Abstract: An apparatus and method for monitoring the torque load condition of a cryopump motor includes a power transducer for monitoring the electrical power input to the cryopump motor. A preferred embodiment of the power transducer includes a Hall-effect multiplier which measures the instantaneous and average electrical power input to the cryopump motor to determine torque load. Another preferred embodiment includes a power transducer which measures the Power Factor of the electrical power input to the cryopump motor to determine torque load. The Power Factor transducer includes a phase detector which detects the phase difference between the input voltage and the input current applied to the cryopump motor.

Abstract: The alarm circuit uses speed detection so that at a fan slowdown speed below a critical low level, a buzzer alarm starts sounding at a low warning volume and then as the fan slows down further the volume increases; that is, the buzzer volume or the buzzing frequency is inversely proportional to the fan speed. The circuit advantageously can be used for a wide range of fans. A pulse detector of a first stage comparator of this circuit detects the pulses or speed of the fan. More particularly, a power supply isolation resistor with an AC coupling capacitor block the DC voltage levels at the fan so that only the AC or pulse component of the fan is picked up. The isolation resistor prevents the power source from attenuating the pulses. The second stage comparator of the circuit sets the fan speed at which the alarm is to start buzzing and powers the buzzer accordingly. Particularly, the pulses are amplified by the first stage comparator and they periodically discharge a charging capacitor.

Abstract: A warning device for monitoring the rotational speed of a prime mover which includes: a) a converting unit electrically connected to the prime mover for converting a digital signal representative of the rotational speed of the prime mover to an analog voltage; b) a reference unit for providing a specific analog reference voltage corresponding to the digital signal; c) a comparison unit for comparing the analog voltage with the specific analog reference voltage and generating a comparison signal when the analog voltage is not equal to the specific analog reference voltage; and d) an output unit electrically connected to the comparison unit for generating an alarm signal in response to the comparison signal.

Abstract: Indicators of incremental brush wear are disclosed. Versions of the indicators may comprise signal wire assemblies embedded in brushes so that they continuously contact rotating components of electrical machines. Each such wire assembly typically is chosen so that its nominal electrical resistance differs from that of its corresponding brush, while its mechanical properties remain similar to those of the brush.

Abstract: A rotation detecting means detects rotation of a mechanical movable portion and outputs a detection signal corresponding to the rotation rate of the mechanical movable portion. A rotation monitoring circuit, to which the detection signal from the rotation detecting means is provided, outputs a rotation-existing signal when the detection signal indicates that the mechanical movable portion is rotating. A rotation stop monitoring circuit, to which the detection signal from the rotation detecting means is provided, outputs a rotation-stop signal when the detection signal indicates a rotation rate lower than a predetermined rotation rate, and a movable portion control circuit uses at least either the rotation-existing signal or the rotation-stop signal and an external command signal for input signals to control the mechanical movable portion with logic of these signals.

Abstract: A method and circuit design for establishing the operating status of a direct drive, multiple speed motor. More specifically, the invention furnishes a method for providing feedback to an air distribution system indicating first whether the system motor is operating and second which speed winding has been selected. The circuit design senses the voltage differences between the speed windings of the motor and also between the first speed motor winding and the power supply. The voltage difference sensed by the circuit will determine whether a light emitting diode (LED) illuminates. The illumination of the LED indicates to the system controller whether the motor is operating and the speed winding that has been selected, thus providing the necessary feedback to the air distribution system controller.

Abstract: The axial bearing includes a first ring and a second ring. During operation of the axial bearing, the first ring rotates with respect to the second ring. Over time the foregoing rotation produces wear of the first ring; consequently, exposes layers of the first ring to the second ring. The different layers of the first ring produce variations in the coefficient of friction within the axial bearing. If the axial bearing is associated with a drive motor, then the variations in the coefficient of friction change the load on the drive motor. The change in load upon the drive motor may be monitored to indicate axial bearing wear or the need for axial bearing replacement.

Abstract: A detection means 1 detects changes in impedance generated at a coil TC caused in response to indentations Py1 and Py2 and projections provided at the surface of a movable portion Rot to generate a detection signal thereof. A speed judgement circuit 2, to which the detection signal from the detection means is provided, continuously generates a high level output signal A2i when the detection signal e change interval becomes greater than a specific length of time. A level detection circuit 3, to which the detection signal e is provided, generates a high level output signal A1i when the detection signal e is at or above a specific level. An AND circuit 4, to which the output signal A2i from the speed judgement circuit 2 and the output signal A2i from the level detection circuit 3 are provided, generates an output signal Z resulting from AND calculation of the two output signals A1i and A2i.

