GB/T 19212.1-2023Safety of transformers, reactors, power supply units and combinations thereof - Part 1: General requirements and tests (English PDF)

1 Scope

The document lays down the safety requirements, electrical, thermal and mechanical among them, for transformers, reactors, power supply units and combinations of them.

It applies to the following independent or associated, stationary or portable dry-type transformers, power supply units, switch mode power supply units included, and reactors, and to their safety-related combinations; their windings may be encapsulated or non-encapsulated, and they do not form part of a distribution network. A first note distinguishes the three families: a transformer does not change the frequency, although a transformer such as a constant-voltage transformer may have an internal resonant frequency not exceeding 30 kHz; in a power supply unit the internal working frequency and waveform differ from those of the supply and the internal working frequency does not exceed 500 Hz; in a switch mode power supply unit the internal working frequency and waveform differ from those of the supply and the internal working frequency exceeds 500 Hz but does not exceed 100 MHz. The other parts of GB/T 19212 can be found from the introduction of this document.

Item a) covers stationary or portable, single-phase or polyphase, air-cooled, either self-cooled or fan-cooled, independent or associated isolating transformers and safety isolating transformers whose rated supply voltage does not exceed 1 000 V a.c. and whose rated supply frequency does not exceed 500 Hz; unless another part of GB/T 19212 states otherwise, an isolating transformer has a rated output not exceeding 25 kV.A single-phase and 40 kV.A polyphase, and a no-load output voltage and rated output voltage above 50 V a.c. and not exceeding 500 V a.c., or not exceeding 1 000 V a.c. where the national wiring rules or a particular application so provide; a safety isolating transformer has a rated output not exceeding 10 kV.A single-phase and 16 kV.A polyphase, and a no-load output voltage and rated output voltage not exceeding 50 V a.c. between conductors or between any conductor and protective earth. A note adds that isolating or safety isolating transformers are used where the installation rules or the specification of an appliance, motor-driven toys, electric bells, portable power tools and handheld luminaires among them, call for double or reinforced insulation between circuits.

Item b) covers stationary or portable, single-phase or polyphase, air-cooled, independent or associated separating transformers, auto transformers, variable transformers and small reactors with the same limits of 1 000 V a.c. rated supply voltage and 500 Hz rated supply frequency; unless another part of GB/T 19212 states otherwise, for a transformer that is both independent and associated the no-load output voltage and rated output voltage do not exceed 15 kV a.c., and for an independent transformer the rated output voltage is not less than 50 V a.c., while the rated output does not exceed 1 kV.A for a single-phase transformer, 2 kvar for a single-phase reactor, 5 kV.A for a polyphase transformer and 10 kvar for a polyphase reactor. A note adds that separating transformers are used where the installation rules or the appliance specification do not require double or reinforced insulation between circuits, and a further note explains that transformers of type b) are usually intended to be used with an appliance so as to supply a voltage other than the supply voltage for the functional requirements of that appliance, that their protection against electric shock may be provided by other parts of the associated appliance, its enclosure for instance, and that parts of the output circuit may be connected to the input circuit or to protective earth.

Item c) covers stationary or portable, single-phase or polyphase, air-cooled, independent or associated power supply units and switch mode power supply units incorporating one or more transformers of type a) or type b), whose rated supply voltage does not exceed 1 000 V a.c., whose rated supply frequency does not exceed 500 Hz, and whose internal working frequency does not exceed 500 Hz for a power supply unit and 100 MHz for a switch mode power supply unit. Unless another part of GB/T 19212 states otherwise, a power supply unit or switch mode power supply unit incorporating an isolating transformer has a rated output not exceeding 1 kV.A single-phase or polyphase, and a no-load output voltage and rated output voltage above 50 V a.c. or 120 V ripple-free d.c. and not exceeding 500 V a.c. or 708 V ripple-free d.c., or not exceeding 1 000 V a.c. or 1 415 V ripple-free d.c. where the national wiring rules or a particular application so provide; one incorporating a safety isolating transformer has a rated output not exceeding 1 kV.A and a no-load output voltage and rated output voltage not exceeding 50 V a.c. or 120 V ripple-free d.c. between conductors or between any conductor and protective earth; one incorporating a separating transformer, an auto transformer or a variable transformer has a rated output not exceeding 1 kV.A, and, for a transformer that is both independent and associated, a no-load output voltage and rated output voltage not exceeding 15 kV a.c., the rated output voltage of an independent transformer being not less than 50 V a.c.

The document also applies to transformers, power supply units, switch mode power supply units and reactors incorporating electronic circuits, and to transformers without a limit on the rated output that comply with an agreement between purchaser and manufacturer.

It does not apply to the external circuits and their components intended to be connected to the input and output terminals or to the output socket-outlets of transformers, power supply units, switch mode power supply units and reactors.

Attention is drawn to the following situations: transformers intended for use on vehicles, ships or aircraft may need additional requirements, taken from other applicable standards or national regulations; protective measures against the effect of mould, insects, termites, solar radiation and icing on the enclosure and on the components inside it; the different conditions of transport, storage and operation of transformers; and transformers intended for special environments, tropical environments for instance, for which additional requirements from other applicable standards and national regulations may be adopted.

As transformer technology develops the upper frequency limit may need to be raised, and the document may then be used as a guide.

2 Normative references

The clause lists the documents referred to normatively. The end of that list, on the pages examined, carries IEC 60851-3:2009, IEC 60851-5:2008, IEC 60851-6:2012, IEC 60898 (all parts), with a note referring to GB/T 10963 (all parts), IEC 60906-1, IEC 60990:2016, IEC 61800-5-1, with a note referring to GB/T 12668.501-2013, DIN 43670:1975, DIN 43670-2:1985 and DIN 43671:1975. The earlier part of the list falls on pages that were not among those examined.

3 Terms and definitions

The terms and definitions that follow apply to this document. A note states that further definitions for transformers intended for a particular application are given in the other parts of GB/T 19212.

Where the word transformer is used, it covers, in the applicable cases, transformers, reactors and power supplies.

Unless otherwise specified, the words voltage and current mean the root mean square value for alternating voltage and current, and the corresponding arithmetic mean value for direct voltage and current.

Ripple-free is conventionally taken to mean that the root mean square value of the ripple voltage is not greater than 10 % of the direct component.

3.1 Transformers

3.1.1 Transformer: a static device with two or more windings which, for the purpose of transmitting electric energy, converts by electromagnetic induction the alternating voltage and current of one system into the voltage and current of another system at the same frequency, the values of those voltages and currents usually being different. A note adds that the word frequency also implies that the waveform is kept the same. [SOURCE: GB/T 2900.95-2015, 3.1.1, modified]