Technical Description
www.frei.de General Control transformers are mainly found within the context of control and machine building. The fact that mains systems differ around the world (and sometimes lack a neutral conductor) means that it often
proves impossible to provide the control voltage directly. Instead, this task is handled by control transformers.The primary and secondary windings must be electrically isolated from each other. That is why a controltransformer cannot be designed as an autotransformer winding. From the point of view of dimensioning,
the simultaneous inrush currents of the control devices are key (surge load). The secondary voltage when
the surge load occurs must not drop by more than 5% of the rated output voltage.
The FST, SETB/SETLB and FTEU/SETN series transformers feature primary-side taps of ±5% of therated input voltage, which compensate for voltage deviations in the supply network.We also offer another range of control transformers: our universal control transformers. As their namesuggests the devices that make up the USTN/USTB, USTLB series feature universal windings on the primary side. These can be connected up for mains voltages of 200 – 550 V. Our single-phase controltransformer range includes all our standardised types for the 63 – 12.0 kVA performance range and a frequency of 50/60 Hz. The following series are availableFST This type of single-phase control transformer is suitable for the 63 – 250 VA performancerange. The special coil body with integrated
professional terminal chambers and fixing bracket is made
completely of plastic. This was developed in-house at Frei, where it continues to be produc-
ed. The sophisticated design means that the coil wires are fed directly to the terminals alongplastic channels, thus ensuring protection against direct contact. In addition, blade-type ter-minals measuring 2.8 x 0.8 mm are attached to thescrew contacts, meeting the requirementsof DIN 46 244. The captive screws featuring self-lifting thrust washers that are attached to
the contacts have a combined cross recession/longitudinal slot. A replaceable
thermal cut off
can be installed in the coil body on request. SETB These three-phase control transformers are suitable for the 320 – 2500 V performance range USTB (USTN/USTB 80 – 2000 VA). The coil wires are routed to compact modular transformer ter- USTN minals, which can also be equipped with slotted 6,3/2.8 mm push-on blades.
Subject to change without notice | Version of 0908 – 11 – Gebrüder Frei GmbH & Co. 72461 Albstadt 1.4