Which standard should be apply for mediun voltage converter

志纤陶

Now my company wanna have a UL certification for our medium voltage converter, brief introduction as below:
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Power cell: input:690V/3 phases, output voltage and frequency can be adjusted.
System:6 power cells in series, and then the total output voltage can be very high.
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After checking the UL standards, I think UL508C and UL347A will be used, but UL508C only applies to 1500V and below, UL347A is for more than 1500V. From my side, I think UL347A is a supplement for UL508C, so I feel our products should follow UL508C first for the power cell, then for system, we can use UL347A....

Am I right, or if my friends have other advise or instruction, pls kindly instruct me.

Thanks!