Definition
An inverter mixer is a laboratory mixing equipment that controls the mixing speed by adjusting the working frequency of the motor. It is a kind of electric stirrer, and its core feature is that it adopts frequency conversion technology to achieve stepless speed regulation, so as to adapt to the mixing needs of samples with different viscosities and different phases. It is widely used in laboratories in many fields such as chemical synthesis, material preparation, food inspection, and environmental analysis, such as solution preparation, reaction acceleration, and homogeneous emulsification.
Principle
The working principle of the inverter mixer is based on the frequency conversion speed regulation technology of the AC motor. The equipment is mainly composed of frequency conversion controller, motor and stirring paddle. The variable frequency controller converts the input standard power frequency AC (e.g. 50Hz or 60Hz) into a three-phase AC power with adjustable frequency and voltage to supply the drive motor. According to the formula n = 60f / p(Among them.)nis the motor speed,fis the power supply frequency,pis the number of motor poles), and the synchronous speed of the motor is directly proportional to the frequency of the power supply. By changing the output frequencyf, which can adjust the final output speed of the motor linearly and smoothly over a wide range, and then control the shear force and mixing strength of the stirring paddle on the sample.
Measurement and performance evaluation methodology
The evaluation of the performance of inverter mixers usually focuses on their speed regulation range, speed stability, torque output and mixing effect. The rotational speed can be measured and calibrated by a non-contact phototachometer or a built-in encoder. Torque performance can be tested in a specific viscosity standard and indirectly evaluated by observing whether the mixer can run smoothly without stalling at a set speed. Evaluation of mixing effects depends on specific applications, such as measuring the time it takes for a multiphase system to reach a homogeneous state, or sampling to measure the consistency of its component concentrations. Relevant tests can refer to the technical standards for similar equipment, such as some test concepts in IEC 60335-2-14 on the safety and performance requirements of kitchen machinery, but they need to be adjusted according to the characteristics of the laboratory instruments.
Main influencing factors
The mixing effect is affected by multiple factors. Internal factors include the torque-speed characteristics of the motor, the control accuracy of the frequency converter, and the shape and size of the stirring blades. External factors mainly involve the physical properties of the stirred sample, such as viscosity, density, and solids content. High viscosity fluids require the mixer to provide sufficient torque at lower speeds. The geometry of the vessel and the height of the liquid level affect the flow field morphology, which affects the mixing efficiency. In addition, ambient temperature can affect the heat dissipation of the motor and the rheological properties of certain samples.
Applications
In chemical laboratories, it is used in processes such as polymerization reactions, catalyst dispersion, etc. In materials science, it can be used for homogeneous mixing of nanomaterials, ceramic pastes, or electrode materials. It is commonly used in food testing laboratories for ingredient mixing and simulating homogenization processes. In environmental monitoring, it can be used to mix reagents to water samples during pretreatment of water quality analysis. The common feature is that the mixing process is controllable, repetitive, and accommodating to a wide range of materials, from low-viscosity aqueous solutions to high-viscosity pastes.
Key points to consider in selection
Systematic matching is required during selection. First, the viscosity range of the sample for routine processing and the required container volume should be clarified to determine the necessary motor power and torque. Secondly, according to the requirements of the experimental process for speed accuracy and stability, choose the appropriate frequency conversion control type. The material of the stirring paddle (e.g., stainless steel, Teflon) considers chemical compatibility with the sample. The safety features of the equipment, such as overload protection and abnormal alarms, are also conditions to ensure long-term stable operation. In addition, design details such as whether the human-computer interaction interface is clear and whether it is convenient to clean and maintain are also related to the experience and efficiency of use.