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^ Function block mgv is suitable for controlling actuators that have two states (e.g., open and closed, in and out, etc.), to one of which the actuator is always driven. A typical application is to control a small solenoid valve, which in turn controls the main valve pneumatically. The state of the controlled valve is read from its open and closed limit switches, for which the block has its own inputs called son, and soff, respectively. The block can also be configured to operate with only one limit information or without any limit information at all, by adjusting the corresponding configuration parameters sonu and soffu.
mgv is not suitable for controlling actuators that can be stopped in intermediate positions. These are typically implemented with a positioner associated with the actuator, to which, for example, a 0..100% position command is sent as a current signal or via a digital bus.
For binary control of valves driven to intermediate positions, there are blocks mca, and vlv. The latter is usually used with a pid block operating in incremental mode. In both cases, the valve actuator is controlled by measured pulses in the opening and closing directions.
Function block mtr controls one (on) or two (on, off) binary outputs, which are typically connected either directly or via an auxiliary relay to the control circuit of a contactor located in the electrical cabinet. The motor's running information is usually taken from the contactor's auxiliary contact and connected to the ins input of the mtr block.
There is also a version of the block that can monitor the current drawn by the motor and react to overcurrent. Alarms caused by the starting current peak can be prevented by parameterizing the block appropriately.