Semi-Rotational DC Voltage Transformer
This is to introduce a novel semi-rotational DC voltage transformer (Patent number:- EG/P/2025/1182) designed for efficient and inexpensive conversion of DC voltages from high to low and vice versa. The transformer addresses the limitations of conventional methods that rely on complex electronic circuits, which are often limited in voltage capacity and introduce distortions. The design incorporates a rotating primary core to cut and rotate the DC magnetic field, effectively converting it into a rotating field within the transformer. The device integrates auxiliary components such as a superconducting fault current limiter (SFCL), rectifier, and surge arrester to enhance performance and protection. This innovative approach enables the use of high-voltage direct current (HVDC) in electricity transmission and distribution and facilitates the integration of renewable energy sources. The patent is still pending and can convert the local application into IPC.
[1] DC current or voltage can't be converted/transformed by conventional electrical transformers. This is because DC voltage has a constant/stationary magnetic field that can't be cut through the copper coils of the transformer, thus transferring the voltage to the other core of the transformer. Conventional AC electrical transformers only transform alternating voltage to alternating voltage, but with different values.
[2] Electronic circuits used to convert/transform DC voltage to DC voltage, such as chopper circuits, only operate at low voltages and can't convert/transform voltages with large differences, as they are governed/limited by a conversion factor called the duty cycle, which is the result of dividing the connection/switching-on time by the total time (switching-on time + disconnection time). The value of this factor ranges from zero to 1, which means that such electronic circuits can't be used at medium and high voltages needed by transmission, distribution and generation stations to convert voltages with different differences, such as converting 220 kV to 120 kV or converting 66 kV to 11 kV.
[3] Electronic circuits used to transform DC voltage to DC voltage, such as chopper circuits, are expensive and produce distortions in the electrical network voltage, which prevents their use at medium or high voltages, thus being an obstacle to transmission using high voltage direct current known as (HVDC).
[4] A large inrush current is generated when the transformer is switched on. This current can be up to 6 or 10 times the rated current, and sometimes up to 20 times the rated current. This can cause faulty operation of the protection devices, which can cause the transformer or the network to go out of service until the problem is resolved. Naturally, this current can cause problems for the transformer itself, such as insulation breakage, coils melting, and thermal and mechanical stress.
[1] The DC voltage transformer is similar in structure to the electrical AC transformers we are familiar with, except that its primary core is rotating, not stationary. This is done to cut and rotate the stationary DC magnetic field associated with the DC voltage, creating a rotating field inside the transformer. This rotating part resembles an electric motor; it drives a base with magnetic poles attached to it, which cut and rotate the stationary DC magnetic field. It can move without electricity, as fan blades are installed in the transformer and connected to the rotating part. Air can be used to move the transformer if it is in open spaces exposed to air, or water can be used to move it, as in dams. The invention here functions as an electric generator and an electrical transformer simultaneously, or it can use electricity from an external source, such as solar energy, to move the rotating part. The rotor can also rotate or move linearly in the vertical/y-axis, enabling a part/component of the transformer to cut the stationary DC magnetic field of direct current, thus transferring it to the other core with a different voltage value. Thus, the transformer operation principle is achieved.
[2] The transformer also contains auxiliary components in this invention, such as a superconducting fault current limiter to protect it from short circuit currents and inrush currents. It also includes a rectifier which is a rectifying circuit consisting of several diode units to convert the AC output to DC when needed. It also contains a surge arrester to protect the transformer from discharge voltages. Apart from these important components, the DC transformer contains all the protection and measurement devices that any other transformer contains, such as a current transformer (CT), a voltage transformer (PT), silica gel, a cooling medium, whether mineral oil, air, nitrogen, or any other type of cooling medium depending on the voltage used with the transformer, a Buchholz relay, and so on.
Yes, It makes a major gap as it can convert/transform DC voltage into DC voltage with higher or lower voltage levels using modified AC transformer (normal transformer + added parts) without the need of converter and inverter substations.
Complete Specification
| Country | Current Status | Patent Application Number | Patent Applicant | Patent Number | Title | Google Patent Link |
| Egypt | pending | EG/P/2025/1182 | Mahmoud Ahmed Saad | EG/P/2025/1182 | Semi rotational DC Transformer | Click to open |