Abstract: An electric appliance control system is provided for use with an electric power unit such as an electric lawn mower. The electric appliance control system includes a battery, a selectively operable switch, a relay having first and second contacts, a control means, a charger circuit and an operator presence switch. The relay is operable by the switch to connect the electric power unit to the battery. The first and second contacts of the relay pass amperage therethrough between the battery and the electric power unit. The first contact is normally open and the second contact is normally closed. The control means includes a negative temperature coefficient thermistor in series with the first contact and multiple thermistors arranged in parallel and utilized in series with the second contact. The negative temperature coefficient thermistor variably increases the amperage passing through the first contact of the relay upon the selective operation of the switch to connect the electric power unit to the battery.

Abstract: A detector 1, with its object of detection having operation characteristics that include a shift from a first state to a second state, outputs a signal e1 that corresponds to the operation characteristics of the object of detection. A first state detection circuit 2 generates a first output signal SA corresponding to the first state based upon the signal e1 provided by the detector 1. A second state detection circuit 3 generates a second output signal SB corresponding to the second state based upon the signal provided by the detector 1. The second output signal SB is generated only when the object of detection shifts from the first state to the second state in a normal manner while the first output signal SA is being generated. A state judgement circuit 4 generates a state judgement output signal Z on condition that there has been a period of time during which the first output signal SA and the second output signal SB have been both at high.

Abstract: A detector detects a flow abnormality in a plant compressor which outputs a motor current signal. The detector includes a demodulator/lowpass filter demodulating and filtering the motor current signal producing a demodulated signal, and first, second, third and fourth bandpass filters connected to the demodulator/lowpass filter, and filtering the demodulated signal in accordance with first, second, third and fourth bandpass frequencies generating first, second, third and fourth filtered signals having first, second, third and fourth amplitudes.

Abstract: The invention relates to a motor stopped verification apparatus for verifying if a motor has stopped rotating, and in particular to rotation sensor technology for sampling rotation signals from a motor. With a first aspect of the invention, a high frequency current signal is supplied to the winding of a tachometer generator incorporated in a motor. This high frequency signal is modulated by an output signal from the tachometer generator, and the modulated signal made a motor rotation detection output from a rotation sensor. With a second aspect of the invention, a transducer coil is utilized as a part of an oscillator, and the motor rotation is converted to a change in the oscillation frequency of the oscillator and then sampled. With a third aspect of the invention, the motor rotation is converted by means of a resonance circuit incorporating the transducer coil, into a change in terminal voltage of the resonance circuit and then sampled.

Abstract: An apparatus for monitoring and processing of motor currents to determine motor characteristics under various loads. In the preferred embodiment, the invention employs a spectrum analyzer that having a plurality of digitally controlled switched capacitor filters under control of a personal computer. Sampling of both voltage and current simultaneously allows for calculation of instantaneous motor power and power factor, which are used to monitor the motor's performance. An acoustical output, generated under computer control is used to give the operator feedback on the motor's operation. The output signal is derived from low frequency or infrasonic sensing and is then stepped up to a frequency that the operator can hear. This permits the analyst to "hear" the condition of the motor under load. A CRT display to show the frequency spectrum and time display.

Abstract: An electric rotating machine comprises a rotor body of cylindrical structure and a stator body covering an outer peripheral portion of the rotor body in a non-contact fashion. The stator body includes a stator winding formed with an insulation layer and arranged radially outward of the rotor body with a clearance from the rotor body and a stator core which supports the stator winding.

Abstract: The duty ratio range of a duty signal DCN transmitted from a high-voltage load controller 12 to a field current controller 103 is divided into several subranges, which are assigned to zones, such as a normal voltage control zone, high-voltage control zone, and power generation stop and failure signal zone. The duty signal of a duty ratio in each zone is transmitted to the field current controller 103 for controlling the power generation mode of a generator 2. When a failure in a high-voltage circuit 16 is detected, the duty signal of a duty ratio in the power generation stop and failure signal zone causes power generation of the generator to stop and a pilot lamp 10 to go on for warning. The pilot lamp 10 is also used to warn the operator to a power generation error of the generator 2.

