How Do Master & Standby Drives Determine Takeover Timing During Communication Interruption?

In AU620 and its series systems (e.g., Y620, M740, YS820), the takeover timing determined by master and standby drives during communication interruption is mainly decided by the built-in communication detection logic and Function Code U3-07 (Standby Master Start Delay).

Below are the specific judgment and takeover logic:

1. Judgment of Communication Interruption

Real-Time Monitoring: All drives in the system are connected via RS485 communication cables. The primary master drive (Address 1) sends PID feedback and operation commands to auxiliary drives and the standby master drive (Address 2) in real time.
Signal Loss Judgment: When the standby master drive fails to receive communication signals from the primary master drive for a predetermined continuous period, the system determines a communication interruption (Comm. signal deactivated).

2. Judgment Logic of Takeover Timing (U3-07 Delay)

After communication interruption, the standby master drive will not take over immediately but wait according to parameter settings:

Trigger of Waiting: Once communication abnormality is detected, the system starts a countdown with the value determined by U3-07 (Standby Master Start Delay/Valid Delay).
Standard Timing: The factory default value of this parameter is usually 5.0 seconds. This means that after the communication interruption lasts for 5 seconds, the standby master drive will determine the primary master drive as invalid and prepare to take over.
Role Upgrade: After the delay time is reached, the standby master drive (originally acting as an auxiliary drive) will automatically upgrade to the "master drive" identity and take over the command of the entire pump group system.

3. Prerequisites for Takeover Implementation

To ensure the standby master drive can take over the system accurately and timely after communication interruption, the following settings must be met:

Address Configuration: The local address of the standby master drive must be set to 2 (U3-01=2).
Sensor Redundancy: The standby master drive must be independently connected to a pressure sensor. When pressure signals from the primary master drive cannot be received due to communication interruption, the standby master drive will immediately enable its own connected sensor data to maintain constant pressure control.
Control Mode: The start/stop command and frequency source of the standby master drive usually need to be set to communication reference (U0-10=2, U0-13=2), so that it follows instructions when communication is normal and operates independently after communication interruption and meeting takeover conditions.

The takeover timing depends on the setting value of U3-07. By default, the system triggers the Fault Shift logic 5 seconds after the communication signal disappears, and the standby master drive takes over the work of the primary master drive.