Abstract: An inverter for an electric machine, and a method for operating the inverter, has at least one output stage unit for producing a connection between the electric machine and a power supply network, a control unit for controlling the output stage unit, a supply unit independent of the power supply network for power supply of the output stage unit, at least one emergency operation control assigned to the output stage unit for controlling the output stage unit such that switching elements are switched into a short circuit operation, at least one emergency operation supply assigned to the output stage unit for generating a power supply from the power supply network, and a coordination control, which activates or deactivates the emergency operation control as a function of a status signal of the independent supply unit and a standby signal of the control unit.

Abstract: A fan speed control circuit for controlling the rotation speed of a fan motor unit. The speed control circuit includes a resistor, a voltage stabilizing unit, a transistor and a thermal resistor. The resistor is connected to a power source of the fan motor unit, the voltage stabilizing unit is connected between the resistor and ground. The collector of the transistor is connected to the fan motor unit, the base is connected to a node between the resistor and the voltage stabilizing unit. The thermal resistor is connected between an emitter of the transistor and ground.

Abstract: Provided are compositions and materials that have varistor properties and are suitable for use in electrical stress control devices and surge arrestor devices. The compositions and materials include a polymeric material and calcined calcium copper titanate filler material and have a reversible non-linear current-voltage characteristic.

Abstract: An arrangement and a method for distributing power supplied by a power source to two or more of loads (e.g., electrical vehicular systems) is disclosed, where a representation of the power taken by a particular one of the loads from the source is measured. The measured representation of the amount of power taken from the source by the particular one of the loads is compared to a threshold to provide an overload signal in the event the representation exceeds the threshold. Control signals dependant on the occurring of the overload signal are provided such that the control signal decreases the output power of the power circuit in case the overload signal occurs.

Abstract: A feedback control method of a pulse width modulator (PWM) voltage converter may include generating a control voltage as a sum of an offset voltage and an error signal representing a difference between a scaled replica of a regulated output voltage of the voltage converter and a reference voltage, comparing the control voltage with a ramp signal, the comparing operation generating PWM driving signals for the voltage converter, comparing the regulated output voltage of the voltage converter with an overshoot threshold, and reducing the control voltage when the overshoot threshold is exceeded.

Abstract: An over-temperature protection circuit is adapted to a light source driver coupled to a light-emitting device. The light source driver has a current setting terminal receiving a set current to control the magnitude of a current flowing through the light-emitting device. The over-temperature protection circuit includes a first, second, and third resistors, a thermal resistor measuring temperature of the light-emitting device, and a diode. A first terminal of the first resistor provides the set current to the current setting terminal. The second resistor is coupled between the first resistor and a ground voltage in series. A first terminal of the thermal resistor is coupled to a reference voltage. The third resistor is coupled between the thermal resistor and the ground voltage in series. An anode and a cathode of the diode are respectively coupled to a second terminal of the thermal resistor and a second terminal of the first resistor.

Abstract: A switching power supply includes: a first switch provided between a positive terminal of a DC power supply and a positive terminal of a load; a second switch connected in parallel with the first switch; a first capacitor provided between the second switch and a node of the first switch on a DC power supply side; a first inductor provided between the first capacitor and the positive terminal of the DC power supply; and a control circuit that turns off the second switch after the first switch is turned off and when or before a voltage across the first capacitor becomes zero.

Abstract: Some embodiments include an electrical surge protector. Other embodiments of related systems and methods are also disclosed.

Abstract: The invention relates to a driving circuit comprising a first bridge circuit, a second bridge circuit, a first protection device and a second protection device. The first bridge circuit comprising a first positive input terminal, a first negative input terminal, a first positive output terminal and a first negative output terminal is coupled to an AC voltage source to output a first voltage. The second bridge circuit comprising a second positive input terminal, a second negative input terminal, a second positive output terminal and a second negative output terminal is coupled to the AC voltage source to output a second voltage. The second and the first negative output terminals are both coupled to the ground potential. The first protection device is coupled between the second positive input terminal and the AC voltage source. The second protection device is coupled between the second negative input terminal and the AC voltage source.

