EI Transformer Core Bulk Supply & Custom Manufacturer

Overview of EI Laminated Structure

The core structure of the EI transformer core is composed of E-shaped and I-shaped laminations. All laminations are covered with insulating coatings on their surfaces and form a closed magnetic circuit through interlaced stacking .

The E-shaped laminated plates present a structure of three horizontal and one vertical, responsible for the conduction of the main magnetic flux. The I-shaped laminated plate is long and strip-shaped, used to close the magnetic circuit and reduce magnetic flux leakage.

The thickness of the laminations is usually 0.35 to 0.5mm. They are formed by precise stamping to ensure a tight fit between the laminations, effectively reducing hysteresis loss and eddy current loss, and improving the overall energy efficiency of the core.

This structural design makes the core assembly convenient, allowing the number of laminations to be adjusted as needed, and the thickness and capacity of the core to be flexibly changed.

EI transformer core

Technical Parameters

Specification	A	B	C	D	E	F	G	H	Air GAP	Stack	Hole	Apertureф
EI 16	16	12	4	2	4	10	2
EI 19	19	12.5	5	2.5	4.5	10	2.5
EI 24	24	15	6	6	3	12	3
EI 26	26	18	6	3	7	15	3
EI 28	28	21	8	4	6	17	4		0.25 / 0.4 / 0.45 / 0.5 / 1
EI 28	28	27	8	4	6	23	4
EI 30	30	20	10	5	5	15	5		0.22 / 0.35 / 0.4 / 1.2
EI 30	30	20.8	10	5	5	15.3	5.5
EI 32	32	26.5	9.5	4.75	6.5	21.7	4.75
EI 32	32	22.78	9	4.5	7	18.3	4.5
EI 33	33	22	11	5.5	5.5	16.5	5.5
EI 33	33	28	11	5.5	5.5	22.5	5.5
EI 35	35	24.5	9.6	5	7.7	19.5	5
EI 35	35	23.4	11.6	5.84	5.84	17.46	5.84
EI 35.2	35.2	25.2	12.6	5	6.3	20.1	5.1
EI 36	36	24.5	10	6.5	6.5	18	6.5
EI 38.4	38.4	25.6	12.8	6.4	6.4	19.2	6.4
	38.4	25.6	12.8	6.4	6.4	19.2	6.4		1.2	Yes
	38.4	44.8	12.8	6.4	6.4	38.4	6.4
EI 38.5	38.5	22	14	6	6.2	18
EI 41	41	27	13	6	8	21	6
EI 41	41	27	13	6	8	21	6		1.2 / 2	Yes
EI 42	42	28	14	7	7	21	7	35	0.4 / 0.46 / 0.48 / 0.5 / 0.95 / 1.15 / 1.3 / 2		4	3.5
EI 42	42	28	14	7	7	21	7	35			4	3.5
EI 44	44	30	12	8	8	22	8
EI 48	48	32	16	8	8	24	8	40	0.6 / 0.5 / 0.8 / 0.9 / 0.93 / 1 / 2		4	3.5
EI 48	48	32	16	8	8	24	8	40			4	3.5
EI 50	50	34	14	9	9	25	9
EI 54	54	36	18	9	9	27	9	45	0.95 / 2		4	3.5
EI 56	56	38	16	10	10	28	10	46			4	5
EI 57	57	38	19	9.5	9.5	28.5	9.5	47.5	0.4 / 0.75 / 0.8 / 1.1 / 1.2 / 2		4	4
EI 57	57	38	19	9.5	9.5	28.5	9.5	47.5			4	4
EI 57.2	57.2	39	19	9.5	9.5	31.55	7.45
EI 60	60	40	20	10	10	30	10	50	0.75 / 0.8 / 1 / 1.2 / 1.25 / 1.3		4	3.5
EI 60	60	40	20	10	10	30	10	50			4	3.5
EI 66	66	44	22	11	11	33	11	55	0.8 / 1 / 1.2 / 1.45 / 1.5		4	4.5
EI 66	66	44	22	11	11	33	11	55			4	4.5
EI 67	67	45.4	19	12	12	33.5	12	55			4	5
EI 67	67	46	20	10	13.5	36	10	57			4	5
EI 70	70	47	22	11	13	35	13		2.5
EI 75	75	50	25	12.5	12.5	37.5	12.5	62.5			4	5
EI 76.2	76.2	50.8	25.4	12.7	12.7	38.1	12.7	63.5	1.8 / 2 / 2.54 / 2.2 / 2.5 / 1.3 / 3		4	5
	76.2	50.8	25.4	12.7	12.7	38.1	12.7	63.5			4	5
