Single-Phase Induction Motor Overload Control via Auxiliary Coil Timing
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Solution Overview
Problem
Conventional overload control methods for single-phase induction motors struggle to accurately judge overloads under conditions of low voltage, high temperature, or low temperature, leading to unstable operation and limited use applications, often requiring larger motor sizes for worst-case scenarios.
Innovation Solution
Implementing multiple overload judgment methods, including threshold values for electric power, energizing time ratio, and integrated energizing time of the auxiliary coil, to accurately determine overload conditions, even when main coil current is unstable.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional overload control methods use main coil current threshold to judge overload, then the control is simple, but the judgment is inaccurate under low voltage, high temperature, or low temperature conditions
Solution Approach 1:
The patent segments the overload judgment process into multiple independent methods: (1) main coil current-based judgment, (2) auxiliary coil energizing time ratio-based judgment, and (3) integrated energizing time-based judgment. Each method operates independently and can be selected based on operating conditions, thereby improving measurement precision without creating a single complex unified system.
Solution Approach 2:
The patent changes the judgment parameter from solely main coil current to include auxiliary coil energizing time ratio and integrated energizing time. This parameter diversification allows accurate overload detection under varying conditions (low voltage, high/low temperature) where current alone is insufficient, thus improving measurement precision across different operating scenarios.
2Reliability
If the motor size is increased to prepare for worst-case scenarios, then the reliability is improved, but the device size and cost increase
Solution Approach 1:
The patent implements dynamic overload judgment that adapts to real-time operating conditions. By monitoring auxiliary coil energizing time ratio and integrated energizing time, the system dynamically adjusts its assessment of motor stress, enabling accurate overload detection across varying conditions without requiring oversizing for worst-case scenarios. This maintains reliability while avoiding unnecessary motor size increases.
3Measurement precision
If multiple overload judgment methods are implemented, then the measurement precision is improved, but the device complexity increases
Solution Approach 1:
The patent segments the control system into distinct functional modules: current detection module, energizing time detection module, and judgment execution module. Each module has a specific function, and they can be implemented independently. This segmentation improves measurement precision through multiple detection approaches while managing complexity through modular architecture.
4Measurement precision
If the auxiliary coil energizing time ratio method is used, then the overload judgment accuracy under unstable current conditions is improved, but the control complexity increases
Solution Approach 1:
The patent uses the auxiliary coil energizing time ratio as an intermediary parameter to indirectly assess motor overload conditions. Instead of directly measuring unstable current or torque, the system measures the duration of auxiliary coil energization, which correlates with motor stress levels. This intermediary approach improves measurement precision under unstable conditions while keeping control logic manageable through clear threshold-based decision rules.
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
Enables precise overload judgment across various conditions, preventing damage and expanding the operational range of single-phase induction motors, particularly in electric chain blocks.
Implementation Method 1
an auxiliary coil AL having an X terminal and a Y terminal at opposite ends thereof, respectively. At starting, the main coil ML is supplied with an alternating current from a single-phase alternating-current power supply 200 via an SSR (solid-state relay) power circuit 121, and at the same time, the auxiliary coil AL is also supplied with an alternating current from the single-phase alternating-current power supply 200 via the SSR power circuit 121 and a capacitor C. Consequently, a rotating magnetic field is generated in the stator S
Implementation Method 2
a main coil ML having a U terminal and a V terminal at opposite ends thereof, respectively, and an auxiliary coil AL having an X terminal and a Y terminal at opposite ends thereof, respectively. At starting, the main coil ML is supplied with an alternating current from a single-phase alternating-current power supply 200 via an SSR (solid-state relay) power circuit 121... a rotating magnetic field is generated in the stator S, and a rotor (not shown) rotatably supported opposite to the main coil ML and the auxiliary coil AL starts rotating
Data Source
AI summary
To provide a single-phase induction motor control method and apparatus and an electric chain block which are capable of appropriately judging an overload of a single-phase induction motor even when the single-phase induction motor is in a condition where energization of an auxiliary coil is repeated.Provided is a method of controlling a single-phase induction motor including a main coil ML, an auxiliary coil AL, a capacitor C, and an SSR (solid-state relay) power circuit 121, in which the main coil ML is supplied with an electric current from a single-phase alternating-current power supply 200 through the SSR power circuit 121, and when the load is heavy, the auxiliary coil AL is energized. An overload is judged based on the ratio of energizing time during which the auxiliary coil AL is energized within a predetermined time.