnected from the A.C. power until transients in the line voltage have abated. The circuit reconnects the equipment to the A.C. power source after a preselected time delay from the initial power interruption. The circuit keeps track of time during a power interruption without the use of batteries.

Abstract: An electrically surge protected motor (13) includes a housing (14) which when in a fluid is in communication with electrical ground. The motor (13) has an end ring (17) in contact with the housing (14), stator windings (15) within the housing (14), and power wires (21) which provide electrical power to the windings (15). A surge suppressor (23) is electrically connected between each power wire (21) and the end ring (17) and includes a gas filled chamber (31) within which are spaced electrodes (27). One of the electrodes (27) is electrically connected to the power wire (21) and the other electrode (27) is electrically connected to the end ring (17). The conductivity of the gas in the chamber (31) is such that at a predetermined voltage level in the power wire (21), electrical current will be diverted from the windings (15), pass through the chamber (31) between the spaced electrodes (27), and thereafter pass to ground through the motor housing (14).

Abstract: A system for detecting load has a first detector for detecting load on a generator based on the voltage in a circuit of an armature of the generator, and a second detector for detecting the load on the generator based on the voltage in a circuit inductively coupled to the armature circuit. An output of the first detector is compared with a first reference value by a first comparator and a first overload signal is produced when exceeding the first reference value. A second comparator is provided for producing a second overload signal when exceeding a second reference value. In response to the first and second overload signals alarm lamps are turned on for providing an alarm of the overload.

Abstract: A method and apparatus for controlling the operation of an oil well pumping unit in which the prime mover is a polyphase AC electric motor. The system comprises means for generating a plurality of signals representative of motor fault parameters including a motor winding overtemperature fault, undervoltage fault, and a phase imbalance fault. Upon occurence of a fault, a contactor in the motor supply leads is open to shut down the motor. After such shutdown because of undervoltage or phase imbalance faults the fault parameters are continuously scanned and once the fault has been cleared the motor is restarted. Where motor shutdown occurs because of an over temperature fault, the motor is maintained in a latched off shut down condition until an operator implemented reset occurs. An accessible counting memory is provided having separate registers for each of the fault conditions.

Abstract: An electronic starting motor control having low voltage protection. The starting motor has a solenoid coil which when energized causes solenoid contacts to be closed to energize the motor and to move a pinion into mesh with the ring gear of an engine to be cranked. A plurality of parallel connected field effect transistors connect and disconnect the solenoid coil to and from system direct voltage. When system voltage is below a predetermined value the field effect transistors are turned off and are maintained turned off until a start switch is opened. The system will not turn off the field effect transistors when short term voltages occur that go below the predetermined value. Various other circuits are disclosed for turning the field effect transistors on and off.

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: An electronic starting motor control system for electric starting apparatus of a type that has a solenoid including a solenoid coil. Energization of the solenoid coil causes solenoid contacts to close and causes a pinion to be shifted into mesh with the ring gear of an engine to be cranked. The current supply to the solenoid coil is controlled by a plurality of parallel connected field effect transistors that are turned on and off. The system has a fail safe circuit which operates to cause the wire bonds of the field effect transistors to open in the event that a field effect transistor fails by shorting. The system has an overvoltage protection circuit which during an overvoltage condition shuts off the supply of voltage to the gates of the transistors and shuts off the voltage supply to a plurality of control circuits that are coupled to the gates of the transistors.

Abstract: A motor control device controls a motor driving mechanism which drives a motor according to a motor drive signal for providing a normal drive signal and a locked condition signal. When the motor becomes overloaded while being driven by the motor driving mechanism according to the motor drive signal, the motor driving mechanism is controlled by controlling circuitry which inhibits the motor drive signal from being supplied to the motor driving mechanism. The controlling circuitry, while the motor is in the overloaded state, controls the motor driving mechanism so that power is supplied intermittently to the motor, or so that the supply of power for the regular and reverse rotation is given alternately. The controlling circuitry, when the load of the motor becomes normal, allows driving of the motor according to the motor drive signal.

