Motor Actuator Relay Sequencing Prevents Counter-EMF Damage
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Solution Overview
Problem
When a motor actuator interrupts the current supply path due to an abnormality, the counter-electromotive force generated by the motor can exceed the absolute maximum rating of circuit elements, leading to secondary circuit-element failure.
Innovation Solution
A motor actuator design that includes a first and second solid state relay between the battery and inverter, where the first solid state relay is brought into an OFF state or all field effect transistors are turned OFF, followed by the second solid state relay, to interrupt power supply while suppressing counter-electromotive force-induced failures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the motor actuator interrupts the current supply path to the motor based on detection of an abnormality, then the motor power supply is cut off, but the counter-electromotive force generated by the motor may exceed the absolute maximum rating of circuit elements, causing secondary circuit-element failure
Solution Approach 1:
The patent applies preliminary action by turning off the semiconductor switching elements in the inverter circuit before turning off the fail-safe circuit semiconductor switching elements. This sequential operation ensures that the current supply path is interrupted first, allowing the motor's counter-electromotive force to decay to a safe level before the fail-safe circuit is deactivated, thereby preventing circuit element damage from excessive voltage.
Solution Approach 2:
The patent implements beforehand cushioning by maintaining the fail-safe circuit in an active state during the period when the motor generates counter-electromotive force after abnormality detection. This protective measure acts as a cushion against voltage spikes, ensuring that circuit elements are protected from excessive voltage until the counter-electromotive force naturally decays to safe levels.
2Reliability
If the motor is in a high rotation state when power supply is interrupted, then the counter-electromotive force exceeds circuit element ratings, but delaying power interruption to allow motor deceleration reduces the ability to quickly respond to abnormalities
Solution Approach 1:
The patent applies preliminary action by immediately turning off the inverter circuit's semiconductor switching elements upon detecting an abnormality, which quickly interrupts the motor's power supply. This immediate action stops the motor current while the fail-safe circuit remains active to protect against counter-electromotive force, thus achieving both fast response and circuit protection.
Solution Approach 2:
The fail-safe circuit acts as an intermediary protective element between the inverter circuit and the motor. It remains active after the inverter circuit is turned off, serving as a buffer that protects circuit elements from counter-electromotive force while allowing the system to respond quickly to abnormalities without delaying the primary power interruption.
3Speed
If all semiconductor switching elements are turned off simultaneously, then the response to abnormality is fast, but the counter-electromotive force can damage circuit elements
Solution Approach 1:
The patent applies segmentation by dividing the semiconductor switching elements into two groups: those in the inverter circuit and those in the fail-safe circuit. These groups are turned off at different times - the inverter circuit elements are turned off first to quickly respond to abnormalities, while the fail-safe circuit elements remain active to protect against counter-electromotive force, thus resolving the contradiction between response speed and circuit safety.
Solution Approach 2:
The patent applies preliminary action by first turning off the inverter circuit's semiconductor switching elements before turning off the fail-safe circuit's semiconductor switching elements. This sequential approach ensures that the motor power supply is interrupted quickly while maintaining circuit protection during the transition period when counter-electromotive force is generated.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This design effectively interrupts power supply to the motor while preventing circuit element failure from counter-electromotive force, ensuring the safety and reliability of the motor actuator.
Implementation Method 1
The first solid state relay includes a first diode including a cathode arranged on the battery side and an anode arranged on the inverter side. The second solid state relay includes a second diode including a cathode arranged on the inverter side and an anode arranged on the battery side.
Data Source
AI summary
A motor actuator of the present invention includes, between a battery and an inverter, a first solid state relay and a second solid state relay in which directions of parasitic diodes are opposite to each other. When supply of power from the battery to the inverter is to be interrupted, the first solid state relay is brought into an OFF state or all of a plurality of field effect transistors are brought into the OFF state, and then the second solid state relay is brought into the OFF state.