Do all large motors have shaft current?
Compared with small motors, the bearing system of large motors is more complex. It is not meaningful to talk about motor bearings alone. To talk about motor bearings, we should start with related components such as shafts, bearing sleeves, end caps, and bearing inner and outer covers. The coordination with related components is only mechanical
In the actual operation and use of motors, the most common problem is the noise problem of bearings. The occurrence of such problems may be related to the quality of the bearings themselves, as well as the selection of bearings. Most of the problems are caused by inappropriate and unreasonable production processes that lead to bearing problems.
We know that noise comes from vibration, and to solve the problem of bearing noise, the first priority is to address the vibration issue. Compared with small motors and ordinary motors, large-sized motors, high-voltage motors, and variable frequency speed motors also face the problem of shaft current. To solve this problem, on the one hand, insulated bearings can be used, but the procurement cost of these bearings is relatively high, and some insulated bearings are not yet widely available; On the other hand, a grounded carbon brush is used, but it is more difficult to maintain. In view of this situation, many motor manufacturers have tried to find a solution on the bearing sleeve and invented insulated bearing sleeves. However, the processing of such insulated bearing sleeves is relatively complex. The basic principle is to divide the bearing sleeve into two parts and isolate the bearing chamber part through insulation. This completely cuts off the circuit caused by shaft voltage and current, which is a permanent measure. The following figure is a partial view of an insulated bearing sleeve.
This type of insulated bearing sleeve can be divided into an inner sleeve and an outer sleeve, with insulation filling between the inner sleeve and the outer sleeve. The thickness of the insulation filling layer is 2-4mm. The insulated bearing sleeve separates the inner and outer sleeves through an insulation filling layer, which blocks the shaft current and protects the bearing, thereby extending its service life.
Some motor manufacturers also use insulation boards to achieve this effect, but the insulation performance will be reduced when the insulation board is damp. In addition, there may be air gaps between the two cylindrical surfaces due to uneven thickness of the insulation board or the roundness of the cylindrical surface not meeting the requirements, which may have a certain degree of impact on the performance of the bearing sleeve. It is recommended to take necessary remedial measures.
