1、Large current leads to machine tool alarm. Generally, there are two kinds of possibility, that is, the damage of power drive element in NC speed control unit of machining center and the high current alarm caused by short circuit.

2、High voltage also leads to machine tool alarm. There are generally three possibilities for high voltage alarm. It may be that the NC input voltage of the machining center exceeds the rated value of 10%, or the insulation performance of the servo motor decreases. or the high voltage caused by machining center speed control unit line.

3、If the voltage is too low, the machine tool will be alerted, and the probability of this happen in the machining center are very few, which may be caused by the input voltage being less than 85% of the rated value, or poor connection of power supply

4、The failure of the feedback line of the detection speed leads to the alarm, which is a false alarm，because the airport has no problems, but there is a problem with the detection feedback system. This kind of alarm is mostly caused by the breaking of the speed feedback line of NC servo motor in machining center or poor connection of the detection feedback line.

5、The protection switch is a device for protecting the machine tool. For example, a large voltage will ruin some components or some emergency measure for control. The protection switch will be activated when the situation arises.This behavior is similar to a safety stop to avoid unnecessary component damage.

6、The cause of overload alarm is the abnormal load of NC machine in machining center, or the low limit value of motor current on the speed control unit. The permanent magnet falling off on permanent magnet motor will also cause overload alarm. If the NC motor without brakes in the machining center is hard to turn by hand or shaft when no load, that is to say, permanent magnetic full shedding.

7、The fuse on the CNC speed control unit is burned or Circuit breaker tripped.