Abstract: A motor driver capable of detecting the insulation deterioration of a motor easily and inexpensively is disclosed. The voltage supplied from an AC power supply (1) is rectified by a first rectifying circuit (D1 to D6) and smoothed by a capacitor (C) in a power supply unit (6). The output voltage of the power supply unit (6) is converted into an AC voltage of a frequency and a motor (M) is driven by a motor drive amplifier (8). Elements (R1, C2, R11, C21) are connected between at least one of the positive electrode (4) and the negative electrode (5) of the output line (4, 5) of the power supply unit (6) and the ground (G2, G4). An insulation deterioration circuit (10, 11, 12) detects at least one of the voltage between the elements and the current flowing through the elements.

Abstract: A failure monitor designed to monitor a failure in operation of a motor drive control system. The system works to drive a motor-driven member through an output shaft and includes an angular position sensor for determining an angular position of the output shaft for use in controlling the motor. The failure monitor includes a storage device retaining an output shaft stop position that is the angular position of the output shaft, as determined upon a stop of the motor. The failure monitor detect the presence of failure of the angular position sensor based on a comparison between the angular position of the output shaft, as measured upon initiation of a motor start request, with the output shaft stop position.

Abstract: A method for determining motor velocity includes generating an edge signal including a plurality of edges. The edge signal indicates rotational travel of a motor. Edge counts in the edge signal occurring during periodic sample intervals are determined. The edge counts are filtered over a predetermined number of samples. A velocity feedback signal is generated for the motor based on the filtered edge counts. A drive unit for controlling a motor includes an edge detection unit, a position accumulator, and a velocity filter. The edge detection unit is operable to receive a motor position signal and generate an edge signal including a plurality of edges. The edge signal indicates rotational travel of the motor. A position accumulator is operable to determine edge counts in the edge signal occurring during periodic sample intervals. The velocity filter is operable to filter the edge counts over a predetermined number of samples to generate a velocity feedback signal for the motor based on the filtered edge counts.

Abstract: A control unit for a brushless motor has an upper-arm current detector for detecting an electric current flowing into an upper-arm switching transistor for driving the brushless motor, and a lower-arm current detector for detecting an electric current flowing into a lower-arm switching transistor. The control unit controls the current that flows into the brushless motor based on the upper-arm current value when it is so determined that the lower-arm current value cannot be detected. The control unit detects abnormal condition in the first current detector based on the upper-arm current value.

Abstract: The brush abrasion detector is unnecessary to provide any detecting element for detecting limit of abrasion of a brush in the proximity of the brush. The brush abrasion detector includes: a brush located being slidably press-fitted to a slip ring provided at an end portion of a field winding of a generator, and supplying an excitation current from a battery to the field winding; a current detection circuit for detecting a current value flowing through the field winding via the brush; an output voltage detection circuit for detecting an output voltage value from the generator; and a brush abrasion determination circuit for determining abrasion state of the brush based on a current value detected by the current detection circuit or an output voltage value detected by the output voltage detection circuit.

Abstract: An electric power steering system comprises a three-phase brushless DC motor, a steering torque detector, a resolver for detecting a resolver rotation angle of the three-phase brushless DC motor, a processing unit and a failure detection apparatus. The processing unit supplies a motor rotation angle and a rotational direction command value to the failure detection apparatus. The failure detection apparatus determines whether the processing unit is normal based on the motor rotation angle and the rotational direction command value.

Abstract: A method for monitoring a fan comprises measuring power usage of the fan, determining a derivative of the measured fan power usage, tracking the derivative over time, and predicting impending fan failure based on the tracked fan power usage derivative.

Abstract: The invention concerns a device for and a process for testing electric motors, in particular fan motors, for functionality, wherein electromagnetic alternating fields produced by an electric motor are received by an antenna, wherein the received signals are analyzed for signal components in the frequency range of the rotation value of electric motors or their harmonics via an analysis unit, and wherein upon determination of functionality the results are indicated by an indicator unit.