Abstract: A display apparatus and a power supplying method are provided. The display apparatus includes a signal receiver which receives a video signal; a signal processor which processes the video signal; a display unit which displays an image based on a video signal processed by the signal processor; and a power supply which converts an alternating current (AC) voltage into a direct current (DC) voltage and supplies an operation voltage to the display unit, the power supply including: a power factor correction (PFC) unit which adjusts the DC voltage and corrects a power factor of the power supply; a detector which detects a plurality of voltages in the power supply and outputs a common detection signal indicating whether at least one of the plurality of voltages is abnormal; and a controller which receives the common detection signal, and controls the PFC unit based on the common detection signal.

Abstract: An inrush current control circuit selectively short-circuit bypasses an inrush current limiting resistor (R1) of a power supply that includes a switching transistor (Q1) having a control terminal (gate or base) driven in dependence on a pulse width modulated (PWM) drive signal. The inrush current control circuit includes a bypass transistor (Q3), a first resistor (R3), a capacitor (C2), a second resistor (R2) and a diode (D3), wherein an anode terminal of the diode (D3) is connected to one of the terminals of the switching transistor (Q1) of the power supply.

Abstract: A power supply apparatus and method are provided. A conversion component outputs a first current having a predetermined phase region, an output component outputs a load voltage, a sense component senses a second current value, and a switch element allows current to flow in a first state and impedes current in a second state. The switch element changes between states based on a drive signal forcing the switch into the second state when the first current is in the predetermined phase region and the second current value exceeds a threshold indicating an overcurrent condition. A region determination circuit determines whether the first current is in the predetermined phase region and produces a phase region signal. An overcurrent detection circuit senses the second current value, determines whether it exceeds an overcurrent condition threshold, and produces an overcurrent signal. A protection circuit causes the drive circuit to switch the drive signal.

Abstract: A power supply module includes a rectifying and filtering unit, a pulse width modulation (PWM) unit, a voltage transforming unit, a sampling and comparing unit, and an overvoltage protection unit. The rectifying and filtering unit receives an alternating current (AC) voltage, and generates a filtered primary DC voltage. The PWM unit is configured for generating pulses. The voltage transforming unit transforms the filtered primary DC voltage into the DC voltage according to the pulses. The sampling and comparing unit samples the DC voltage, and generates an overvoltage signal when the sampled DC voltage exceeds a predetermined DC voltage. The overvoltage protection unit is coupled between the sampling and comparing unit and the PWM unit. According to the overvoltage signal, the overvoltage protection unit generates a first control signal to disable the PWM unit, and the overvoltage protection unit is self-locked.

Abstract: The present invention relates to a protection circuit, a resonance converter having the same, and a protection method thereof. A resonance converter having high-side and low-side switches senses a current flowing through the low-side switch and determines a zero voltage switching failure by using a width of a current flowing to a negative direction of the low-side switch.

Abstract: There is provided a control system and method related to the use of insulated gate bipolar transistor (IGBT) devices in vehicles. An exemplary control method includes receiving a status signal that indicates a fault condition in the operation of an IGBT device of an affected converter. The exemplary method also includes sending a control signal that turns off all IGBTs of the affected converter. The exemplary method additionally includes receiving a second status signal for each of the IGBTs that indicates whether each of the IGBTs successfully turned off. The exemplary method further includes generating an indication that the fault condition relates to a saturation condition or a power supply being outside a designated range, depending on a duration of the fault signal.

Abstract: The short-circuit protection circuit includes a first logic circuit that outputs the first logic signal so as to turn off the fourth MOS transistor in a case where the first gate voltage signal has a value that turns on the first MOS transistor and the switching terminal has a terminal voltage between a predetermined first threshold value and the second potential. The short-circuit protection circuit includes a first detecting circuit that compares a first detected voltage between the second end of the first resistor and the first end of the third MOS transistor with a predetermined first reference voltage and outputs, in a case where the first detected voltage is closer to the second potential than the first reference voltage, a first detection signal indicating that the switching terminal and the second potential are short-circuited.

Abstract: A surgical generator and related method for mitigating overcurrent conditions are provided. The surgical generator includes a power supply, a radio frequency output stage, an overcurrent detection circuit in operative communication with an interrupt circuit, and a processor. The power supply generates a power signal and supplies the power signal to the radio frequency output stage. The radio frequency output stage generates a radio frequency signal from the power signal. The overcurrent detection circuit detects an overcurrent of the power signal and/or an overcurrent of the radio frequency signal. The interrupt circuit provides an interrupt signal in response to a detected overcurrent. The processor receives the interrupt signal and supplies a pulse-width modulation signal to the power supply and incrementally decreases the duty cycle of the pulse-width modulation signal in response to the interrupt signal. The radio frequency output stage may be disabled in response to the detected overcurrent.

