1. Is the bearing used for normal clearance or C3 clearance?
2. What are the differences, advantages and disadvantages of 2Z, 2RZ and 2RS?
3, I have a generator bearing, long-term continuous work at 70-90 degrees, 1500-3000 rpm, select 6203/C3, shaft tolerance 17j5, the hole is aluminum shell, choose H7 or H6 good?
The first question: The type you are talking about contains all the motors (motors and generators), so sure your answer is uncertain.
The second question: This is related to the type of bearing, the type of motor, the load of the motor, the temperature, etc., and the same can not be said in a word.
The third problem, the three closed ways are different, 2Z is a dust cover, not a seal, only a rough ability to protect solid particles, so English is shield, not sealed. For the latter two (from your model, it is very likely that you are talking about SKF bearings), one is a light contact seal, and the other is a contact seal. Contact seals have the best protection. However, due to the sealed contact, the bearing's rotational speed capability is the worst. (God is fair, gives you the ability to seal, it will not give you the ability to rotate.) These three protection methods are like this, the better the sealing performance, the lower the speed capability.
The fourth problem is that the tolerance of the aluminum shell motor is tighter than that of the cast iron base. But this is not the best way. The best way is to add an o-ring to prevent the outer ring from running.