Abstract: The present invention provides a control system (100, 200, 300) for controlling a single phase induction motor (150, 250) with a main winding (151, 251) and with an auxiliary winding (152, 252), the control system (100, 200, 300) comprising a first bidirectional switching element (101) and a second bidirectional switching element (102), wherein the first bidirectional switching element (101) is arranged between a phase supply input (103, 203) of the single phase induction motor (150, 250) and the main winding (151, 251) and wherein the second bidirectional switching element (102) is arranged electrically parallel to the main winding (151, 251), and a control unit (105, 205) coupled to the first bidirectional switching element (101) and the second bidirectional switching element (102).

Abstract: Provided are a complex multifunctional relay system capable of complexly performing an overcurrent blocking function, an arc blocking function, and an earth leakage blocking function by a relay circuit, and a control method therefor. The complex multifunctional relay system includes an AC circuit including a hot line and a neutral line, a power control means connected in parallel to the hot line, insulation differential amplifiers circuit-connected to the hot line and the neutral line through current shunts, a microprocessor connected to the power control means and the insulation differential amplifiers to perform monitoring and control the power supply of the power control means, a first comparator connected to the current shunt and the insulation differential amplifier and connected to the microprocessor so as to check ground fault, and a second comparator connected between the current shunt/the insulation differential amplifier and the microprocessor so as to check arc fault.

Abstract: A method is provided for determining an operational readiness state of an electric motor, a pump motor for pumping an operating fluid, for example, an aqueous urea solution, in a vehicle. The method includes applying an electric drive voltage to the electric motor according to a prescribed drive voltage curve in order to drive a rotor of the electric motor to rotate through a prescribed angle of rotation, detecting a response behavior of the electric motor, and determining the state of the electric motor based on the results determined in step b).

Abstract: An efficient and reliable power conversion method for converting an input voltage which is a single-phase AC voltage into output voltages forming a two-phase AC voltage includes: receiving an input voltage; designating, as a first target voltage representing consecutive target values of a first-phase output voltage and a second target voltage representing consecutive target values of a second-phase output voltage, AC voltages forming a two-phase AC voltage and having (i) an amplitude 1/?2 times smaller than an amplitude of the input voltage, and (ii) phase differences of +45 degrees and ?45 degrees relative to the input voltage; and designating a frequency other than a frequency twice a frequency of the input voltage, as a frequency of the first target voltage and the second target voltage.

Abstract: A rectifier circuit comprising an AC input, at least one thyristor coupled to the AC input, a DC bus driven by the at least one thyristor, a controller arranged to: derive a first current in the DC bus, derive a maximum current demand on the DC bus, and provide a trigger signal to the at least one thyristor based on the derived maximum current and the derived first current.

Abstract: A method is provided. A command to correspond to a target speed of a motor is received. A rotational speed of the motor is measured, and a brake-to-off ratio for a braking interval is calculated based at least in part on the rotation speed, the target speed, a braking parameter. An off state for an inverter that is coupled to motor is induced during an off portion of the braking interval, and a brake signal is applied to the inverter during a braking portion of the braking interval.

Abstract: A temperature protection device basically includes a temperature detector, a temperature estimator, an overheated determining component and an overheating protection component. The temperature detector detects a temperature of a semiconductor component. The temperature estimator estimates an estimated temperature of the semiconductor component. The overheated determining component determines whether the semiconductor component is in an overheated state based on the detected temperature and the estimated temperature by using a first estimated temperature as the estimated temperature at a time point when the detected temperature has reached a first threshold temperature and a second estimated temperature that is estimated subsequent to the time point as the estimated temperature when the detected temperature has reached the first threshold temperature.

Abstract: A steering control apparatus includes a direct current power source, a three-phase alternating current motor, and a motor driving circuit. An emergency switching element is provided on at least two phases of a three-phase power supply line connected to the three-phase alternating current motor within the motor driving circuit, and the emergency switching element is turned off when an abnormality occurs such that the motor driving circuit is disconnected from the three-phase alternating current motor. The emergency switching element is a MOSFET, and the MOSFETs are provided in pairs in each of the two phases of the three-phase power supply line. Further, parasitic diodes of the pairs of MOSFETs are disposed in opposite orientations to each other.

