Many accidents occur when cleaning, maintaining or repairing the mixer. Generally, the automatic mixer all-in-one truck has the limit of the mixer cover. As long as the cover is lifted, the control circuit will be cut off. This is a simple protection. Once someone cleans the cover in the mixer and closes it for some reason, it is very dangerous; In addition, due to the large vibration of the mixer in the working process, the cover protection switch is often easy to contact poorly. During production, the mixer is turned off. Sometimes, in order to continue production, the switch is temporarily short circuited, and the safety switch is in vain, which also brings trouble

搅拌车电机烧坏了，实际上控制系统的性设计好的话，就不可能发生这种事故。一般在搅拌机控制上，采用了三个保护：过流保护、过载保护和过热保护。其中过流、过载保护国内同行都在使用，但是好多设计者都不大注意过热保护，实际上这种保护措施很管用。

The motor of the mixer truck is burnt out. In fact, if the safety of the control system is well designed, such an accident can not occur. Generally, three protections are adopted for mixer control: overcurrent protection, overload protection and overheating protection. Among them, overcurrent and overload protection are used by domestic peers, but many designers pay little attention to overheating protection. In fact, this protection measure is very effective.

对于电机在短时间内过载，电流快速上升的情况，过流、过载保护开关在短时间内就会切断电源，可是如果负载是慢慢增加的情况，过流、过载保护就很难及时反应了。烧电机往往发生在两种情况下，一是堵料后，频繁强行启动搅拌机；二是在中间斗有泄漏时，搅拌机里有一拌料正拌着，中间斗慢慢把下一拌的材料加到搅拌机里，等到搅拌机拌不动了，电机也就烧毁了，这种情况我们已遇到过多次了，现场分析表明故障往往就是中间斗关门限位失灵所致。

When the motor is overloaded and the current rises rapidly in a short time, the overcurrent and overload protection switch will cut off the power supply in a short time. However, if the load increases slowly, the overcurrent and overload protection is difficult to respond in time. Motor burning often occurs in two cases: one is to frequently forcibly start the mixer after material blockage; Second, when there is leakage in the intermediate bucket, there is a mixing material in the mixer. The intermediate bucket slowly adds the next mixing material to the mixer. When the mixer fails to mix, the motor will be burned. We have encountered this situation for many times. Field analysis shows that the failure is often caused by the failure of the closing limit of the intermediate bucket.

在现场往往看到搅拌车的电动机里明明有两根细细的热敏电阻的引线，但是大家未重视，没有很好利用，导致电机烧坏，提高了运行成本。热敏保护确实能在电机缓慢过载时及时切断电源进行保护。

It is often seen at the scene that there are two thin thermistor leads in the motor of the mixer truck, but they are not paid attention to and are not well used, resulting in the motor burning out and increasing the operation cost. Thermal protection can indeed cut off the power supply in time for protection when the motor is slowly overloaded.