Does the stop motor signal sent by the instrument to the electrical system have built-in retention?
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1. First, let’s talk about the signals sent by the instruments to control the valves. For example, if a pressure transmitter detects high pressure, it sends a signal of 1 to activate the solenoid valve. As long as the pressure remains high, the solenoid valve continues to receive this signal of 1; only when the pressure returns to normal does the solenoid valve receive a signal of 0, causing its position to change. 2. Let’s discuss the signal to stop the electrical motor again: when the pressure from the pressure transmitter is high, a signal of 1 is sent to stop the electrical motor. As long as the pressure remains high, this signal of 1 will continue to be sent. Can the electrical motor then remain in a stopped state? It still has to do with the number of contacts for starting and stopping the electrical system. If separate contacts are provided for starting and stopping, then even if the signal ‘1’ is maintained, the electrical system will not remain in stopped state. In such a case, if someone accidentally activates the start signal, the motor will start up? That’s why it is necessary to set up a power-on signal. But if the on/off is made into a contact, wouldn’t the electrical side then have a holding function? But nowadays, electrical systems usually have two points, which is safer.
It’s obvious from the poster that they’ve never worked with electricity! The form of the start/stop signal at the electrical side depends on the electrical control circuit; generally, a pulse signal is used for start/stop operations. There are systems with self-locking mechanisms on the electrical side, and then there are those in which the instrument’s signal is used to disconnect in order to stop and connect in order to start. For interlocking purposes with such signals, SR flip-flops are generally used; it’s best to add a reset button to avoid the issues you’re worried about
This post was last edited by lurker on 2018-3-23 14:21. Hello, thank you for your answer; I’ve always only had a superficial understanding of electrical matters. Regarding the second scenario you mentioned, where starting and stopping are controlled by instrument signals along with SR flip-flops, this is essentially a situation where a contact on the electrical side is used to control start and stop, right? The logic here is the same as that used for interlocking switch valves with SR flip-flops; after the pump stops due to interlocking, to start it again, manual reset is required under conditions where there is no interlocking in effect. In the first scenario you mentioned, where start/stop is controlled by 2 contacts, the electrical system needs to receive pulse signals; does this mean that the interlock signal output by the system should also be in pulse form? I don’t seem to have seen this on the interlocking diagram; will the manufacturer handle it during configuration? In this case as well, after an interlock shutdown, a start signal can be given to start the motor, so a logic that permits starting needs to be implemented.
It is recommended to use a pulse level signal; the power-off signal is usually a closed signal. The motor stops immediately when the signal is cut off, and if that state is maintained, the motor will not start again on subsequent attempts. It is necessary to stop the motor each time and then reset it
There should be a reset button! I remember that for the previous experiment on starting and stopping via clicking, it was necessary to reset it
If the normal start/stop is in pulse form, then the configuration is set up for pulses; but in the case of an interlocked stop (which is considered an abnormal shutdown), the stop signal generally needs to remain active, that is, it should be continuously output to ensure that the equipment stays in a locked stopped state until it is reset. Reset usually involves a separate reset button. It would be best to include accident interlock in the logic that allows startup, but this can only ensure that no output is generated at the startup point. And if something unexpected happens, it cannot be handled according to conventional methods; therefore, the locking mechanism that stops things in place still needs to be maintained.
This interlock signal is a pulse signal, and manual confirmation and reset are required after it activates. In particular, oscillation is not allowed in the control of the motor.