Abstract: Provided is a sensorless BLDC motor system. The sensorless BLDC motor system includes a BLDC motor, a comparator, a motor controller, a three-phase inverter, and a mode selector. The BLDC motor includes first to third coils. The comparator compares a voltage of a specific coil of the first to third coils with a neutral-point voltage to output the compared result. The voltage of the specific coil becomes equal to the neutral-point voltage and a specific time elapses, and then the motor controller generates first and second coil control signals based on the compared result. The three-phase inverter supplies a source voltage or ground voltage to the specific coil, or floats the specific coil, in response to the first and second coil control signals. The mode selector selects a driving mode of the BLDC motor by adjusting the specific time.

Abstract: On condition that output of a torque of not lower than a preset reference torque from a motor continues for at least a predetermined time period in a vehicle stop state with output of a corresponding torque from the a second motor based on a detected accelerator opening, a torque command of the second motor is set to decrease the output torque of said motor by a torque decrease rate, which is set according to the corresponding torque and the accelerator opening in the vehicle stop state (initial accelerator opening). After a changeover of a current crowding phase in the second motor, the torque command of said motor is set to increase the output torque of said motor by a torque increase rate, which is set according to the accelerator opening in the vehicle stop state.

Abstract: A feedback switching device and a method allow a drive control loop for a servo motor to actively switch the feedback mode in accordance with the rotating speed of the servo motor. When the servo motor is under a high speed operation, a sensorless position estimation feedback technology is used as the feedback mode; on the other hand, when the servo motor is under a low speed operation, the switching mode is automatically switched to a position sensing feedback technology. Therefore, the development needs for multi-function, high performance and low cost in the field of the servo motor control are met, and the conventional problem is solved that, when being applied to a servo driving system having a wide speed range, the single use of the position sensing feedback technology or the sensorless position estimation feedback technology fails to satisfy the application for a wide speed range.

Abstract: Aspects of the present invention pertain to a method of power control for an electrical motor using a control bypass feature that allows for the delivery of full supply voltage to a motor when it is operating at or above a certain load threshold level. Advantages of the present invention include the ability to provide power savings at low loads while still a motor to operate at full rated capacity under high load conditions. Also, a load sensor and an override unit that are independent of the phase lag compensation portion of power control allows for faster response to rapid load changes.

Abstract: A protective circuit arranged on a Printed Circuit Board (PCB) has two conductor loops. At least one supply voltage track, at least one semiconductor switch and at least one control component are arranged on the PCB. A first terminal of the control component and a first terminal of the semiconductor switch are connected electrically. A first conductor loop of the protective circuit is arranged on the PCB so that it surrounds an electrically conducting connection between the supply voltage track and the semiconductor switch and/or the control component. A second conductor loop is arranged on the PCB so that it surrounds the electrically conducting connection between the first terminal of the control component and the first terminal of the semiconductor switch, and thereby screens the same from the semiconductor switch and at least from those regions of the control component that are also connected to the supply voltage track.

Abstract: The method for the automatic adjustment of a protective device includes determining an integral of the square of a motor current over time on the basis of a time motor current profile of an asynchronous motor on a load, after switching on and reversing and deriving a tripping time of the overcurrent release on the basis of the determined integral, the integral, which corresponds to a heating of the asynchronous motor, being related to a multiple of the square of the rated current, and the motor current profile including at least the starting current, the transient and the selected motor rated current.

Abstract: A low-pin count fan speed control system and a method thereof include primarily an activation unit to drive a fan to operate. When the fan starts completely, the fan slows down to a pre-determined rotation speed through an idle speed regulation unit. After achieving a pre-determined temperature through a temperature transition unit, the fan speed beings to increase from the idle speed. When the fan is operating, the rotation speed is properly increased in proportion to the temperature, using a positive temperature regulation slope unit. Therefore, through this method, the rotation speed will not be decreased by foreign objects when the fan is operating and a computer host can be provided with proper heat dissipation.

Abstract: A method and apparatus comprises a filter receiving an input voltage signal from a drive circuit, and a filter producing an output voltage signal with reduced resonance and transients. The amplitude of the output voltage signal is boosted using the filter.

Abstract: An electric motor circuit for controlling an electric motor of a mirror adjustment mechanism includes a switch-off circuit that is provided with a current sensor for measuring the electrical supply current and, depending thereon, generating a voltage. In an embodiment, a current branch is configured to be rendered conductive in response to the generated voltage; an electronic switch is configured to interrupt the supply current as a result of the current branch being rendered conductive. The current branch may be configured to form a first branch of a current mirror which is out of balance and is dimensioned such that the first branch does not carry current under normal operating conditions of the motor, and a second branch is conductive. In an embodiment, upon the occurrence of a supply current that is greater than a predetermined critical level, the first branch is also rendered conductive.

