1. Motor power, working current, large heat.
2. Fan blade less, resulting in a small amount of wind.
3. Fan speed is low, wind pressure, air volume is small.
4. Vacuum pump motor where the bus voltage is 380V, due to the cable voltage drop and load distribution is uneven, the actual voltage of the motor is only 365V, the voltage is too low to cause the running current.
5. Motor with dust, oil, reduce the heat capacity