Abstract: A system for turning on thyristors is presented, the system comprising: an input configured to be coupled to a power source; an output configured to be coupled to a load; a first branch coupled between the input and the output and including a first thyristor having a first threshold voltage; a second branch coupled between the input and the output and coupled in parallel with the first branch, the second branch including a second thyristor having a second threshold voltage higher than the first threshold voltage; and at least one controller configured to control the system to selectively generate a biasing voltage across the second thyristor to induce a change in a voltage across the second thyristor from a first voltage to a second voltage, the first voltage being less than the second threshold voltage and the second voltage being greater than the second threshold voltage.

Abstract: A charging apparatus includes at least one housing including a compartment, an access door connected to the housing and covering the compartment, the access door being movable from an open position to a closed position, a releasable latching mechanism configured to latch the access door in the closed position, a charging terminal in the compartment, a voltage sensing terminal, and a door release circuit coupled to the voltage sensing terminal and to the releasable latching mechanisms and configured to sense a charging voltage applied to the voltage sensing terminal. The door release circuit is configured to selectively unlatch the releasable latching mechanism in response to a voltage within a predetermined voltage range being applied to the voltage sensing terminal.

Abstract: In a method for protecting lines, in which a reactor device for reactive power compensation is provided on an electrical line, a resonant current is measured on the line side of the reactor device by a first measuring device after an opening of a circuit breaker. A voltage is measured by a second measuring device after the opening of the circuit breaker. A current in the reactor device is calculated by an evaluation device on a basis of the measured voltage, and the calculated current is subtracted from the measured resonant current by the evaluation device in order to obtain a corrected current.

Abstract: A semiconductor device, including a control circuit that has a gate control circuit driving a power semiconductor element. The control circuit further includes a plurality of alarm detection circuits respectively detecting a plurality of abnormalities, a protection circuit stopping the gate control circuit responsive to the detection of any abnormality, an alarm signal generation circuit generating an alarm signal responsive to the detected abnormality, a warning detection circuit detecting a warning before any of the abnormalities is detected, and a pulse generation circuit generating a warning signal while the warning is being detected. The alarm signal is a one-shot pulse having a pulse width thereof corresponding to the detected abnormality, such that alarm signals generated responsive to different abnormalities have different pulse widths. The warning signal includes a plurality of successive pulses, each of which has a pulse width smaller than any of the pulse widths of the alarm signals.

Abstract: An exemplary system, method, and computer-accessible medium for determining a property(ies) regarding an electrical grid(s) can be provided, which can include, for example, receiving a video(s) of the electrical grid(s), determining a flicker(s) in the electrical grid(s) based on the video(s), and determining the property(ies) based on the flicker(s). The flicker(s) can be a 120 Hertz flicker. The flicker(s) can be a flicker in a light(s) recorded in the video(s). A frequency and a phase of the flicker(s) can be determined.

Abstract: An alternating current power supply configured to provide a high-voltage alternating current power output from two or more low-voltage alternating current power sources is provided. The alternating current power supply comprises a first alternating current power input, a second alternating current power input, and an alternating current power output having a first output conductor and a second output conductor. The alternating current power supply includes a first switch means for coupling the first alternating current input to the first output connector and the second alternating current input to the second output connector. The first switch means is sequentially responsive to the first current flow followed by the second current flow. The alternating current power supply further comprises an isolation means connected between the first switch means and the alternating current power output, wherein the isolation means is configured to isolate the first current flow from the second current flow.

Abstract: A clamp circuit including a power dissipation circuit having at least one transistor and a resistor which dissipates power from the surge across the resistor and the transistor by turning on the at least one transistor and forming a voltage divider between a source impedance and the resistor thereof disposed in series with a channel of the transistor; and the resistor holding a portion of transient pulse seen by the load to a low voltage and adding of the low voltage to a threshold voltage of the transistor; and a sub-circuit which tests a functionality of the power dissipation circuit.

Abstract: A method for phase controlled energizing of a power transformer includes acquiring electrical voltage signal from a voltage sensing device connected to the power transformer. Determining a first characterizing data in the voltage signal within a pre-determined set of cycles at about an opening operation of a circuit breaker and determining a second characterizing data within the pre-determined set of cycles in the voltage signal subsequent to the opening operation of the circuit breaker. Estimating a level of magnetization of the core of the power transformer based on at least one of second characterizing data, and the first characterizing data and the second characterizing data. Operating the circuit breaker at a determined instant of switching based on the estimated level of magnetization for a phase controlled energizing of the power transformer by the circuit breaker.