Abstract: An over-current protection device for multiple high-voltage motive devices is provided. The over-current protection device includes a comparison module and a logic operation module. The comparison module receives a plurality of voltages generated from a plurality of operating currents of a plurality of high-voltage motive devices and respectively compares the voltages with at least one reference voltage to generate a plurality of comparison results, wherein the high-voltage motive devices are solenoids, electronic clutches, or a combination of solenoids and electronic clutches. The logic operation module receives the comparison results and generates at least one control signal for a plurality of high-voltage motive device driving circuits according to the comparison results. The high-voltage motive device driving circuits respectively drive the high-voltage motive devices according to the control signal.

Abstract: An isolated type power supply includes a transformer, and a power switch and a current sense resistor serially connected to a primary coil of the transformer, and a protection apparatus and method monitor a control signal which is used to switch the power switch in normal operation, and trigger a signal to stop the power from switching when the control signal becomes greater than a threshold. This protection apparatus and method can more quickly detect short circuit of the current sense resistor, and prevent the isolated type power supply from overcurrent impact.

Abstract: A solid state power controller system can include a direct current load, a solid state power controller apparatus including an alternating current sensor coupled to the direct current load, a direct current sensor coupled to the direct current load, a voltage sensor coupled to the direct current load, a main switch coupled to the direct current load via the alternating and direct current sensors, an auxiliary switch coupled in parallel to the main switch, a current limiting resistor coupled in series to the auxiliary switch and a solid state power controller coupled to the main switch, the auxiliary switch, the alternating current sensor, the direct current sensor, and the voltage sensor, and a direct current power source coupled to the solid state power controller apparatus.

Abstract: An embodiment bridgeless power factor correction circuit comprises a first boost converter and a second boost converter connected in parallel. A first switch is coupled between the input of the first boost converter and ground. A second switch is coupled between the input of the second boost converter and ground. Both the first switch and the second switch help to reduce the common mode noise of the bridgeless power factor correction circuit. The bridgeless power factor correction circuit further comprises two surge protection diodes coupled between the inputs of two boost converters and the output of the bridgeless power factor correction circuit.

Abstract: A plant for transmitting electric power includes a high voltage DC line, a DC breaker connected in series therewith and configured to break a fault current upon occurrence of a fault, a device configured to detect occurrence of a fault current, a control unit configured to control the DC breaker for protecting equipment connected to the DC line upon occurrence of the fault current and a device configured to dissipate energy stored in a faulty current path of the DC line between the location and the device's upon occurrence of the fault to the moment of the control of the DC breaker. The energy dissipating device includes a series connection of an energy consuming braking resistor and a free-wheeling rectifying member connected between ground and the DC line to conduct current while forming a free-wheeling path therethrough upon the control of the DC breaker upon occurrence of the fault.

Abstract: An apparatus for providing power from a vehicle power source to at least one portable electrical device includes: (a) a power interface unit for coupling with the vehicle power source; (b) a power converter unit coupled with the power interface unit; (c) at least one first voltage output connection structure coupled with the power converter unit; the at least one first voltage connection structure presenting at least one first voltage output; the at least one first voltage output connection structure being configured for effecting universal serial bus coupling; and (d) first short-circuit protection circuitry coupled with the power converter unit and the at least one first voltage output connection structure.

Abstract: Provided herein are circuits, systems and methods that monitor for a fault within a multi-phase DC-DC converter. This can include monitoring the channels of the DC-DC converter for way out of balance (WOB) conditions, and monitoring for a component fault in dependence on detected WOB conditions. A fault can be detected if, during a predetermined period of time, one of the WOB conditions occurs at least a specified amount of times more than another one of the WOB conditions. The DC-DC converter and/or another circuit can be shut-down in response to a fault being detected. Additionally, or alternatively, a component fault detection signal can be output in response to a fault being detected.

Abstract: An over-current protection device is employed to control switching associated with a switched mode power supply to prevent the excessive buildup of current. The device includes a function for relating the switching of the SMPS with a monitored output of the SMPS. This function is selectively modified to ensure the current associated with the SMPS does not exceed a maximum value and does not fall below a minimum value.