Abstract: A microcomputer compares a low voltage LV and a middle voltage MV to a predetermined voltage Vth set at a value in the vicinity of the grounded voltage (0 V) on the basis of detected phase voltages Vu, Vv and Vw, and thus, detects a break in a power supply line.

Abstract: A motor start circuit for an AC induction motor employs a DC relay whose NC contacts are placed in series with the start capacitor. A half full-wave rectifier arrangement has an AC input connected to the junction of the relay switch and the start capacitor, and DC outputs applied across the relay actuator coil. In the event of intermittent application of power to the motor, any residual charge on the start capacitor will feed current to the actuator coil to hold the relay switch open until the residual charge has decayed sufficiently, to avoid damage to the motor from capacitive discharge. A high magnetic retentivity core can be used to hold the relay off for sufficient time for stored energy to dissipate.

Abstract: The electrical isolation circuit of the present disclosure includes a switch coupled between the DC power source and the electrical application and a comparator for controlling the switch by receiving inputs from the DC power source and the electrical application. The comparator causes the switch to switch ON when the DC power source has a higher voltage than the electrical application allowing the normal operation of the electrical application. However, when the electrical application has a higher voltage than the DC power source, the comparator causes the switch to switch OFF thereby preventing flow of current from the electrical application to the DC power source.

Abstract: When a fan drive current has become excessive, a fan drive device intercepts that current, waits for just a fixed time period T1, and thereafter flows that current for a second time. The fan power supply current flowed to the fan drive device is detected by a shunt resistor R. The value of the fan power supply current detected by the shunt resistor R is inputted to a controller, and the cause of any abnormality of the fan is decided upon by this controller, based upon the magnitude of the above described fan power supply current and the time period over which it has continued.

Abstract: An electronic trip unit for a motor circuit breaker of an electric motor includes at least one detection unit configured to sense at least one current that is delivered to the electric motor. The unit further including a discriminator circuit, the discriminator circuit being in a first state when no measured current value exceeds a predefined trip threshold, and being in a second state when at least one measured current value exceeds the predefined trip threshold. The discriminator circuit includes an output for controlling the motor; a voltage-limiting component having a breakdown voltage; a resistor; and a switching unit configured to, in the first state, switch the control signal to the first level, and, in the second state, switch the control signal to the second level, the switching unit being configured to be switched by a voltage drop across the resistor.

Abstract: A method is provided for the electrical protection of an electrical household appliance that is used to prepare food. The appliance includes an electric pump which is supplied with alternating current in order to convey a liquid through a conduit, and a heating element to raise the temperature of the liquid. The instantaneous value of the current I supplied to the pump is measured at regular time intervals. The method includes calculating the average value ?n of m current I measurements taken over a pre-determined time period T; comparing the average value ?n with a reference value ?ref calculated as the average value of the current I measurements taken over an earlier period of the same length; and opening the pump's power supply circuit when the difference between the average values ?ref and ?n exceeds a pre-determined threshold value ?1 for at least two successive time periods T as a result of low average current indicative of dry running.

Abstract: When it is determined that a battery temperature is lower than a threshold value, an inverter control circuit alternately switches an operation point of an AC motor between an optimum operation point and a motor loss increase point. At the motor loss increase point, an increase in the amplitude of the motor current increases copper loss occurring in the three-phase coil of the AC motor. On the other hand, at the optimum operation point, a reduction in the amplitude of the motor current reduces copper loss. Corresponding to the cyclical increase/reduction in the copper loss, the battery is cyclically charged/discharged by the electric power corresponding to the copper loss. The change in the battery current occurred by the charge/discharge causes the internal resistance to generate heat, whereby the temperature of the battery is increased.

Abstract: A motor start circuit for an AC induction motor employs a DC relay whose NC contacts are placed in series with the start capacitor. A half full-wave rectifier arrangement has an AC input connected to the junction of the relay switch and the start capacitor, and DC outputs applied across the relay actuator coil. In the event of intermittent application of power to the motor, any residual charge on the start capacitor will feed current to the actuator coil to hold the relay switch open until the residual charge has decayed sufficiently, to avoid damage to the motor from capacitive discharge. A high magnetic retentivity core can be used to hold the relay off for sufficient time for stored energy to dissipate.

