1. Short circuit protection for motor winding and wire insulation damaged, control, electronics and circuit to damage accidentally touch line caused by short circuit fault, such as the measures of protection appliances quickly cut off power supply short circuit protection. Common short-circuit protection electric fuse and the automatic air circuit breaker. The commonly used is the fuse and circuit breaker short circuit protection components. Protected the fuse melts in series circuit, when the circuit short circuit or serious overload occurs, it automatically fusing, cut off the circuit thereby, achieve the goal of protection. 2. Weak magnetic protection with protection appliances to ensure dc motor work under magnetic field of a certain intensity, does not cause field weakening or disappearing, avoid to make motor speed rise rapidly, even coasters phenomenon occurs, the protection for weak magnetic protection. 3. Overload protection when the motor load is too large, frequent starting operation or phase operation, can make the working current of the motor for a long time more than the rated current, lead to shorten or damage to the motor life. When the motor overload, the measures of protection appliances to cut off the power supply overload protection. 4. Protect the production machinery at work, pressure loss in the sudden power cut due to some reason, when to restore power supply, protection appliances to ensure the production machinery to start to work, not personal and equipment accident, the protection for the loss of pressure,Zero pressure)Protection. Loss of pressure (Zero pressure)Protection of electrical contactor and intermediate relay.