GB2073498A

GB2073498A - Apparatus for the recovery of heat dissipated by static electric machines

Info

Publication number: GB2073498A
Application number: GB8100959A
Authority: GB
Original assignee: Individual
Current assignee: Individual
Priority date: 1980-01-31
Filing date: 1981-01-13
Publication date: 1981-10-14
Also published as: DE3101697A1; FR2475199A1; BE887013A; IT8004729V0

Abstract

An apparatus for the recovery of heat dissipated by static electric machines, especially electrical transformers. The apparatus includes an initial closed hydraulic circuit 7 in which there is mineral oil 4 with high electrical insulation. A static electric machine 1 within casing 2 forms the heat generator for circuit 7 which is equipped with an initial heat exchanger 10. A second closed hydraulic circuit 11 with hydraulic circulation separate from circuit 7. The second circuit contains mineral oil 12 with high electrical insulation. The heat exchanger 10 forms the heat generator of the circuit 11 which is equipped with a second heat exchanger 13. A third/closed hydraulic circuit 14 contains water with hydraulic circulation separate from circuits 7 and 11. This third circuit is intended to put to use the heat dissipated by the machine 1 and has a third heat exchanger 15 and a heat generator formed by the heat exchanger 13. A fourth heat exchanger 16 is inserted into a branch 17 of a by-pass (including flow dividers 18, 18%) of the initial closed hydraulic circuit 7. Sleeves 8, 9 of electrical insulation material connect circuit 7 with casing 2. <IMAGE>

Description

SPECIFICATION Apparatus for the recovery of heat dissipated by static electric machines The apparatus which is the subject of this invention has application in the sphere of static electric machines which - as is well known - carry out the transportation of an electrical power into another electrical power having different characteristics.

It is known that this power transformation gives rise to losses which not only lowerthe performance of the machine, but also limit the power obtainable: in fact, these losses increase with the increase of the power yield and - transforming themselves into heat - bring about an overheating of the machine. Therefore the power obtainable by the machine is limited without the temperature exceeding the acceptable limit for good performance. As is wellknown, this obtainable power is increased by keeping the temperature of the machine within predetermined values, carrying out a suitable cooling of the static electric machines or with oil circulation, or by ventilation. Therefore, with the raising of the power of the machine, the necessity increases to dispose of.

the heat produced from the losses by the Joule effect, for this reason, except for the very reduced power units, the static electric machines - and especially the electrical transformers - are provided with systems for the cooling of the conductors by means of the circulation (natural or forced) of mineral oil with a high electrical insulation.

The fundamental disadvantage of this method of procedure is due to the fact that the heat generated during the working of the static electric machines is wholly dispersed, even with the expenditure of supplementary energies (by the utilization, for example, of ventilation palnts or similar).

The aim of this invention is to recuperate this generated heat, and to transfer it - opportunely and without danger - to the utilization. The problem on which the invention is based refers to the recuperation of the heat generated by the static electric machines, and to the danger brought about by the putting into communication of the utilizable form of heat, directly in contact with persons (for example by means of radiators for the heating of environments), with the static electric machines, especially with electrical transformers, in which there are normally - electrical currents in play in the region of tens of thousands of volts. Therefore, the eventuality of putting "under tension" the hydraulic circuit of the water utilized must be absolutely avoided, as for example- in the radiators for heating the environments or, more generally, in contact with persons.

The problem is solved, in accordance with the invention, by means of an apparatus for the recovery of the heat dissipated by static electric machines, characterized by the fact of including at least an initial closed hydraulic circuit, the heat generator of which consists of a static electric machine, also fitted with an initial heat exchanger; at least a second closed hydraulic circuit, with hydraulic circulation separate from the preceding one, the heat generator of which consists of the said initial heat exchanger, and fitted with a second heat exchanger.

Advantageously, the electrical insulation of the water circuit (the third closed hydraulic circuit), the heat generator of which consists of said second heat exchanger, is guaranteed, in accordance with the further characteristics of the invention, by the presence of a dielectric fluid in at least one of said initial or second closed hydraulic circuits; which prevents the voltage discharge through the fluids existing in the hydraulic circuits. This voltage exchange through the fluids is also avoided more effectively with the use of a heat exchanger of the thick finned piped type, inserted in the initial closed hydraulic circuit, which ensures an absolute resistance to cracking (which could happen with other types of heat exchangers) thus avoiding direct contact between the fluids in the above-mentioned separate hydraulic circuits.

Advantageously, the voltage discharge through the piping which constitutes said hydraulic circuits, is prevented - in accordance with a further characteristic of the invention - by the fact that the initial closed hydraulic circuit has the connection piping with its heat generator, (or with the casing in which the static eletric machine is enclosed) fitted with sleeves made of dielectrical material. The eventual voltage discharge through the fluids existing in the hydraulic circuits is also prevented, in accordance with a further characteristic of the invention, due to the fact that the pressure of each fluid existing in each of said separate hydraulic circuits is respectively greater than the pressure of the fluid in the circuit immediately upstream, in respect to the direction of the flow of heat generated by said static electric machines.

The main advantages deriving from the apparatus, according to the invention, are the following: the recovery and utilization of heat produced by the losses in static electric machines, especially in electrical transformers; - the possibility of the installation of large transformers even in closed environments, due to the fact that - in accordance with the inventon - they need not necessarily be exposed to the air in order to disperse the heat produced; - the reduction of the dimensions of the electrical transformers, due to the fact that - with the same power there is a more efficient removal of the heat produced, due to the more favourable conditions for the heat exchange, caused by the existence - in accordance with the invention - of a plurality of hydraulic circuits, and of the relative heat exchangers.