Abstract: An energy storage device charging system applied to a solid state transformer structure is coupled to a power grid and charges a plurality of energy storage devices, or feeds power back to the power grid from the energy storage devices. The charging system includes a conversion module, a bus path, a charging module, and a control unit. A total power conversion capacity of the conversion module is less than a total charging power capacity of the charging module. The control unit respectively allocates a plurality of demand power capacities of the charging units according to a power conversion upper limit value of the total power conversion capacity.

Abstract: Test device having a signal input with a positive pin and a negative pin, between which an-input signal may be applied. Test device has a separation unit which is connected to the positive pin and to the negative pin and is configured to separate a positive signal component in the form of a positive track from the input signal, to output said signal component at a first pin, to separate a negative signal component in the form of a negative track from the input signal and to output said signal component at a second pin. The use of the test device to test a control unit of the switching device is described, wherein the test device simulates the switching device, the signal input of the test device is connected to the control unit and the control unit outputs an input signal to the signal input.

Abstract: An implantable medical lead may include an electrode at a distal portion of the lead that is configured to monitor or provide therapy to a target site. The lead may include a visible indicator that is visible to the naked eye of a clinician at a medial portion of the lead that is configured to indicate when the electrodes of the lead are longitudinally and radially aligned properly to monitor or treat the target site. A clinician may insert the lead into the patient using an introducer sheath inserted to a predetermined depth into the patient and subsequently aligning the distal portion of the lead by orienting the indicator at an entry port of the introducer sheath.

Abstract: Disclosed is a power supply switching circuit comprising: a first switch pair for selectively connecting a first power supply node to an output node, a second switch pair for selectively connecting a second power supply node to the output node; and a switch control circuit. The switch control circuit is operable such that a first switch of each of the first switch pair and the second switch pair is controlled by a respective first control signal and a second switch of each of the first switch pair and the second switch pair is controlled by a respective second control signal, so as to connect no more than one of the first power supply node or the second power supply node to the output node at any one time.

Abstract: The invention relates to a pumping system (1), in particular, for transporting gaseous and/or liquid media having two parallel hydraulically operated oscillating piston pumps (2, 3) whose pistons (8) are moved by means of electromagnetic fields, whereby the electromagnetic fields are generated in field coils (10, L1, L2) by means of half-wave direct current pulse. The invention distinguishes itself by a circuit arrangement (19) that can be connected to an alternating current source having two parallel electric branches that are connected to the field coils (L1, L2) of one of the oscillating pumps (2, 3) respectively, wherein the circuit arrangement (19) is equipped in such a way that the field coils (10, L1, L2) are operated electrically out of phase so that the oscillating piston pumps (2, 3) are operated with a phase displacement of 180°.

Abstract: A vehicle includes an Alternating Current (AC) source, a receptacle, and a switch. The AC source has a line and neutral potential. The receptacle is carried by a body of the vehicle and includes line, neutral, and ground conductors, and a ground fault interrupter (GFI) circuit. The switch is coupled between the AC source and the GFI circuit configured to selectively short the neutral and ground conductors.

Abstract: A well system with an electrical control and sensing system includes a first conductor and a second conductor. A first switching circuit is coupled between the first conductor and the second conductor. The first switching circuit includes a first electrically powered device and a first diode coupled to the first electrically powered device. A sensor circuit is coupled between the first conductor and the second conductor. The sensor circuit includes a sensor and a sensor diode coupled to the sensor and configured to permit current flow through the sensor circuit from the second conductor to the first conductor.

Abstract: An integrated circuit (IC) includes a switch transistor, a gate driver circuit, a current sensor circuit, a voltage drop regulation circuit, and a charge-release circuit. The switch transistor is connected between input and output ports of the IC, and receives an input signal from a power source and provides the input signal as an output signal to the output port. The current sensor circuit detects the current through the switch transistor. The gate driver circuit drives the switch transistor using a control signal. The voltage drop regulation circuit is activated when the current flowing through the switch transistor is low. The voltage drop regulation circuit controls the control signal to increase the voltage across the switch transistor. When the power source is disconnected, the charge-release circuit transfers residual charge from the input port of the IC to ground.

