There is described a method of verifying a function of a power supply monitor in a digital control system, wherein the power supply monitor is adapted to monitor whether or not a power supply voltage is between a lower threshold value and an upper threshold value. The method comprises: setting the power supply voltage to a first value, the first value being below the lower threshold value, checking, as a first check, that the power supply monitor indicates that the power supply voltage is below the lower threshold value, setting the power supply voltage to a second value, the second value being above the lower threshold value and below the upper threshold value, checking, as a second check, that the power supply monitor indicates that the power supply voltage is above the lower threshold value, and verifying the function of the power supply monitor if both the first check and the second check are successful. There is also described a corresponding device and computer program.

A motor control device includes a rectifier which converts AC power into DC power and outputs it to a DC link, an inverter which converts the DC power of the DC link into AC power for each motor and outputs it, an AC voltage detection unit which detects an AC voltage value on the AC input side of the rectifier, a state determination unit which determines that a voltage dropped state has been set when the AC voltage value is smaller than a certain specified voltage and that a normal state has been set when the AC voltage value is equal to or larger than the specified voltage, and an output control unit which controls each motor in accordance with the amount of voltage drop with respect to the specified voltage of the AC voltage value when the state determination unit determines that the voltage dropped state has been set.

A motor control device includes a rectifier which converts AC power into DC power and outputs it to a DC link, an inverter which converts the DC power of the DC link into AC power for each motor and outputs it, an AC voltage detection unit which detects an AC voltage value on the AC input side of the rectifier, a state determination unit which determines that a voltage dropped state has been set when the AC voltage value is smaller than a certain specified voltage and that a normal state has been set when the AC voltage value is equal to or larger than the specified voltage, and an output control unit which controls each motor in accordance with the amount of voltage drop with respect to the specified voltage of the AC voltage value when the state determination unit determines that the voltage dropped state has been set.

The invention relates to a method for actuating a mode selection switching element of an installation by means of a safe control operation, wherein the installation has a functional controller and communication connections, and wherein the functional controller has a storage unit, a (sequence) control apparatus, a display and a user interface. The method has the following steps: providing a mode-selection actuating element on a user interface; receiving a user input to change the operating mode at the user interface; transmitting the data relating to the change of operating mode to the mode-selection switching element; transmitting the data relating to the change of operating mode from the mode-selection switching element back to the functional controller; checking whether the operating mode of the data which have been transmitted back matches the operating mode selected by the user; transmitting a confirmation to the mode-selection switching element; and changing the operating mode by means of the mode-selection switching element.

The invention provides for an arrangement for operating a technical installation comprising a number of machines, the arrangement comprises a control structure, the control structure being adapted for generating a schedule for sending requests to the machines by means of a simulation and in consideration of expectation values of the machines, for monitoring the operation achieved by switching of the machines, wherein switching of the machines is performed by the machines themselves, in order to achieve a template illustrating the switching of the machines, and for comparing the generated schedule with the template.