Abstract: A single source of energy is used to determine up to four armature coil or winding resistances and effectively up to four armature winding weld resistances for each test connection or index position of an armature being tested to thereby reduce the test time required for testing commutated armatures while reducing the complexity of the apparatus and test methods applied. Two preferably substantially diametrically opposite driven current paths through the armature windings are driven, and current and voltage measurements are taken at various commutator bars including commutator bars located adjacent current input ends and current output ends of the driven current paths. The resulting measurements and computations using these measurements are used to determine the winding resistances and ultimately the winding weld resistances for armatures and, in particular, for testing armatures for compliance with required specifications.

Abstract: Apparatus and method are provided for determining indicating if certain types of circuit failures have occurred in a D.C. motor circuit such as a locked rotor condition, a short-circuit or an open circuit. The method includes the steps of, and the apparatus involves, applying a voltage to two leads of the D.C. motor sufficient to cause motor rotation, determining if flyback exists, determining if back EMF exists, and, finally, if a back EMF does not exist and flyback does exist then indicating a locked rotor condition. However, if a back EMF does not exist and flyback does not exist then an indication is provided that either an open-circuit or short-circuit condition exists. The same apparatus and method can be used with a voltage not sufficient to cause motor rotation, although given this limitation only flyback can be detected, so that only an open-circuit or short-circuit condition can be indicated.

Abstract: A process and a circuit arrangement are proposed for electronically monitoring the overload on electric motor drives and in the case of which process and circuit arrangement speed is .monitored in addition to the known methods for real power monitoring. This also enables monitoring of the operating state of an electric motor drive, which is subject to a load, below the nominal rotation speed. This allows monitoring of the overload not only in the case of electric motor drives in the direct-current mode but also in the pulsed mode, as well as in the case of stepping motors.

Abstract: The axial bearing includes a first ring and a second ring. During operation of the axial bearing, the first ring rotates with respect to the second ring. Over time the foregoing rotation produces wear of the first ring; consequently, exposes layers of the first ring to the second ring. The different layers of the first ring produce variations in the coefficient of friction within the axial bearing. If the axial bearing is associated with a drive motor, then the variations in the coefficient of friction change the load on the drive motor. The change in load upon the drive motor may be monitored to indicate axial bearing wear or the need for axial bearing replacement.

Abstract: The present invention relates to a judgement circuit for determining rotation or non-rotation of a motor, and to a motor stopped verification apparatus using such judgement circuit. A signal from a rotation sensor which detects rotation of the motor is input to the judgement circuit and a threshold value judgement made using a fail-safe two input window comparator. That is, respective predetermined threshold value ranges (windows) are set for each terminal of the window comparator, so that when the motor is stopped and the judgement circuit and the sensor are normal, the level of the signal input to each terminal comes within the range of the window, and an output of logic value 1 is generated from the window comparator.

Abstract: The present invention relates to a current sensor for detecting current flowing in a current line, and a motor rotation sensor which utilizes this current sensor. A first transformer is inserted in a current line which is connected in parallel with a motor, so that a high frequency signal generated by a signal generator is transmitted to the current line by means of the first transformer. This high frequency signal is extracted by a second transformer inserted into another current line, and is transmitted to a receiver.

Abstract: A diagnostic tool may be attached to the control panel of a piece of machinery within a plant or factory which includes an electric motor. The diagnostic tool includes indicators for providing information to an operator of the equipment for which the control panel provides power. These indicators inform the operator of various modes of operation of the control circuitry within the control panel which regulate the power going to the motor. In this manner, the operator may determine if the machinery is ready to run, and if not, if it is necessary to call a technician.

Abstract: The electrical current drawn by a drive motor for the compressor unit of a chiller is monitored relative to a real time alarm limit for this electrical current. The real time alarm limit is computed from time to time by a microprocessor. The value of the computed alarm limit will vary with the cooling load being experienced by the chiller's evaporator unit.

Abstract: A determining device for determining a failure in a motor compressor system, comprising a current detecting sensor for detecting a current input to a motor for driving a compressor, a mass flow sensor for detecting mass flow of compressible fluid sucked into the compressor, a compression ratio detecting sensor for detecting a compression ratio of the compressor, a reference value generating unit for generating a limit reference value for determining whether or not a failure in the motor compressor system has occurred by comparing the current detected by the current detecting sensor with the limit reference value, and a failure determining unit for determining that a failure in the motor compressor system has occurred when the current is beyond the limit reference value. The limit reference value is increased in accordance with an increase of the mass flow or an increase of the compression ratio.

