The reasons are:
1: Improper operation. If the mixing drum is not stopped when the mixing table is discharged, the motor is reversed, resulting in excessive inrush current: the stirring motor starts with a load, and the starting time is too long and the contactor is burned out.
2 :The concrete mixer is seriously out of guarantee, the friction resistance of each movement pair is too large, and the motor is not working normally, resulting in excessive working current and burning out the contactor.
3:The control box is not tightly sealed, and the dust on the construction site is large, resulting in dirt accumulated on the contacts of the contactor.
4:The contactor is unqualified, the contact contains less silver, and the current is slightly larger, and the action is not flexible. In view of the above reasons, the following countermeasures should be taken: for correct operation, the mixer must stop rotating before reversing the material, and then load the material after the mixer is turned; strengthen the maintenance of the machine to keep the machine in good condition: keep the contactor clean: buy Qualified components. It should be noted that in actual use, in order to reduce the trouble and cost of replacing the contactor, some people simply use the reverse switch to control the stirring and discharging. This is wrong, it is neither safe nor convenient, and it should be avoided.
