sequential (76) motor

https://wodewangzhishime.blogspot.com/2021/12/battlefield-backlines-discriminating.html

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Ref: https://wodewangzhishime.blogspot.com/2023/08/2001-4-airplanes-were-hacked.html 

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Rotor resistance is used to safely "brake" a car.

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The lower the Rotor resistance, the speed of maximum torque is higher. [ It is dangerous to brake a train which is moving forward at a high speed. . That mean, the rotor resistance of the reverse-moving motor must be high, otherwise, it is dangerous. . ]

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The higher the Rotor resistance, the speed of maximum torque is lower. [ If a train is moving forward rapidly, the resistance of the "reverse-moving" must be high, otherwise, it is dangerous. . ]

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Me: The above picture is divided into 2 parts. . Upper part is a motor which is moving forward. . The lower part is a motor which is braking. .

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Note: Braking of a motor , means, a motor is moving reverse. . 

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Me: If a motor is moving forward rapidly, is it "safe" to let the motor reversely-move suddenly ??

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John: No, it isn't safe. . . . . It is very dangerous for us to suddenly brake a motor which is moving forwards rapidly.

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T1, T2, T3, T4, stands for transistor 1,2,3,4

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1) When a motor is moving forward rapidly, T1,T2,T3,T4, are saturated, that means, the motor reach its maximum torque.

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There is an integrated circuit within the motor. . This integrated circuit plays the role of sensor. . . When the sensor sense that T1,2,3,4 are saturated, the "integrated circuit" will automatically cut off T5,6,7,8.

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John: You mean, we can't manually control the on/off of T5,6,7,8.

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Me: We can't. . 

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OK. . Now, a car is moving forward rapidly, I brake it. . Can the motor reverse-moving immediately ?? No, It can't. . Because, Transistors 5,6,7,8 are Cut off.. 

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R5,6,7,8 stands for Resistors 5,6,7,8

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That mean, the reverse-moving of a motor must "slip" over R5,6,7,8.

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1) when the reverse-moving slip through R5, T5 is saturated.

2) when the reverse-moving slip through R6, T6 is saturated.

3) when the reverse-moving slip through R7,

T7 is saturated.

4) when the reverse-moving slip through R8,

T8 is saturated.

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5) Finally, the reverse-moving of a motor reach maxium torque and then the motor brake.

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Me: Last time, a train of China was hacked and crash. . . It was what the passengers exmplain.

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A passenger: The train suddenly brake, as if, it hit somethings. . However, I look outside the windows..  I see that nothing is hit by the train.

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John: How can a rapidly moving forward train brake so suddenly ?? The brake must "slip" over R5,6,7,8 . .

Me: The reverse-moving didn't "slip" over Resistors 5,6,7,8.

John: Why didn't ??

Me: Transistors 5,6,7,8 are saturated..

John: Transistors 5,6,7,8 are controlled by a sensor within the integerated circuit. . How can they be saturated ??

Me: Hackers hack the integrated circuit of this train, and then, hackers let Transistors 5,6,7,8 be saturated. . Therefore, the train can brake so suddenly.