Abstract: A detection and alarm circuit for protection of electronic components includes a fan motor current sensing resistor for producing a pulse that is amplified and introduced to a frequency-to-voltage converter for generating a filtered and processed voltage level for application to a voltage comparator. A reference voltage circuit supplies a voltage level to the comparator for matching with the filtered and processed voltage level and depending on the mismatch, an output signal is introduced to a transistor switch for operating an alert alarm device.

Abstract: A supplemental monitoring device which issues an error signal when the monitoring device loses motor drive pulses is disclosed. Also disclosed is providing a manufacturing system with a normally closed relay which controls the flag, thus advantageously providing a semiconductor system which automatically interrupts the ion beam in the event of a system malfunction.

Abstract: A pulse detection and conditioning circuit senses and conditions commutation pulses produced by a DC permanent magnet motor to determine motor position. The pulses are sensed using a resistor coupled in series with the motor, so that motor current and the included pulses are continuously sensed, even during motor braking. The serially coupled resistor also provides for sensing and conditioning of pulses of both polarities produced by bi-directional operation of the motor. The pulse detecting and conditioning is performed by circuitry which performs amplitude qualification as well as frequency filtering to effectively detect valid commutation pulses to the exclusion of noise and other unwanted signals. Capacitors coupled to the motor and internal capacitors provide the frequency filtering, while the amplitude qualification is provided by a balanced differential gain stage coupled through an adjustable differential gain stage with adjustable gain to a unity gain comparator.

Abstract: Motor current and voltage waveforms are measured and converted to digitized current and voltage waveforms. A weighted discrete fourier transform is applied to the digitized current and voltage waveforms to obtain negative sequence current and voltage phasors; and the negative sequence current and voltage phasors are used to determine the existence of a turn fault. The use of the negative sequence current and voltage phasors can be performed by employing one of several techniques. In a first embodiment, an apparent negative sequence impedance is estimated by dividing the negative sequence voltage phasor by the negative sequence current phasor for comparison with a threshold negative sequence impedance. In a second, related embodiment, a current differential is estimated by dividing the negative sequence voltage phasor by a characteristic negative sequence impedance and subtracting the result from the negative sequence current phasor for comparison with a threshold current differential.

Abstract: In a method and device for monitoring the operation of a motor, the current drawn by the motor is sensed a preselected time after a peak of current is sensed. This sensed current is then compared to both a minimum and a maximum current threshold value to determine whether the sensed current is inside or outside the range of currents defined by the minimum and maximum current threshold values. The minimum and/or maximum current threshold values are dynamically adjusted as a function of the comparison.

Abstract: Apparatus may be inserted in the casing of a d.c. motor or a d.c. generator for measuring not only the magnetic fields prevailing in the machine but developing other useful information. The magnetic fields between the field poles and the armature, and also the armature/mmf fields aligned with the brushes may be measured. The measurements of the fields permits a complete plot of the fields in the machine and also permits a test to be performed to see if the brushes are at their optimum positions. If a brush is not at its optimum position, the brush may be shifted back and forth until the maximum mmf, due to the current through the armature is aligned midway between the leading and trailing ends of the brush area coverage on the commutator.

Abstract: A current detecting circuit for detecting excess current. The current detecting circuit has a circuit which corresponds a reference value for detection with application of power to a load and temporarily makes the reference value for detection high. Faulty detection of rush current can be prevented without providing a timer circuit.

Abstract: A diagnostic tool may be attached to the control panel of a piece of machinery within a plant or factory which includes an electric motor. The diagnostic tool includes indicators for providing information to an operator of the equipment for which the control panel provides power. These indicator inform the operator of various modes of operation of the control circuitry within the control panel which regulate the power going to the motor. In this manner, the operator may determine if the machinery is ready to run, and if not, if it is necessary to call a technician.

Abstract: A monitor and indicating circuit for an electric appliance detects the absence of the energization voltage for the appliance exceeding a predetermined threshold and provides a brilliant flash from a xenon lamp which is visible from great distances. The circuitry is contained within a sealed housing and includes a self-contained battery supply and attachable to a fence post. The circuit employed is specifically designed to conserve battery power by controlling the flash frequency and the charging time for the storage capacitor used with the xenon flash tube.