Abstract: Provided is a gain control amplification device having a wide range and high accuracy and configured to adapt measurement target current to the input range of an A/D converter. The gain control amplification device includes: a plurality of differential amplifiers having different gains with respect to measurement target current or voltage; a threshold control circuit for comparing output of the differential amplifier with threshold voltage; a switch for selecting output of one of the plurality of differential amplifiers on the basis of output of the threshold control circuit; and an offset control circuit OF and an addition circuit for adding offset voltage to output of one of the differential amplifiers.

Abstract: An intelligent power component module operable to be driven by a negative gate voltage integrates a wide bandgap semiconductor power unit, an adjustment unit and a driving unit so as to adjust a voltage level of the driving unit by the adjustment unit. Accordingly, the wide bandgap semiconductor power unit, in a driven state, comprises a driving voltage level alternating between a positive and a negative voltage.

Abstract: In a power supply control apparatus, when a semiconductor switch is switched ON, a charging circuit increases a base voltage. A first switch is ON if a differential voltage obtained by subtracting a gate voltage from a base voltage is at least a first reference voltage, and is OFF if the differential voltage is smaller than the first reference voltage. If the first switch is ON, a battery or a capacitor charges parasitic capacitors of the semiconductor switch.

Abstract: One embodiment describes a tangible, non-transitory, computer-readable medium storing instructions executable by a processor in a control circuitry. The instructions include instructions to receive an instruction to make a switching device; determine, using the control circuitry, a voltage waveform of a power source; determine, using the control circuitry, a desired time to make the switching device based at least in part on the source voltage waveform; determine, using the control circuitry, an expected make time of the switching device; and determine, using the control circuitry, when to apply a pull-in current to make the switching device at the desired time based at least in part on the expected make time and the desired time to make.

Abstract: A wide-range positive-negative adjustable high-voltage DC power supply includes the following components: a high-voltage generator, a negative high-voltage terminal, and a positive high-voltage terminal; a first driving circuit, a first voltage regulating unit, a current detection and amplification circuit, a second driving circuit and a second voltage regulating unit that are connected in turn; and an adjustable high-voltage output terminal; as well as an instruction input terminal, an instruction voltage circuit and an error amplifier that are connected in turn, and a voltage feedback circuit.

Abstract: A polarity-selectable high voltage direct current power supply including a first drive assembly that transforms a first low voltage DC input into a first medium voltage alternating current output; a first HV output assembly that transforms the first LV AC output into a first HV DC output, wherein the first HV output assembly defines a first input stage; a polarity selector coupled between the second output junction of the first drive assembly and the first and second input stages of the first HV output assembly, the polarity selector operable between a first configuration and a second configuration; wherein in the first configuration the first HV DC output has a positive polarity; and wherein in the second configuration the first HV DC output has a negative polarity.

Abstract: A switching element drive circuit that drives a main switching element by providing a control terminal of the main switching element with a drive signal that has asymmetric positive and negative potentials with respect to a reference potential, the main switching element including a ground terminal, which is a source terminal or an emitter terminal, and to which the reference potential is connected.

Abstract: A power supply system has a lithium battery. The system includes an uninterruptible power supply (UPS) connected between a commercial power source and a device of a first type. A lithium battery is connected to the uninterruptible power supply. A voltage drop protector (VDP) is connected to the lithium battery and connected between the commercial power source and a device of a second type. Tolerable error thresholds for a voltage and frequency required for the device of the first type are smaller than tolerable error thresholds for voltage and frequency required for the device of the second type.

Abstract: A vehicle powertrain includes a variable voltage converter, a bypass diode and a controller. The bypass diode may be coupled in parallel with the converter and configured to clamp an output of the converter to a battery voltage. The controller may be configured to, while in a boost mode and in response to a rate of change of a converter inductor current exceeding a boost threshold, open switches of the converter to divert propulsive energy through the bypass diode. The controller may also be configured to, while in buck mode and in response to a magnitude of a converter inductor current exceeding a buck threshold, open switches of the converter to divert regenerative energy through the bypass diode, while reversed biased, to the battery.

