4NC51 window-type current transformers, used as pin-wound transformers, Classes 1 and 3, from 5 A to 75 A

Pin-winding increases the primary current of the current transformer. Consequently, window-type current transformers can also be used for low primary currents.

	Basic type		4NC51 12	4NC51 13	4NC51 15	4NC51 17	4NC51 21	4NC51 22	4NC51 23
	Rated primary current	A	50	60	75	100	150	200	250
	Service	VA	2.5	2.5	2.5	2.5	2.5	5	5
	Primary current to be measured		Number of required pin windings
		A	Class 3			Class 1
4NC51 used as pin-wound transformer		5	10	–	–	–	–	–	–
		10	5	6	–	10	–	–	–
		15	–	4	5	–	10	–	–
		20	–	3	–	5	–	10	–
		25	2	–	3	4	6	8	10
		30	–	2	–	–	5	–	–
		40	–	–	–	–	–	5	–
		50	–	–	–	2	3	4	5
		75	–	–	–	–	2	–	–