Abstract: A dispenser of foodstuff is particularly well adapted to deliver cheese for pizza making. A refrigerator contains a bin which may be completely removed from said refrigerator for cleaning, as in a dishwasher, for example. The bin features inwardly sloping walls so that the cheese does not normally stick to the wall. An auger delivers the cheese to a spout where a star wheel meters flow and breaks up any clumps in the cheese. A spring biased trap door closes the spout, especially when the bin is removed from the refrigerator. The refrigerator contains parts which control the opening and closing of the trap door and the turning of the auger. The entire system operates under the control of a programmable microprocessor which includes means for detecting when the bin is empty or is failing to delivery the cheese.

Abstract: Apparatus and method are disclosed for use with a starting circuit to prevent start-up of an electric motor when the motor's insulation resistance is of a value below a selected insulation resistance limit value below which the motor should not be energized. The selected limit value is a selected percentage of a known maximum value. A variable resistance device, such as a potentiometer, having first and second adjustable resistance portions is adjusted so that the adjusted resistance value of the second portion is of the same percentage of the total resistance value of the first and second portions as the selected percentage discussed above. A DC test voltage of a known value is applied to the motor's insulation resistance to cause a test current to flow therethrough. The test current is directed to flow through the second resistance portion to develop a test voltage.

Abstract: An apparatus for controlling a load lifting implement of a work vehicle in response to the condition of a motor brush is provided. The vehicle has a frame and the load lifting implement is connected to the frame and elevationally moveable relative to the frame between first and second directions. A brush wear indicator senses the wear of the motor brush and produces a warning signal in response to a predetermined amount of wear of the motor brush. A control system receives the warning signal and responsively controllably inhibits the elevational movement of the load lifting implement in at least one of the first and second directions.

Abstract: An automatic insulation tester tests the insulation resistance of electrical equipment when the electrical equipment is inoperative. The automatic insulation tester is automatically rendered operative when the electrical equipment is inoperative, and is automatically rendered inoperative when the electrical equipment is operative. The automatic insulation tester applies a voltage on the order of the rated voltage of the electrical equipment to the electrical equipment and measures and displays the insulation resistance of the electrical equipment. When the insulation resistance falls below a predetermined value, an indicator is activated, and remains in an activated state until the insulation resistance of the electrical equipment rises above the predetermined value and the automatic insulation tester is manually reset.

Abstract: The invention relates to a test and repair test kit for auxiliary power units for military vehicles. The test and repair test kit allows the easy diagnosis of problems and the ability to verify their repair on a mobile platform without the need of the vehicle. The test and repair test kit is self contained and provides the auxiliarry power unit with fuel and power allowing the complete operation of the auxiliary power unit. Repairs of the auxiliary power unit are facilitated because the operator is allowed easy access to major components while attached to the test and repair stand.

Abstract: Method of operation of an air cleaner used in a motor vehicle, comprises the steps of: intermittently turning off a blower motor of the air cleaner at a given interval; detecting ripple components included in an output voltage developed by a dynamo driven by an engine of the motor vehicle by detecting the output voltage between dc power supply lines connected from the dynamo to the air cleaner; and maintaining turn off condition of the blower motor when the ripple component is lower than a given level during intermittently turning off the blower motor. When the engine is stopped, during the on interval of the blower motor, stoppage of the engine cannot be detected by watching the ripple components included in power supply lines. However, during the following intermittent turning off interval, stop of the engine can be detected because the ripple component due to operation of the blower motor is not developed.

Abstract: A method and apparatus measured and calculates the derived thermodynamic state of a heat-pump or air conditioning system using information from transducers sensing elementary thermodynamic variables in the system. Elementary signals such as pressure, temperature, power, humidity, air flow, and others as required are derived using transducers from closed and open portions of the thermodynamic system, and which signals are then transmitted using appropriate transmission media. These signals are input to a computer, which could take many forms (electrical analog, electrical digital, pneumatic, hydraulic, and others), and these signal inputs along with known and tabulated thermodynamic characteristics of the working fluid (refrigerant) and psychrometric properties of the cooled media (air for example), are used to calculate thermodynamic output variables such as entropy, enthalpy, pressure, temperature, and volume at various states in the thermodynamic cycle.