Abstract: A thermal overload protection for an electrical device, particularly an electric motor (M), measures a load current supplied to the electrical device (M), and calculates the thermal load on the electrical device on the basis of the measured load current, and shuts off (S2) a current supply (L1, L2, L3) when the thermal load reaches a given threshold level. The protection comprises a processor system employing X-bit, preferably X=32, fixed-point arithmetic, wherein the thermal load is calculated by a mathematic equation programmed into the microprocessor system structured such that a result or a provisional result never exceeds the X-bit value.

Abstract: A motor driver circuit comprising a diving circuit for driving at least one motor, a plurality of DC/DC converters, and a stopping circuit for stopping the DC/DC converter if failure is detected in an output of the DC/DC converter, wherein a first signal is outputted when a specific DC/DC converter of the plurality of DC/DC converters is stopped by the stopping circuit, and a specific DC/DC converter is recovered when a second signal is inputted. A CPU of an apparatus incorporated with the motor driver circuit is informed that the specific DC/DC converter has been stopped by the stopping circuit. Moreover, the stopped DC/DC converter can be recovered without need for turning off a power supply of the motor driver circuit itself.

Abstract: A PWM motor drive circuit includes a drive IC member, a PWM converter circuit and a potential limiter. The drive IC member electrically connects with a motor coil and further includes a pin electrically connected with the PWM converter circuit. The potential limiter has a first terminal electrically connected with a point between the pin of the drive IC member and the PWM converter circuit, and a second terminal electrically connected with a power source to supply an initial voltage to the pin of the drive IC member via the potential limiter. When the motor starts, the potential limiter can adjust of the initial voltage supplying to the pin of the drive IC member so that the drive IC member cannot unexpectedly enter a stop or high-speed mode.

Abstract: A control device for driving a regulating motor driven by direct current (DC) includes a changeover mechanism having a first normally closed (NC) switch, a second NC switch, a first normally open (NO) switch, and a second NO switch, a power-supply module for providing DC for the regulating motor, a first operating switch for driving the regulating motor to rotate in a first direction while the two NC switches become open circuit and the two NO switches become short-circuit resulting from that the first operating switch is short-circuit, and a second operating switch for driving the regulating motor to rotate in a second direction opposite to the first direction. In light of these, the control device can control the rotational direction of the regulating motor by means of simple circuitry.

Abstract: A motor driver circuit includes a diving circuit for driving at least one motor, a plurality of DC/DC converters for respectively generating different voltages, a detection circuit to detect an output failure in the plurality of DC/DC converters, and a stopping circuit for stopping a specific DC/DC converter if failure is detected in an output of the specific DC/DC converter. In addition, a signal output circuit outputs a first signal if the specific DC/DC converter of the plurality of DC/DC converters is stopped by the stopping circuit, recovery means recovers the specific DC/DC converter when a second signal is inputted, and a reset circuit stops the rest of the plurality of DC/DC converters, if the stopping circuit stops any one of the plurality of DC/DC converters other than the specific DC/DC converter.

Abstract: A motor drive unit is adapted to detect a motor lock-up condition (in which an electric motor is accidentally locked during driving) based on the fact that motor drive current increases in that event. Then, a capacitor for generating a voltage signal is charged with an arbitrarily adjustable charging current to overcome the motor lock-up. To do this, an IC is formed to incorporate therein such components as a first discharging circuit for discharging the electric charge of the capacitor and a hysteresis-type comparison circuit for comparing the charging current with a threshold level to thereby adjust the charging current suitable for the motor used. Such a versatile IC as described above enables adjustment of the motor startup trial period for individual motors having different characteristics.

Abstract: A motor controller system includes solid state switches for connection between an AC line and motor terminals for controlling application of AC power to a motor. Voltage sensors sense voltage across each of the solid state switches and AC line voltage. A control circuit controls operation of the solid state switches. The control circuit compares the sensed voltages across each of the solid state switches with the AC line voltage in a non-run mode to determine if there is a shorted solid state switch.

Abstract: In a parallel relay circuit, only one of a plurality of relays is turned on sequentially while turning the rest of the relays off. It is determined whether the motor is applied with voltage via a voltage detection resistor when each of the relays is turned on individually such that a disconnection abnormality in the respective relays is detected. As the disconnection abnormality in each of the relays can be detected individually, it is possible to detect a disconnection abnormality that has been occurred at least in a part of the relays, and to alert a driver for the abnormality.

