The core difference between two-wire control and three-wire control of frequency converter is reflected in the way of maintaining control signal, number of wiring, safety and applicable scenarios. The following is a specific comparison:

I. Wiring and control logic

1. Two-wire control (Two-Wire Control)

·Wiring method:

·Usually use 2 terminals (X1, COM) to connect the control signal, and control the start, stop or direction by the presence or absence of level signal.

·Typical wiring: one terminal is connected to the control signal (such as switch or relay contact), and the other terminal is connected to the common terminal (COM).

·ontrol logic:

·Start: When the control signal (X1) is connected (closed) to COM, the frequency converter starts to run.

·Stop: When the control signal is disconnected, the frequency converter stops running.

·Features: The control signal needs to be maintained continuously (that is, the switch needs to be closed all the time), otherwise the frequency converter will stop.

2. Three-Wire Control

Wiring method:

Use 3 terminals (such as X1, X2, COM) or specific combinations (such as start, stop, common terminal) to control start and stop through pulse signals, without continuous power supply.

Typical wiring:

Start signal (such as X1): short-circuit once (pulse signal) to trigger start, and keep running after the signal disappears.

Stop signal (such as X2): short-circuit once (pulse signal) to trigger stop, and keep stopping after the signal disappears.

Control logic:

Start: give a short closed signal (pulse) to the start terminal (X1), the inverter starts and keeps running, without continuous power supply.

Stop: give a short closed signal (pulse) to the stop terminal (X2), the inverter stops and keeps stopping.

Features: The control signal is an instantaneous pulse, which does not need to be maintained continuously, similar to the "button" logic.

II. Typical application scenarios

1. Applicable scenarios for two-wire control

·Simple equipment: such as small fans and water pumps, which can be started and stopped directly by a switch.

·Low-cost requirements: No independent stop button is required, saving wiring and component costs.

·Emergency stop scenario: When the line is disconnected (such as the emergency stop switch is triggered), the machine can be stopped immediately.

2. Applicable scenarios for three-wire control

·Industrial automation: Equipment such as machine tools and production lines that require reliable start and stop control to avoid misoperation due to signal interference or poor contact.

·Remote control: Remote operation is achieved through two independent buttons (start/stop), and the signal stability is higher.

·Scenarios with high safety requirements: such as elevators and cranes, it is necessary to clearly distinguish between start and stop commands to prevent misoperation.