AC Rotary Machine Control Apparatus for Stable High-Speed Reactivation
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Solution Overview
Problem
Existing methods for reactivating AC rotary machines, particularly permanent magnet motors, face instability and excessive current issues due to mismatched induced voltage and output voltage vectors during high-speed operation, leading to unnecessary torque and potential overcurrent protection activation.
Innovation Solution
A control apparatus with an activation current instruction unit and a start phase setting unit that generates current instructions and sets an initial rotation phase based on the rotation direction and current polarity, reducing excessive current and torque shock during reactivation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If sensorless vector control is performed during reactivation of high-speed AC rotary machine, then torque control based on rotor position is achieved, but excessive current flows and unnecessary torque occurs due to mismatched induced voltage and inverter output voltage vectors
Solution Approach 1:
The patent applies preliminary action by performing current feedback control before sensorless vector control during reactivation. The control device first executes current feedback control to suppress excessive current, then transitions to sensorless vector control after confirming stable operation. This sequential approach prevents the mismatch problem between induced voltage and inverter output voltage vectors by establishing stable current control first.
2Reliability
If only current feedback control is performed during reactivation without sensorless control, then excessive current is suppressed, but induced voltage vector and inverter output voltage vector remain mismatched causing unnecessary torque
Solution Approach 1:
The patent uses preliminary action by implementing current feedback control as a preliminary step before sensorless vector control. During the initial reactivation period, current feedback control suppresses excessive current while the system prepares for transition to sensorless control, which will subsequently eliminate unnecessary torque through accurate rotor position-based control.
Solution Approach 2:
The patent maintains continuity of useful action by seamlessly transitioning from current feedback control to sensorless vector control. The control device continuously monitors current and voltage vectors, ensuring that when sensorless control begins, the system is ready to eliminate unnecessary torque while maintaining stable current control without interruption.
3Productivity
If inverter is reactivated during high-speed rotation with large induced voltage amplitude, then operation resumes, but overcurrent protection operation occurs and reactivation becomes impossible
Solution Approach 1:
The patent applies preliminary action by implementing a preparatory current feedback control phase before full sensorless vector control during reactivation. This preliminary control suppresses excessive current that would otherwise trigger overcurrent protection, enabling successful reactivation even during high-speed rotation with large induced voltage amplitude.
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 stable and assured reactivation of AC rotary machines without triggering protection operations, maintaining control stability across the entire rotation rate region from zero to high speeds.
Implementation Method 1
a current detector 5 provided on the AC feed paths Iu, Iv, and Iw for three phases, and detects AC phase current flowing from the power converter 3 to the synchronous electric motor 4
Implementation Method 2
the power converter 3 receives switching instructions su*,sv*, and sw* from the control circuit 2, and based on the switching instructions, generates three-phase AC power having controlled output voltage and controlled angular frequency
Implementation Method 3
the synchronous electric motor 4, which is a synchronous electric machine using permanent magnet, converts the three-phase AC power into a rotational driving force (torque)
Data Source
Figure 1
Figure 2
Figure 3
AI summary
A control apparatus (1) for an AC rotary machine includes a control circuit (2), a power converter (3), a current detector (5), and a voltage detector (7). The control circuit (2) has: an activation current instruction unit (18) which generates a current instruction for activation; and a start phase setting unit (20) which sets an initial rotation phase for activation control, based on the rotation direction of the AC rotary machine (4) just after activation and on the polarity of current detected by the current detector (5) just after activation. Thus, the current amplitude and torque shock just after activation control has been started can be reduced, and assured and stable reactivation is allowed without causing the protection operation.