Electric Motor with Galvanic Isolation for On-Board Charging
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Solution Overview
Problem
Existing on-board chargers for electric vehicles add weight, volume, and cost, and lack galvanic isolation, which are essential for integrated systems, and current integrated chargers often suffer from the absence of galvanic isolation.
Innovation Solution
The integration of an electric machine with two sets of galvanically isolated windings and two inverters, where a switching arrangement isolates one inverter from the electric machine during charging to induce voltage in the other set, allowing current to flow from a charge port and charge the traction battery while keeping the source isolated from the battery.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a separate on-board charger is added to charge the traction battery, then the charging capability is improved, but the weight, volume, and cost increase
Solution Approach 1:
The patent combines the charging function with the existing electric machine by using one set of windings for motor operation and another set for charging. The second inverter is used to convert AC power from the charge port to charge the traction battery, eliminating the need for a separate charger and reducing weight, volume, and cost.
Solution Approach 2:
The electric machine is designed with dual functionality: one set of windings serves as the motor winding for propulsion, while the other set serves as the charger winding for battery charging. The same inverter hardware is used for both motor control and charging operations, making the system multi-functional and eliminating redundant components.
2Reliability
If galvanic isolation is implemented in the charger, then the safety and reliability are improved, but the device complexity increases
Solution Approach 1:
The galvanic isolation function is merged into the electric machine's magnetic circuit. The transformer action occurs naturally through the magnetic coupling between the motor winding and charger winding sets, providing galvanic isolation without requiring separate isolation transformers or complex isolation circuitry.
Solution Approach 2:
The magnetic circuit of the electric machine itself provides the galvanic isolation function. The transformer action is achieved through the inherent magnetic coupling between the two sets of windings, eliminating the need for additional isolation components and reducing overall system complexity.
3Reliability
If traditional charger components (rectification stage, DC/AC converter) are included, then the charging function is complete, but the size, cost, and weight increase
Solution Approach 1:
The rectification and DC/AC conversion functions are merged into the existing inverter hardware. The second inverter, which would normally be redundant, is utilized to perform both rectification and voltage conversion during charging, eliminating the need for separate power conversion stages and reducing overall charger volume.
Solution Approach 2:
The inverter is designed to serve dual purposes: controlling the motor during propulsion and performing rectification plus DC/AC conversion during charging. This multi-functionality eliminates the need for dedicated rectification stages and DC/AC converters, significantly reducing the charger's size, weight, and cost.
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 provides galvanic isolation, reduces the need for additional charger components, increases efficiency by using the electric motor as a transformer, and eliminates the rectification and DC/AC converter stages, thereby minimizing size, cost, and weight while ensuring unity power factor operation.
Implementation Method 1
current from a charge port coupled with a source flows through one of the sets and induces a voltage in the other of the sets to charge the battery
Data Source
AI summary
A vehicle includes an electric machine with two sets of galvanically isolated windings, first and second inverters, a switching arrangement, and a controller. During charge, the controller operates the switching arrangement to isolate the first inverter from the electric machine to permit charge current to flow through one of the sets and induce a voltage in the other of the sets. During propulsion, the controller operates the switching arrangement to couple the first inverter with the one of the sets such that the first and second inverters are configured to only power one of the sets.