Dynamic Overvoltage Protection Circuit for EC Motors
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Solution Overview
Problem
Existing overvoltage protection circuits for motor electronics, particularly EC motors, face challenges in providing effective protection against overvoltage pulses while also allowing for high-voltage testing, as gas arresters used in prior art often fail to respond adequately during slow voltage increases, leading to increased energy dissipation and potential damage during testing.
Innovation Solution
A circuit arrangement with two series-connected gas arresters, parallel resistors, and a capacitive element, where the breakdown voltage is controlled based on the edge steepness of the applied voltage, allowing for a high breakdown voltage during slow voltage increases (like high-voltage testing) and a lower breakdown voltage during rapid voltage rises (like overvoltage pulses), ensuring optimal protection and testability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the breakdown voltage of the gas arrester is increased to allow high-voltage testing, then the device can pass insulation tests, but the protective effect against overvoltage pulses is reduced
Solution Approach 1:
The gas arrester's breakdown voltage is made dynamic rather than fixed. The parallel capacitor creates a time-dependent response: during slow high-voltage testing, the capacitor charges and allows high breakdown voltage; during rapid overvoltage pulses, the capacitor remains discharged and enables low breakdown voltage for immediate protection. This dynamic behavior resolves the contradiction between testability and protection effectiveness.
Solution Approach 2:
The electrical parameters of the gas arrester system are changed based on the rate of voltage change. By introducing a parallel capacitor, the system's effective breakdown voltage parameter varies with the dv/dt of the applied voltage. This parameter change allows the same device to exhibit different voltage thresholds under different operating conditions, simultaneously achieving high-voltage testability and overvoltage protection.
2Object-affected harmful factors
If the gas arrester responds to slow voltage increases during high-voltage testing, then protection is provided, but the test fails due to unwanted current flow
Solution Approach 1:
The response characteristics of the gas arrester are made dynamic through the parallel capacitor. During slow high-voltage testing, the capacitor charges up and prevents premature ignition of the gas arrester. During rapid overvoltage pulses, the capacitor cannot charge quickly enough and remains non-conductive, allowing the gas arrester to ignite and protect the electronics. This dynamic response ensures test passage while maintaining protection capability.
Solution Approach 2:
The parallel capacitor performs a preliminary action by charging during the slow voltage ramp of high-voltage testing. This preliminary charging state prepares the circuit to prevent gas arrester ignition during testing. When a rapid overvoltage pulse occurs, the capacitor's charged state creates a voltage division that allows the gas arrester to respond appropriately, thus the preliminary action during testing enables subsequent proper protection response.
3Device complexity
If a single gas arrester is used, then the circuit is simple, but it cannot provide different breakdown voltages for testing and protection
Solution Approach 1:
The parallel capacitor is integrated into the gas arrester circuit to create a multi-functional system. The same gas arrester configuration serves dual purposes: enabling high-voltage testing by allowing high breakdown voltage during slow ramps, and providing overvoltage protection by enabling low breakdown voltage during rapid pulses. This universal design eliminates the need for separate testing and protection circuits, maintaining simplicity while achieving adaptability.
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
This solution enables effective protection against overvoltage pulses while allowing the circuit to pass high-voltage tests without igniting the gas arresters, thereby ensuring the safety and functionality of motor electronics.
Implementation Method 1
at least one capacitive element (preferably a capacitor) connected in parallel with a protective device
Implementation Method 2
Above a component-specific ignition voltage, however, a gas discharge ignites in the gas arrester and the terminal voltage on it is reduced within a few microseconds in the event of currents caused by an arc discharge (arc ignition)
Data Source
Figure 1~3
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Figure 6~7
AI summary
The invention relates to an overvoltage protection circuit (1) for protecting the electronics of a motor, in particular an EC motor, against overvoltage pulses, comprising two protective devices (FS1, FS2), which are arranged in series between two connections (10, 20), wherein a resistor (R1) or (R2) is connected in parallel to each of the protective devices (FS1, FS2) and at least one capacitive element (C1) is arranged in parallel with the first protective device (FS1), wherein the overvoltage protection circuit (1) has, between the connections (10, 20), at least a first (lower) and a second (higher) breakdown voltage point at a voltage UZ1 or UZ2 in dependence on the voltage change over time k=(dU/dt) of a voltage UGA at the connections (10, 20).