How many DOs are required to control the start and stop of a motor using DCS?
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Dear teachers, how many DOs are required to control the start and stop of a motor using DCS? In simple terms, the DCS continuously supplies a 24V voltage to the relay; this causes the motor to start rotating. Once the DCS stops supplying power to the relay, the motor stops. The two outputs consist of one DO that is a normally closed contact and one that is a normally open contact, used to control stop and start respectively. Which method is better?
This depends on the actual control circuit of the motor; the DCS works in conjunction with the electrical system
In principle, it’s possible to achieve this, but what I’ve seen is mostly systems with two-point control, where the self-protection circuit is integrated into the electrical circuit
Thank you. I work in the electrical field, and I think both options are fine, so I came to ask.
Check whether the pump under control is a high-pressure pump or a low-pressure pump； For pumps operating at low pressure, when the relay in the DCS control circuit closes, the contactor for control electrical circuits is activated; under normal circumstances, continuous control is permitted ； For high-voltage pumps, it is not possible to keep the control contactor in a closed state; usually, a pulse signal is used for control. Therefore, two contacts are required for high-voltage applications, and an isolation relay must also be used.
Generally, two DO points are used to control start and stop respectively, and pulse signals are employed. It also depends on whether it is a high-voltage motor or a low-voltage motor; the type of DCS output signal needs to be determined based on the control principles and design rules of electrical engineering. As for the start and stop of the motor after the pulse signal is sent, this is handled by the electrical engineering team.
If your motor requires pre-lubrication, then it must be controlled individually; separation is not allowed. To prevent the oil pump from stopping and resulting in a failure of the motor stop signal line, which would prevent the stop signal from being sent.
Choose 2 DOs; this will reduce the scope of troubleshooting in case the equipment stops working due to an anomaly. Additionally, keeping electronic components powered on constantly creates an additional risk, so reducing abnormal shutdowns of the equipment is the fundamental goal of the design