Abstract: A protection circuit for preventing an over-current condition if the semiconductor power controller in an electric train power control circuit is defective. The power controller is connected in series through first and second switches to a D.C. power source. A capacitor is also connected to the power source through the two switches and through a charging resistor connected in parallel with the second switch. When the first switch is closed, the capacitor is charged through the first switch and the resistor. After the capacitor voltage reaches a set reference voltage during a predetermined time interval, the second switch is closed to permit the power control equipment subsequently to apply power to the driving motor of the train. If the capacitor voltage does not reach the reference voltage during the predetermined time interval, then the second switch remains open and the first switch is re-opened to completely disconnect the power control equipment from the D.C. power source.

Abstract: Motor control systems having solid-state components are commonly used on industrial vehicles such as lift trucks. Such solid-state components are easily damaged by excessive transient voltages. The subject invention includes a power supply for supplying direct current to a motor circuit, wherein the direct current has a nominal direct current voltage value and as associated transient voltage component. A pulse control circuit supplies current pulses from the power supply to a motor. A sensing device controllably produces a fault signal in response to the amplitude and frequency of occurrence of the transient voltage component exceeding a predetermined maximum value. An override circuit receives the fault signal and responsively modifies the current pulses delivered from the power supply to the associated motor.

Abstract: A snubber circuit comprising two stages regulates the gate current of a MOSFET in relation to the drain voltage at turnoff to clamp transient inductive voltages to a nondestructive level. At the onset of the turnoff, a current source is activated to discharge the gate capacitance, and the snubber controls the magnitude of such current in relation to the sensed drain voltage to stabilize the drain voltage at a nondestructive level. When the drain voltage approaches its limit value, a current injection circuit supplies additional current to the gate to sustain the MOSFET conduction, again in relation to the sensed drain voltage. When the inductive energy stored in the load is substantially dissipated, the drain voltage falls; at such point, the current injection circuit is disabled and the conduction of the current source is increased to complete the turnoff of the MOSFET.

Abstract: In a high voltage circuit interrupter (30) or recloser, an auxiliary undervoltage lockout mechanism (300) provides a backup lockout means to deenergize circuit contactor closing solenoid (78). Auxiliary undervoltage lockout device (300) provides a backup means to lock out recloser (30) after a period of time longer than the normal functioning time of the recloser to prevent damage to closing solenoid (78) in the event of low voltage or other unexpected conditions on the power line.

Abstract: System and method for detecting arcing faults in a dynamoelectric machine by monitoring the neutral lead of the machine for a radio frequency voltage produced by arcing, providing a warning signal in response to a change in the radio frequency voltage, and providing a shutdown signal in response to a radio frequency voltage greater than a predetermined level. An RF voltage coupler is capacitively coupled ot the neutrla lead, and a radio frequency monitor connected to the voltage coupler detects peaks in the RF voltage.

Abstract: In an active shaft ground system for maintaining a rotating shaft (4) of a machine substantially at ground potential, which system includes a circuit coupled to the shaft (4) for monitoring the voltage on the shaft (4) relative to ground and a brush (6) coupled to the circuit and contacting the shaft (4) for conducting to the shaft (4) a compensating current having an amplitude and polarity adjusted for maintaining the shaft voltage substantially at ground potential, there is provided shaft condition detection circuitry (18,20,24,26,28,34,36) coupled to the circuit for monitoring the voltage on the shaft (4) relative to ground and the current flowing between the brush (6) and the shaft (4) and for producing a fault indication when the voltage on the shaft (4) relative to ground is outside of a selected range at the same time that the current flowing through the brush (6) is substantially equal to zero.

Abstract: A safety device for a tool powered by an electric motor. It has a main switch, electronic controls, and a tachometer-generator. In order to provide a device for switching off a motor as a function of motor speed that is simple and economical and that will retain the same nominal switch-off value for the total life of the device, a relay is wired in parallel with the motor and controls the supply of power to the motor through a relay contact.

