RU2235445C2 - Transformer-type electric water heater - Google Patents

Abstract

FIELD: fast water heating and hot-water supply for domestic and industrial needs.

SUBSTANCE: heater has three-phase transformer with laminated magnetic core made of electric steel whose legs carry aluminum-wire primary winding. Heating element is made in the form of single-turn three-phase short-circuited secondary winding made of nonmagnetic electricity conducting tubes. Novelty is specific mechanical design of secondary winding in which short-circuited turn of each phase has active and passive sections. Active section is placed on magnetic core phase leg over primary winding and passive section encloses all three legs of transformer core; it is made in the form of two parallel conductors whose ends are connected to active section. Short-circuited phase turns are connected in series at water path and shorted out through welded joints. Proposed design is best suited to meet specific requirements to short-circuited secondary windings.

EFFECT: enhanced performance characteristics, safety, and reliability of electric heater.

1 cl, 2 dwg

Description

The invention relates to electric heating devices and is intended for use in everyday life, in small industrial and agricultural facilities for the preparation of fixed temperature hot water in a quick manner.

The closest in technical essence to the claimed invention is an induction electric heater (application No. 4602140, USA, MKI N 01 B 6/10, publ. 07/22/86), which includes a three-phase magnetic circuit, a primary winding, designed for a voltage of a certain fixed frequency. The magnetic circuit has three rods on which the primary winding is located. The secondary winding includes many direct non-magnetic electrically conductive pipes located between and outside the cores of the magnetic circuit, connected at the ends with the lids of the tanks, which serve to close the fluid circuit and phase currents. All pipes are parallel to each other between two tanks. The tanks have removable covers for inspecting the inner surface of the pipes.

The disadvantages of this device include the complex technology of connecting the ends of the pipes to the lids of the tanks, a large number of welded joints are required here, which leads to the likelihood of a defect during assembly.

The invention consists in the following. The invention is aimed at improving the operational properties of an electric heater.

In the process of solving the problem, a technical result is achieved, which consists in increasing the safety and reliability of the electric heater.

This is achieved by using a three-phase magnetic circuit in an electric water heater with a primary winding laid on its rods. As a heating element, a three-phase single-turn short-circuited secondary winding in the form of curved non-magnetic electrically conductive pipes, consisting of three short-circuited turns, is used. The short-circuited turn consists of two parts, the first, active part, is laid directly on the phase terminal of the transformer magnetic circuit, the electromotive force (emf) of the phase is induced in it, the second, passive part covers all three phase terminals of the transformer magnetic circuit, the emf is not induced in it, since the resulting magnetic flux from the three phases of the transformer is zero. Since both parts of the coil are connected in series, the same current flows through them, causing heat losses that are evenly distributed over the surface of the coil. The turns of a three-phase single-turn short-circuited secondary winding are connected in series through water, i.e. Heated water sequentially washes all three turns of the winding.

In the proposed electric heater, the design of a three-phase single-turn short-circuited secondary winding satisfies the following requirements. It has one short-circuited coil in each phase, which is necessary to ensure the required safety during operation of the electric heater, the electromotive force of the phase of the three-phase single-turn secondary winding should not exceed 2 ... 4 volts, moreover, the use of one short-circuited coil gives the minimum leakage inductance, which provides the maximum possible value of the power factor of the device, which leads to an improvement in its energy performance. On the other hand, the short-circuited coil has a sufficiently large contact surface with the heated medium, which provides the required specific surface power, and therefore, eliminates the formation of scale on the inner surface of the tube. This design provides the highest possible active resistance of the secondary winding, which is necessary to achieve a given power at minimum current.

The invention is illustrated in figures 1 and 2. Figure 1 shows the assembled active part of the electric heater. The primary winding 2 is located on the rods of the three-phase magnetic core 1. The heating element is a three-phase single-turn short-circuited secondary winding 3. The short-circuited turn of each phase of the secondary winding consists of an active part 4 and a passive part 5. The turns of the secondary winding are short-circuited by welded joints 6. Figure 2 shows a short-circuited turn each phase of the secondary winding, consisting of the active part 4 and the passive part 5.

A primary winding made of aluminum wire is laid on the rods of a three-phase charged magnetic core made of electrical steel. A three-phase single-turn short-circuited secondary winding, laid on the terminals of the magnetic circuit over the primary winding, is bent from a non-magnetic electrically conductive tube. The short-circuited coil of the secondary winding consists of an active and passive part. To create a short-circuited coil in each phase of the winding of the tube are welded in three places indicated in figure 1.

The electromagnetic calculation is based on the required temperature of the heated water.

The device operates as follows. The primary winding located on the magnetic circuit is connected to a three-phase AC network. A current begins to flow through the winding, creating an alternating magnetic field in the three-phase magnetic circuit. This magnetic field induces in the active part of the short-circuited coil of the three-phase secondary winding of the emf. The current caused by this emf flows both in the active and in the passive part of the coil. The heat losses caused by this current are used to heat the water. The heat transfer rate depends on the speed of the water flowing through the pipe, as well as on the area of the heat transfer surface.

Thus, in this invention, the required level of safety and reliability of the device is achieved, the proposed invention is similar to the prototype in terms of water heating efficiency, but in contrast to it, the above requirements for the constructions of secondary short-circuited windings are best satisfied here.

Claims (1)

A transformer-type electric heater containing a three-phase magnetic circuit with primary and short-circuited secondary windings laid on its rods, characterized in that the coil of each phase of a three-phase single-turn secondary winding is made in the form of curved non-magnetic pipes and contains active parts laid on the transformer core of the phase core over the primary winding , as well as passive parts, covering all three rods of the phases of the transformer magnetic circuit, and I connect the turns of the individual phases sequentially across the water and short-circuited.

Images