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Toroids, toroidal cores

Toroidal cores (toroids) for mains transformers; low noise, low magnetising current, fast assembly, low cost. Cores are wound from cold rolled grain oriented (CRGO) silicon steel strips. Isomatic manufactures toroids (toroidal cores) for transformers produced in its own factory. Any core can be supplied to other manufacturers or users.

For enquiries for toroidal cores: E-mail by clicking including delivery location so we can use an appropriate currency and estimate transport costs. Please note that we can only supply business quantities, not one-offs.

Toroidal core A series

The cores are wound by an automatic core winding machine from a continuous silicon steel strip and are annealed in a high vacuum furnace under protection atmosphere or in a continuous tunnel furnace. The impregnation is undertaken with vacuum impregnating equipment. The advanced manufacturing process makes full use of grain orientation of silicon steels, so that the core enjoys advantages such as compact volume, light, low magnetic leakage and hum, high efficiency, stable quality etc.

Toroidal cores

Toroidal core A series can be supplied:

1. Uncut, not impregnated
2. Uncut, edge bonded
3. Uncut, impregnated
4. Uncut, epoxy coated
5. Cut, impregnated.

Typical applications are power transformers, current transducers, instrument transformers, inductors, ballasts, AF transformers, magnetic amplifiers, voltage stabilisers and regulators, etc.

Size limitations are:
Maximum outer diameter is 600mm
Minimum inner diameter is 6mm
Minimum strip width is 5mm
Maximum strip width is 300mm.
Other sizes are available on request.

The A series toroidal core material list is shown in the following table.

Code
thickness
(mm)
Frequency
Material iron loss
(W/kg @ 1.7T/50Hz)
 23ZH90
 0.23
 50 Hz
 0.9
 23ZH100
 0.23
 50 Hz
 1.0
 27ZH100
 0.27
 50 Hz
 1.0
 30ZH120
 0.30
 50 Hz
 1.2
 30Z130
 0.30
 50 Hz
 1.3
 M3
 0.27
 50 Hz
1.3
 M4
 0.27/0.30
 50 Hz
1.4
 M5
 0.30
 50 Hz
1.5
 M6
 0.30
 50 Hz
1.65
 0.10mm
 0.10
 400 Hz
6,at 400Hz

Toroidal core B series

These cores are wound from short silicon steel strips, 1-2 metres long, equivalent to M1-M5 quality. Each core is annealed in a high vacuum furnace under protection atmosphere or in a continuous tunnel furnace. They have all of the general advantages of normal toroidal cores, but the price is only 50-60% of a normal toroidal core price. B series are widely used to replace EI transformers with rated power over 30VA and to replace existing toroidal transformers with low requirements. Due to the extremely low price of these cores, toroidal transformers with rated power over 100VA are even cheaper than EI transformers, although the performance is superior !

Toroidal cores

Compared with an EI core, B series toroidal cores have the advantages of compact volume, low temperature rise, low weight, strong over-load capacity, free design and convenient mounting etc. They have all of the basic features of A series toroidal cores but, as there are joints in the core, they are inferior to the A series in terms of magnetic leakage and stability.

B series toroidal cores can replace conventional EI transformers, especially those with rated power over 100VA where the toroidal cost is lower. For transformers with rated power over 500VA, the cost of a B series toroidal transformer is only 50% of the cost of the equivalent EI transformer. However, its performance is superior, e.g. lighter, lower temperature rise, free design, easy mounting etc.

B series toroidal cores can replace existing toroidal transformers that do not have strict requirements on magnetic leakage. It is recommended that A series toroidal cores be used in transformers that require very low magnetic leakage or in small transformers with rated power below 20VA.

B series cores are widely used in applications that require compact volume and low temperature rise such as lighting, household electric equipment, portable electric equipment, electronic devices etc.

Design key points:
Due to B series characteristics and low prices, some adjustments should be made in designs:
1. As there are joints in the core, the stacking factor reduces to 0.90-0.91.
The cross-section area can be enlarged reasonably:
S=K x root P
K= 0.60-0.75
S: core cross-section area (square cm)
P: rated VA of transformer
K: cross-section factor

This design can minimize the cost of the transformer.

In order to avoid saturation and ensure reliability, the design protection margin should be increased by 5-10%, compared with that of an A series toroidal core.

B series toroidal cores can be supplied:
1. Uncut, not impregnated
2. Uncut, impregnated
3. Uncut, epoxy coated
4. Cut, impregnated.

Typical applications are power transformers, current transducers, instrument transformers, inductors, ballasts, AF transformers, magnetic amplifiers, voltage stabilisers and regulators, etc.

Size limitations are:
Maximum outer diameter is 600mm
Minimum inner diameter is 15mm
Minimum strip width is 8mm
Maximum strip width is 200mm.
Other sizes are available on request.

The B series toroidal core material list is shown in the following table.

Material Code
Material thickness (mm)
Frequency
Iron loss
(W/kg, 1.7T/50Hz, actual value measured)
 B1
 0.18-0.20
 50 Hz
 0.75-0.80
 B2
 0.20-0.23
 50 Hz
 0.80-0.90
 B3
 0.27-0.30
 50 Hz
 0.90-1.00
 B4
 0.30
 50 Hz
 1.00-1.10

Toroidal mini core

These cores are wound by an automatic core winding machine from a thin silicon steel strip and are annealed under protection atmosphere in a continuous tunnel furnace. The advanced manufacturing process ensures that the cores have precise dimensions, excellent stability and high permeability.

Toroidal cores

Typical applications are power transformers, current transducers, instrument transformers, ballasts, etc.

Size limitations are:
Maximum outer diameter is 60mm
Minimum inner diameter is 5mm
Minimum strip width is 3mm
Maximum strip width is 20mm.

The toroidal mini core material list is shown in the following table.

Material Code
Material thickness (mm)
Frequency
Material iron loss
(W/kg @ 1.7T/50Hz)
 23ZH90
 0.23
 50 Hz
 0.9
 23ZH100
 0.23
 50 Hz
 1.0
 27ZH100
 0.27
 50 Hz
 1.0
 0.10mm
 0.10
 400 Hz
6, at 400Hz



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