Field-Guided Motor Braking With Two-Phase Current Control
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Solution Overview
Problem
Existing electric motor braking methods in power tools experience delays in acceleration after braking due to limitations in recuperation current, leading to disruptive operation and inefficient energy recovery.
Innovation Solution
A method that divides braking into two phases, maintaining a constant current amplitude in the first phase and adjusting the field-generating motor current component to ensure rapid braking, while allowing immediate acceleration, with a switch to a variable amplitude phase to enhance braking power without exceeding battery charging limits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the torque-generating motor current component iq is increased to enhance braking power, then the braking performance is improved, but the recuperation current exceeds the maximum permissible charging current of the battery pack
Solution Approach 1:
The patent changes the parameter distribution of motor current by introducing a non-zero field-generating current component id alongside the torque-generating component iq. This parameter change allows the system to achieve the required braking power through the combined effect of both current components, while keeping the recuperation current (derived from iq) within the battery pack's maximum permissible charging current limit.
2Object-affected harmful factors
If the motor current amplitude is limited to protect the battery pack, then the battery safety is improved, but the braking time is extended and acceleration response is delayed
Solution Approach 1:
The patent changes the parameter distribution of motor current by introducing a non-zero field-generating current component id alongside the torque-generating component iq. This parameter change allows the system to achieve the required braking power through the combined effect of both current components, while keeping the recuperation current (derived from iq) within the battery pack's maximum permissible charging current limit.
3Power
If the field-generating motor current component id is set to non-zero during braking, then the braking power is increased through ohmic power loss, but the current distribution control complexity increases
Solution Approach 1:
The control device dynamically adjusts the field-generating current component_id based on the motor's operating conditions, such as rotational speed and load. This dynamic control allows the system to optimize braking power at different operating points while managing the overall control complexity through adaptive rather than static current distribution.
Solution Approach 2:
The patent changes the parameter distribution of motor current by introducing a non-zero field-generating current component id alongside the torque-generating component iq. This parameter change allows the system to achieve the required braking power through the combined effect of both current components, while keeping the recuperation current (derived from iq) within the battery pack's maximum permissible charging current limit.
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
Enables rapid braking and immediate acceleration of electric motors in power tools, optimizing energy recovery and maintaining battery safety by controlling current distribution during braking.
Implementation Method 1
the field windings are energized by the control device from the battery pack, depending on the rotational position of the rotor. In motor operation, to generate a driving electromagnetic rotating field
Implementation Method 2
In regenerative braking operation, the voltages induced in the field windings of the stator when the rotor is rotating produce a torque-generating motor current component iq
Implementation Method 3
This ohmic power loss caused by the field-forming motor current component id increases the braking power of the electric motor
Data Source
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AI summary
The invention relates to a method and a device for operating a field-guided electric motor (1) on a battery pack (3). During motor operation, the motor current (7) consists of a field-generating motor current component (id) and a torque-generating motor current component (iq), which together form a current amplitude (A, A') of the motor current (7). To enable rapid braking of the electric motor, with the option of switching back to acceleration at any time, the braking operation is divided into two temporally separated braking phases (B1; B2). In a first braking phase (B1), the current amplitude (A) of the motor current (7) is kept constant by adjusting the field-generating motor current component (id), while in a second braking phase (B2), the current amplitude (A') of the motor current (7) is variable.The switching of the braking operation from the first braking section (B1) to the second braking section (B2) takes place when the speed (nG) of the electric motor (1) falls below a predetermined speed (nG).