The centrifuge bearing and rotor are the heart of the speed-regulating system.

　    Centrifuge When the bearing connection is configured in a lateral manner, the resulting stiffness is finite. This leads to a reduction in the damping coefficient of the rotor system, an extension of the low-frequency precession period, and ultimately a decrease in the stability of the centrifuge. Moreover, this change becomes more pronounced as the rotor speed increases. The significance of studying lateral connection stiffness lies in its ability to enable a more accurate description of the rotor system's motion and a more reliable assessment of the centrifuge's operational stability.

　　To reduce the coefficient of friction, centrifuges typically employ as little mechanical contact area as possible. As a support structure for the spindle, they usually use slender, elastic needle shafts with spherical ends. In research studies, the dynamic model of the centrifuge rotor system traditionally assumes that there is no lateral relative displacement at the connection between the needle shaft and the bearing—that is, the lateral connection is assumed to have infinite stiffness.

　　Whether the sample loading is balanced directly affects the operational performance of the centrifuge. Imbalanced loading can cause abnormal vibrations and noise, leading to damage to the electric bearing system. In severe cases, it may even result in deformation of the electric shaft or, worse yet, shaft failure. If the shaft suddenly breaks during high-speed rotation, the centrifuge rotor will lose its support and begin to spin wildly within the centrifuge chamber, potentially causing the entire centrifuge to shift or even overturn. Should nearby personnel or equipment be present at that moment, this could lead to serious accidents resulting in injuries or fatalities as well as damage to equipment.

　　When using various centrifuges, first balance the centrifuge tubes, tube caps, baskets, and adapter accessories on a balance. During balancing, the weight difference must not exceed the range specified in the centrifuge’s instruction manual. The balancing requirement stipulates that the deviation must not exceed... 0.1 g; for routine applications, the requirement is generally more than 1 g. Hanging baskets and matching accessories are usually labeled with their respective weights. During balancing, be careful not to mix up the corresponding hanging baskets and accessories. The balancing tubes used for load balancing should be filled with materials of similar density—for example, after centrifuging from a culture medium, you can use the medium itself for balancing. However, cesium chloride can be balanced using water. In rotors, try to avoid loading an odd number of centrifuge tubes. When the rotor is only partially loaded, distribute the tubes evenly to ensure that the load is uniformly distributed across the rotor body. When loading solutions, follow the specific operating instructions for each type of centrifugation carefully. Select appropriate centrifuge tubes based on the properties and volume of the solution to be centrifuged. If using open-top centrifuge tubes, do not overfill them, as excessive liquid could spill out during centrifugation, potentially disrupting rotor balance, causing rusting, or leading to corrosion. For preparative ultracentrifugation, capped centrifuge tubes generally require being filled completely to prevent the upper part of the plastic centrifuge tubes from deforming due to vacuum-induced collapse during centrifugation.

　　When loading samples into a centrifuge’s angle rotor, it is essential to ensure balanced placement and strictly control the sample mass, making sure the samples are evenly distributed. When using a swinging-bucket rotor, in addition to balancing the sample load, the basket and accessories must also be pre-balanced and properly assembled to guarantee overall system balance of the rotor assembly. Test tubes and sample containers used for centrifugation should always be securely capped (using screw caps). Before each use, thoroughly clean any stains from the centrifuge tubes, rotors, and centrifuge chamber. In the event of specimen spillage: first, spray a solution containing chlorine at a concentration of... Apply an appropriate amount of the 5000 mg/L solution to the area where the specimen has spilled, and allow it to act for 30 minutes. Then, use tweezers to carefully remove the absorbent paper and blot up the mixture of contaminants and liquid. Dispose of the absorbent paper in the “biohazard” waste bin. Next, clean the spill area again using a solution containing 5000 mg/L of chlorine. Only after the area has been thoroughly dried can the centrifuge be used normally once more.

　　The speed-regulating system is the core component of a centrifuge, consisting of three major elements: control, power drive, and motor. Its primary function is to regulate the motor's rotational speed. In the development of centrifuges, DC speed control has played an indispensable role. Its key features include excellent starting and braking performance, a wide speed-regulating range, simple structure, low cost, and relatively mature theoretical and practical foundations. Consequently, before the 1980s, DC speed control was widely adopted in centrifuges and remains in use today, undergoing continuous improvements. For instance, advancements have been made in enhancing the wear resistance of the copper commutator and carbon brushes used in DC motors, thereby extending the motor’s service life and increasing the intervals between carbon-brush replacements.

　　The thyristor-phase-controlled DC speed regulation system for centrifuges is a classic DC speed-control solution characterized by its simple structure and mature technology, which basically meets the requirements of centrifuge speed control. Consequently, it has been widely adopted both domestically and internationally in centrifuge applications. Its main drawbacks include poor rectifier waveform, significant current ripple, and a tendency to experience current interruption under light loads. To maintain continuous current flow in the DC motor, a bulky smoothing inductor must be added, thereby increasing the size and weight of the instrument. Since the 1980s, with the development of power semiconductor devices for centrifuge control—such as power transistors and field-effect transistors—switching power conversion technology has gradually been applied to DC speed-regulation systems for centrifuges. This technology primarily works by frequency-modulating DC chopping, adjusting the pulse width ratio to vary the output voltage and supply power to the DC motor. Due to the high switching frequency—typically below— At 50 kHz, a smooth DC current can be achieved simply by the motor's inherent electrical filtering, thereby overcoming the drawbacks of thyristor-phase-controlled DC speed regulation. As a result, the speed becomes smoother and the speed-regulating range is wider.

　　Open-loop speed control is a simple speed-control solution that can be implemented with as few as a dozen discrete components or just a single integrated circuit. For this reason, some low-cost centrifuges in China still rely on this approach today. Its main drawbacks include the need for manual speed adjustment, the inability to control the motor’s current, and relatively low speed accuracy and technological added value. Given the limitations of open-loop speed control, most centrifuges both domestically and internationally now commonly adopt a dual-loop speed-control scheme that incorporates both current feedback and speed feedback. The key advantages of this dual-loop system are automatic speed regulation, rapid acceleration, minimal overshoot in rotational speed, high precision, and current-limiting functionality that prevents motor damage due to overcurrent.