The invention discloses a three-phase power supply default phase and power failure detection 
system and a braking method. The detection 
system comprises a three-phase power supply RST, a rectification circuit, a 
relay circuit, an IPM circuit, two optocoupler 
processing circuits, a 
DSP processor, a braking circuit, a 
Nixie tube and a 
servo motor and is applicable to a 
motor control system of a 
servo driver. The braking method comprises the following steps: judging abnormal conditions such as default phase and power failure of the three-phase power supply, then closing a PWM 
signal by the 
DSP processor, 
cutting off a 
busbar power supply by virtue of the 
relay circuit, starting and accessing the braking circuit, connecting a braking power 
resistor among three-phase windings of the 
servo motor in series for realizing short connection of the three-phase windings, and generating current in a short connection loop by virtue of residual 
magnetism potential of a 
stator winding, so that the motor is rapidly braked. The detection system and the braking method, which are disclosed by the invention, have the advantages that security protection effect on 
electrical equipment and personnel is realized, implementation is easy, cost is low, and the problems that a motor in existing 
electrical equipment adopts a band-type 
brake module, price is high, size is large and control and wiring are complex can be solved, so that the detection system and the braking method have a good application prospect.