Electric Machine Torque Determination via Iterative Current Limits
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Solution Overview
Problem
Current methods for determining the maximum adjustable torque of electrical machines, particularly in motor and generator operations, are inefficient due to limitations in existing technologies for real-time adjustments and consideration of parameters like magnetic saturation, temperature, and inverter constraints.
Innovation Solution
A method using a computing unit to iteratively calculate maximum adjustable torque by determining the maximum permissible excitation current, phase current, and total current, taking into account parameters such as magnetic saturation, temperature, and inverter limitations, and providing these values through an interface for real-time adjustments in d-q coordinates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If iterative calculation method is used to determine maximum adjustable torque considering magnetic saturation and temperature, then measurement precision and reliability are improved, but computing time and device complexity increase
Solution Approach 1:
Lookup tables are pre-calculated and stored containing torque values for different operating conditions (excitation current, phase current, temperature, speed). During real-time operation, the control unit simply retrieves the appropriate torque value from the lookup table based on current sensor readings, avoiding iterative calculations while maintaining high precision.
Solution Approach 2:
Instead of performing complex iterative calculations in real-time, the patent creates simplified copies of the calculation results in the form of lookup tables. These tables store pre-computed torque values that can be quickly accessed and interpolated during operation, effectively copying the outcome of complex calculations into a easily queryable format.
2Reliability
If real-time torque determination is implemented considering multiple parameters (excitation current, phase current, temperature, speed), then reliability and adaptability are improved, but device complexity increases
Solution Approach 1:
The control system is segmented into distinct functional modules: excitation current control, phase current control, temperature monitoring, speed sensing, and torque calculation. Each module independently handles a specific aspect of the control task, making the overall complex system manageable through modular design where each segment can be developed, tested, and maintained separately.
Solution Approach 2:
Lookup tables serve as intermediaries between the complex physical relationships (described by differential equations considering magnetic saturation and temperature) and the real-time control decisions. The tables pre-process the complex relationships and provide simplified torque recommendations that the control unit can directly apply without solving complex equations in real-time.
3Reliability
If maximum permissible currents are strictly limited by inverter constraints, then reliability is improved, but productivity and power utilization decrease
Solution Approach 1:
The maximum permissible currents are not fixed but dynamically adjusted based on real-time operating conditions such as temperature, speed, and excitation current. The control system continuously monitors these parameters and adjusts the current limits accordingly, allowing the system to operate closer to the true physical limits rather than conservative fixed limits, thereby improving power utilization while maintaining reliability.
Solution Approach 2:
The patent changes the parameters used to determine maximum permissible currents from static inverter ratings to dynamic values that consider temperature-dependent resistance changes, magnetic saturation effects at different flux levels, and speed-dependent back-EMF. By adjusting these parameters based on actual operating conditions, the system maximizes power utilization while preventing overloads.
Data Source
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AI summary
The invention relates to a method for determining a maximally adjustable torque (Mmin, Mmax) of an electric machine in motor and/or generator mode for a present operating point, wherein: a presently maximally adjustable voltage (Udc) and a present angular frequency (ωel) of the electric machine are determined; parameters (P) of the electric machine are iteratively determined using a maximally permitted excitation current (lex,max) for the electric machine, and variables comprising a maximally possible q-current (Iq,min, Iq,max) and a maximally possible d-current (Id.min, Id,max), in each case for the motor and/or generator mode, are determined from said parameters using a maximally permitted phase current (Idq.Limit) and a maximally permitted total current (Idc.Limit) for the motor mode and/or the generator mode; a maximally possible torque (Mmin, Mmax) of the electric machine for the motor mode and/or generator mode is determined from the variables; and a determined value for the maximally possible torque for the motor mode and/or generator mode is provided via an interface.