Blower Motor Control for Constant Airflow Without Flow Sensors
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Solution Overview
Problem
Existing control systems for electric motors, particularly backward-curved blowers and certain types of fans, struggle to maintain constant fluid-flow production due to multiple fluid-flow values corresponding to given torque-speed pairs, especially at high operating ranges, limiting their efficiency and effectiveness in HVAC and refrigeration systems.
Innovation Solution
A control system that computes and adjusts motor torque or speed based on correlations between fluid-flow, system resistance, and static pressure, using algorithms that define torque as a function of speed and fluid-flow, or speed as a function of torque and fluid-flow, to maintain constant fluid-flow production without the need for sensors, enabling operation in both torque and speed control modes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If backward-curved blowers are operated at given torque and speed, then efficiency is improved, but multiple different fluid-flows are produced making constant fluid-flow control difficult
Solution Approach 1:
The control system dynamically switches between torque-control mode and speed-control mode based on the operating range. At low fluid-flows, torque-control mode is used, while at high fluid-flows, speed-control mode is used. This dynamic adaptation allows the blower to maintain constant fluid-flow across the entire operating range while preserving efficiency benefits.
Solution Approach 2:
The system changes the controlled parameter (torque vs. speed) depending on the operating conditions. By monitoring the fluid-flow demand and operating range, the control algorithm selects the appropriate control mode, effectively changing the system's control parameter to match the operating requirements and maintain constant fluid-flow.
2Device complexity
If traditional torque-control or speed-control modes are used, then control simplicity is maintained, but constant fluid-flow production cannot be achieved with backward-curved blowers
Solution Approach 1:
The control system employs dynamic mode switching between torque-control and speed-control based on real-time operating conditions. The control algorithm monitors fluid-flow demand and automatically selects the appropriate control mode, providing a seamless transition that maintains constant fluid-flow without requiring complex additional hardware.
Solution Approach 2:
The control system is designed to operate in multiple control modes (both torque-control and speed-control) using a single integrated algorithm. This multi-functional approach allows the same control system to handle different operating ranges and fluid-moving apparatus types, maintaining simplicity while achieving constant fluid-flow production.
3Reliability
If forward-curved or radial blowers are used, then constant fluid-flow control is easier, but efficiency and power consumption are worse compared to backward-curved blowers
Solution Approach 1:
The control algorithm replicates the successful constant fluid-flow control strategy used with forward-curved blowers, but adapts it for backward-curved blowers. By implementing a dual-mode control algorithm that accounts for the specific characteristics of backward-curved blowers, the system achieves both efficiency and constant fluid-flow control.
Data Source
AI summary
A control system is provided for an electric motor configured to drive a fluid moving apparatus to generate a fluid-flow. The control system includes a drive circuit configured to regulate power supplied to a stator of the motor to turn a rotor and generate the fluid-flow, and a processor that computes a value proportional to at least one of a system resistance or a static pressure for the fluid moving apparatus based on a fixed set point for a first control parameter and a feedback parameter. The processor receives a fluid-flow rate demand and computes an operating set point for a second control parameter based on the fluid-flow rate demand and the value proportional to the system resistance or the static pressure. The processor controls the drive circuit based on the operating set point to supply power to the motor and operate the fluid moving apparatus to generate the fluid-flow.