Motor Protection Relay Soft Start Control
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Solution Overview
Problem
Existing motor starting techniques face challenges with high initial start currents and loads, requiring additional devices and increasing installation costs, making soft starting of motors inefficient and difficult to implement effectively.
Innovation Solution
A motor protection relay with a sensing unit, input unit, and control unit that variably controls start power by sensing current and voltage, generating start signals, and sequentially increasing power supply to the motor, allowing for soft starting without external devices.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If traditional motor starting methods (line-start, Y-D, reactor) are used, then motor starting capability is achieved, but start current and start load become excessively large
Solution Approach 1:
The patent applies dynamics by making the start power variable rather than fixed. The control unit dynamically adjusts the start power supplied to the motor during the starting phase, transitioning from high power to lower power as the motor accelerates. This dynamic control enables the motor to overcome initial inertia while preventing excessive start current, resolving the contradiction between needing sufficient start power and avoiding harmful high current.
Solution Approach 2:
The patent changes the parameter of start power from a constant high value to a variable value that decreases over time. By implementing a decreasing start power profile controlled by the control unit, the system maintains adequate power for motor acceleration while progressively reducing the harmful start current, thus resolving the technical contradiction.
2Object-affected harmful factors
If additional starting devices (soft starters, reactors) are added to reduce start current, then start current is reduced, but device complexity and installation cost increase
Solution Approach 1:
The patent merges the motor starting function with the existing motor protection relay. Instead of adding separate starting devices, the control unit of the relay is enhanced to perform both protection functions and starting control functions. This integration eliminates the need for additional external starting devices, reducing device complexity while maintaining the ability to control start current through the relay's internal control capabilities.
Solution Approach 2:
The motor protection relay is designed with multi-functionality, serving both as a protection device and a starting control device. The control unit can operate in different modes: motor protection during normal operation and motor starting control during startup. This universal design allows a single device to perform multiple functions, eliminating the need for separate starting devices and reducing overall system complexity.
3Speed
If high start power is supplied to rotate stopped motor, then motor rotation is achieved, but motor loss and energy consumption increase
Solution Approach 1:
The patent implements periodic action through a time-based control strategy where start power is supplied in a controlled sequence. The control unit provides high start power initially to overcome motor inertia and achieve rotation, then progressively reduces power as the motor accelerates to operating speed. This time-varying power supply pattern enables motor rotation while minimizing energy loss by avoiding continuous high power supply.
Solution Approach 2:
The control unit performs preliminary action by predicting the motor's acceleration needs and adjusting start power accordingly. High power is supplied only during the initial acceleration phase when needed, and power is reduced once the motor gains momentum. This preliminary, targeted power supply achieves motor rotation efficiently while minimizing unnecessary energy consumption and motor loss.
Data Source
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AI summary
The present disclosure relates to a motor protection relay and a method for starting a motor of the motor protection relay, and particularly, to a motor protection relay capable of softly starting a motor, without a separate starting device, and performing soft starting of the motor more stably, effectively, and simply, by variably controlling start power (S1...Sn) for starting the motor to the motor through controlling of the relay itself and supplying the variably controlled start power to the motor, and a method for starting a motor thereof.