Abstract: The invention concerns a method for generating an alarm signal in a motor which comprises a rotor (50) whose actual rotation speed during operation lies in a normal zone (nSoll, TSoll), can deviate from that normal zone in the event of a fault, and is to be monitored against a malfunction or fault state, comprising the following steps: At least one alarm switch-on rotation speed (nAOn, TAOn) and at least one alarm switch-off rotation speed (nAOff, TAOff) are defined, of which the latter is located closer to the normal zone than the former, an associated pair of alarm switch-on rotation speed and alarm switch-off rotation speed defining between them a hysteresis zone. When the rotation speed to be monitored arrives, coming from the hysteresis zone, at the alarm switch-on rotation speed, an alarm switch-on criterion (Flag DIR=0) is generated. The duration of this alarm switch-on criterion is monitored. When this duration reaches a predetermined value (tdOn), an alarm signal (ALARM) is activated (FIG.

Abstract: A rotating machinery monitor provides a warning that is indicative of a developing problem with the rotating machinery. The rotating machinery monitor has at least one current sensor for detecting shaft grounding current and/or at least one voltage sensor for detecting shaft voltage in the rotating machinery; a monitoring device for monitoring real-time shaft grounding current values and/or real-time shaft voltage values over time; a detector for determining the change and/or determining the rate of change, in the shaft grounding current and/or in the shaft voltage; an evaluation system for producing a warning as a function of the change and/or rate of change, in the shaft grounding current and/or the shaft voltage wherein the warning generated is indicative of a developing problem with the rotating machinery.

Abstract: An axial position detection circuit detects the axial position of a rotor from the difference in voltages generated at axial position detection coils disposed at both ends in the axial direction of a stator of a canned motor. An axial zero point adjustment circuit uses a voltage supply, which varies proportionately with the power supply voltage of the canned motor, as a bias power supply to adjust the voltage difference of the axial position detection coils to zero when the rotor is at a reference position in the axial direction. Even if the power supply voltage of the canned motor varies, since the bias power supply of the axial zero point adjustment circuit varies in likewise manner, the zero point adjustment by the axial zero point adjustment circuit is not affected and axial bearing wear detection of high precision is enabled.

Abstract: If a motor becomes defective, e.g. stops running, runs too slowly, or becomes too hot, many customers demand the generation of an alarm signal, i.e. ask for an alarm device provided on the motor. The following method is used for configuring this alarm signal: At least one parameter for configuring the alarm device of the motor is inputted via a input interface (80, 82); the at least one parameter is stored in a parameter memory (74; 109); the execution of at least one routine of the alarm device provided in the microprocessor (23) is influenced by said stored parameter or by a parameter derived therefrom. The invention furthermore concerns a motor for carrying out such a method. In a motor of this kind, the alarm device can easily be configured in accordance with a customer's present needs.

Abstract: An airflow blockage detection apparatus for a permanent split-capacitor single-phase cooling fan motor measures and compares electrical currents in main and auxiliary windings of the motor to detect airflow blockage. Main and auxiliary current sensors detect AC currents in the main and auxiliary windings, respectively, and a blockage detection circuit forms a difference between the detected currents. An airflow blockage alarm is activated when the current difference exceeds a specified setpoint indicative of abnormally low airflow.

Abstract: The subject invention is directed to methods, processes and decisions on test outcomes for testing for faulty, therefor dangerous, performance of zero speed indicators that are used to control the opening of barriers guarding moving machine components. The indicators may be tested by removing them from the components during operation without shutting down production or in certain situations the indicators may be tested during the run down phase of the components caused by machine stop initiations. The tests allow to anticipate and hence prevent hazardous opening of barriers due to a faulty zero speed indication. Additionally, the invention is directed to testing of the insertion of motion interference devices in conjunction with zero speed indicators, both of which must perform correctly in order to permit the unlocking and opening of the protective barrier. There are included various exemplary devices for effecting the testing function.

Abstract: A method for detecting a shorted turn in a synchronous machine having a rotor using a magnetic flux probe is disclose having the steps of: monitoring a signal from the flux probe during on-line operation of the machine; integrating the flux probe signal to generate a flux density data trace that repeats during each rotor revolution; upon detecting movement in the flux density zero-crossing, capturing the flux probe signal for a current rotor revolution for a variety of machine load conditions, and performing a shorted turn analysis with the captured flux signal data.

Abstract: A load indicator for an electric motor, comprising a first means (II, IU, CPU) for repeated determination of the motor load, a second means (CPU) for comparing the current motor load, as determined by the first means, with a preset load limit, and a third means (CPU), PP) for indicating that the current motor load exceeds the load limit. Moreover, a meant (T, CPU) is arranged to initiate a presetting of the load limit. This means is adapted to be actuated, when the motor runs in normal operation, for presetting of the load limit as the current motor load changed by a predetermined deviation value stored in the load indicator.

