EV Motor Controller Surge Suppression With Back-EMF Recovery
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Solution Overview
Problem
Electronic vehicles face damage from surge currents caused by back-EMF energy when the main relay breaks contact or power is turned off, which can harm power switches and other devices on the DC bus.
Innovation Solution
A motor controller with a power distribution unit and control unit, featuring a main relay, first and second protecting circuits, where the first protecting circuit uses a diode and current limit resistor to feed back surge current into the battery, and the second protecting circuit uses a discharge switch and resistor to release it to a reference voltage range, preventing damage and recycling energy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the main relay breaks contact or power is turned off, then the motor controller can be powered down, but surge current from back-EMF energy damages power switches and other devices
Solution Approach 1:
The patent converts the harmful back-EMF energy into a beneficial resource by recycling it back to the battery. The first protecting circuit with diode and current limit resistor guides the back-EMF current flow back to the battery, transforming the harmful surge current into useful charging energy while protecting power switches and devices from damage
Solution Approach 2:
The patent introduces protecting circuits as intermediary components between the motor controller and the battery. These circuits include current limit resistors and diodes that mediate the energy flow, limiting current to safe levels and directing it appropriately - either back to the battery or to the DC bus - thereby protecting sensitive components from surge current damage
2Use of energy by moving object
If back-EMF energy is allowed to flow freely, then energy can be recovered, but surge current damages power elements on the DC bus
Solution Approach 1:
The patent changes the parameters of energy flow by introducing current limit resistors that control the magnitude and direction of current. The protecting circuits modify the electrical parameters (current limit, voltage levels) to enable safe energy recovery by directing back-EMF current to the battery while preventing dangerous surge currents from damaging power elements on the DC bus
3Reliability
If a protecting circuit is added to suppress surge current, then device reliability improves, but circuit complexity increases
Solution Approach 1:
The patent segments the protecting function into two distinct circuits: a first protecting circuit with a diode and current limit resistor for guiding back-EMF current to the battery, and a second protecting circuit with a discharge switch and current limit resistor for releasing energy to the DC bus. This segmentation allows each circuit to perform its specific function with simple, reliable components, achieving comprehensive protection without excessive overall complexity
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
Effectively suppresses surge currents and recycles back-EMF energy into a high-voltage battery, limiting DC bus voltage and preventing damage to power switches and other devices, while ensuring efficient energy reuse.
Implementation Method 1
the first protecting circuit comprises a diode and a first current limit resistor, wherein, the diode is connected in series with the first current limit resistor
Implementation Method 2
a first current limit resistor
Implementation Method 3
the second protecting circuit comprises a discharge switch and a second current limit resistor, wherein the discharge switch is coupled in series with the second current limit resistor
Implementation Method 4
the discharge switch and the second current limit resistor of the second protecting circuit release the surge current to a reference voltage range
Implementation Method 5
the motor back-electromotive force (back-EMF) energy may flow through an internal current path to charge a high-voltage battery
Data Source
AI summary
A motor control method for coupled an electronic vehicle is provided. The motor controller controls a motor and is powered by a battery. The motor control method includes: when a main relay of the motor controller suddenly breaks contact, in a first phase, feeding back a surge current into the battery to suppress the surge current by a diode and a first current limit resistor of a first protecting circuit of the motor controller; and, in a second phase, conducting a discharge switch of a second protecting circuit of the motor controller by a control unit of the motor controller, and releasing the surge current to a reference voltage range by the discharge switch and a second current limit resistor of the second protecting circuit.