I have a question regarding normally open and normally closed contacts

The question is too general to answer

Control of start/stop involves low voltage regulating high voltage; frequency conversion is not a digital type but an analog one, while the field status is represented by digital signals

Common wiring on the instrument side: the operation signal is connected to an open circuit, the fault signal is also connected to an open circuit, the start signal is connected to an open circuit, while the stop signal is connected to a closed circuit. The frequency setting is provided as an active 4–20 mA signal, and the frequency feedback is in the form of a passive 4–20 mA signal

Actually, there’s no need to worry too much about it; generally, design institutes will specify whether it should be normally open or normally closed

Most of the control signals for the engine unit are connected in normally open configuration; normally closed connections are used rarely. Specifically, you need to consider the actual conditions in your area.

Normally open; normally closed doesn’t matter – what’s important is isolation, hehe

The operating status of the on-site generators and equipment – the electrical cabinets send the status signals to the control room, which then receives and displays them； Start/stop control, variable frequency control – The central control unit sends start, stop, interlock, and signal commands to the electrical system in order to control the equipment based on the actual operating conditions. Variable frequency control can directly supply the frequency value from the central control unit to the inverter ； Signals such as feedback, current signals, and fault indications – the inverter sends signals regarding the actual operating current, frequency, and inverter faults to the central control system. Regarding the normally open and normally closed contacts in the electrical MCC, owners usually have preferences as to whether they should be set to normally open or normally closed for operation, and similarly for interlocks. Generally, however, it’s possible to get it right during sequential debugging; as long as the owner agrees, that’s fine. Additionally, for interlocking purposes, we generally use normally closed signals here; the circuit remains in a normally closed state when the unit is operating normally, and it is disconnected as soon as any issue arises, thereby triggering the interlocking signal. It seems to be called fault safety. I’ve only been doing this for two or three years; in my opinion, it’s entirely done in a casual manner… just watch it as is