Abstract: A filter condition sensing circuit includes current and voltage sensors and a data processor. The current and voltage sensors produce signals indicating magnitudes of electrical current and voltage, respectively, provided to an electric motor used to move a fluid (a gas or liquid) through a filter element. During a first time period, the data processor uses the signals to determine an acceptable range of electrical power required by the motor. During a second time period, the data processor uses the signals to determine a magnitude of electrical power required by the motor. When the magnitude of electrical power is within the acceptable range of electrical power, the data processor generates a signal indicating a normal condition of the filter element. A described filter condition indicating system includes the circuit. A method is for determining a condition of a filter element.

Abstract: A monitoring system for motors, particularly electric motors, monitors the operating conditions of the motor using a plurality of sensors. Data relating to the operating conditions is compared to predetermined criteria to determine if a threshold has been exceeded, with a warning indication provided. The data is stored within a data storage device that may be removed from the monitoring system for access thereto.

Abstract: An airflow blockage detection apparatus for a permanent split-capacitor single-phase cooling fan motor measures and compares electrical currents in main and auxiliary windings of the motor to detect airflow blockage. Main and auxiliary current sensors detect AC currents in the main and auxiliary windings, respectively, and a blockage detection circuit forms a difference between the detected currents. An airflow blockage alarm is activated when the current difference exceeds a specified setpoint indicative of abnormally low airflow.

Abstract: A flap to be identified is caused to move over the whole of its angular range of travel. The number of motor steps is counted during this movement, and the number of steps counted is compared with at least one pre-recorded information item corresponding to a particular flap or type of flap. The method is applicable to the checking of the correct fitting of actuator housings in an air-conditioning installation, or to the allocation of addresses to actuators connected to an information bus.

Abstract: A filter condition sensing circuit is disclosed including current and voltage sensors and a data processor. The current and voltage sensors produce. signals indicating magnitudes of electrical current and voltage, respectively, provided to an electric motor used to move a fluid (a gas or liquid) through a filter element. During a first time period, the data processor uses the signals to determine an acceptable range of electrical power required by the motor. During a second time period, the data processor uses the signals to determine a magnitude of electrical power required by the motor. When the magnitude of electrical power is within the acceptable range of electrical power, the data processor generates a signal indicating a normal condition of the filter element. A described filter condition indicating system includes the circuit. A method is disclosed for determining a condition of a filter element.

Abstract: Aspects for integrating speed control and fault detection in a fan assembly are described. The aspects include a fan, a first circuit is coupled to the fan for regulating speed of the fan, and a second circuit coupled to the fan and to the first circuit for detecting a fault condition in the fan. A ripple regulator is integrated as the first circuit, and a pulse missing detector circuit is integrated as the second circuit.

Abstract: DC motor rotation speed alarm circuitry includes an input node, a connection node, a ground node, a comparison circuit and a signal generator. When the rotation speed of the DC motor changes during operation, floating voltage is generated between the driving circuit and the ground node. If the floating voltage is less than a preset voltage of the comparison circuit, the alarm signal outputted by the signal generator indicates that the DC motor is operating normally. If the floating voltage is greater than the preset voltage of the comparison circuit, the alarm signal outputted by the signal generator indicates that the DC motor is operating abnormally.

Abstract: The present invention is a visualization luminous device adapted for electric motors of equipments supplied by three-phase voltage, allowing a person to visualize with certainty whether there is presence of voltage downstream blades of a disconnecting switch or circuit breakers which had been placed in an off-position.

Abstract: DC motor rotation speed alarm circuitry includes an input node, a connection node, a ground node, a comparison circuit and a signal generator. When the rotation speed of the DC motor changes during operation, floating voltage is generated between the driving circuit and the ground node. If the floating voltage is less than a preset voltage of the comparison circuit, the alarm signal outputted by the signal generator indicates that the DC motor is operating normally. If the floating voltage is greater than the preset voltage of the comparison circuit, the alarm signal outputted by the signal generator indicates that the DC motor is operating abnormally.

Abstract: There is described a circuit for controlling the operation of a fan. The circuit operates to control the speed of the fan and to operate the means to monitor fan malfunctioning.

