CE certification is the basic requirement for electrical products entering EU market, for VDE or ENEC certified products, can be self-declared comply with CE by manufacturer, no need to apply CE certificate again.

Commonly used lampholders are made in porcelain or steatite, what’s the difference?

If the COB chip dimensions are all the same, still need to see the bonding pad dimensions are all the same or not. the contact finger of the connector is fixed, if the bonding pad is different, poor contact defect could happen.

According to lighting industrial standard, E27 and E39 are UL lampholders, comply with edison socket standard in UL496, while E27 and E40 are VDE lampholder, comply with edison socket standard in IEC60238. Actually the thread dimensions between E26&E27 and E39&E40 have slightly difference, can be measured with standard gauge.

Commonly the voltage marked onto wire is rated voltage, is different concept of pulse rating. A rated marked 300V wire, can pass 2.5KV pulse rating test, a ordinary HID lampholder, match with 1KV rated wire is enough.

In steatite sintering the temperature is more than 1000℃, while in practical usage, when temperature changes high and low, lead ceramic swell-shrink uneven, cause ceramic broken. Actually the bottleneck of lampholder related to other components like contacts, spring etc. The temperature of lampholder usage should not more than rated temperature suggested by its manufacturer.

If in actual use the working temperature not exceed the wire rated temperature, yes. While when there is detailed wire description in certificate, the wire chosen for lampholder must comply with certificate requirement.