Abstract: An embodiment bridgeless power factor correction circuit comprises a first boost converter and a second boost converter connected in parallel. A first switch is coupled between the input of the first boost converter and ground. A second switch is coupled between the input of the second boost converter and ground. Both the first switch and the second switch help to reduce the common mode noise of the bridgeless power factor correction circuit. The bridgeless power factor correction circuit further comprises two surge protection diodes coupled between the inputs of two boost converters and the output of the bridgeless power factor correction circuit.

Abstract: The present disclosure provides a management device for a charging circuit and a wireless terminal, which belong to the technical field of management control of a linear charging circuit. The device includes a power supply management module (5), a buck switching voltage converter (1) and a linear charging circuit (2). The power supply management module (5) includes an adjustable Low Dropout (LDO) linear regulator (6) and an Analog-to-Digital Converter (ADC) (4), wherein the output terminal of the adjustable LDO linear regulator (6) is connected with the feedback terminal of the buck switching voltage converter (1) through a first preset resistor (R62). The input terminal of the ADC (4) is connected with the anode of a battery (3). The control terminal of the power supply management module (5) is connected with the control terminal of the linear charging circuit (2). The output terminal of the buck switching voltage converter (1) is connected with the input terminal of the linear charging circuit (2).

Abstract: Provided herein are circuits, systems and methods that monitor for way out of balance (WOB) conditions within a multi-phase DC-DC converter, and adjust a balance between currents through channels of the DC-DC converter, in dependence on detected WOB conditions.

Abstract: A soft-stop overvoltage protection circuit, into which a soft-stop overvoltage detection voltage proportional to a direct current output voltage is input, reduces the output of a multiplier in accordance with the soft-stop overvoltage detection voltage when the soft-stop overvoltage detection voltage exceeds a first threshold value. An overvoltage protection circuit, a second threshold value higher than the first threshold value being set, compulsorily turns off a switching element by outputting an overvoltage detection signal when the soft-stop overvoltage detection voltage exceeds the second threshold value. The soft-stop overvoltage protection circuit compulsorily increases the output of a voltage error amplifier circuit on the output voltage decreasing. When the output of the voltage error amplifier circuit increases suddenly, and the output voltage rises excessively, the soft-stop overvoltage protection circuit decreases the output of the multiplier, thus curbing the rise of the output voltage.

Abstract: A hybrid power plant is characterized by a substantially constant load on generators regardless of momentary swings in power load. Short changes in power load are accommodated by DC components such as capacitors, batteries, resistors, or a combination thereof. Resistors are used to consume power when loads in the power plant are generating excess power. Capacitors are used to store and deliver power when the loads in the power plant demand additional power. Reducing rapid changes in power load as seen by the generators allows the generators to operate at higher efficiencies and with reduced emissions. Additionally, power plants employing combinations of generators, loads, and energy storage devices have increased dynamic performance.

Abstract: An embodiment high efficiency power regulator comprises a three-terminal converter and a protection device. The three-terminal converter comprises a first terminal coupled to a positive terminal of an input voltage bus, a second terminal coupled to a positive terminal of an output voltage bus and a third terminal coupled to the protection device. The protection device comprises an inrush current limiting element connected in series with a reverse polarity protection device.

Abstract: A circuit (S) for protecting a DC network having DC loads (1) and connectable to the circuit (S), the circuit (S) is suitable and configured to supply the DC network with electric power via a three-phase rectifier (G) and wherein the circuit (S) includes a means (2, 3, 4, TH1, LS, CS, DU, DV, DW) for detecting an overvoltage, wherein the means is suitable and configured to detect an overvoltage at the input of the DC network, and the circuit (S) includes a means (2, 3, 4, TH1, LS, CS, DU, DV, DW) for transferring a current, wherein the means is suitable and configured to supply current to one or several current-carrying thyristors (THU1, THV1, THW1) of the rectifier (G), wherein the current causes the thyristor or thyristors (THU1, THV1, THW1) to turn off as soon as the detection means has detected an overvoltage.

Abstract: A circuit arrangement for increasing the safety of an electronic operating device comprising: mains input terminals (3), a mains input filter (1) with X capacitors (XC1, XC2), which are connected in parallel with the mains input terminals, a rectifier part (2) with a full-wave rectifier (D1-D4) and a smoothing capacitor (C1), which is connected between the output terminals of the full-wave rectifier (D1-D4), and a DC-DC voltage converter (4), which is connected to the output terminals of the rectifier part. When the mains voltage is disconnected from the terminals, a load is switched on for a defined time span, the load and the time span being matched in such a way that the load consumes the residual energy which is stored in the capacitors (XC1, XC2, C1), and thus lowers the voltage across the mains input terminals (3) to a value which is unhazardous for humans within a very short period of time.

