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Learn About Factors Affecting Toroidal Transformer Size & Cost

Supply Frequency:

The size and cost of a transformer increases when the Rated Frequency is the lowest frequency which will allow Max. Supply Volts without saturating the core.

Primary Configuration:

The size and cost of a transformer increases when you move down the listing of primary windings. A 5-LEAD primary requires more copper than 2+2 primary. A LADDER is the least economical primary.

US/Foreign Version:

A transformer for 60Hz with a single primary will always cost less and be smaller than a multiprimary 50Hz transformer. The savings are often large enough to make it economical to use two different versions of a transformer, one for the domestic market, and another for foreign markets, in spite of the smaller lot sizes of each transformer.

Rectifier Circuit:

DHW circuits and CTB circuits with unsymmetric load require a larger and costlier transformer than regular FWB circuits. Circuits with L-filter (FWBL and DHWL) require a smaller transformer than circuits with capacitor filter (FWB and DWH), but the inductor adds size and cost to the system.

UP/UPnom:

The size and cost of a transformer increases rapidly when UP/ UPnom is decreased for constant output.

Duty Cycle:

The size and cost of a transformer goes down with decreasing DUTY CYCLE, but the LOAD REGULATION increases.

Load Regulation:

If you specify more than one set of data for the same secondary, you do in reality specify LOAD REGULATION in addition to rated data. The AC LOAD REGULATION for a transformer varies with its Rated Power when it is designed for normal temperature rise, from about 20% for a very small transformer to about 2% for a large transformer.

If you specify data corresponding to a smaller LOAD REGULATION than normal for the transformer’s power rating, the size and cost of the transformer will increase.

If you specify data corresponding to a larger LOAD REGULATION than normal for the transformer’s power rating, your specification cannot be met without overheating of the transformer, unless you provide forced cooling and/or external resistors in series with the transformer.