Abstract: An electrical circuit for providing electrical energy to an electric motor which operates a liquid pump. The motor and the pump are adapted to be submerged in the liquid which is pumped by the pump. The circuit disclosed herein senses the phase angle between the current and the voltage applied to the electric motor. When the phase angle indicates that the motor is operating without a load, the circuit deenergizes the electric motor. Thus, the motor and the liquid pump are protected against damage. Recognizing that harmonics may exist in the current flow through the motor, the circuit provides for obtaining a filtered signal proportional to the fundamental frequency of the current flowing through the motor. Thus, an accurate measurement of the loading of a motor is obtained. The circuitry of this invention also provides an accurate method of compensation for applied line voltage variations, so that a change in the applied line voltage does not produce a false indication that the motor loading has changed.

Abstract: There is disclosed a protecting apparatus for a secondary excitation type variable speed AC generator/motor having a primary winding connected to an electric power system and a secondary winding each phase of which is AC excited by an independent power converter unit. The protecting apparatus is arranged to detect an electrical event which includes at least one of an overvoltage and overcurrent appearing at each phase of the secondary winding of the AC generator/motor, to decide whether the detected electrical event meets a predetermined condition and to close, when the electrical event detected in respect to any of phases of the secondary winding is decided as meeting the predetermined condition, a switch circuit connected in the corresponding phase of the secondary winding.

Abstract: In order to improve the interference suppression of an electric-motor auxiliary motor-vehicle drive, particularly in the direction of electromagnetic compatibility (EMV), a protective circuit branch (2, 3) with two Zener diodes (D1; D2) or with one varistor (V1) is provided parallel to the armature circuit branch (1) of the commutator motor (M), where, for reducing the number of external solder joints, the Zener-diodes (D1; D2) or the varistor (V1) are combined with the interference suppression capacitors (C1; C2) in common integration component (6) which has only three external terminals.

Abstract: A static switch is provided for controlling the closing and opening of an AC electric circuit including an inductive load. This switch includes an inhibitable thyristor having an RCD network for protection against the voltage gradients on turn-off. The anode-cathode path of the inhibitable thyristor and its protection network are connected to the AC energy source through a full wave rectifier device, whereas a voltage clipping member is disposed at the terminals of the rectifying device.

Abstract: A system for use with electrical machines allows fast transfers to be made from one power source to another or fast reconnections to be made to a momentarily interrupted power source without subjecting the machines to unsafe voltage levels. The system short circuits the electrical machines to bring their residual voltage down quickly to a level at which the machines may be safely connected to a power source, and works with both induction and synchronous machines. No interlocking devices are necessary to the system, thus further speeding up fast transfer while minimizing the effects of inadvertent direct short circuiting of the power source.

Abstract: A control device for supplying current to electrical appliances and particularly appliances having single phase capacitor start motors wherein the control device includes a changeover switch which is mounted between a source of power and the appliance motor and which changeover switch includes selectively operated components for controlling the power supply to the appliance motor or to terminate the power supply thereto. In one embodiment of the invention, a second circuit is provided intermediate the power source and the appliance motor for detecting the amount of current flowing in the circuits so as to insure connection of the starting capacitor of the motor, braking of the single phase motor when power is terminated and to provide an indication of overcurrent in the motor.

Abstract: System and method of detecting arcing faults in dynamoelectric machines by monitoring the voltage on the neutral grounding lead to detect RF voltages produced by arcing in the machine. The voltage is monitored by an RF voltage coupler and an RF monitor having a high impedance input amplifier. In one embodiment, the voltage coupler is clamped onto the neutral lead, and in another it is connected electrically in series with it.

Abstract: A device for protecting a DC series electric motor from the voltage surge which occurs when the motor fields collapse. Electrical resistances are connected in parallel with the series field coils and the commutating field coils of the motor. The resistances safely absorb any voltage surge resulting from field collapse and also protect the motor from externally generated voltage spikes.

Abstract: Overload protection for the series resistance of an electric motor in which a voltage drop across the electric motor is monitored. During the occurrence of a reduced voltage drop, for example, as a result of a blocking of the motor or of a fan driven by the electric motor, the series resistance is short-circuited by a relay so that the blocking can be overcome by an increased driving torque of the electric motor or a fuse in the load current input line to the motor responds. As a result thereof, an effective overload protection is created which is of simple construction, involves no additional wiring expenditure and requires few additional components and which also permits to dimension the series resistance for normal operating currents and to be able to dispense with a thermal monitoring.

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: 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.