Auxiliary Motor Charging With Galvanic Isolation for EVs
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Solution Overview
Problem
Existing electric vehicle charging systems require additional components like onboard chargers and isolation stages, which increase cost and weight, and necessitate either a clutch or rotor lock to allow the traction motor to charge the battery without being engaged with the wheels.
Innovation Solution
Utilizing an auxiliary motor, already present in many electric vehicle architectures, to provide galvanic isolation between the traction battery and the external power source during charging, allowing the rotor to rotate freely without the need for a clutch or rotor lock.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the traction motor is used to charge the battery without being engaged with the wheels, then galvanic isolation is provided, but a clutch or rotor lock is required which increases device complexity
Solution Approach 1:
The auxiliary motor is designed to perform multiple functions: it can operate as a motor to drive the compressor, and it can operate as a generator to charge the traction battery. This multi-functionality eliminates the need for separate charging equipment and avoids the complexity of clutches or rotor locks by using the auxiliary motor's natural rotational capability for both propulsion assistance and energy storage charging.
2Reliability
If an onboard charger with isolation stage is used, then galvanic isolation is provided, but additional cost and weight are incurred
Solution Approach 1:
The auxiliary motor serves dual purposes: driving the compressor during normal operation and providing galvanic isolation during battery charging. By utilizing existing auxiliary motor equipment for charging functions, the patent eliminates the need for separate onboard chargers and isolation stages, thereby reducing vehicle weight and cost while maintaining safety requirements.
Solution Approach 2:
The auxiliary motor's electromagnetic structure inherently provides galvanic isolation between the AC charging port and the DC battery system. The motor's stator and rotor windings act as built-in isolation components, eliminating the need for additional isolation equipment and reducing overall system weight.
3Productivity
If the auxiliary motor rotor is allowed to rotate during charging, then electromagnetic coupling efficiency is enhanced, but traditional charging systems require rotor locking
Solution Approach 1:
The auxiliary motor is designed to operate in generator mode during charging, where the rotor naturally rotates to generate electricity from the AC input. This rotational operation during charging enhances electromagnetic coupling efficiency and eliminates the need for rotor locking mechanisms, as the rotation is the fundamental charging mechanism rather than an obstacle to be managed.
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 improves the efficiency of the charging system by allowing the rotor to spin, enhancing electromagnetic coupling, and eliminates the need for additional costly components, thereby reducing weight and increasing versatility in electric vehicle charging.
Implementation Method 1
receive alternating current for exciting windings of the stator so as to cause rotation of the rotor by electromagnetic coupling
Implementation Method 2
establishing a connection between the power electronics and the first windings while isolating the traction battery from the charge port
Data Source
AI summary
An integrated charger for electric vehicles employs a multi-phase auxiliary motor on the vehicle to charge the traction battery. The stator of the electric motor includes first windings and second windings that are phase-staggered. One of the sets of windings is put into connection with an external AC power source via a switching unit, which also isolates the vehicle's traction battery from the external source. The AC current excites an alternating current in the second windings, which is rectified and used for charging the traction battery.