A method of modulating a cascaded three-phase VFD, including: obtaining space voltage vectors according to states and output levels of switches of power units in each stage, and dividing the vectors into large vectors, medium vectors, small vectors and zero vectors according to their lengths; arranging the vectors into a vector space, and dividing the vector space into sectors, wherein each sector corresponds to a group of the large vector, the medium vector, the small vector and the zero vector; determining a sector in which a reference voltage vector is located, wherein the reference voltage vector is composed by the group of vectors; calculating action time of the vectors in the group; allocating an action order to the vectors; and generating a three-phase modulated wave signal based on the action orders and the action time.

A method of modulating a cascaded three-phase VFD, including: obtaining space voltage vectors according to states and output levels of switches of power units in each stage, and dividing the vectors into large vectors, medium vectors, small vectors and zero vectors according to their lengths; arranging the vectors into a vector space, and dividing the vector space into sectors, wherein each sector corresponds to a group of the large vector, the medium vector, the small vector and the zero vector; determining a sector in which a reference voltage vector is located, wherein the reference voltage vector is composed by the group of vectors; calculating action time of the vectors in the group; allocating an action order to the vectors; and generating a three-phase modulated wave signal based on the action orders and the action time.

A generator starter of a turbomachine, including an asynchronous electric machine configured so as to operate in motor mode during a starting phase of the turbomachine while being supplied by an electrical source, and so as to operate in generator mode after the starting phase of the turbomachine in order to supply an electrical load. An inverter is arranged between the electrical source and the asynchronous machine with at least two alternating current terminals coupled to the asynchronous machine, and a control unit for the inverter configured to supply the asynchronous machine with a starting current in motor mode and a magnetisation current in generator mode. The asynchronous machine includes at least one first stator winding connected to the alternating current terminals to be supplied with the starting current in motor mode and with the magnetisation current in generator mode, and at least one second stator winding connected to the electrical load in generator mode.

A generator starter of a turbomachine, including an asynchronous electric machine configured so as to operate in motor mode during a starting phase of the turbomachine while being supplied by an electrical source, and so as to operate in generator mode after the starting phase of the turbomachine in order to supply an electrical load. An inverter is arranged between the electrical source and the asynchronous machine with at least two alternating current terminals coupled to the asynchronous machine, and a control unit for the inverter configured to supply the asynchronous machine with a starting current in motor mode and a magnetisation current in generator mode. The asynchronous machine includes at least one first stator winding connected to the alternating current terminals to be supplied with the starting current in motor mode and with the magnetisation current in generator mode, and at least one second stator winding connected to the electrical load in generator mode.

In a method for operating a double-fed asynchronous machine, an exciter winding of the rotor is excited by adjusting an amplitude or a frequency of a voltage or current independently of armature values of the stator to attain a predetermined phase position and amplitude in the stator. While the stator is disconnected from an electrical grid, the rotation speed of the rotor is increased during startup and the amplitude of the voltage and/or of the current flow is adjusted to less than a start-up limit value, while the frequency of the voltage and/or of the current flow is adjusted to a grid frequency. The winding arrangement is then connected to the electrical grid, and the amplitude of the voltage and/or of the current flow is adjusted to an operating value which is greater than the start-up limit value by a predetermined amount.

In a method for operating a double-fed asynchronous machine, an exciter winding of the rotor is excited by adjusting an amplitude or a frequency of a voltage or current independently of armature values of the stator to attain a predetermined phase position and amplitude in the stator. While the stator is disconnected from an electrical grid, the rotation speed of the rotor is increased during startup and the amplitude of the voltage and/or of the current flow is adjusted to less than a start-up limit value, while the frequency of the voltage and/or of the current flow is adjusted to a grid frequency. The winding arrangement is then connected to the electrical grid, and the amplitude of the voltage and/or of the current flow is adjusted to an operating value which is greater than the start-up limit value by a predetermined amount.

Embodiments of a mixing device power system generally include a power control module, an AC motor, and a variable frequency drive, wherein upon application of AC power to the system, electrical power is provided to the power control module which transmits electrical power to the AC motor, whereby rotation of a mixing spindle is initiated. After the spindle has begun rotating, transmission of electrical power from the power control module to the AC motor is ceased, and substantially simultaneously electrical power transmission is commenced from the power control module to the variable frequency drive which transmits electrical power to the AC motor, whereby rotation of the mixing spindle is continued. A method of using the mixing device power system to mix a fluid sample is also provided.

A motor starter includes: a motor circuit breaker which has an electronic tripping device; a contactor which is correspondingly interconnected to the motor circuit breaker for forming the motor starter; and at least one control line disposed between the motor circuit breaker and the contactor, via which control line a control signal, which is generated depending upon a switching signal for switching the contactor, is transmitted from the contactor to the electronic tripping device. The electronic tripping device generates a tripping signal for switching off a current flow across the switching contact or switching contacts of the motor circuit breaker, depending upon the control signal and current flow across one or more switching contacts of the motor circuit breaker.

A motor starter includes: a motor circuit breaker which has an electronic tripping device; a contactor which is correspondingly interconnected to the motor circuit breaker for forming the motor starter; and at least one control line disposed between the motor circuit breaker and the contactor, via which control line a control signal, which is generated depending upon a switching signal for switching the contactor, is transmitted from the contactor to the electronic tripping device. The electronic tripping device generates a tripping signal for switching off a current flow across the switching contact or switching contacts of the motor circuit breaker, depending upon the control signal and current flow across one or more switching contacts of the motor circuit breaker.

A reactive power system comprises a plurality of electrical capacitor banks, with each electrical capacitor bank electrically connected in series with an electrical switch. The electrical switches may be electrically connected to a system such as, for example, an electrical induction motor starter system. A controller is coupled with the motor starter system and each of the electrical switches. The controller, in response to receiving a signal from the motor starter system, determines which of the plurality of electrical capacitor banks from which electrical power should be provided for the motor starter system. For the determined or identified electrical capacitor bank(s), the controller identifies the corresponding electrical switch(es) and communicates a signal to close the switch(es). Closing the switches results in the capacitors in the corresponding electrical capacitor banks to be electrically connected to the motor starter system and to provide current to the motor starter system.