Abstract: A motor control system for detecting motor run condition comprises power switches for connection to an AC line for controlling application of AC power to the motor. An input receives a motor start command. A controller is connected to the input and controls operation of the switches responsive to a motor start command. The controller includes a counter and a timer and is operable to disable the power switches if number of starts during a select interval exceeds a first threshold and to disable the power switches if motor run time after a motor start command exceeds a second threshold.

Abstract: There are included a control circuit to control sequence of excitation of a stepping motor, a switching circuit to switch electric power to be supplied to the stepping motor based on an instruction from the control circuit, and a stop circuit to stop an operation of the switching circuit in a case where temperature of the switching circuit becomes a specified temperature or higher, and the control circuit controls the switching circuit in a mode where the stop circuit operates before the stepping motor is damaged by heat.

Abstract: The invention concerns a starter for a line start electric motor having at least one main winding (4) and at least one start winding (12) and which start winding is connected in series with a run capacitor (14) with which a start capacitor (17) and a PTC-thermistor (19) are connected in parallel. In order to make a simply constructed starter for a line start electric motor the start capacitor (17) and the PTC-thermistor (19) are connected in series with a switch mechanism (20). The series connected circuit made up of the start capacitor (17), the PTC-thermistor (19) and the switch mechanism (20) is connected in parallel with the run capacitor (14).

Abstract: A system and method of controlling motor temperature is based on computed motor power dissipation and a thermal model of the motor, rather than a measured motor temperature, in a control loop that limits the motor drive to prevent overheating. An ambient temperature sensor senses the ambient temperature near the motor, and a determination is made of the motor power dissipation. The motor winding temperature is estimated based on the sensed ambient temperature and the determined motor power dissipation. A maximum motor power dissipation that would raise the motor temperature to a predetermined maximum temperature value is determined based on the estimated temperature. The motor power dissipation is limited to a value that is below the determined maximum power dissipation.

Abstract: To a neutral point of a motor is connected a positive electrode of an auxiliary battery and an auxiliary load. Voltage on a power supply line to the auxiliary load, a neutral point voltage, is detected, and disconnection of the auxiliary battery is determined when an increase of ripples in the neutral point voltage is detected. When a voltmeter cannot be used, control of the neutral point voltage is continued by measuring current of the auxiliary battery and performing control such that the current value becomes 0. A resolver is further provided on the motor for detecting the rotor angle with high accuracy. A control circuit generates, in accordance with an output of the resolver, a voltage control signal for each phase current having the same amplitude as the carrier amplitude during startup, and compares the voltage control signal to carrier to obtain a gate signal having the same frequency as the carrier frequency.

Abstract: A control system for a motor including a rotor comprises a sensorless sensor module that includes a saliency-based estimator module that generates a first rotor position signal based on saliency and a back electromotive force (emf) estimator module that generates a second rotor position signal based on back emf. A selector selects the first rotor position signal for rotor speeds below a first rotor speed and the second rotor position signal for rotor speeds above the first rotor speed. A rotor position sensor senses a position of the rotor and generates a third rotor position signal. A fault detection module senses faults in the rotor position sensor and outputs the third rotor position signal when a fault is not detected and one of the first and second rotor position signals when the fault is detected. An indirect field oriented control (IFOC) system controls the motor based on a selected one of the first, second and third rotor position signals.

Abstract: A motor starting device employs a relay to connect and disconnect an auxiliary start capacitor in parallel with the existing start capacitor of a single-phase split-capacitor induction motor. The relay is normally closed and in the initial state connects the auxiliary start capacitor in parallel with the existing start capacitor. After a source of alternating current voltage is connected to the motor, a control circuit energizes the relay to disconnect the auxiliary start capacitor after a delay time. When the source of alternating current voltage is disconnected from the motor, a relay protection circuit maintains the relay switch open until the charge has dissipated from both the existing start capacitor and the auxiliary start capacitor.

Abstract: A configurable motor controller includes solid state switches for connection between an AC line and motor terminals for controlling application of AC power to the motor. A control circuit controls operation of the solid state switches. The control circuit comprises a programmed processor for commanding operation of the solid state switches. A memory is connected to the programmed processor storing configuration information relating to operation of the solid state switches. A user configuration device selects the values for the stored configuration information. The configuration information comprises adjustable values within a range. The configuration device is adapted to select any adjustable value within the range.

