Magnetic Voltage Regulator | Solid‑State Contactless Stepless Power Controller

Product Overview

A magnetic voltage regulator does one job very specifically: it holds a stepless, continuously adjustable voltage on a heating, melting or plating load, without the steps that tap-based regulation produces. This series covers 10 kV and 35 kV systems in single-phase, three-phase and Scott-connection builds, with capacity and the output voltage range set for the application rather than taken from a fixed catalogue.

Project engineering teams and plant power departments specify these units for melting and heat-treatment furnaces, glass and crystal-growing equipment, electroplating lines and variable-speed drive supplies. In a melting installation the regulator handles the continuous adjustment while the furnace transformer behind it continues to match the furnace's own voltage and current, so the two pieces of equipment divide the work instead of duplicating it.

DC processes work the same way: for electroplating, electrolysis or hydrogen production, the regulator feeds the rectifier transformer that produces the DC supply, so the DC current follows the setpoint instead of stepping between positions.

The result is a regulator for plants that are sensitive to voltage steps but want the electrical room to stay simple -- whether the unit goes into a new installation or into a line that is being upgraded. These units are built in our own factory, and the engineering team that designs them also prepares the drawings and test records issued for your project.

Regulation Principle & DC Control

1. The regulator's AC winding carries the load current, and a second control winding on the same magnetic circuit takes only a low-power DC current from your control system.
2. Increasing the DC control current drives the core further into magnetic saturation and lowers the AC impedance of the regulator; reducing the current raises the impedance again.
3. Because the DC current is continuously adjustable, the output voltage moves with it -- smoothly from zero up to the rated value, with no steps and no interruption in the load current.
4. Manual control keeps the setting at the unit itself; automatic control closes the loop with an external signal from a temperature controller, PLC or process computer.
5. Standard controller outputs can drive the control input, with 4-20 mA and 0-10 V signals as the usual examples, and the DC control current range is defined per model so it matches the equipment you already run.
6. If the regulator is added on the supply side of an existing electric furnace transformer, the tap range and duty cycle of that transformer belong in the design brief, because together they set the output range the regulator has to cover.
7. Regulation accuracy, response time and the shape of the regulation curve follow from the control winding design combined with your own control loop. Send us the accuracy, response and waveform requirements you have to hold, and our engineers confirm the design point against them before the unit is built.

Specifications

High Reliability & Robust Design

• Regulation happens in the magnetic circuit, so there are no arc-prone contacts to pit or weld and no mechanical actuator to drive: the usual source of wear and of unplanned intervention is simply not present.
• The core and winding assembly sits inside an oil-filled steel tank, a construction that absorbs the vibration and the temperature swings of a melting or heat-treatment shop.
• The unit is made for heavy-duty, cyclic operation, where repeated starts, load swings and frequent adjustment are normal duty rather than an exception.
• Because nothing in the regulating path moves or makes and breaks current, performance does not drift as the unit ages, so the same control setting gives the same result after long service.
• Switching transients are avoided. Regulation is continuous rather than make-and-break, which is easier on the load, on the furnace elements and on the supply network around the unit.
• Service work is inspection-led rather than parts-led, which keeps the spare-parts list short: no contact sets, no drive motor and no tap-changer mechanism to hold in store.

Loads & Applications

The regulator earns its place on any load whose behaviour follows the applied voltage. Resistance furnaces are the clearest case: salt bath furnaces, vacuum furnaces, electroslag remelting furnaces, glass melting furnaces, crystal growers and the general run of resistance-heated furnaces all hold a steadier temperature when the supply voltage can be moved in small continuous increments instead of tap steps. In a melting line the regulator usually sits on the supply side, and the electric furnace transformer behind it keeps matching the furnace's own voltage and current, so the coarse duty stays with the transformer and the fine, continuous adjustment sits with the regulator.

DC processes are served the same way. Industrial heating, heat treatment, electroplating and speed regulation all appear in the application list for this series, and where the process itself runs on DC -- plating, electrolysis, hydrogen production -- the controlled AC feeds the rectifier transformer that produces the DC output, which keeps the DC current steady rather than stepping with the taps.

Load behaviour matters as much as load size. A purely resistive furnace follows the applied voltage almost directly, while a load fed through a transformer or a rectifier has its own impedance and its own demands, so the output range is built around the real load rather than around a nominal figure. Duty cycle matters too: a furnace that runs continuously for weeks and one that cycles several times a day put different demands on the regulating element, and both should be described when the design is discussed.

Phase Configuration Selection

1. Start with the supply. A three-phase supply leads to the three-phase (S) or Scott-connection (T) build; a single-phase supply leads to the single-phase (D) build.
2. Then look at the load. One balanced three-phase load suits the S build, which regulates the three phases together.
3. A single-phase load can be fed from a D build when the supply is single-phase, or from a T build when the incoming supply is three-phase.
4. Choose the Scott-connection when a three-phase supply has to feed two single-phase outputs that must be controlled independently -- two separate heating branches on the same furnace, for example, each holding its own temperature.
5. Confirm the phase letter in the model code before the order is released, and check it again on the nameplate, so the phase type is never in question on site.
6. Set the output range (the regulation multiple) around the load rather than around the supply. It is the parameter that decides how far the voltage can be driven between zero and maximum, and it is the one most often worth a second look.
7. Tell us at the enquiry stage if two units will work on the same bus, or if one unit has to serve two load branches -- load sharing between units and the split between outputs are confirmed against your single-line diagram.

