Synchronous Motor Torque Control for Centrifugal Dryer
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Solution Overview
Problem
Existing centrifugal foodstuff drying apparatuses face issues with oversized dimensions due to overheating asynchronous three-phase electric motors at low speeds, peak power absorption, and limited torque adjustment, while hydraulic motors are complex and prone to contamination.
Innovation Solution
An apparatus utilizing a synchronous three-phase electric motor with an encoder and feedback control system to adjust torque output across a wide speed range, ensuring uniform torque and reduced dimensions, and incorporating a rotating joint for motor placement between the centrifugation basket and housing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If asynchronous three-phase electric motors are used in centrifugal drying apparatuses, then the motor can drive the centrifugation basket, but the motor overheats at low speed and requires oversized dimensions with cooling devices
Solution Approach 1:
The patent changes the operational parameters of the asynchronous motor by using a variable frequency drive to control the supply frequency and voltage. This allows the motor to operate efficiently across a wide speed range (from very low speeds during loading/unloading to high speeds during centrifugation) without overheating, eliminating the need for oversized cooling devices while maintaining reliability.
Solution Approach 2:
The patent implements dynamic control of the motor operation through electronic speed regulation. The motor transitions from static oversized design to dynamic adaptive operation, adjusting its speed and torque output according to the operational phase (loading, centrifugation, unloading), thereby optimizing its dimensions and eliminating permanent cooling infrastructure.
2Power
If asynchronous three-phase motors are used, then the motor can provide power for centrifugation, but it has peak power absorption at start with very low torque generated
Solution Approach 1:
The patent applies variable frequency control to modify the motor's torque-speed characteristics. By adjusting the supply frequency and voltage during startup and low-speed operation, the motor delivers high torque at low speeds during loading and unloading phases, then transitions to high-speed operation during centrifugation, eliminating the peak power absorption issue while maintaining ease of operation throughout the cycle.
3Speed
If transmission pulleys and electronic speed regulators are added to asynchronous motors, then speed reduction is achieved, but the device complexity increases and the adjustment range is limited
Solution Approach 1:
The patent replaces the mechanical transmission system (pulleys and belts) with an electronic control system (variable frequency drive). This substitution eliminates mechanical complexity while providing a much wider and more precise speed adjustment range, allowing smooth transitions from very low speeds during loading to high speeds during centrifugation, all controlled electronically without mechanical intermediaries.
4Force
If hydraulic motors are used to provide even torque with low regime, then torque uniformity is improved, but the apparatus becomes huge and complex with contamination risk from oil leakages
Solution Approach 1:
The patent replaces the hydraulic motor system with an electric asynchronous motor controlled by variable frequency drive. This substitution eliminates the risk of oil leakage and product contamination entirely, while achieving the same torque uniformity through electronic control. The system maintains even torque during low-speed operation and transitions smoothly to high-speed centrifugation without hydraulic fluids or associated contamination risks.
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
The solution enables a high-capacity, compact, and reliable drying apparatus with precise torque control across a wide speed range, reducing the risk of overheating and contamination, and improving the efficiency of the drying process.
Implementation Method 1
said motor is a asynchronous three-phase electric motor
Implementation Method 2
drying said product by its rotation... exploiting centrifugal force for removing said residual humidity
Implementation Method 3
said control means can comprise an encoder for detection of the rotation speed or of the position of said motor
Data Source
Figure 1~2
Figure 3
AI summary
The invention relates to an improved apparatus (1) for drying foodstuffs, comprising at least a centrifugation basket (5) for drying said product by its rotation, the lateral surface of said basket (5) being holed; a pin (13) rotating coupled with said at least a centrifugation basket (5); and a motor (12), mechanically coupled with said rotation pin (13); said apparatus (1) being characterised in that said motor (12) is a synchronous three-phase electric motor (12) and in that it comprises means (16) for controlling rotation of said motor (12) for adjusting the torque output by said motor (12) with respect to its rotation speed.