Is the allowable start signal for the instrument a long signal or a pulse signal?

The pulse signals used vary from one manufacturer to another. Our instruments here have two passive points, and the electrical components are responsible for the wiring. The start and stop of the pumps are determined by the production process programming, so it’s not possible for them to stop when they shouldn’t

After the motor starts, if this permit-to-start signal is no longer satisfied and is disconnected, will the motor shut down via interlock? There are also start signals, which are usually in the form of pulse signals. Isn’t there a self-locking circuit in the electrical secondary circuit?

The electrical system has a self-locking feature; under normal conditions, the pump will not stop unless the conditions for stopping it are met. If the conditions for starting the pump are not satisfied, it will only affect the starting process. Are you an electrical technician, an instrumentation specialist, or a production worker?

I’m a instrumentation technician; thank you for your help. Is there a typical secondary circuit diagram for motor start-stop? I’d like to learn about it*.

The secondary circuit can use self-holding wiring to achieve pulse initiation

This depends on the interlock requirements, but in most cases it is a long signal, and the electrical secondary circuit does not have self-interlocking. Two situations: 1. It is both a start condition and a stop condition: a long signal, with the electrical secondary circuit not self-locking. 2. The start condition is not the stop condition; there are other stop conditions. For example, regarding the compressor lubrication oil pressure, 2 BAR triggers the shutdown of the compressor, while 4 BAR allows it to start. 4BAR allows the compressor to start. If it is self-locked and the pressure once reached 4 but then dropped to 3, then 3BAR is also sufficient to start the compressor. Once the compressor starts up, use the compressor’s operation signal to bypass this \"4BAR start permission signal\" (this can be done either electrically or via instruments); otherwise, the compressor will stop at 4 BAR, and unit 2 will have nothing to do.

　　The start/stop signal sent by the instrument to the electrical system is usually a short signal. 　　A so-called short signal is one that is issued and then revoked when certain conditions are met. For example, in a device start/stop control program, when the device starts, a start signal is sent; once a signal indicating that the device is operating is received, this start signal is revoked. Why should this signal be removed? Because if it is a long signal, it will definitely cause the device to fail to shut down or to restart repeatedly; the same is true for turning it off – a long signal will certainly prevent the device from starting up. 　　The condition signal from the instrument to the electrical system (the signal indicating that action/operation is permitted) is generally a long-duration signal, and it is preferable that it be a signal which is closed, conductive, and energized under normal conditions. 　　Conditional signals are usually related to safety. If pulse signals are used, if there is a problem with the instrument or the signal lines, the signal may not reach the electrical system, which can lead to a series of problems. If a long signal is used, any issue with the instrument or the signal circuit will cause the signal to disappear, and the device will automatically enter a safe state. 　

Generally, the start permit signal is a logical combination of process conditions; when these conditions are met, the contact corresponding to the electrical secondary circuit for start permission closes, and otherwise it opens. However, to prevent shutdowns caused by changes in the process conditions related to start permission during operation, a self-locking mechanism can be added on the MCC or DCS side

It is generally made into a pulse signal; passive dead point