	76.2	50.8	22	11	16.1	39.8	11	65.2			4	5
	76.2	50.8	22	11	16.1	39.8	11	65.2			4	5
EI 78	78	52	26	13	13	39	13	65	1.1 / 1.35 / 1.6 / 2		4	5
		53	22	14	14	39	14	64
		53	22	14	14	39	14	64			4	5
EI 84	84	56	28	14	14	42	14	70			4	5
									2.5		4	5
									2.08		4	4.5
EI 85.8	85.8	57.2	28.6	14.3	14.3	42.9	14.3	71.5	1.3 / 1.5 / 1.75 / 1.85 / 2.25 /2.8 / 2.85 / 3		4	5
EI 85.8	85.8	57.2	28.6	14.3	14.3	42.9	14.3	71.5
EI 90	90	60	30	15	15	45	15	75			4	6
EI 94	94	64	26	17	17	47	17	77			4	6
EI 96	96	64	32	16	16	48	16	80	1.15 / 1.5 / 2.2 / 2.3 / 2.45 / 2.5 / 2.7 / 3 / 5		4	6.3
											4	6.3
									Offset hole		4	6
EI 105	105	70	35	17.5	17.5	52.5	17.5	87.5	1.2 / 1.5 / 1.6 / 1.8 / 2 / 2.3 / 2.45 / 2.65 / 2.7 / 2.8/ 3 / 3.4 / 10.5		4	6
EI 106	106	72	30	19	19	53	19	87			4	7
EI 108	108	72	36	18	18	54	18	90			4	5.5
EI 111	111	72.7	34	17.2	21.3	55.5	17.2				4	5.5
EI 114	114	76	38	19	19	57	19	95	1.3 / 3 / 4 / 12.7		4	7
EI 114	114	76	38	19	19	57	19	95			4	7
EI 118	118	80	38	19	21	59	21	99			4	7
EI 120	120	80	40	20	20	60	20	100	1.5 / 2 / 3 / 3.6 / 4		4	7
EI 120	120	80	40	20	20	60	20	100	chamfer		4	7
EI 123	123	83.5	35	22	22	61.5	22	101			4	7
EI 126	126	84	42	21	21	63	21	105			4	7
EI 132	132	88	44	22	22	66	22	110			4	7
EI 133.2	133.2	88.8	44.4	22.2	22.2	66.6	22.2	111	2.8 / 3 / 3.3 / 4 / 6 / 6.73 / 14		4	7
EI 144	144	98	40	26	26	72	26	118			4	7
EI 150	150	100	50	25	25	75	25	125			4	8
EI 150	150	100	50	25	25	75	25	125	1.5		4	8
EI 152.4	152.4	101.6	50.8	25.4	25.4	76.2	25.4	127			4	8
EI 153	153	127	43	25	30	99	30	135			4	6.8
EI 154	154	104	50	25	27	77	27	129			4	8
EI 160	160	102.5	43	25	33.5	107.5	33.5	135			4	7
EI 162	162	108	54	27	27	81	27	135	8.2		4	8.5
EI 162	162	189	54	27	27	162	27	135			4	6.4
EI 168	168	112	56	28	28	84	28	140			4	10
EI 171	171	114	57	28.5	28.5	85.5	28.5	142.5	9.1 / 9.2		4	9
EI 171	171	114	57	28.5	28.5	85.5	28.5	155.4			4	7
EI 174	174	116	58	29	29	87	29	145			4	10.5
EI 180	180	120	60	30	30	90	30	150			4	9
EI 180	180	210	60	30	30	180	30	150			4	7
EI 181.2	181.2	120.86	60.5	30.1	30.1	90.5	30.1	151			4	8
EI 181.2	181.2	120.8	60.4	30.2	30.2	90.6	30.2	151			4	8
EI 182	182	123.9	56	30	33	100	33	149			4	8
EI 182	182	124	56	30	33	91	33	149			4	8
EI 192	192	128	64	32	32	96	32	160			4	9
EI 192	192	128	64	32	32	96	32	160			4	11
EI 195	195	195	65	32.5	32.5	162.5	32.5	162.5			4	11
EI 200	200	150	60	30	40	120	40				4	10
EI 200	200	150	60	30	40	120	30				4	10
EI 210	210	140	70	35	35	105	35	175			4	9
EI 218	218	164	70	35	39	129	35	183			4	11
EI 222	222	149	70	38	38	111	38	184			4	10
EI 222	222	148	74	37	37	111	37	185			4	10
EI 228	228	152	76	38	38	114	38	190			4	10.3
EI 228.6	228.6	152.4	76.2	38.1	38.1	114.3	38.1	209.6	8.1 / 8.2		6	9.6
EI 240	240	160	80	40	40	120	40	200			4	12
EI 270	270	180	90	45	45	135	35	235			4	10
EI 288	288	196	80	52	52	144	52	236			4	12
EI 300	300	200	100	50	50	150	50	250			4	12
EI 360	360	240	120	60	60	180	60	300			4	12