Abstract: A digital clamp meter includes a common input, a voltage/resistance input, a current transformer, a voltage/resistance measuring circuit, an AC measuring circuit, a MPU and a displayer. A detecting input of the voltage/resistance measuring circuit is connected to the voltage/resistance input, a detecting output of the voltage/resistance measuring circuit is connected to a signal input of the MPU, and a controlled terminal of the voltage/resistance measuring circuit is connected to a controlling output of the MPU. The signal output of the MPU is connected to the displayer. The common input is grounded. A detecting input of the AC measuring circuit is connected to a secondary winding of the current transformer, a detecting output of the AC measuring circuit is connected to the signal input of the MPU, and a controlled terminal of the AC measuring circuit is connected to the controlling output of the MPU.

Abstract: A jump-starting arrangement is provided for a motor vehicle, wherein the motor vehicle has an engine control unit and a starter for an internal-combustion engine. The motor vehicle is equipped with at least two partial onboard power systems, which are mutually coupled by way of at least one electric separator element. Each partial onboard power system, respectively, is equipped with at least one rechargeable electric energy accumulator. The two partial onboard power systems each have a jump-starting base, and the respective jump-starting bases are galvanically separated from one another.

Abstract: Systems and methods are provided for a three-phase compensation system, whereby an electric circuit is configured to be connected with three input phases of a power source and to supply three respective output phases, said electric circuit further configured to compensate for one or two malfunctioning input phases of said three input phases by supplying current from a functioning input phase of said three input phases to replace a malfunctioning input phase.

Abstract: A circuit breaking system includes an output device for outputting an output signal; a control device controlled by the output signal; a power input terminal provided in the output device, for supplying power to the control device; a power supply to the output device, which has a ground terminal; a break circuit disposed between a power output terminal and the power input terminal; a switching circuit disposed between the break circuit and the power output terminal; and a short circuit disposed between a ground and a node which connects the power input terminal and the break circuit. The break circuit and the short circuit are operated so as to not be closed at the same time. When the switching circuit is closed, the break circuit is closed while the short circuit is open. When the switching circuit is open, the break circuit is open while the short circuit is closed.

Abstract: An electrical power restoration system for a circuit assembly having a circuit breaker, an electrical load and a circuit conditioner (e.g., a UPS) includes a circuit controller that is positioned along the circuit assembly between the circuit breaker and the electrical load. The circuit controller is electrically connected to the circuit conditioner, and controls activation and/or deactivation of the circuit conditioner. The circuit conditioner is positioned along the circuit assembly between the circuit controller and the electrical load and provides alternative AC power to the electrical load as determined by the circuit controller. The electrical power restoration assembly includes a first hot conductor and a second hot conductor. The first hot conductor conducts AC power from the circuit breaker to the circuit controller. The second hot conductor conducts AC power or alternative AC power from the circuit controller to the electrical load as determined by the circuit controller.

Abstract: In general, a branching configuration used in a wavelength division multiplexed (WDM) optical communication system, consistent with the present disclosure, includes a power feed branching unit (PFBU) having a multi-port DC/DC converter (DDCM) arrangement capable of a plurality of operating modes to distribute power in a bi-directional manner. The DDCM arrangement may include a plurality of ports for electrically coupling to one or more trunk path cable segments and for electrically coupling to a branch cable segment. A plurality of PFBUs may be disposed along a trunk path, with each PFBU powering an associated branch path, without each branch path necessarily having local power feed equipment (PFE). In instances where a branch path includes a local PFE, an associated PFBU may draw power from the branch path in order to make power available to the trunk path as needed.

Abstract: An alternating current power supply configured to provide a high-voltage alternating current power output from two low-voltage alternating current power sources is provided. The alternating current power supply comprises a first alternating current power input, a second alternating current power input, and an alternating current power output having a first output conductor and a second output conductor. The alternating current power supply includes a first switch means for coupling the first alternating current input to the first output connector and the second alternating current input to the second output connector. The first switch means is sequentially responsive to the first current flow followed by the second current flow. The alternating current power supply further comprises an isolation means connected between the first switch means and the alternating current power output, wherein the isolation means is configured to isolate the first current flow from the second current flow.

Abstract: A generator system includes an AC machine including a plurality of armature coils and a rectifier circuit electrically coupled to the armature coils. The rectifier circuit includes a plurality of switches. The generator system additionally includes a sensor device electrically coupled to a control circuit. The sensor device is configured to determine a rotor position of the AC machine. The control circuit determines a desired phase angle between a phase current and an induced voltage of the AC machine and provides a control signal to the rectifier circuit to switch the switches on and off to convert an AC signal to a DC signal and to control the rotor position of the AC machine to achieve the desired phase angle.

