The method of judging the fault of the electrical system of CNC vertical lathe can include the following points:

1. Fault codes and alarm information: CNC vertical lathes are usually equipped with fault codes and alarm systems to indicate faults in the electrical system. Check the display screen or operation interface of the machine tool to see if there are error codes or alarm prompts. According to the code or prompt information, the type and location of the fault can be preliminarily located.
2. Power supply check: Check the power supply of the CNC vertical lathe. Make sure the power is on, check for blown fuses, and loose or damaged power cords. Sometimes a power problem can cause the electrical system to malfunction.
3. Connection inspection: Check the connection of the electrical system, including cable connection, plug and socket connection, etc. Make sure the connection is tight, making good contact and nothing is loose or disconnected.
4. Check the electrical components: carefully check the electrical components in the CNC vertical lathe, such as contactors, relays, circuit breakers, etc., to see if they are burnt, damaged or loose. If necessary, a multimeter or other testing equipment can be used to test and measure electrical components.
5. Programming and parameter checking: Check whether the programming and parameter setting of the CNC system are correct. Incorrect programming or parameter setting may cause malfunction or abnormality of the electrical system. Check the program and parameter settings to ensure their correctness.
6. Sensor and switch inspection: CNC vertical lathe uses many sensors and switches to detect workpiece position, tool position and other information. Check these sensors and switches to confirm whether they are in normal working condition and eliminate possible faults.
7. Historical alarm and fault records: CNC vertical lathes usually record historical alarm and fault information. Viewing historical records to understand previous alarms and failures can help to judge current electrical system failures.

Please note that the above method is only a common method for preliminary judgment of the electrical system failure of CNC vertical lathe. For more complicated faults, it may be necessary to rely on the guidance of professional maintenance technicians, equipment manufacturers or suppliers for accurate fault diagnosis and repair. Before performing any maintenance operations, please ensure that the machine tool is powered off and follow relevant safety operating procedures.