An AC-AC power converter, such as a motor soft starter, includes an input connectable to an AC source with a disconnect switch, an output connectable to an AC load, and phase lines connecting the input and output to transmit power. In-line solid-state switching blocks are connected between line terminals and load terminals of the AC source and AC load, respectively, such that each phase line includes a solid-state switching block connected thereto. Free-wheeling solid-state switching blocks are connected to the load terminals at one end and together at a common connection at another end, such that each phase line includes a free-wheeling solid-state switching block connected thereto. Each of the in-line and free-wheeling solid-state switching blocks comprises a bi-directional switching block that selectively controls current and withstands voltage in both directions. The switching blocks also provide soft-starter functions, variable speed control, and integrated circuit breaker protection capability.

A progressive protection method automatically adapts a protection trip delay or fault timeout for a motor that is a member of a group of motors performing mutually similar or related tasks, based on the occurrence of a fault in another motor within the group, without requiring manual intervention. If the user requires stringent protection of the motors in a particular application, then the trip delay time for all of the motors in the group, may be shortened in response to recently-detected similar trips of other motors within the group. Alternatively, if the user prefers continuity of service for a particular application, then the trip delay time for all of the motors in the group, may be increased in response to recently-detected similar trips of other motors within the group, based on past experience with the occurrence of fault self-clearing for the motors in the group.

A progressive protection method automatically adapts a protection trip delay or fault timeout for a motor that is a member of a group of motors performing mutually similar or related tasks, based on the occurrence of a fault in another motor within the group, without requiring manual intervention. If the user requires stringent protection of the motors in a particular application, then the trip delay time for all of the motors in the group, may be shortened in response to recently-detected similar trips of other motors within the group. Alternatively, if the user prefers continuity of service for a particular application, then the trip delay time for all of the motors in the group, may be increased in response to recently-detected similar trips of other motors within the group, based on past experience with the occurrence of fault self-clearing for the motors in the group.

An electronic motor starter has a main switch configured as a semiconductor, forming a semiconductor contactor and having at least one semiconductor switch for switching a phase of a supply of a motor winding, a first connection of each semiconductor switch being connected to a corresponding first main current contact of the motor starter; an auxiliary switch configured as a semiconductor switch and connected between at least one pair of auxiliary contacts of the motor starter; a transducer for measuring currents connected between a second connection of each main semiconductor switch and a corresponding second main power contact of the motor starter; and a controller foe the main and auxiliary switches being powered via motor starter control contacts, for being fed transducer measurement signals, and being configured to control the main and/or auxiliary switch according to the supply via the control contacts and/or according to the transducer measurement signals.

A method of operating a protection device arranged between an electrical three-phase power source and at least one electric motor, the method including for each phase of the power source, acquiring over time a corresponding phase current flowing from the power source to the at least one electric motor; based on the acquired phase currents, detecting in which current stage each electric motor is, among an initial stage, an intermediate stage successive to the initial stage and a steady-state stage successive to the intermediate stage; calculating an active threshold value depending on the detected stage of each electric motor, the active threshold value during the intermediate stage following a predetermined decreasing function over time.

Method for the protection of electric motors from critical operating states wherein, as the electric motor is operating, a motor current value and/or a motor voltage value is/are measured and compared with a permissible operating range wherein an output signal is generated when leaving the permissible operating range and, while the electric motor is operating, the permissible operating range is determined and adjusted continuously from the measured motor current value and/or from the measured motor voltage value.

An AC-AC power converter, such as a motor soft starter, includes an input connectable to an AC source with a disconnect switch, an output connectable to an AC load, and phase lines connecting the input and output to transmit power. In-line solid-state switching blocks are connected between line terminals and load terminals of the AC source and AC load, respectively, such that each phase line includes a solid-state switching block connected thereto. Free-wheeling solid-state switching blocks are connected to the load terminals at one end and together at a common connection at another end, such that each phase line includes a free-wheeling solid-state switching block connected thereto. Each of the in-line and free-wheeling solid-state switching blocks comprises a bi-directional switching block that selectively controls current and withstands voltage in both directions. The switching blocks also provide soft-starter functions, variable speed control, and integrated circuit breaker protection capability.

An electronic motor starter has a main switch configured as a semiconductor, forming a semiconductor contactor and having at least one semiconductor switch for switching a phase of a supply of a motor winding, a first connection of each semiconductor switch being connected to a corresponding first main current contact of the motor starter; an auxiliary switch configured as a semiconductor switch and connected between at least one pair of auxiliary contacts of the motor starter; a transducer for measuring currents connected between a second connection of each main semiconductor switch and a corresponding second main power contact of the motor starter; and a controller foe the main and auxiliary switches being powered via motor starter control contacts, for being fed transducer measurement signals, and being configured to control the main and/or auxiliary switch according to the supply via the control contacts and/or according to the transducer measurement signals.