Control transformers

Our control transformers

A control transformer supplies the auxiliary circuits of a control panel or a machine: contactor and relay coils, indicator lamps, solenoid valves, automation equipment. Our standard models range from 63 VA to 20 kVA, with a price shown for every power rating:

• 230 V to 24 V control transformer: the most common control voltage, for coils and automation equipment running on 24 V AC.
• 400 V to 24 V control transformer: the primary connects between two phases, for a panel supplied in three-phase without a neutral.
• 230 V to 48 V transformer and 230 V to 12 V transformer: for circuits and equipment running on 48 V or 12 V AC.
• 220 V to 110 V transformer: for the 110–115 V control circuits of North American machines.
• 230 V / 230 V isolation transformer: a 230 V control circuit separated from the mains.
• 230 V to 96 V transformer: for circuits supplied at 96 V AC.
• An equivalent of the ABT7PDU100B, with a 0-230-400 V primary and a 2 × 24 V secondary, to replace an existing control panel transformer.

To supply machines or a whole panel in three-phase, see our three-phase transformers, from 1 to 100 kVA.

What is a control transformer?

A control transformer, or control circuit transformer, provides the voltage for the control circuits, separate from that of the power circuits. Its primary is connected to the panel supply, at 230 V or 400 V; its secondary, a separate winding, delivers the voltage used by the control devices. The control circuit is thus kept independent of the power supply, and at 24 V it works at extra-low voltage.

A control transformer delivers alternating current (AC). If the PLC or device needs 24 V DC, you need a DC power supply, not a transformer.

How to choose a control circuit transformer

Secondary voltage

This is the voltage of the contactor and relay coils, indicator lamps and solenoid valves on the circuit: 24 V AC in most control panels, 48, 110 or 230 V depending on the equipment. It is marked on the coil or on the rating plate of the device.

Primary voltage

230 V between phase and neutral, or 400 V between two phases when the panel is supplied in three-phase without a neutral. Models with a dual-voltage primary accept either.

Power rating

Add up the consumption of everything the transformer supplies, multiply by 1.25 and choose the next rating up. A contactor coil draws more when it pulls in than when it is holding: on a circuit that switches several contactors at once, allow a margin.

Mounting and protection

Inside a panel, the open-frame transformer (IP00) is the usual choice; IP23 and IP54 versions are available for mounting outside a panel. Connections are made on screw terminals up to 55 A and on lugs above that. On the primary side, fit an aM fuse or a type D circuit breaker, both of which withstand the inrush current at switch-on; on the secondary side, protection rated for the output current. The fuse and breaker sizes for each power rating are listed on the product pages.

Standards and extra-low voltage

Our single-phase transformers come under EN 61558: Part 2-4 for isolating transformers, which separate circuits, and Part 2-6 for safety isolating transformers at extra-low voltage, such as our 12 V and 24 V models. See also our safety transformers and our isolation transformers. Thermal protection can be added on request.

Wound and tested in Gailhan, with a 2-year warranty

ABL Transfo has been manufacturing transformers since 1993 in its workshop in Gailhan, in the Gard (southern France). Our single-phase control transformers are wound, wired and 100 % tested there before they leave; they carry a 2-year warranty, and standard models are dispatched from France within 24 to 48 hours.

Panel builders, system integrators and industrial buyers: a trade account shows prices excluding VAT, with an immediate 5 % discount, and white-label supply is possible.

Several primaries and secondaries: a bespoke control panel transformer

A control circuit often needs more than one voltage. For a bespoke control transformer, configure the custom single-phase transformer online, from 63 VA to 20 kVA: several primaries and several secondaries, tappings, connection type and IP rating, with an instant price. For a production run or to replace an existing reference, request a quote: we reply within 48 hours.