Motor Control Device Induced Voltage Protection
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Solution Overview
Problem
Existing motor control devices risk destruction due to induced voltage when an electric motor rotates by external force during uncontrolled stopping, as they lack effective mechanisms to manage and discharge this voltage without additional components.
Innovation Solution
A motor control device with a switch element and rotation speed detector that controls the electric motor's operation, turning on the switch element when the motor's rotation speed exceeds a predetermined value to discharge induced voltage to the battery, preventing damage to the drive circuit.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the switch element is kept off during uncontrolled stopping to save power, then power consumption is reduced, but the drive circuit is vulnerable to induced voltage damage
Solution Approach 1:
The controller turns on the switch element before the motor completely stops when reverse connection is detected, creating a protective path in advance. This preliminary action ensures that when the motor generates induced voltage during uncontrolled stopping, the voltage is safely discharged through the battery rather than damaging the drive circuit, while minimizing power consumption by only activating the switch when needed
2Reliability
If additional components like diodes or cut-off preventing circuits are added to protect against induced voltage, then drive circuit safety is improved, but device complexity increases
Solution Approach 1:
The switch element serves multiple functions: it acts as a power supply connector during normal operation, a protective discharge path during reverse connection, and a controlled connector during uncontrolled stopping. By making the existing switch element multi-functional through intelligent control, the patent eliminates the need for additional protective components like diodes or cut-off preventing circuits, maintaining circuit simplicity while ensuring drive circuit safety
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
Prevents destruction of the drive circuit by equalizing the voltage at the drive circuit to the battery voltage, reducing the risk of semiconductor damage and unnecessary power consumption, without requiring additional components.
Implementation Method 1
When the induced voltage is applied to the drive circuit to increase a voltage at the drive circuit, a risk of destroying the drive circuit is generated due to a damage of a semiconductor element in the drive circuit. In Japanese Unexamined Patent Publication Nos. 11-41703 and 8-111902, the electric motor and the switch element (relay) are connected to each other through a cut-off preventing circuit and a diode. Therefore, a control current by the induced voltage of the electric motor is supplied to the switch element to close a contact of the switch element
Data Source
AI summary
A motor control device has a drive circuit that drives an electric motor with a battery as a power supply, a switch element that is provided between the battery and the drive circuit, the switch element supplying a current from the battery to the drive circuit when being turned on, the switch element cutting off the current from the battery to the drive circuit when being turned off, a rotation speed detector that detects a rotation speed of the electric motor, and a controller that operates the drive circuit to control the electric motor. The controller turns on the switch element when the rotation speed of the electric motor, which is detected by the rotation speed detector, is greater than or equal to a first predetermined value during stopping of the control of the electric motor.