Motor Starter Contact Tilting to Reduce Semiconductor Heat Stress
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Solution Overview
Problem
There is a need for compact and economically produced motor starters for electric motors that reduce the stress on semiconductor switches and eliminate the need for large cooling devices.
Innovation Solution
A motor starter design featuring a semiconductor switch in parallel with an electromechanical switch, where the electromechanical switch takes over current flow in stationary operation, reducing heat loss and allowing the semiconductor switch to operate with reduced arc voltage and current gradient, thereby minimizing wear and increasing reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If a semiconductor switch is used to interrupt current flow in motor starter, then the device can be made more compact and controllable, but the semiconductor switch generates significant heat loss requiring large cooling devices
Solution Approach 1:
The patent applies dynamic switching between two operational states: during motor starting, the semiconductor switch actively controls current flow with pulse-width modulation; during steady-state operation, the electromechanical switch takes over to carry the full load current. This dynamic role assignment allows the semiconductor switch to operate only during transient periods when precise control is needed, eliminating the need for continuous cooling capacity.
Solution Approach 2:
The electromechanical switch serves as an intermediary that relieves the semiconductor switch from carrying continuous high current. The control system monitors motor current and automatically transfers load from the semiconductor switch to the electromechanical switch once the motor reaches operating speed, allowing the semiconductor switch to be downsized and eliminating large cooling devices.
2Device complexity
If the contact piece detaches from both fixed contacts simultaneously, then the switching action is simple, but the arc voltage becomes too high causing excessive current gradient and stress on the semiconductor switch
Solution Approach 1:
The contact detachment process is segmented into two sequential stages rather than a single simultaneous action. The tiltable contact piece first detaches from the first fixed contact (creating controlled arc voltage for current commutation), then subsequently detaches from the second fixed contact. This temporal segmentation of the detachment process allows precise control of arc voltage timing and magnitude, protecting the semiconductor switch while maintaining functional simplicity.
Solution Approach 2:
The contact piece is made tiltable to enable sequential detachment through controlled movement. By tilting the contact piece around a pivot point, the system dynamically controls which contact separates first, creating the desired arc voltage profile during current transfer from the electromechanical switch to the semiconductor switch, then completing the opening action without excessive voltage stress.
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 design reduces the stress on semiconductor switches, eliminates the need for complex cooling systems, and allows for a more compact and cost-effective motor starter with increased reliability and extended service life.
Implementation Method 1
In at least one of the current-carrying phases, a semiconductor switch, in particular an antiparallel thyristor pair, which is designed to interrupt the current flow in the corresponding phase
Implementation Method 2
An electromechanical switch is arranged parallel to the semiconductor switch and is also designed to interrupt the current flow through the corresponding phase
Implementation Method 3
The contact piece is connected to a contact piece carrier, which is connected to a magnetic drive
Data Source
Figure 1
Figure 2
Figure 3~6
AI summary
The invention relates to a motor starter (10) for operating an electric motor (30) connected to a multiphase power supply (12). In at least one current-carrying phase (14, 16, 18), a semiconductor switch (22) and an electromechanical switch (24) arranged in parallel are provided. Furthermore, the electromechanical switch (24) has a movable switching element (31). According to the invention, the movable switching element (31) is designed to tilt in order to reduce a current gradient (52) present in the semiconductor switch (22). The invention also relates to an operating method (100) for operating such a motor starter (10) and a computer program (80) configured to implement the operating method (100) according to the invention. Likewise, the invention relates to a motor starter arrangement (60) with an electric motor (30) that is operated via a motor starter (10) according to the invention.