Abstract: A motor control having mechanical switching and pressure reponsive components for connecting and intercepting a circuit between an A.C. source and an A.C. motor in response to pressure changes in a pressure system. The control includes a microcomputer chip and components that detect a voltage across the motor and a current through the motor and provide signals indicative of the level of the motor voltage and current. The control in response to the signals determines the power factor of the current and in response to the detected signals protects the motor from operating malfunctions when the voltage is too high or low, the current is too high or too low, the time of operation of the motor is too long or too short and in response to the character of the malfunction provides a visual coded lamp indication of the cause of the malfunction.

Abstract: A direct current fan's status is monitored electronically using a current monitoring circuit. Normally, when a fan is running it exhibits a pulsating current input. The resulting alternating current signal is monitored via the current monitoring circuit to detect whether the fan is running or not.

Abstract: A variable speed, constant frequency aircraft power system uses current sensing diodes to rectify the power generator output. The current flow through pairs of diodes is compared to generate phase currents to detect feeder faults.

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 dc commutator motor can be switched off when the motor rotor is short-circuited by the rotor's coming to a halt, by an operating switch (10). The switch is provided in the line connecting the brushes to a radio suppression network in a compact and simple design. The switch is operated by an ac voltage induced when the motor is running, with a frequency corresponding to the motor speed. A sensing winding connected to the operating switch for inducing the operating ac voltage is wound preferably around a radio interference suppression choke of the radio suppression network.

Abstract: An arrangement for measuring the slip of electric induction motors determines the relative measure of the difference between rotary field speed and rotor speed of induction motors by utilizing the nonlinearity effects of the magnetization characteristics of ferromagnetic materials. Slip-proportional current and/or voltage signals are detected at the terminals of the induction motor. By suitable processing of these slip-proportional signals, such as frequency conversion and filtering, a frequency-proportional measure of the slip is provided which is then subjectable to measuring or further processing.

Abstract: A monitor for an electric motor, the monitor capable of connection to a supply of electrical energy for the motor, has a microcomputer for measuring the power factor of a voltage applied to the motor and a current flowing to the motor, for storing a desired value of power factor, for comparing a measured value of power factor with the desired value of power factor, and for disconnecting the motor from the supply of electrical energy if the measured value of the power factor differs from the desired value of power factor by an amount that exceeds a predetermined amount. Further, the monitor has means for operating the motor while driving a desired load; means for commanding the microcomputer to measure a power factor of the voltage applied to the motor and the current flowing to the motor while the motor is driving the desired load; and, means for storing the measured value of the power factor, measured while the motor is driving the desired load, as the desired power factor.

Abstract: A method and apparatus for measuring the resistance of a winding of a converter-fed single- or three-phase machine during operation by means of a d-c measuring current. The firing instant of at least one up-commutating valve of a maching converter is delayed by a predetermined variable setting angle for generating d-c measuring currents in the phase currents, whereby the current conduction time of the up-commutating valve is shortened and the current conduction time of a valve commutating down with the valve which is commutating up with delay, is lengthened. The generated d-c measuring current is filtered out of the measured machine current and the generated interlinked d-c measuring voltage is filtered out of a measured terminal voltage of the single- or three-phase machine, and the winding resistance is determined from the linked d-c measuring voltage and the d-c measuring current by forming a quotient.

Abstract: It is known to detect a single breakdown of the electrical insulation separating the rotor winding from the earthed rotor body of a generator: such a failure does not lead to intense arcing, however, as there is no return path for current flowing to earth. Disclosed is a potential divider network which allows continuous monitoring of the voltages between earth and the two ends of the winding: a second breakdown can be rapidly detected since it results in a shift in both the position and magnitude of the effective resistance to earth from that associated with the first breakdown.

Abstract: A spa or whirlpool tub includes an A.C. motor coupled to drive a pump. The motor includes a frame having a mounting portion. A motor winding within the frame is connected to an A.C. power supply. An electronic control unit includes a housing and is mounted to the frame. The control unit has a cable connecting the electronic control to a power receptacle. The cable includes a power plug for connecting to a power receptacle. A connecting cable is wired to the motor windings. The connecting cable includes a connector plug corresponding to the power cable unit, and the electronic unit includes a complementing connector receptacle. The incoming motor power supply can be alternately made through the electronic control unit or directly to the winding, for monitoring the operating state of the motor and control unit. A separate cable having a light and connector plug is inserted in the control unit receptacle, to separately monitor the operating state of the control unit.