Single-Phase Motor Protection Circuit for Thermal Stress Relief
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Solution Overview
Problem
Existing electric motors with single-phase windings face issues of thermal stress and high thermal load on switching elements due to avalanche breakdowns, leading to potential thermal destruction and limited power capacity, with existing solutions like US 2008/272722 A1 and US 4,584,506 A not adequately addressing these concerns.
Innovation Solution
A protective circuit is implemented using electrical power components like power Zener diodes or bipolar power transistors in parallel with switching elements to divert and convert stored energy into thermal energy, combined with an RC attenuator to manage switching edges and improve EMC performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If freewheeling diodes are not used and avalanche breakdown is allowed, then the circuit structure is simplified, but the switching elements suffer from high thermal stress and limited power capacity
Solution Approach 1:
A Zener diode is introduced as an intermediary component connected in parallel with the switching element. The Zener diode clamps the voltage during avalanche breakdown to a safe level (e.g., 20V), preventing excessive thermal stress on the switching element while allowing the simplified circuit structure without freewheeling diodes.
Solution Approach 2:
The Zener diode provides beforehand cushioning by being pre-positioned in parallel with the switching element to absorb and dissipate the energy from avalanche breakdown before it can cause thermal damage to the switching element.
2Power
If higher motor power is desired, then more power is needed, but thermal destruction of components is expected due to limited thermal load capacity
Solution Approach 1:
The Zener diode acts as an intermediary that protects the switching element from thermal damage, enabling the system to handle higher motor powers without exceeding the thermal load capacity of the switching components.
Solution Approach 2:
The voltage parameter is changed and clamped by the Zener diode to a safe level during breakdown, allowing higher power operation while maintaining component safety through parameter control.
3Use of energy by moving object
If switching elements are subjected to high voltage pulses, then the circuit can handle higher energy, but the switching elements may be damaged due to limited voltage tolerance
Solution Approach 1:
The Zener diode provides beforehand cushioning by being positioned in parallel with the switching element to clamp and dissipate high voltage pulses before they can damage the switching element, enabling higher energy handling while protecting components.
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
The solution provides thermal protection for switching elements, reduces heating and power losses, enhances EMC behavior, and allows for smoother operation and robust circuit design by managing high voltage pulses.
Implementation Method 1
The energy stored in the partial coil (5 or 6) is converted into thermal energy via the resistance of the power component
Implementation Method 2
an RC attenuator (snubber network) consisting of a snubber resistor (17) and a snubber capacitor (18) is connected between one winding end of a partial coil and ground
Data Source
Figure 1~2
Figure 3~4
AI summary
The invention relates to a protective circuit of an electric motor with a single-phase winding (3), consisting of two coil sections (5, 6) with a centre tap (7), wherein the two winding ends of the coil sections (5, 6) are connected to earth (10) via a switching element (8, 9) in each case. The problem addressed by the invention is that of ensuring thermal relief of the switching elements, an improved running smoothness, reduced heating of the printed circuit board, an improved EMC behaviour, a more robust design of the overall circuit, targeted conduction of the losses and additional protection against other overvoltage pulses from a supply network in the case of an electric motor of the generic type. According to the invention, this problem is solved by the features of claims 1, 11 and 14.