Transport Refrigeration Voltage Control via Prime Mover Speed Modulation
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Solution Overview
Problem
In all-electric transport refrigeration systems, the prime mover inefficiently cycles between high and low speeds due to generator voltage fluctuations in cold weather, leading to inefficient operation.
Innovation Solution
A controller monitors and compares the voltage and speed of the electric generation device and prime mover, initiating a continuous voltage control cycle to maintain optimal speed and voltage levels, preventing excessive cycling by adjusting the prime mover speed to maintain a stable output.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If the prime mover operates at high speed to provide maximum cooling in cold weather, then the cooling capability is improved, but the generator voltage exceeds the voltage limit causing inefficient cycling
Solution Approach 1:
The system dynamically adjusts the prime mover speed based on real-time voltage measurements. Instead of operating at fixed high or low speeds, the controller continuously modulates the speed to maintain voltage within acceptable limits while providing adequate cooling, transforming the system from static to dynamic operation
Solution Approach 2:
The system implements a feedback control mechanism where the controller monitors generator voltage output and uses this information to adjust prime mover speed. The voltage sensor provides continuous feedback to the controller, which then modulates the prime mover speed accordingly, creating a closed-loop control system that prevents voltage excursions and inefficient cycling
2Reliability
If the prime mover cycles between high and low speed to maintain voltage limits, then the voltage control is improved, but the continuous cycling reduces operational efficiency
Solution Approach 1:
The system transitions from discrete on/off or high/low speed cycling to continuous dynamic speed modulation. The prime mover operates at variable speeds within a range, allowing smooth transitions that maintain voltage stability without the inefficiencies of repeated full cycling between extreme operating points
Solution Approach 2:
The system changes the operating parameters of the prime mover from fixed discrete speeds to continuous variable speeds. By modulating the speed parameter continuously rather than switching between fixed values, the system maintains voltage control while improving operational efficiency and reducing wear from frequent cycling
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 solution prevents inefficient cycling of the prime mover, ensuring consistent refrigeration performance by maintaining the prime mover at optimal speeds and voltage levels, enhancing energy efficiency and cooling/heating capability.
Implementation Method 1
a prime mover, most commonly a diesel engine, carried on and considered part of the transport refrigeration system, drives an AC synchronous generator that generates AC power
Implementation Method 2
Air or an air/ gas mixture is drawn from the interior volume of the cargo space by means of the evaporator fan(s) associated with the evaporator, passed through the airside of the evaporator in heat exchange relationship with refrigerant whereby the refrigerant absorbs heat from the air
Data Source
Figure 1
Figure 2
AI summary
A method of operating a transport refrigeration system (20) is provided. The method includes controlling, using a controller (30), a first plurality of components of a refrigeration unit (22), wherein controlling comprises operating a prime mover (26) and an electric generation device (24). The method also includes operating, using a controller (30), the prime mover (26) at a selected high speed. The method further includes monitoring, using a controller (30), a plurality of operating parameters of the refrigeration unit (22), wherein at least one of the operating parameters is at least one of a voltage of the electric generation device (24) and a speed of the prime mover (26). The method yet further includes comparing, using a controller (30), the voltage of the electric generation device (24) to a selected voltage. The method also includes comparing, using a controller (30), the speed of the prime mover (26) to a selected speed.