Certification

VDE approval pending.

Uniform standards

The standard EN 61558 distinguishes between transformers for short-time loading and those for permanent loading.

Failsafe with PTC

Siemens transformers for permanent loading are protected against short circuit or moderate overload by a PTC resistor. If a disconnection occurs, the transformer must be switched off for approx. 30 min to cool down the PTC resistor.

Two secondary voltages

The 12 V outputs must be switched in parallel or in series. In parallel connection, they can be used, e.g. for 12 V or 16 VA, in series connection; for 24 V or 16 VA. In these types of circuits, the PTC resistor ensures full protection of the transformer.

Hum-free

The transformers with 24 and 40 VA cores are molded, which means that they are virtually hum-free and highly suitable for installation in sound-sensitive distribution boards.

Voltage stability

The standard EN 61558-2-2 specifies that the difference between the non-loaded output voltage and the output voltage loaded with the rated load for transformers for permanent loading must not exceed 10 %. This requirement places the highest demands on the design of this type of transformer. It can only be met by using high-quality core materials and a core design with an extraordinarily high efficiency, such as type EI according to DIN 41302.

Typical applications

AC voltage/current supply for 8, 12 or 24 V AC, up to 40 VA as safety extra-low voltage with a mounting depth of 55 mm for the supply of calibration circuits, switching relays or Insta contactors in continuous duty.