Abstract: An electric motor selectively connectable to receive one of a plurality of supply voltages, the plurality of supply voltages comprising a low supply voltage and a high supply voltage. The motor can comprise a stator having a first winding and a second winding, a shaft rotatable about a motor axis, and a rotor supported by the shaft for rotation with the shaft relative to the stator. The motor can also comprise a voltage selection device, a first motor protector, and a second motor protector. The voltage selection device can include a first setting and a second setting and can be configured to connect the first winding in parallel with the second winding when set to the first setting and to connect the first winding in series with the second winding when set to the second setting. The first motor protector can be configured to limit current through the first winding and the second winding when an overload condition exists.

Abstract: A simple and economical mechanism providing automatic motor control. The mechanism includes a motor-rated relay directly connected to line voltage and the input terminal of a motor winding, and receiving a signal from a sensing device connected to line voltage and to a signal input on the relay. The relay and sensing device may be housed within a waterproof enclosure, or may be separately housed within a connection enclosure and a separate sensing device enclosure remote from the connection enclosure, the two enclosures being connected by a cable. The sensing device triggers the relay to control the supply of current to the motor winding.

Abstract: A safety-guard detective circuit of a fan motor includes a resistor being adapted to limit a large current input into the motor driver circuit, and a discharge member being adapted to perform grounding to discharge the large current limited by the resistor. The resistor and the release member are commonly connected to the third lead of the motor driver circuit.

Abstract: A three-phase motor protector uses two toroids to monitor all three phases of a three-phase motor. Current and phase loss are monitored directly in phases A and B while the phase C current level is determined by analysis of the phase A and B relationship. Current is induced into the phase A and B toroids from the motor supply lines with the resulting wave fed to an input of high-gain inverting amplifiers to provide A and B square waves which are inputted to separate channels of a microprocessor (U3). The square waves are processed by an AND gate providing an output square wave with a 16.66 percent duty cycle for normal operation. Upon loss of phase C the ANDed result is a digital low since the individual waves of phases A and B become an inverse of one another. In order to prevent nuisance tripping an AND output of less than 2 percent duty cycle is treated as a phase loss.

Abstract: If a speed instruction value is less than a predetermined value, the output current of a power-conversion unit is controlled to be larger than a current value in an ordinary no-load operation, or a frequency instruction value is calculated based on a speed instruction value in place of an estimated speed.

Abstract: There is provided a voltage-controlled electronic relay for starting a single-phase induction motor, which includes: a power supply unit 310, configured of a bridge diode BD, for supplying power to circuit elements of the starting relay when AC power of the induction motor is turned on; a triac 306 for applying the AC power to a starting coil W3 of the induction motor or cutting off the AC power; a signal input unit 322 for sensing a voltage induced to the starting coil; a hysteresis unit 324 for outputting an ON control signal at the initial starting stage, generating an OFF control signal for turning off the switch when the induced voltage sensed by the sensing element reaches a predetermined OFF reference voltage, and generating the ON control signal for turning on the switch again when the induced voltage becomes lower than a predetermined ON reference voltage during a normal operation period; and a triggering unit 330 for turning on the switch according to the ON control signal of the hysteresis unit and

Abstract: A method and apparatus for controlling an electric motor pump. The method includes the acts of providing an AC power signal having a positive half cycle and a negative half cycle, measuring the voltage of the AC power signal and generating a first two-state output signal that is in a logic high state when the measured voltage is on the positive half cycle and that is in a logic low state when the measured voltage is on the negative half cycle, and measuring the current of the AC power signal and generating a second two-state output signal that is in logic high state when the measured current is on the positive half cycle and that is in a logic low state when the measured current is on the negative half cycle.

Abstract: An exemplary embodiment of the invention is a method for detecting a potentially locked axle on a vehicle propelled by an AC motor. The method includes conducting a speed test by estimating axle speed and comparing estimated axle speed to measured vehicle speed. The existence of a potential locked axle condition is determined based on the comparing of estimated axle speed to measured vehicle speed. Additional tests are disclosed for determining a potential locked axle condition and a sensor fault condition.

Abstract: The present invention makes possible a safety function for speed monitoring in the case of all induction machines operated on an inverter without a sensor system, in that a determined setpoint stator frequency value (&phgr;5*) is limited and monitored in a two-channel mode in two systems with approximate redundancy, deriving from this in each system respective sets of control signals for the electrical valves of the inverter, which can be compared with one another in two systems of monitoring electronics. In the event of fault detection, two-channel switching off takes place. The circuit arrangement according to the invention can additionally be subjected to enforced dynamization.