A centrifuge is a specialized equipment that uses centrifugal force to quickly separate mixed solutions. Its applications are very extensive, such as in biochemical research on studied objects such as biological cells, viruses, and serum. The separation, concentration, extraction, and preparation of samples such as protein and other organic and inorganic solutions, suspensions, and colloids. Among them, ordinary centrifuges (with a speed of 4000-5000 r/min) are the most common. Below is a brief introduction to the maintenance and repair of ordinary centrifuges as an example

A regular centrifuge consists of an electric motor, a turntable, and a speed controller. Composed of casing, base, etc., the motor has a high speed under light load, but the speed will sharply decrease with the increase of load.
1. Use and maintenance
(l) Before using the centrifuge, it must be placed on a stable and sturdy ground (table)
(2) The chassis should be grounded during use
(3) When in use, the load must be balanced, and when installed, it must be symmetrically placed
(4) When turning on the switch, the speed control knob should be in the "0" position
(5) The correct way to turn the speed control knob to the maximum when opening the switch is to slowly shift it up
(6) After use, the speed control knob should be rotated to "0" step by step, and then let it stop rotating on its own. It is strictly prohibited to open the hood while it has not stopped or is running
(7) If abnormal sound is found during use, the device should be turned off immediately and checked and repaired
(8) Regularly (about a year) check the wear of the commutator and electric brush. If there is excessive wear, it should be replaced immediately
(9) The bearings of the electric motor should be regularly lubricated with grease

2 Common Troubleshooting Methods

(l) After power on, if the motor does not turn: First, check the power cord, plug, and socket. If there is any damage, replace them. If there is no problem, check whether the band switch or variable resistor is damaged or the wiring is disconnected. If it is damaged or disconnected, replace the damaged component and re solder the wiring. If there is no problem, check whether the motor magnetic field coil is disconnected or broken (internally). If the wiring coil is disconnected, it can be re soldered. If the coil is internally disconnected, it can only be rewound

(2) If the motor speed does not reach the rated speed: First, check the bearings. If the bearings are damaged, replace them. If there is a lack of oil or too much dirt inside the bearings, clean the bearings and add lubricating grease. Check if there are any abnormalities on the surface of the commutator or if the brush matches the commutator surge surface. If there are any abnormalities on the commutator surface or if there is a layer of oxide, use fine sandpaper to polish it. If the commutator does not match the brush, adjust it to a good contact state. If there is no such problem, check if there is a short circuit in the rotor coil. If there is, rewire the coil

(3) Intense vibration and loud noise: Check for any imbalance issues. Loosen the nuts that secure the machine. If so, tighten them. Check if the bearings are damaged or bent. If so, replace the bearings. If the machine casing is deformed or in the wrong position, friction may occur. If so, adjust it

(4) Low speed gear cannot be started in cold weather: lubricating oil solidifies or deteriorates, dries up, and sticks. At the beginning, you can use your hands to assist in re turning or actively re oiling after cleaning

(5) The gap between the commutator and the electric brush is too large: Check whether the surface of the commutator is flat. If the surface is uneven, it can be polished with sandpaper. If the problem is poor contact between the electric brush and the commutator, use fine sandpaper to polish the part and readjust the fit between the electric brush and the commutator. The quality of the electric brush is not qualified. If this is the fault, only the electric brush can be replaced. If there is no problem above, check whether there is a local short circuit or ground connection in the magnetic field coil or a local short circuit or open circuit in the rotor coil. If any of the above situations occur, the magnetic field coil or rotor coil must be rewound