I use MOS tube relays to power the brushless DC motor, and MOS relays are added to the positive and negative poles of the DC bus. During operation, it was found that when the brushless DC motor rotates forward and reverses suddenly, it will cause the MOS relay switch of the DC bus to break down, making the DC power supply unable to control the switch, and the DC power supply is always on to power on the motor. May I ask my gods, what causes this? After checking the information, it is said that because the forward rotation suddenly reverses, the DC bus voltage will increase, exceeding the withstand voltage of the MOS relay switch, and the MOS tube will be broken down. It is also said that the sudden reverse rotation will cause the motor to output a large current and burn the MOS transistor relay.
The schematic diagram of the MOS switch relay is as follows. It is designed by ourselves, not a purchased product. The MOS tubes are damaged, and the TVS tube SMAJ58A is also burned. The motor is a 48V@2000W DC motor.
Adriano Posté sur September 22, 2020
When the motor reverses suddenly, the transient current will be very large, exceeding the normal working current by an order of magnitude. It is easy to know whether the overcurrent is caused by the motor parameters and relay parameters. Similarly, there are parameters to follow for withstand voltage, but if you suddenly turn to this working condition, overcurrent should be more concerned. When the motor power is large and the load is heavier, such working conditions are not allowed.
Adria Posté sur September 22, 2020
Although I don't know the models and functions of U10 and U12, this circuit seems to be unable to control the forward and reverse rotation of the DC motor. To put it simply: the connection of the four power tubes in the circuit is wrong.
Kirby Posté sur September 22, 2020
U10 and U12 are gate drive modules made by themselves. This circuit controls the switch of the DC power supply of the motor. It does not control the direction of rotation of the DC motor. The motor has its own driver. The fault is that the motor's forward rotation suddenly reverses, which will burn the MOS relay and the TVS tube will also be destroyed.
Shelly Posté sur September 22, 2020
Yes, this is due to the limited size of the circuit and the use of this self-made MOS switch, so as you said, only one MOS tube bears the reverse voltage. But the DC current is also very large, how to deal with it?
Denny Posté sur September 22, 2020
Your circuit is just a switch, so your circuit design is incredible. Just as a switch, you always know the common PMOS power switch and NMOS load drive circuit. What you need to do is to increase the current-carrying capacity by connecting multiple tubes in parallel on the basis of this type of circuit. In addition, a two-kilowatt motor is no longer small, especially after carrying a rated load, it already belongs to the category of sudden reversal as described in the previous post.
