Common problem processing (dc motor controller 1)

Use dc motor controller, will encounter this or that kind of problem, such as the speed is not normal to do? Dc motor controller in speed abnormal reasons are: 1. High speed; 2. Speed is too low. For two reasons for this approach are: 1. Check whether the power supply voltage is too high, the main magnetic field is too weak, the motor load is too light. 2. Check to see if the armature winding in open circuit, short circuit, grounding fault; The pressure of brush and brush position is normal; The power supply voltage is too low;