Abstract: A multi-functional hybrid contactor has a motor protection function against an abnormal state in addition to the starting, running and stopping of the motor, the same effect as the case that an electronic motor protection relay (EMPR) is connected in parallel can be obtained with only one multi-functional hybrid contactor. Also, the size of the product is much reduced compared to the case that the electric motor protection relay (EMPR) is connected in parallel, and its cost can be reduced. In addition, since the semiconductor switch is turned on only in the initial stage of starting and stopping, the rated current capacity and size of the semiconductor switch can be considerably reduced compared to the conventional soft starting method in which the semiconductor switch is used for controlling of all of starting, running and stopping.

Abstract: A method monitors an operational condition of an electric motor, and stores in a memory device general trend, prognostic, diagnostic, and hazardous event information indicative of the motor's operational condition. The method includes the steps of sensing characteristics indicative of the operational condition of the electric motor, such as vibration, temperature, magnetic flux, and the voltages applied to the motor's windings, and generating sensor signals related to the sensed characteristics. Upon the occurrence of a first circumstance, such when measurements of the motor's speed, winding temperature, and voltage, indicate that the motor is operating within its normal load profile, prognostic information is extracted from the sensor signals. The prognostic information provides a profile of the motor's operational condition over time without the influences of fluctuating loads, temperature, and voltage.

Abstract: A device is provided which allows a personal computer user to monitor the operational parameters of the central processing unit's cooling fan. This device, called the CPU cooling fan speed monitor, characterizes the normal operating speed range of the CPU fan and the fan speed and provides warnings of improper fan speed. The fan speed monitor is a microcontroller-based device which has two principle modes of operation: the characterization mode; and the monitor mode. In the characterization mode, the fan speed monitor determines the “normal” operating speed range of the cooling fan. In the monitor mode, the fan speed monitor provides audible and visual indication of the operating speed of the CPU cooling fan.

Abstract: A temperature monitoring apparatus for microprocessors, having a fan device for producing an air stream for cooling the microprocessor. The temperature of the microprocessor is sensed by means of a heat sensing resistor mounted in the area of the surface thereof, and a regulator circuit is provided for increasing the speed of the fan at rising temperatures, and decreasing it at falling temperatures, based upon the temperature sensed by the heat sensing resistor. A speed monitoring device is also provided for monitoring a presettable speed range of the fan, and emits a warning signal in cooperation with an electronic circuit, in order to notify a user of an apparatus operated with the microprocessor, to manually switch off the same when the preset speed range of the fan is exceeded. This effectively prevents an overheating of a microprocessor.

Abstract: A timing circuit for providing an output to a microcontroller indicating whether an engine is operating, wherein the engine has a magneto. The circuit includes a triac coupled to the magneto for switching output generating circuitry between an engine on condition to an engine off condition in response to an operating condition of the engine. The output generating circuitry provides a signal indicating that the engine is not operating to the microcontroller when the circuitry is in an engine off condition and provides a signal indicating that the engine is operating to the microcontroller when the circuitry is in an engine on condition.

Abstract: A broadband test procedure detects the onset of stator winding insulation damage, identifies the failure mechanism, determines the winding's susceptibility to further damage, and predicts stator winding failure. This is accomplished by realizing that changes in the stator winding insulation and/or geometry are reflected as changes in the capacitance between the individual windings and, hence, as changes in the stator winding's broadband impedance response. In the currently preferred approach, the impedance response includes the frequency, magnitude, width, and phase of the resonant impedance.

Abstract: The present invention provides a method of manufacturing an integrated circuit using a conditioning wheel status indicator with a polishing apparatus having a conditioning wheel and a polishing pad. In one embodiment, the conditioning wheel status indicator comprises a drive motor, an ammeter, and an indicator. The drive motor is coupled to the conditioning wheel and configured to rotate the conditioning wheel against the polishing pad at a prescribed rotation rate. The ammeter is coupled to the drive motor and configured to measure a current of the drive motor. The current registered is a nominal current when the conditioning wheel is new. The indicator is coupled to the ammeter and configured to register an excess current that exceeds the nominal current when the conditioning wheel has incurred an undesirable degree of wear.