Abstract: A thermoelectric energy harvesting system for charging an energy store from ambient thermal energy includes a thermoelectric energy generator (TEG), an automatic polarity monitor, and switching matrix. The polarity monitor detects when the polarity of an input voltage in the system is reversed relative to a standard voltage polarity, and causes the switching matrix to switch the inputs from the thermoelectric energy harvester.

Abstract: A set of generators are connected in parallel using an electrical bus. One of the generators includes selectively connected inputs including a first input associated with a generator and a second input associated with the bus. A controller is configured to receive a first electrical characteristic from the first input assigned to a first connection and a second electrical characteristic from the second input assigned to a second connection. The controller is configured to generate a switching signal to assign the first input to the second connection or assign the second input to the first connection in response to a difference between the first electrical characteristic and the second electrical characteristic exceeding a threshold.

Abstract: An apparatus for providing protection to an electric circuit includes a P-channel MOSFET; a freewheeling diode coupled to a drain of the P-channel MOSFET and coupled to a load; and a charge pump coupled to a gate of the P-channel MOSEFT. In a normal operating mode, the charge pump receives a voltage from a voltage regulator, and is configured to multiply and reverses the polarity of the voltage to supply to the gate of the MOSFET. In a reverse battery operating mode, the charge pump receives no voltage from the voltage regulator to supply to the gate of the MOSFET causing the MOSFET to deactivate such that when the MOSFET deactivates, current is prevented from flowing through the freewheeling diode to protect the freewheeling diode.

Abstract: An image forming apparatus includes a phase controller for controlling input power applied to a heating body through phase control. The image forming apparatus includes a fuser having the heating body, a switching unit supplying the input power to the heating body, and a phase controller determining an input phase of the input power based on a temperature of the fuser, in which the phase controller further controls the switching unit to vary a phase of the input power supplied to the heating body within a phase range set based on the input phase, for each control cycle of the input power.

Abstract: A negative voltage signal generation circuit is described. The first thin film transistor (TFT) connects the first ground terminal to the control signal generation unit. The second TFT switch connects to the first TFT switch, the control signal generation unit and the negative voltage signal output terminal. The first capacitor connects to the first TFT switch, the second TFT switch and the control signal generation unit. The present invention is capable of improving the stability of the negative voltage signal generation circuit.

Abstract: A solid state relay for controlling a three-phase AC motor running direction is provided, a driver module, power components module, phase sequence detection module, phase lack detection module, and automatic phase correction and phase lack protection logic module. The input of the phase sequence detection module is connected to the three-phase power supply, and the output is connected to the automatic phase correction and phase lack protection logic module, to provide phase sequence detection and a phase sequence signal to the automatic phase correction and phase lack protection logic module. The input of the phase lack detection module is connected to the three-phase power supply, and the output is connected to the automatic phase correction and phase lack protection logic module, to detect a lack of phase and provide the lacking phase signal to the automatic phase correction and phase lack protection logic module.

Abstract: A semiconductor integrated circuit device is configured such that if, due to an erroneous connection or the like, an abnormal state is entered in which an output voltage is lower than a ground potential VSS, an N-type DMOS transistor and a first P-type MOS transistor are turned off and a voltage is applied to their parasitic diodes in the opposite direction, preventing a current from flowing. In a normal state in which the output voltage is higher than the ground potential, at least one of the N-type DMOS transistor and first P-type MOS transistor, which are connected in parallel, is turned on, preventing a current from flowing into the parasitic diode of the N-type DMOS transistor.

Abstract: Disclosed is a plug-in power adapter connectable into a screwing portion of a conventional lamp holder by a screwing connection, and power is supplied to the power adapter, and the power adapter is provided for connecting a power cable of an electric appliance to supply power to the electric appliance. When two bare ends of the power cable are connected to the power adapter and clamped by two wire clipping ends respectively to prevent the power cable from falling out easily, so as to achieve the effects of connecting the power cable securely and preventing the cable from being loosened or separated by external forces.

Abstract: The present invention relates to a cell contacting arrangement for an energy storage module having a plurality of electrochemical storage cells, each storage cell having at least two electric connection terminals, the arrangement comprising: a carrier plate which is mountable on the energy storage module, and at least one cell connector inserted into the carrier plate for connecting at least two of the connection terminals of different storage cells, the carrier plate comprising at least one catch spring having a detent for fixing the cell connector in the carrier plate.

