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.

Abstract: The present disclosure refers to a method for controlling the speed of a reciprocating load motor, wherein the motor speed is a function of two input variables, namely a user defined speed set-point and a load dependent input variable. According to the disclosure, the load dependent input variable is a function of the motor current. The disclosure also refers to a variable frequency drive for controlling the speed of a reciprocating load motor, wherein the drive is programmed to perform the presently described method.

Abstract: A method for detecting low impedance condition at an output (15) of an electrical converter (10), a control unit (1000), a computer program product, and an electrical converter (10) are presented. The method includes determining (110) a first current value (I1(T1)) of a first current (I1), and a second current value (I1(T2)) of the first current (I1), and determining (120) a first current difference (?I1) between the first (I1(T1)) and the second (I1(T2)) current values, and comparing (130) the first current difference (?I1) to a first current difference threshold (I1_TH), and if the first current difference (?I1) is of predefined magnitude with respect to the first current difference threshold (I1_TH), such as higher, turning off (140) a first voltage (U1) driving the first current (I1), such as by switching off a corresponding switch or switches for applying the first voltage (U1) to the output (15).

Abstract: The present invention relates to a motor controller providing a dual-channel func-tional-safety (FS) safe-torque-off (STO) function when controlling a motor. The motor controller includes an inverter with low-side switches and high-side switches, a low-side gate drive connected to the low-side switches, a high-side gate drive connected to the high-side switches, a first functional-safety safe-torque-off circuit connected to the high-side gate drive and a second functional-safety safe-torque-off circuit connected to the low-side gate drive, and a non-reinforced high-voltage isolation barrier.