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Reasons for the high temperature of high-speed shaft bearings

For high-speed shafting, high-speed bearings are generally used. The alarm temperature of the high-speed axis generally does not exceed 75℃, and it is recommended to keep it within 60℃ for long-term operation. High bearing temperature is generally caused by the following reasons:
(1) The coaxiality of the shaft system has deteriorated
(2) The lubrication state of the bearing has deteriorated, and grease needs to be added or the bearing needs to be replaced
(3) If there is a floating end bearing in the shaft system, the floating function of the floating end may fail
(4) Bearings wear out due to prolonged use
(5) For bearings that have been used for a period of time, there is a general relationship between temperature and vibration, and vibration will cause the temperature to rise. The fault of the bearing can be judged from the spectrogram.

Causes of high vibration value of high-speed rotating machinery

For high-speed rotating machinery, there are generally several reasons for excessive vibration values:
(1) The shafting coaxiality is poor. Generally, the rotation speed exceeds 8000rpm, and the coaxiality needs to reach 0.02mm~0.03mm
(2) There are soft feet in the drive motor
(3) Poor shaft dynamic balance
(4) Resonance occurred in some frequency bands
(5) The bearings and other supporting parts of the shaft system are malfunctioning

High-speed motor inverter selection

For high-speed motors, when the IGBT switching frequency of the inverter is increased, the output harmonics will increase. Because the reactance of the high-speed permanent magnet synchronous motor is small, the harmonics will cause the motor to generate serious heat. The magnet will demagnetize, and the control will be unstable, so the output harmonic of the inverter needs to be weakened.</span><br><span> The switching frequency of the drive is generally selected to be 12-15 times the maximum operating frequency of the motor. The higher the motor frequency, the higher the corresponding ratio of the required switching frequency.

Dynamometer selection method

According to different motor models, there are two types of S1 curve (continuous duty system) in the operating stage from static to rated operating point: using the maximum torque allowed in temperature and using constant torque (usually using constant torque). The power will increase with the speed according to the torque type. This is followed by a period of constant power, during which field weakening occurs. The field weakening range is limited by the voltage limit value. The overload capacity is generally implemented according to the S6 (40%) work system.

The selection of dynamometer needs to consider the following factors:

For the rated power, rated speed, maximum speed, overload factor, etc. of the tested motor, it is generally required that the S1 curve of the dynamometer can cover the peak curve of the tested motor. If in order to save costs, or the dynamometer selection is difficult, you can also consider using the dynamometer’s S6 curve to envelope the peak curve of the tested motor, but you must consider that the dynamometer’s overload time cannot exceed the design requirements.

Guidance for Selecting Motor Testing System

1.According to the tested motor type, parameters, and test function requirements, comprehensively consider the selection of a series of dynamometers (GZC series hysteresis dynamometer, GZF series magnetic particle dynamometer, GZW series eddy current dynamometer, GZDL series electric dynamometer machine).

2.Select a certain range dynamometer according to the parameters of the motor under test
1). The speed of the motor to be tested cannot be greater than the maximum speed of the dynamometer.

2). The rated torque of the motor under test should be within 10%-100% of the full scale.

3). If temperature rise test is required, the rated power of the motor under test cannot be greater than the continuous operating power of the dynamometer.

3.Choose a suitable test system according to the type of motor under test and test function requirements to form a complete dynamometer system.

If it is difficult to choose, you can provide us with the rated parameters and peak parameters of the motor (you can also send us samples directly), and we will provide a more reasonable solution.