I’m asking experts to explain how DCS controls the switching and speed of motors
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I’m a beginner, and my supervisor has asked me to learn the principles of using DCS to control motors. I really don’t understand anything about electrical systems. If there are anyone who knows about this, please help explain it to me. Thank you. Could you explain it in simple terms? What are the various electrical components involved, and how do they enable control over the motor’s speed? Thanks
In DCS systems, passive DO points are connected in series within the motor’s control circuit; they function as dry contacts, and a selector switch is usually installed
Controlling the speed requires a frequency converter
Upon receiving the control command from the DCS, it activates or deactivates the relay; the dry contact of the relay closes, which is equivalent to pressing the start/stop button on the field control panel – this also causes the corresponding dry contact to close. The control circuit of the motor typically uses low-voltage components such as contactors, frequency converters, and soft starters, while high-voltage components like vacuum contactors or circuit breakers are used; when the coil is activated, the main circuit of the motor is connected or disconnected, thereby enabling the motor to operate or stop.
The DCS outputs 4~~20mA to the motor inverter, corresponding to 5~~50Hz (this is the standard in our facility), and it is the inverter that controls the motor speed.