Abstract: The present invention is directed at a method for evaluating the degradation level of capacitors of a power filter connected to an adjustable speed drive (ASD) or a power converter. The invention is also directed at an adjustable speed drive and a power converter provided for performing the method.

Abstract: A method for determining a motor type of an electric motor includes several phases, wherein two or more pulses are applied to the motor, respective currents are measured and the motor type is determined based on the pulses. Further, a motor control apparatus is configured to perform such a method.

Abstract: The invention relates to a motor drive for monitoring operational measurement data (34) of an electric motor (12) having at least one operating point (78, 80, 82, 84), wherein the electric motor (12) is configured to drive a load (21), the motor drive (10) comprising a measurement unit (14) for acquiring initial measurement data (118) for at least one of the operating points (78, 80, 82, 84) of the electric motor (12), wherein the initial measurement data comprises sensor data and/or estimated data; a processing unit (26) for determining a baseline (58, 60, 62, 64) from the initial measurement data (118) for the at least one operating point (78, 80, 82, 84); an output unit (28); characterized in that the processing unit (26) is configured to generate at least one threshold level (36, 38, 40) for the at least one determined baseline (58, 60, 62, 64), while the electric motor (12) is on an on state or an off state; wherein the at least one threshold level (36, 38, 40) defines a level of deviation from the deter

Abstract: A method for providing thermal protection for a pre-charge unit (PRC) in an electric power conversion system, such as a medium-voltage adjustable-speed drive with a step-up transformer and DC link. The method includes identifying the electrical and thermal parameters of the PRC, estimating the current through the step-up transformer of the PRC based on input voltage, and estimating the thermal level of the transformer from the current. A protection logic then compares the estimated thermal level to a pre-determined trip threshold and outputs a trip signal if the threshold is exceeded. The disclosure also covers an electric power conversion system configured to perform this thermal protection method.

Abstract: A voltage balancing circuit for capacitor banks or voltage cells connected in series. The circuit includes a DC-link with at least two capacitors or voltage cells connected in series and at least two emitter follower balancing circuits connected in parallel. At least one emitter resistor is provided between the emitter of each emitter follower balancing circuit and the mid-point of the DC-link. The gate emitter voltage applied to each emitter follower balancing circuit may be equal to its common gate voltage minus the voltage drop on the corresponding emitter resistor. The invention is also directed at a variable frequency drive for driving an electric motor or a power converter, having a corresponding voltage balancing circuit.

Abstract: The invention discloses systems (100) and methods (200, 300) for reducing the effect of even-order harmonics in supply voltage on the DC side components in AC-DC converters having any kind of controlled power electronic switches or their combinations. The method involves modifying the time of firing the various switches (112, 114) through a control logic arrives at through either measuring or estimating the DC bus voltage or the input AC voltage. The proposed control methods are useful in ASDs where full bridge configuration is used for AC to DC conversion. The proposed control may also be used in ASDs where a half bridge rectifier system is used. The proposed method reduces the stress on the DC bus capacitor and increases the lifetime of the capacitor. It further reduces the peak current through the device, which reduces stress on the rectifier components. It also reduces the Total Harmonic Distortion (THDi) of the line current.

Abstract: The present invention is directed at a method for operating rotating machinery, such as an electric motor, by means of a variable speed drive (VSD). The variable speed drive is provided for identifying mechanical resonance points by means of a sensor and corresponding speeds of the machinery; storing the speeds at which the identified mechanical resonance points occur; and bypassing the speeds at which the identified mechanical resonance points occur during operation of the rotating machinery. The invention is also directed at a variable speed drive for performing said method.

Abstract: A power electronic device includes an input which is connected to an over-current-protection device arrangement and a DC-link, wherein the DC-link includes a series connection of at least two DC-link capacitors. In such a power electronic device the risk of a fire hazard should be minimized. To this end fault detecting element(s) are provided detecting an imbalance between the DC-link capacitors or an overload of at least one of the DC-link capacitors, wherein the fault detecting element(s) control maximum current inducing element(s) connected to the DC-link.