CPT nomenclature

[philly]

I was hoping someone could help refresh my understanding of CPT nomenclature.

Looking at a CPT rated for 7200/12470Y which to me indicates this is a PT with the primary winding rated for 7200V and is intended to be connected L-N (L-G) and not L-L? To me the first 7200V number indicates the L-L voltage rating of the PT with the second number deriving the wye connected voltage (same 7200V number).

Am I looking at this backwards? Would a CPT rated for L-L connected voltage have a different nomenclature?

 

[Carultch]

I was hoping someone could help refresh my understanding of CPT nomenclature.

Looking at a CPT rated for 7200/12470Y which to me indicates this is a PT with the primary winding rated for 7200V and is intended to be connected L-N (L-G) and not L-L? To me the first 7200V number indicates the L-L voltage rating of the PT with the second number deriving the wye connected voltage (same 7200V number).

Am I looking at this backwards? Would a CPT rated for L-L connected voltage have a different nomenclature?

The 7200V indicates line-to-neutral voltage. 12470 indicates line-to-line voltage. Notice that the ratio between these numbers is the square root of 3? Just like this ratio occurs for 480 and 277, and for 208 and 120.

CPT stands for control power transformer. It is a small single phase transformer, used for transforming from the line-to-neutral voltage into a utilization voltage that can power your control circuits. Most examples I've seen, connect it line-to-neutral on the primary, and step the voltage down to 120V. So in this case, it would be

 

[philly]

The 7200V indicates line-to-neutral voltage. 12470 indicates line-to-line voltage. Notice that the ratio between these numbers is the square root of 3? Just like this ratio occurs for 480 and 277, and for 208 and 120. CPT stands for control power transformer. It is a small single phase transformer, used for transforming from the line-to-neutral voltage into a utilization voltage that can power your control circuits. Most examples I've seen, connect it line-to-neutral on the primary, and step the voltage down to 120V. So in this case, it would be

Thanks for feedback. I understand the two values and their relationship, I was more looking to confirm that given this listed rating that its primary winding is rated for 7200V maximum and therefore cannot be connected on a 12.47kV system L-L?

 

[synchro]

Looking at a CPT rated for 7200/12470Y which to me indicates this is a PT with the primary winding rated for 7200V and is intended to be connected L-N (L-G) and not L-L? To me the first 7200V number indicates the L-L voltage rating of the PT with the second number deriving the wye connected voltage (same 7200V number).

... I was more looking to confirm that given this listed rating that its primary winding is rated for 7200V maximum and therefore cannot be connected on a 12.47kV system L-L?

I believe you are correct.
In 5.12.3 of IEEE Std C57.12.00 it says the nomenclature E/E₁Y "shall indicate a winding of E volts that is suitable for Δ connection on an E volt system or for Y connection on an E₁ volt system."