Abstract: A pulse detection circuit, a method of operation and a fan assembly test circuit employing the same. In one embodiment, the pulse detection circuit includes a charge pump that receives an input signal and varies a charge in a charge storage device based on the input signal. The pulse detection circuit further includes a level detector, coupled to the charge pump, that compares a voltage across the charge storage device with first and second reference voltages, and a signaling circuit, coupled to the level detector, that generates an output signal based on the comparison and indicating an existence of the pulse. The pulse detection circuit may be a part of a fan assembly test circuit adapted to receive an input signal from a cooling fan under test.

Abstract: A brush warning indicator for an electric motor is described. The brush warning indicator includes a contact spring having a non-conductive bushing connected to a conductive member. The contact spring is connected to a brush yoke by a terminal. The non-conductive bushing contacts a brush in a brush holder and biases the contact spring in relation to the brush holder. Once the brush moves beyond a predetermined point, the conductive member contacts a contact rivet and relays a voltage to a remote location where an indicator signals that the brush has worn beyond the predetermined point.

Abstract: An information processing apparatus includes a fan sensor for detecting a failure of a fan for cooling an inside of the apparatus and for outputting a cooling fan failure signal, a counter for starting time counting when the cooling fan failure signal is output and for outputting a time-out signal when counting to a predetermined value, and a power supply unit for supplying a power to the information processing apparatus and for stopping the power supply responding to the time-out signal, so as to prevent electronic components from being damaged by heat. If a cooling fan failure signal is output, the apparatus notifies a user of the fan failure and of a stop warning and performs a software protective operation during time counting with the counter.

Abstract: Problems associated with delta motors and motor controllers being subjected to the potentially damaging combination of extremely low motor torque and very high overcurrent conditions resulting from a single dead ended motor winding are eliminated in a motor controller that automatically inhibits operation of the delta motor upon detecting that the two leads of a single motor winding have both been connected to the supply lines for a single phase of a three phase power source.

Abstract: A method and apparatus for detecting motor contamination utilizes zero-sequence currents in a sensing coil to detect contamination. The detector includes a current transformer comprised of a magnetic core and a sensing coil wound about the core. A processor processes a sub-trip level current from the sensing coil to detect contamination. Three contamination detection methods, which may be used separately or in desired combination, are based on current trends, current leakage, and current clustering. An alarm is triggered when predetermined alarm criteria have been met.

Abstract: For use with a DC fan, a detection circuit and a method of detecting an operational condition thereof. In one embodiment, the detection circuit includes: (1) a sensor, coupled to the DC fan, that senses a current through the sensorless DC fan and produces an intermediate signal based thereon and (2) an alarm circuit, coupled to the sensor, that compares the intermediate signal to a range defined by an upper limit signal and a lower limit signal and generates an alarm signal when the intermediate signal is outside of the range.

Abstract: A speed detecting device is adapted for use with a direct current motor, and includes a coupling circuit adapted to be connected electrically to a power input line of the motor, a one-shot circuit, a converter circuit, a comparator, and an alarm device. The one-shot circuit is triggered by a current-coupled pulse output, which is generated by the coupling circuit and which corresponds to current flowing through the power input line, and generates a pulse train signal in a form of a series of constant-width pulses, where spacing between adjacent ones of the constant-width pulses varies according to instantaneous operating speed of the motor. The converter circuit receives the pulse train signal, and generates a test signal having a magnitude that varies in accordance with the spacing between the adjacent ones of the constant-width pulses to provide an indication of a detected average operating speed of the motor.

Abstract: An on-line monitor for electrical faults in the stator of an ac motor has a single di/dt current transformer or three separate di/dt current transformers coupled to the three phase conductors of the ac supply. The windings of the transformer, or transformers, are selected to generate a single sensed signal containing a linear combination of components of current in the three phase conductors weighted relatively so that algebraic differences between components from any two phase conductors is non-zero, such as preferably 2A+B-C or 3A+2B+C. The single sensed current signal is bandpass filtered to generate a pulse signal which is applied to an analyzer. The analyzer, preferably implemented by a microcontroller, generates an output based upon a combination of the amplitude and frequency of occurrence of the current pulse signal including a time attenuated accumulation of the pulses.

Abstract: An apparatus using a vibration motor as a drive source is arranged to inhibit a starting action of the vibration motor when the motor is found to be in a sticking state and not drivable. The arrangement effectively prevents inconveniences from being caused by an attempt to drive the motor by continuously applying a driving signal to the motor when the motor is in the sticking state.