Abstract: A method for shutting down an electric machine having a pulse-controlled inverter in the event of a malfunction. Undesirable side effects during shut-down of the electric machine may be minimized and the regular machine operation may be maximized when the electric machine is first switched to a disconnect mode in which all switches of the pulse-controlled inverter are open and subsequently is switched to a short-circuit mode in which the switches connected to the high potential are open and the switches connected to the low potential are closed.

Abstract: To provide a control circuit of power supply unit, power supply unit and control method thereof capable of setting and adjusting a voltage value of output voltage flexibly corresponding to an instruction from outside, a voltage adjusting portion AD for adjusting first voltage setting information inputted from outside to real voltage information is provided and the voltage value of the output voltage of the power supply unit is controlled based on real voltage information outputted from the voltage adjusting portion AD. The first voltage setting information inputted from outside enables a desired output voltage to be set up by adjusting the real voltage information flexibly even if information relating to the setting of voltage set as output voltage to an external device which is a supply destination is different from actually necessary voltage value.

Abstract: This relates to detecting unwanted couplings between a protected terminal and other terminals in an integrated controller of a power supply. Offset and clamp circuitry may apply a positive or negative offset voltage and clamp current to one or more terminals of the controller. In the event that a terminal having the offset voltage and clamp current is accidentally coupled to the protected terminal, the offset voltage and clamp current may be applied to the protected terminal. The protected terminal may be coupled to a fault detection circuitry operable to detect a fault signal at the protected terminal. The fault detection circuitry of the controller may cause the power supply to shut down in response to a detection of the fault signal at the protected terminal or may cause the power supply to shut down in response to a detection of a predefined threshold number of cycles in which the fault signal is detected.

Abstract: An integrated circuit is configured to be coupled to a current sensing element and a set resistor having a resistance Rset. The integrated circuit comprises a sense resistor having a resistance Rsense. The sense resistor is coupled to an input of the integrated circuit such that a first sensed current from the current sensing element flows through the sense resistor. The integrated circuit also comprises a reference resistor having a resistance Rreference which is a fixed multiple of Rsense; and circuitry configured to produce an output current such that the value of the output current is proportional to a value of Rset and a fixed ratio between Rsense and Rreference.

Abstract: According to one embodiment, a smart photovoltaic (PV) panel comprises a plurality of PV cell groups each including at least one PV cell. The smart PV panel also includes at least one serial boost combiner circuit (SBCC) configured to receive an output from the plurality of PV cell groups as inputs. Each SBCC comprises several boost blocks connected in parallel, each of the boost blocks including a switching device and a respective boost block output directly connected to an output node of the SBCC. In addition a corresponding power terminal of each of the switching devices is directly connected to a common ground node of the SBCC. In one embodiment, the smart PV panel also includes a power inverter coupled to the one or more SBCCs and a communication unit interfaced with a local controller.

Abstract: Disclosed herein is an overvoltage protection apparatus and method of a high voltage inverter adapted to protect a load without any adverse effect from an overvoltage aroused by voltage fluctuation attributable to an impedance difference among an inverter, a load and a cable connected between the inverter and the load, wherein the apparatus and method converts a voltage command signal given as a digital signal into an analog reference signal by a main control unit, compares the analog reference voltage with a sawtooth wave having a predetermined voltage level and frequency in order to generate a PWM (Pulse Width Modulation) signal, determines the pulse width of the PWM signal, and converts the pulse width of the PWM signal to have a predetermined time interval in a case the pulse width of the PWM signal is less than a predetermined time interval.

Abstract: A power supply system for a display panel includes a power supply regulator that regulates a power supply voltage of a display driver of a power supply circuit connected to the display panel, and a protection circuit that protects the display driver against an overvoltage.

Abstract: A DC/DC converter and a method protect a MOSFET driven by the converter from overcurrent conditions. No extra pins are required to sense the current, which saves IC package area and cost.

Abstract: The present invention relates to a protection circuit, a resonance converter having the same, and a protection method thereof. A resonance converter having high-side and low-side switches senses a current flowing through the low-side switch and determines a zero voltage switching failure by using a width of a current flowing to a negative direction of the low-side switch.