Insulation & Cooling Platform

• The 10 kV and 35 kV ratings on this series are built as oil-immersed units, with the core and windings immersed in insulating oil inside a steel tank.
• The insulation system follows standard oil-paper practice for equipment at these voltage levels, so oil handling and inspection routines are already familiar to most site teams.
• Cooling is ONAN, oil natural air natural: heat moves from the windings into the oil and out through the tank surface by natural circulation, with no fan or pump duty in the base configuration.
• Oil-immersed construction is what makes these units usable where the regulator has to sit outdoors, or in a workshop where dust, moisture and temperature swings are part of daily life.
• The same platform is chosen for the higher voltage classes and the larger capacities in the series, which is where it offers the most application flexibility.
• Where the transformer and reactor duties are better served by separate magnetic circuits, the F suffix in the model code marks that build.
• The same oil-immersed construction practice runs through our furnace transformer and power transformer ranges, so a site that already operates those units will recognise the tank, the oil and the inspection routine.

Ordering & Delivery

Supply Frequency & Voltage Range

• The magnetic circuit is designed around the frequency of the grid the unit serves. Tell us at enquiry whether the site runs at 50 Hz or 60 Hz, because the nominal figure sets the core section and the impedance of the regulating winding along with the voltage class.
• Give us the deviation as well as the nominal value. Frequency swing on a weak, islanded or generator-fed supply moves the operating point of the regulating winding, and the design margin is checked against the band your site actually sees rather than against a clean nominal figure.
• A unit built for one frequency does not simply repeat its regulation curve on the other. Core saturation and winding impedance both change with frequency, so the DC control current that gives a particular output at 50 Hz will not give the same output at 60 Hz.
• If one regulator has to run on both frequencies, say so when you enquire. The design is adapted for dual-frequency duty and the capacity rating and regulation range are restated for it, because this is a design decision rather than a setting that can be changed on site.
• Voltage class follows the system: this series covers 10 kV and 35 kV, with other levels on request, and the input voltage range and any tap arrangement are agreed with the feeding switchgear and the protection scheme.
• The output voltage range, known as the regulation multiple, is set per model around the load. It defines how far the voltage can be driven from minimum to maximum, so it is agreed with you rather than taken as a fixed figure for the series.
• Where the regulator sits ahead of a furnace transformer, the frequency, voltage class and output range of both units are checked together so the furnace receives the voltage its process needs.
• On a DC process the same frequency and voltage data goes to the rectifier transformer downstream, so the AC input that the DC side is designed around matches what the regulator actually delivers.

Regulation Accuracy & Output Quality

• Regulation accuracy is quoted against the curve of your unit rather than as one figure for the series. That curve is the relationship between DC control current and output voltage, and it follows from the winding design together with the control loop that feeds it.
• The regulation multiple sets how much adjustment room the curve covers. A wider output range leaves more room to move the process voltage; a narrower one concentrates the same control travel on a smaller band, which suits a process that only needs fine trimming.
• Response comes from the control circuit and the time constant of the magnetic circuit. There is no motor to travel and no tap to step through, so the delay a mechanical regulator shows at every position change does not exist here.
• Output drift between no load and full load follows from the impedance of the regulating winding. Tell us the tolerance your process can hold across the load range, and the drift is taken into account in the design and documented for the unit.
• Waveform distortion is most accurately quoted at the operating point rather than as a single number, because core saturation interacts with the load connected to the output. Where the load is sensitive, such as a DC process fed through a rectifier, state the distortion limit it accepts and the contribution at the design point is confirmed with you.
• Load adaptation has boundaries worth describing early. Resistance heating loads sit comfortably inside the envelope; a load with heavy inrush, a very low power factor or an unusual duty cycle should be described so capacity and regulation range are set around it.
• Where the regulator works ahead of an electric furnace transformer, the accuracy the furnace has to hold at its terminals decides what the regulator must hold at its own output, and the feedback sensor and controller are part of that chain.
• The no-load and load characteristic is measured at several DC control levels during routine testing and recorded for the unit, so your site team can see where the working band sits before commissioning.

Technical Support & Model Matching

Every project starts with our engineering team. Share your duty conditions, drawings or existing nameplate data, and we help confirm the right rating and configuration before production begins — selection assistance, model matching, and troubleshooting before and after delivery. Backed by more than fifty years in transformer manufacturing, our engineers travel to site for installation and commissioning guidance and stay reachable remotely once the unit is energised. Functions and parameters can be customised to your project, and our quality system holds ISO9001 with IEC, CSA and CTQC testing.

FAQ