Magnetic flux path description

The magnetic flux path of the EI transformer core follows a closed loop design. When an alternating current is passed through the coil, an alternating magnetic field is generated. The magnetic flux enters from the middle column of the E-shaped laminates, is conducted through the two side columns to the I-shaped laminates, and then returns to the middle column from the I-shaped laminates, forming a complete closed magnetic circuit. This path design can minimize magnetic flux leakage to the greatest extent, enhance magnetic permeability and ensure the efficiency of electrical energy conversion. Meanwhile, the insulating coating of the laminated plates can block the path of eddy currents, prevent excessive heat generation due to eddy currents, stop the core from overheating and being damaged, and extend the service life of the transformer.

Why EI cores are widely used in transformers ?

The reason why EI cores have become the mainstream choice in the transformer field is mainly due to four advantages:

It features a simple structure, mature manufacturing process, and can achieve automated batch production, significantly reducing manufacturing costs
It has strong adaptability. It can not only meet the requirements of standard specification transformers, but also be customized in size and thickness according to customer needs, adapting to the usage requirements of different power and scenarios.
Stable performance, made of high-quality silicon steel material, featuring low iron loss and high magnetic permeability, can effectively enhance the energy efficiency of transformers and meet the national requirements for improving the energy efficiency of power equipment

4.Easy maintenance with a simple disassembly structure. Low-cost subsequent maintenance and replacement, widely compatible with power distribution equipment across multiple sectors including power, industrial, and building applications.

Product classification and specifications

Series Name	Type	Main Applications	Characteristics
EI28 Series	Small EI Core	Small power adapters, micro-transformers	Compact size, low power consumption, suitable for low-power electronic devices
EI35 Series	General-purpose small core	Household small transformers, LED drive power supplies	Suitable for a moderate power range, excellent cost-effectiveness, strong mass production stability
EI41 Series	Medium-small core	Transformers for industrial control equipment and small power distribution equipment	Combines advantages in size and performance
EI57 Series	Medium core	Industrial control transformers, voltage stabilizers	Wide power coverage, strong anti-interference ability, stable magnetic properties
EI66 Series	Medium-large core	Power transformers, distribution transformers	High power carrying capacity, outstanding low iron loss performance
Custom Size Series	Non-standard EI core	Various devices suitable for special power and installation scenarios	Customized according to customer’s technical drawings and size parameters, supports full-process services from design to mass production

Classify by material grade

Material Type	Sub – Grade	Characteristics	Suitable Scenarios	Advantages
CRGO Oriented Silicon Steel	M3	High magnetic permeability and extremely low iron loss; has the lowest iron loss among CRGO oriented silicon steels	High – energy – efficiency scenarios for medium – and high – end power transformers	Meets high – energy – efficiency requirements and reduces energy loss
CRGO Oriented Silicon Steel	M4	High magnetic permeability and extremely low iron loss; offers good cost – effectiveness	Conventional industrial transformers	Reduces the no – load loss of transformers, meets energy – saving requirements, and has relatively reasonable costs
CRGO Oriented Silicon Steel	M5	High magnetic permeability and extremely low iron loss; offers good cost – effectiveness	Civil transformers	Reduces the no – load loss of transformers, meets energy – saving requirements, and has relatively reasonable costs
Non – Oriented Silicon Steel	–	Good machinability, moderate cost, and stable magnetic properties	Medium – and low – power transformers, small power distribution equipment, household appliances, and small industrial equipment	Meets the usage requirements in conventional scenarios and balances performance and cost
Low – Loss Silicon Steel Material	–	Higher standards, with no – load loss reduced by more than 60%	Transformer scenarios with energy – saving requirements	Significantly reduces no – load loss and improves energy – saving effects

Application scenario presentation

Industrial control transformer core
Small distribution transformer core
UPS uninterruptible power supply transformer
Switching power supply, power equipment transformer
Electrical control cabinet, automation equipment dedicated transformer

Production manufacturing capacity

Precision shearing and punching equipment: High-speed precision stamping line, with high dimensional accuracy and strong consistency
Automatic laminating equipment: Automated stacking, tight lamination, high efficiency and low loss
Quality inspection process: Iron loss testing, thickness testing, full inspection of flatness
Batch consistency control: The dimensions, materials and performance of the same batch are highly unified
Monthly production capacity description: Monthly production of EI laminated sheets exceeds one million pieces, and the number of finished iron cores exceeds tens of thousands, meeting the requirements of large-scale orders
Factory image display: Standardized workshop, dust-free testing area, real scene display of finished product warehouse