Abstract: A system for the detection of fire in an apparatus or device having a fan and a pump, comprising means 20, 25 for detecting the presence of a pre-condition of fire, control means 30 for deactivating the fan on detection of said precondition, and fire detector means 35 for detecting smoke or fire in the absence of air movement.

Abstract: A motor is provided in which zero-point positioning of the stator and rotor in the axial direction is simple. The operation of replacing the rotor or stator can be done easily. A motor is provided in which zero-point positioning of the stator and rotor in the axial direction is simple and the detection precision can be improved. In a canned motor, a bearing wear monitoring device monitors the wear of the bearings that supports the rotor. The wear of the bearings is determined by measuring the displacement of the rotor based on the output signal of detection coils that are provided in embedding core units on both axial ends of the stator. The center of the embedding core unit at one axial end of the stator and the end face of one axial end of the stator are positioned to coincide with one another. The other axial end of the rotor is made to protrude outside the embedding core unit of the other axial end of the stator by a prescribed dimension.

Abstract: A bearing detection system for an electrical generator (10) includes auxiliary bearings (29) for supporting a rotating shaft (39) upon failure of main bearings (62). The auxiliary bearings (29) are mounted on the shaft and have a slight gap (64) between their outside diameters and bearing liners 33. The gap corresponds to the main bearing permissible wear. During normal functioning of the main bearing, the auxiliary bearing frame (34) rotates with the shaft and a magnet (35) with a small clearance between its face and auxiliary bearing outer ring (32) forces the synchronized rotation of inner (37) and outer (32) races. The auxiliary bearing outer ring or race (32) has a coaxial groove (31) on its outer diameter and a detection sensor (30), mounted on the bearing liner, gives a signal per rotation of the shaft to a control circuit (40).

Abstract: A current magnitude sensing circuit for detecting a malfunction of a DC brushless fan. The current magnitude sensing circuit detects drops in the current magnitude in windings of a fan motor. Depending on the frequency of the current drops in the fan current, the current magnitude sensing circuit outputs either a high or a low voltage signal. The current magnitude sensing circuit operates by charging a capacitor beyond a certain voltage and thereby providing a high fan fail output signal when a fan is spinning too slowly for proper cooling of a device. Another capacitor is charged at a different time constant for setting the fan fail output of the current magnitude circuit low for indicating that the fan is spinning sufficiently fast.

Abstract: A method and apparatus for monitoring a three-phase electric motor which has been disconnected from the electrical mains and is running down, one phase of the voltage generated by the motor being checked respectively in each of two channels for zero crossings and, if a zero crossing occurs, a signal being produced which, after DC-decoupling, is used to control the operation of a safety device. The safety devices are mutually interlocked and control signals therefor are produced only when the period between zero-crossings detected in both channels indicates that the motor output shaft has ceased rotation.

Abstract: A hybrid vehicle comprises a motor driving the vehicle's wheels, multiple batteries supplying electric power to the motor, and a generator driven by an internal combustion engine to generate electric power for charging the batteries. Battery sensors detect terminal voltages of the batteries. An ECU controls a DC/DC converter to distribute electric power to independently charge the batteries through charge lines in accordance with the shortage of charge in respective batteries when excess electrical power is available from the generator even after a required amount of electrical power from the generator is used to rotate wheels.

Abstract: A method and apparatus for real-time electric motor diagnostics and condition monitoring. While the motor is energized, dynamic operating parameters are determined and a notification signed is generated if predetermined criterion are satisfied. The diagnostic apparatus is integrated with the motor and includes a set of sensors, a processing unit, a memory and an output interface for communicating alarms, warnings and calculated operating parameter values or the like to a display device and to an external supervisor having wireless paging capability to alert a remote operator or maintenance personnel. In a normal operating mode, the processing unit calculates a general class of derived motor operating parameters such as over-temperature, over-voltage, over-current, excessive vibration, and phase imbalance.

Abstract: The present invention relates to a sensor for verifying that a motor has stopped rotating including rotation due to inertia.Respective signal input lines are connected to three power supply lines of a three phase AC motor. A high frequency signal current is supplied to one of the power supply lines, and the difference in the current flowing in the other two power supply lines is sampled from the signal input lines connected to the two power supply lines, and made an output from a sensor section. The sensor output is subjected to a threshold value operation in a signal processing circuit, and the resultant threshold operation output is output from an on-delay circuit as a motor rotation presence judgment output.