Special transformers - industrial dry transformers designed specifically for electric networks and energy consumers, which are characterized by special conditions - for example, increased load or a special mode of operation. Such transformers are designed primarily for industrial enterprises, as they protect industrial electrical appliances and direct current. Transformers of a special type can reduce the ripple of the electric current, adjust the frequency of the current and change the number of phases.
Types of Transformers
A special group of transformers include:
- Matching.
- Separating.
- High frequency.
- Welding transformers.
- Autotransformers and many others, created for a narrow range of tasks.
Isolation transformers
Special isolation transformers are widely used in areas requiring additional safety measures when working with power tools. They are used in medical equipment where direct contact with the human body is required.
In order to ensure electrical safety, two windings of identical design are placed on the common magnetic circuit, which allows you to get the same voltage at the output as at the input.
In the case of a breakdown in the insulation of the wire, a potential is formed that can affect a person and cause electrical injury. The optimal use of power supply of electrical equipment is possible with galvanic separation of the circuit, while it simultaneously eliminates the likelihood of electrical injury in the event of a breakdown of the secondary insulation circuit to the housing.
High frequency transformers
Special-purpose transformers that differ from conventional equipment in the material of the magnetic circuit, which allows high-frequency signals to be transmitted without distortion.
Matching Transformers
Designed for matching resistances in an electronic circuit. Matching special transformers are widely used in audio frequency amplifiers and antenna devices.
Welding transformers
Welding-type transformers are used in industrial enterprises, while at the same time enjoying considerable popularity with radio amateurs.
The primary winding is formed with a large number of turns, due to which electrical energy is processed with a voltage at the input of 220 or 380 volts. The number of turns in the secondary winding is less, but the current flowing through it is high and can reach thousands of amperes.
Transformers for electric arc welding
A step-down special-purpose single-phase transformer capable of converting 220 or 380 V mains voltage to 60-70 V. necessary for burning an electric arc. Since the resistance of the electric arc is minimal, the welding inverter operates under conditions as close as possible to a short circuit. In this regard, a choke with a movable core is connected in series to the secondary circuit of the transformer to limit the current value. The magnitude of the welding current and inductance of the inductor can be adjusted by changing the magnitude of the air gap in the magnetic circuit.
Moving core transformer
A special transformer, the core of which consists of two parts - movable and stationary, moreover, movable with a secondary winding is located inside a stationary with a primary winding. The primary winding of such a transformer is made of two opposed coils connected. Connecting such a transformer to the circuit simultaneously with a boost transformer allows you to adjust the secondary direction.
Transformers for rectifiers
The secondary circuit of such transformers includes valves, thanks to which the alternating current is converted into pulsating. The dimensions and mass of special transformers for rectifier installations are much larger than similar devices with identical output power, but there is a sinusoidal current in their windings. This is explained by the fact that in transformers connected to rectifier circuits, the useful power depends on the component of the secondary current, and the heating of the windings depends on the total primary and secondary currents with higher harmonics.
The main or primary winding of three-phase rectifier transformers is connected to a "triangle" or "star", and the secondary - valve - is connected so that the single and three-phase current is converted to multiphase with the number of phases required for a particular conversion circuit. The larger the number of phases, the lower the ripple of the rectified voltage. Single-phase rectifiers installed on electric locomotives operate on two-phase circuits, on traction substations - six-phase and twelve-phase.
Adjustable transformer
A transformer, the mode of operation of which depends on a change in the magnetization of the shunts and has three combined windings, one of which is supplied with direct current. The voltage at the transformer output changes with a change in the DC bias circuit.
Pulse transformers
Designed for the transformation of voltage pulses while maintaining their shape without changes. The windings of pulsed transformers of a special type are performed in small layers in order to reduce distortions caused by hysteresis, stray capacitances, eddy currents and dissipation inductances. Cores are made of permalloy or electrical cold-rolled steel.
Peak transformers
Transformers designed to convert a sinusoidal voltage to a peak voltage, required to open thyratrons, controlled gates - thyristors and similar equipment. Peak transformers are double-winding transformers with linear active or inductive resistance in the primary circuit and a highly saturated magnetic circuit. Due to this structure, the EMF is induced on the secondary winding in the form of short-term pulses, while the moments of the current passing through zero correspond to the pulse maxima.
Chokes
Electromagnetic static equipment used in electrical circuits due to its inductance. The reactor, or inductor, is a coil with a ferromagnetic core. Depending on the purpose and mode of operation, transformers are divided into several types:
- Smoothing. Designed to smooth the ripples of the rectified current and used in the chains of traction motors of electric trains and electric locomotives.
- Transitional. Switch the transformer leads.
- Current-limiting. Reduce short circuit currents.
- Dividing. Evenly distribute the load currents between valves connected in parallel.
- Interference Suppression Eliminate interference arising from the operation of apparatus, equipment and electrical machines.
- Inductive shunts. Distribute the current between the windings of the operating traction motors and resistors connected in parallel to them during transients.
The types of special transformers listed above are among the most popular and frequently encountered.