Inverter Capacitor Warm-Up Using Motor Current at Low Temperature
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Solution Overview
Problem
Conventional inverter devices face challenges in quickly raising the internal temperature of electrolytic capacitors in low temperature environments without exceeding permissible ripple voltages, leading to prolonged non-operating times and potential capacitor destruction.
Innovation Solution
An inverter device with a temperature sensor and control device that adjusts the current flowing through the electric motor before startup to control the ripple voltage within permissible limits, using specific switching elements to warm up the electrolytic capacitor by Joule heat while keeping the motor stopped, with current rates adjusted based on input voltage and temperature.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional warming up mode is used to raise the internal temperature of the electrolytic capacitor, then the internal resistance component is reduced, but the non-operating time becomes long
Solution Approach 1:
The control device performs preliminary warming-up of the electrolytic capacitor by controlling specific switching elements before the motor starts rotating. This preliminary action reduces the internal resistance component in advance, so that when the motor enters normal operation, the capacitor is already in a reliable state, thus shortening the overall non-operating time while ensuring capacitor reliability.
Solution Approach 2:
The control device dynamically adjusts the on/off states of specific switching elements during the warming-up period before motor rotation. By changing the switching patterns over time, the system optimizes the warming-up process to raise the capacitor temperature efficiently without requiring excessively long non-operating periods, thereby resolving the contradiction between reliability improvement and time loss.
2Reliability
If the number of electrolytic capacitors is increased to reduce internal resistance component, then the ripple voltage is lowered, but costs and device size increase
Solution Approach 1:
The invention extracts and utilizes the existing motor and switching elements in the inverter device to perform the warming-up function. Instead of adding more capacitors or complex capacitor configurations, the system repurposes existing components (specific switching elements and the motor) to generate heat for warming up the electrolytic capacitor, thereby reducing ripple voltage without increasing device complexity or 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 approach allows for quicker temperature increase of the electrolytic capacitor, reducing non-operating times and preventing capacitor destruction, while maintaining ripple voltage within safe limits.
Implementation Method 1
an electrolytic capacitor which smooths an input voltage to generate a DC voltage
Implementation Method 2
execute a warming up operation of allowing a current capable of controlling a ripple voltage of the DC voltage within a permissible range to flow through the electric motor at a predetermined rate of increase while keeping the electric motor stopped
Data Source
AI summary
An inverter device is provided which is capable of more quickly raising an internal temperature of an electrolytic capacitor within a permissible range of a ripple voltage to shorten a non-operating time. The inverter device includes an electrolytic capacitor, an inverter circuit, a temperature sensor, and a control device. When the ambient temperature of the electrolytic capacitor detected by the temperature sensor is lower than a predetermined temperature, the control device on-drives specific switching elements of the inverter circuit before the start of a normal operation of a motor, and executes a warming up operation of allowing a current capable of controlling a ripple voltage of a DC voltage within a permissible range to flow through the motor at a predetermined rate of increase while keeping the motor stopped.