Abstract: Aspects of the invention are directed to methods and apparatus to protect an inverter from failure due to neutral lifting. In one aspect, the present invention provides a method of controlling an inverter in a UPS, the inverter being selectively coupled to a power line and comprising an input to receive an input voltage from the power line. The method comprises acts of monitoring the input voltage, detecting based on the act of monitoring, that the input voltage exceeds a predetermined high threshold value, isolating the inverter from the power line responsive to detecting that the input voltage exceeds a predetermined high threshold value, determining whether or not a neutral lifting condition exists on the power line, indicating that the inverter is in a fault state if the neutral lifting condition exists, and reconnecting the inverter to the power line if the neutral lifting condition does not exist.

Abstract: Various apparatuses, methods and systems for damping a current driver are disclosed herein. For example, some embodiments provide an apparatus for supplying current, including an output transistor connected between a voltage supply and a current output, and an active clamp connected between the current output and a current sink. The active clamp is adapted to connect the current output to the current sink when a voltage at the current output reaches a predetermined state relative to a voltage at a control input of the output transistor.

Abstract: The present invention discloses a switching regulator control circuit which distinguishes the output short-circuit condition, which imposes immediate danger, from other mild over current conditions. The switching regulator control circuit includes: an over current judgment circuit comparing a current sense signal with a current limit to generate an over current indication signal; a time comparison circuit comparing the over current indication signal with a clock signal to generate an output short-circuit indication signal; and a timer receiving the over current indication signal and the output short-circuit indication signal, wherein when the output short-circuit indication signal does not indicate output short-circuit, the timer counts a first time period, and when the output short-circuit indication signal indicates output short-circuit, the timer counts a second time period shorter than the first time period, for better safety protection.

Abstract: A power protection circuit includes a fuse, a plurality of voltage converters, and controller. The fuse is electrically connected to a power source to transfer electric energy. The controller controls the fuse and the voltage converters, and the voltage converters are selectably electrically connected to or disconnected from the power source through the fuse. When the output voltage of a voltage converter exceeds a predetermined voltage of the voltage converter, the controller blows the fuse to the voltage converters. Hence, a computer cannot be restarted immediately before troubleshooting and replacement of the blown fuse, which can protect the voltage converters and the adjacent components in the computer due to direct reboot.

Abstract: A power source circuit includes a voltage converter circuit and a control circuit that includes a voltage divider circuit and a protective circuit. The protective circuit includes a first oxide semiconductor transistor in which an off-state current is increased as temperature is increased, a capacitor that accumulates the off-state current as electric charge, a second oxide semiconductor transistor, and an operational amplifier including a non-inverting input terminal to which a reference voltage is input. The first oxide semiconductor transistor is provided near the voltage converter circuit or an element that generates heat in the control circuit.

Abstract: An LED driving circuit for driving an LED module is provided. The LED module is coupled to an inductor and a flywheel unit to provide a continuous current conduction of the inductor. A terminal of a converting switch is coupled to the LED module, and another terminal thereof is coupled to ground through a current detection unit that generates a current feedback signal to a controller, so as to stabilize a current flowing through the LED module. The LED driving circuit also includes a protecting circuit, which detects a potential of one end of the LED module to generate a detection signal and makes/has the converting switch to be turned off responsive to the detection signal. If the converting switch is turned off, driving of the LED module is stopped.

Abstract: A DC-to-DC converter includes a switching control circuit adapted to provide a control signal having a duty cycle. A switching regulator is adapted to receive both a supply voltage having the first voltage level and the control signal. The switching regulator is further adapted to provide an output signal at the second voltage level as a function of both the supply voltage and the control signal. In addition, a current sensing circuit is adapted to provide at least one alarm signal based the duty cycle of the time-varying signal. Other systems and methods are also disclosed.

Abstract: The aim of the invention is to reduce the frequency change of a electric network in fault situations so that there is no need for protection operations during relatively short imbalances between electricity production and demand thereof. The aim is achieved by means of an apparatus, system and method for electric power supply according to main claims for directing electric power to the electric motor (7). The apparatus according to the invention monitors the frequency of the network (1). In case the frequency of the network changes sufficiently, the apparatus reacts by changing the amount of electric power directed to the electric motor (7). The electric supply network (1) is provided with an opportunity to change the amount of produced electric energy in a controlled way so that the electric supply network is continuously in operation.