What is a control transformer and what are its advantages

What is a control transformer and why is it used

Control transformers are mostly used in electronic circuits which require constant voltage and constant current with low power or volt-amp rating. Filtering devices such as capacitors are used to minimize the variations in output and the result would be more constant voltage or current. Control transformers are mostly used for industrial purposes, where electromagnetic devices such as relays and solenoids are used. Control transformer can minimize the inrush capability and output voltage regulation when electromagnetic devices are primarily energized. These transformers have high-quality insulation materials and this insulation will provide electrical protection for the turn to turn, layer to layer windings, primary to secondary windings and ground. Control transformers are vacuuming permeated with VT polyester resin and over-cured and this would seal the surface and removes the moisture.

How to select a control transformer

In order to select the control transformer properly, three characteristics of the load circuit must be determined in addition to the minimum voltage required to operate the circuit. These are steady-state VA, total inrush VA, and inrush load power factor. The sealed VA or total steady-state VA is the volt-amperes that the transformer must deliver to the load circuit for an extended period of time. The inrush VA or total inrush VA is the volt-amperes that the transformer must deliver upon when the control circuit is initially energized. Energizing the electromagnetic device takes 30-50 milliseconds and during this inrush period, the electromagnetic control device draw many times the normal current. The inrush load power factor is difficult to understand without a detailed vector analysis of all the load components. This analysis is not possible therefore power factor is assumed as 40 percent.

Industrial control transformers are selected by certain methods they are, selection of the transformers by determining the supply and load voltages, the supply voltage is the available voltage to the control transformer and the load voltage is the operating voltage of the devices that will be connected to the transformer output.

What is a control circuit

This type of circuit is a special circuit that is designed to control the working of a power circuit. Control circuits are supplied from an A.C source, control transformers can be used for supplying the control circuits. Such transformers have separate windings. Conductors of control circuits directly connected to the supply voltage and of circuits supplying control circuit transformers must be protected against overcurrent. Conductors of the control circuits supplied by a control circuit transformer or DC supply must be protected against overcurrent. Unearthed control circuits could operate in unexpected ways, mostly in the events of multiple earth faults.

What is a control circuit transformer

Control circuit transformers are used to energize the coils of electromagnetic devices such as motor starters and contractors by providing a reduced control voltage. These devices make up the majority of the loads supplied by the control circuit transformer. Control circuit transformer is also referred to as industrial control transformers, machine tools transformers, and control power transformers.

What are the advantages of using a control transformer

The advantage of using a control transformer is the ability to transfer a stable voltage and its ability to handle extreme current peaks. Control transformers can supply power which is safer and more efficient and they can be used for high voltage applications. These transformers are capable to handle inrush current excellently use of lower voltages in a control circuit provides the workers using stop and start buttons in a hazardous environment with safety.

What are the applications of control transformer

A control transformer is used in many industrial applications

  • It can be used in hospital, office buildings and in industrial plants
  • Schools and commercial building
  • Apartment and high rise buildings
  • Shopping centers
  • Motor drives and controls
  • Induction heating and melting
  • Aviation applications
  • Mining equipment and power supplies
  • Marine and medical applications
  • Heavy industries