Abstract: A charge pump includes a voltage multiplier core and a clocking circuit. The voltage multiplier core includes first and second cross-coupled CMOS devices, first and second output CMOS devices, a first capacitive node coupled between the first cross-coupled CMOS device and the first output CMOS device, and a second capacitive node coupled between the second cross-couple CMOS device and the second output CMOS device. The clocking circuit configured to control the first and second output CMOS devices to inhibit a drop in respective output voltages there from, while simultaneously controlling the first and second cross-coupled CMOS device and input voltages applied to the first and second capacitive nodes to minimize leakage from the first and second capacitive nodes.

Abstract: A method for converting DC power from a source into AC power by means of an inverter which includes three bridge branches, each having a phase output, is described. During grid-connected operation, the bridge branches are actuated in such a way that the AC power is fed, as three-phase grid-compliant power, into a grid. During emergency operation of the inverter, the AC power is provided as single-phase island grid by two of the three bridge branches at the phase outputs thereof, wherein the inverter is disconnected from the grid.

Abstract: A generator, for example a three-phase generator including an associated rectifier system, is used, for example for the electrical voltage supply of a motor vehicle. The AC voltage produced by the generator is rectified by the rectifier system having a plurality of rectifying elements 2, 7. Rectifying elements 2 of the rectifier have a plurality of series connections of a self-conducting n-channel JFET and a self-conducting p-channel JFET, the gate terminals being connected to the outer source or drain terminals of the other transistor. Alternatively, the self-conducting JFETS of the rectifying element 2 in FIG. 1 may be replaced by self-conducting MOS field effect transistors (depletion mode MOSFET). The p-channel JFET of the exemplary embodiment according to FIG. 1 is replaced by a self-conducting p-channel MOSFET and the n-channel JFET is replaced by a self-conducting n-channel MOSFET. Furthermore, the gate terminals are connected to the diametrically opposed outer terminals.

Abstract: An indoor unit performs a control operation to not supply power to a load device through a power/communication line simultaneously with other indoor units. An air conditioning system may includes an indoor unit including a microcomputer to output a power application signal to supply power to a load device through a power/communication line, and a duplicate power application prevention unit to interrupt the power application signal from the microcomputer when the power is simultaneously applied to the power/communication line by a different indoor unit, to prevent the power from being duplicately applied to the power/communication line.

Abstract: A switching circuit controls the flow of current between its input and output in accordance with the state of a control signal applied to the circuit. When the control signal is in a first state and the voltage applied to the input is higher than the voltage at the output, the circuit provides a low resistance path between its input and output terminals thereby enabling current to flow from the input to the output. When the control signal is in the first state and the voltage at the output is higher than the voltage at the input, the circuit inhibits current flow from the output to the input. When the control signal is in a second state, the circuit is turned off thus inhibiting current flow between the input and the output.

Abstract: A set of generators are connected in parallel using an electrical bus. One of the generators includes selectively connected inputs including a first input associated with a generator and a second input associated with the bus. A controller is configured to receive a first electrical characteristic from the first input assigned to a first connection and a second electrical characteristic from the second input assigned to a second connection. The controller is configured to generate a switching signal to assign the first input to the second connection or assign the second input to the first connection in response to a difference between the first electrical characteristic and the second electrical characteristic exceeding a threshold.

Abstract: A method and device for a provision of control power for a power supply network in which control power is provided, wherein an energy producer and an energy consumer are jointly operated, wherein the power which the energy consumer removes from the power supply network is restricted to provide a positive control power, and the power which the energy producer feeds into the power supply network is restricted to provide a negative control power.

Abstract: A demand response unit (DRU) interposed between a utility's electrical power line (PL) and at least one load (L1-Ln) to which power is supplied by the utility over the line. A detector (Fdet or Vdet) measures a characteristic (frequency F, voltage V) of an electrical waveform (W) by which power is transmitted by the utility to the load. The detector determines both when the measured frequency or voltage exceeds a predetermined threshold for a first predetermined period of time; and, if the threshold is exceeded, when the frequency or voltage exceeds the second predetermined threshold for a second predetermined period of time. For this purpose, the detector processes a predetermined number of intervals of the waveform and produces an average value of the characteristic which is compared to the threshold. This is done to reduce the effect of extraneous events which may temporarily change the value of the frequency or voltage.