Brushless Motor Fail-Safe Circuit for Two-Phase Fault Operation
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Solution Overview
Problem
Existing brushless electrical motors, particularly permanent magnet synchronous motors (PMSMs), face challenges in maintaining operation during phase faults without redundant systems, which incur additional costs and complexity.
Innovation Solution
A fail-safe circuit is implemented in the electronic power system that switches between normal and emergency driving circuits using diverter relays to maintain motor operation with two active phases, even in the absence of one phase, by applying out-of-phase voltages to the remaining phases via a star point connection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If redundant motors or windings are used to maintain operation during phase faults, then reliability is improved, but device complexity and cost increase
Solution Approach 1:
The invention changes the electrical parameters by injecting a specific voltage sequence (0, 120°, 240°) into the star point connection during fault conditions. This parameter change enables the motor to continue operating with two phases by creating artificial balance in the voltage distribution, resolving the contradiction between maintaining reliability and avoiding redundant mechanical parts
Solution Approach 2:
The star point connection serves as an intermediary element that, when connected to an emergency driving circuit during phase faults, enables continued motor operation. This intermediary mechanism allows the system to maintain reliability without requiring redundant motors or windings, thus reducing device complexity
2Reliability
If the number of phases is increased to five or six phases, then safety and reliability are improved, but circuit complexity and fault probability increase
Solution Approach 1:
The invention makes the three-phase motor universal by enabling it to function both in normal three-phase operation and in emergency two-phase operation through the star point connection. This multi-functionality allows the same motor design to meet higher safety requirements without increasing the number of phases or circuit complexity
3Device complexity
If a three-phase motor operates with only two active phases during fault, then cost and complexity are reduced, but maintaining proper phase balance becomes difficult
Solution Approach 1:
The invention stabilizes phase balance by changing the voltage parameters through star point injection. The emergency driving circuit generates a voltage sequence of (0, 120°, 240°) that compensates for the missing phase, maintaining proper voltage distribution and magnetic field balance even with only two active phases
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
Ensures safe and reliable motor operation during phase faults without the need for redundant mechanical parts, reducing costs and engineering complexity while meeting safety standards.
Implementation Method 1
a fail-safe circuit intervenes, allowing the motor to resume its operation (i.e., its rotation) in a temporary operating condition
Data Source
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Figure 2
Figure 3~4
AI summary
Power system for a three-phase brushless motor (M), comprising: a normal operating driving circuit (inverter) (1) of the motor, an emergency driving circuit (inverter) (2) of said motor, a control circuit (3) which manages the communication between the two driving circuits and their connection to the motor via a group of connection switches (4). Both the normal operating and emergency driving circuits by powering each phase (A, B, C) of the three-phase motor with a star or delta connection. In the presence of an engine operating anomaly, the control circuit detects such anomaly through a message of incorrect operation to the control circuit, which in turn activates the connection switches (4), which switch by disconnecting from the motor (M) the normal operating driving circuit and connect the emergency driving circuit (2) in its place.