According to the invention, the apparatus will now be more fully described with reference to a preferred form of execution, illustrated, for exemplifying but not restrictive purposes, in the attached drawing,.in which is shown a diagram of the plant relative to the apparatus in question. With reference to the diagram, 1 indicates an electrical transformer enclosed in a metal casing 2 which is sealed, and which is completely insulated on the outside bythermo- insulating material 3. The electrical transformer 1, which when working generates heat due to the Joule effect, is totally immersed in mineral oil with high electrical insulation 4 which completely fills the casing 2.

The casing 2 is connected to an initial closed hydraulic circuit 7 by means of pipes 5 and 6. This initial closed hydraulic circuit 7 consists - in its portions of connectiori to the pipes 5 and 6 - of two sleeves 8 and 9 made of dielectrical material (inserted hydraulically sealed into the pipes 5 and 6 respectively, and in the corresponding pipes of the initial closed hydraulic circuit 7), which have the purpose of electrically insulating the initial circuit7 from the metal casing 2.In the inital closed hydraulic circuit 7, inside which the circulation of the oil 4 is forced by an initial pump 19, an initial heat exchanger 10 is inserted, of the thick finned pipe type (in order to guarantee the maximum cracking resistance), which acts as a heat generator for a second closed hydraulic circuit 11, with separate hydraulic circulation from the preceding one, in which circulates mineral oil with high electrical insulation 12. In said second closed hydraulic circuit 11, in which the oil circulation is forced by a second pump 20, a second heat exchanger 13 of the finned pipe type is inserted, which in its turn acts as a heat generator for a third closed hydraulic circuit 14 with hydraulic circulation separate from the preceding hydraulic circuits 7 and 11, in which circulates water by natural convection.In the third closed hydraulic circuit 14 is inserted a third plate type heat exchanger 15, assigned for the use of the heat dissipated from the transformer I (a radiatorforthe heating of environments or similar.

The initial closed hydraulic circuit 7 is fitted with a fourth heat exchanger 16, of the drilled plate and finned type, which is inserted into a branch 17, of said initial closed hydraulic circuit 7, of the by-pass of said initial heat exchanger 10.

The flow of the mineral oil 4 inside the piping which forms said branch 17 is determined by the position of the dividers 18,18', which are manually or automatically controlled, and determine the flow in the branch 17 when the transport is not desired from the initial circuit 7 to the second circuit 11, and thus to the utilization, by means of the third circuit 14 and the third heat exchanger 15. In this case, the fourth heat exchanger 16 simply carries out a cooling action (without heat recovery) of the mineral oil 4, and therefore the transformer 1, preventing it from overheating. This with the object of ensuring the good performance of the transformer 1, even in the case in which it is not desired to use the heat dissipated by it.

As an extreme safety measure, the pressure of each fluid existing in each of the separate hydraulic circuits is respectively greater than the pressure of the fluid in the hydraulic circuit immediately up stream, in respect to the direction of the flow of the heat generated by the electrical transformer 1.

Obviously numerous structural variants, such as different configurations and/or arrangements of the various component elements, can be carried out on the apparatus in question, and moreover without breaking away from the sphere of protection of the same.

Claims

1. An apparatus for the recovery of heat dissi pated by static electric machines, comprising an initial closed hydraulic circuit having a heat gener ator comprising at least one said static electric machine, said initial circuit being provided with an initial heat exchanger, a second closed hydraulic circuit with hydraulic circulation separate from said initial circuit, the second circuit having a heat generator comprising said initial heat exchanger, said second circuit being provided with a second heat exchanger, and means for the electrical insula tion of said initial and second closed hydraulic circuits in relation to the static electric machine.

2. An apparatus for the recovery of heat accord ing to claim 1, including a third closed hydraulic circuit with hydraulic circulation separate from the initial and second circuits, the third circuit having a heat generator comprising the second heat exchan ger, and said third circuit being provided with a third heat exchanger destined for the use of the heat energy dissipated by said static electric machines.

3. An apparatus for the recovery of heat accord ing to claim 1, or claim 2, in which said means for the electrical insulation comprises dielectrical fluid in the initial closed hydraulic circuit.

4. An apparatus for the recovery of heat accord ing to any one of the preceding claims, in which there is dielectric fluid in the second closed hydraulic circuit.

5. An apparatus for the recovery of heat accord ing to any one preceding claim, in which said means of electrical insulation comprises sleeves of dielec trical material, the initial closed hydraulic circuit being connected with its heat generator by connect ing pipes fitted with said sleeves.

6. An apparatusforthe recovery of heat accord ing to claim 1 or claim 2, in which the initial closed hydraulic circuit is provided with a fourth heat exchanger inserted into a branch of the initial closed hydraulic circuit, said branch being a by-pass of the initial heat exchanger.

7. An apparatus for the recovery of heat accord ing to any one preceding claim, in which the initial heat exchanger is of the finned pipe type. -

8.. An apparatus for the recovery of heat accord ing to any one preceding claim, in which the initial heat exchanger is of the plate type.

9. An apparatus for the recovery of heat accord ing to any one preceding claim, in which the pressure of each fluid in each of said separate hydraulic circuits is respectively greater than the pressure of the fluid existing in the circuit immedi ately upstream in respect to the direction of flow of heat generated by the static electric machine.

10. An apparatus for the recovery of heat dissi pated by static electric machines, substantially as herinbefore described with reference to the accom panying drawing.