Chiller Motor Control System with DC Bus Capacitor Backup
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Solution Overview
Problem
Existing motor control systems in cooling systems fail to maintain continuous operation of both the chiller motor and motor controller when AC power is lost, as the motor controller may shut down due to lack of power, disrupting synchronous operation.
Innovation Solution
Incorporating a DC bus with a capacitor that stores capacitive charge to supply power to both the chiller motor and motor controller, allowing them to continue operation even during AC power loss, with inverters connected to both components to ensure continuous AC power output.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the motor controller is connected directly to AC power source through VFD, then the system structure is simple, but the motor controller shuts down when AC power is lost
Solution Approach 1:
The patent merges the power supply paths for the motor and motor controller by connecting both to a common DC bus. The first inverter supplies AC power to the motor while the second inverter supplies AC power to the motor controller, both drawing from the same DC power source. This unified architecture ensures that when AC power is lost, both components continue operating from the DC bus, eliminating the shutdown issue without requiring completely separate power systems.
Solution Approach 2:
The DC bus acts as an intermediary power source between the AC power source and both the motor/motor controller loads. By introducing this intermediate DC power stage, the system can decouple the AC power loss from the DC power availability, allowing the capacitor on the DC bus to maintain power supply to both the motor and controller during AC power interruptions.
2Duration of action of moving object
If a capacitor is added to the DC bus to store power, then continuous operation during AC power loss is enabled, but the system complexity and cost increase
Solution Approach 1:
The DC bus and capacitor infrastructure serves multiple functions simultaneously: it provides the power source for both the motor and motor controller through respective inverters, and acts as an energy storage system that maintains operation during AC power loss. By making the DC bus multi-functional, the patent avoids adding separate dedicated backup power systems, thereby reducing overall complexity despite the dual inverter configuration.
3Reliability
If dual inverters are used to power both motor and controller, then synchronous operation is maintained during power loss, but the device complexity increases
Solution Approach 1:
The patent segments the power conversion function into two separate AC-to-DC inverters, with the first inverter dedicated to motor power and the second inverter dedicated to motor controller power. Both inverters draw from the common DC bus, allowing independent power management for each load. This segmentation ensures that the motor controller receives reliable power independently of the motor's power demands, maintaining synchronous operation during power loss events.
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 the chiller motor and motor controller to maintain synchronous operation for approximately 5-15 minutes during AC power loss by utilizing stored capacitive charge, ensuring system continuity and reliability.
Implementation Method 1
the rectifier operative to receive AC power and output direct current (DC) power
Implementation Method 2
a DC bus with a capacitor that stores capacitive charge to supply power
Implementation Method 3
inverting DC power from the capacitor into AC power
Data Source
AI summary
A chiller system (200) includes a motor (212), a motor controller (214) connected to the motor (212), the motor controller (214) operative to send a control signal to the motor (212), a rectifier (206) connected to an alternating current (AC) power source (204), the rectifier (206) operative to receive AC power and output direct current (DC) power, a DC bus (208) connected to the rectifier (206), a first inverter (210) connected to the DC bus (208) and the motor (212), the first inverter (210) operative to receive DC power from the DC bus (208) and output AC power to the motor (212), and a second inverter (213) connected to the DC bus (208) operative to receive DC power and output AC power to the motor controller (214).