Induction type heater

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Heat­ing devices, the prin­ci­ple of which is based on induc­tion heat­ing, are called induc­tion heaters. They are used both in indus­try and in every­day life, and in indus­try the impor­tance of their use can hard­ly be over­es­ti­mat­ed.

Let’s take a clos­er look at these devices.

The device and principle of operation of the induction heater

Sim­pli­fied, the induc­tion heater con­sists of three com­po­nents:

  • alter­na­tor (1);
  • induc­tor (2);
  • core (3).

A con­duc­tive (met­al, graphite) rod is placed in a coil, con­sist­ing of a cer­tain num­ber of turns of a con­duc­tor of a giv­en cross-sec­tion­al area, with­out direct con­tact with it, after which volt­age is applied to the coil con­tacts from an alter­na­tor. An elec­tro­mag­net­ic field is formed around the turns of the coil, under the influ­ence of which Fou­cault eddy cur­rents arise in the rod, heat­ing the core. Thus, there is no heat trans­fer to the core, heat is gen­er­at­ed by it inde­pen­dent­ly under the influ­ence of cur­rents wan­der­ing in it, and can be trans­ferred using a coolant. The tem­per­a­ture of the rod ris­es not simul­ta­ne­ous­ly through­out the mass, but from the sur­face lay­ers to the cen­ter, depend­ing on the ther­mal con­duc­tiv­i­ty of the core mate­r­i­al. At the same time, increas­ing the fre­quen­cy of the alter­nat­ing cur­rent reduces the depth of induc­tive heat­ing, but increas­es its inten­si­ty. Par­tic­u­lar­ly note­wor­thy is the fact that the coil around the core remains almost cold dur­ing oper­a­tion.

Visu­al­ly, this process looks like this:

Areas of use

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In indus­try, induc­tion heaters are used to per­form the fol­low­ing com­plex process­es:

  • ultra-pure melt­ing of met­als (pro­duced in chan­nel — non-con­tact induc­tion fur­naces);
  • bend­ing steel pipes of large diam­e­ter;
  • per­for­mance of sur­face hard­en­ing of steel prod­ucts (build­ing fit­tings, details of trans­mis­sion mech­a­nisms of machine tools, etc.);
  • heat treat­ment of small parts of com­plex con­fig­u­ra­tion;

In every­day life, induc­tion heat­ing devices are also quite wide­spread. Their areas of appli­ca­tion:

  • house­hold autonomous heat­ing sys­tems (for sum­mer cot­tages, apart­ments, pri­vate hous­es);
  • induc­tion hobs and tiles for the kitchen;
  • cru­cible fur­naces of small vol­ume for domes­tic met­al smelt­ing;
  • jew­el­ry craft.

Since the main top­ic of the arti­cle is an induc­tion heater, we will dwell in detail on a heat­ing boil­er, the basis of which is the idea of ​​​​induc­tive heat­ing of the coolant.

Induction heater — heating boiler

Since home­own­ers began to install autonomous heat­ing sys­tems in their homes, the issue of the effi­cien­cy of heat­ing boil­ers remains one of the most impor­tant for them. Accord­ing to this indi­ca­tor, at least among devices that gen­er­ate heat from elec­tric­i­ty, induc­tion heat­ing boil­ers are in the lead. At the same time, their pow­er, which is not com­pa­ra­ble with the iden­ti­cal para­me­ter of such a device as a plinth heater, allows the units to be used as the main heat­ing method in large areas.

Induc­tion heat­ing boil­ers con­sist of two cir­cuits — pri­ma­ry (elec­tro­mag­net­ic) and sec­ondary (heat exchange pip­ing). The first cir­cuit, con­sist­ing of a volt­age con­vert­er and a heat gen­er­a­tor with an induc­tion type heater, cre­ates an elec­tro­mag­net­ic field, eddy cur­rents and gen­er­ates heat. The sec­ond cir­cuit, which includes a heat exchang­er with a pip­ing sys­tem, trans­fers this heat through the cir­cu­la­tion of the coolant to the radi­a­tors of the heat­ing sys­tem. Pure water or with addi­tives is used as a heat car­ri­er.

In addi­tion to these two cir­cuits, the heat­ing sys­tem includes automa­tion respon­si­ble for the oper­a­tion of indi­vid­ual units of the unit.

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Mod­ern induc­tion heat­ing boil­ers are installed only in a closed-type heat exchange cir­cuit, which has a mem­brane-type expan­sion tank and a forced cir­cu­la­tion pump in its design. The use of a cir­cu­la­tion pump is a forced mea­sure and is due to the small vol­ume of the coolant at a high heat exchang­er heat­ing inten­si­ty. The pos­si­bil­i­ty of nat­ur­al cir­cu­la­tion in such a sys­tem is exclud­ed — with­out a pump, water will boil before it begins to move through the pipes.

Impor­tant! The induc­tion boil­er must be ground­ed. In addi­tion, when installing the heat­ing sys­tem, for safe­ty rea­sons, the heat car­ri­er dis­tri­b­u­tion cir­cuit must be mount­ed from plas­tic pipes, or the heat­ing unit must be iso­lat­ed from the steel cir­cuit by insert­ing polypropy­lene fit­tings.

Induc­tion heat­ing boil­ers are clas­si­fied iden­ti­cal­ly to oth­er heat­ing elec­tric units — in terms of pow­er, design, para­me­ters of elec­tric­i­ty con­sumed. But these devices also have a clas­si­fi­ca­tion accord­ing to the design solu­tion of the elec­tri­cal part.

Varieties of induction boilers

There are the fol­low­ing types of induc­tion-type heat­ing boil­ers, des­ig­nat­ed both by the prin­ci­ple of oper­a­tion and by the brand of the man­u­fac­tur­er:

  • SAV — a vari­ety and at the same time a trade­mark of a new gen­er­a­tion of boil­ers with a capac­i­ty of 2.5 to 100 kW, since 2007 pro­duced by the Euro­pean com­pa­ny CJSC NPK INERA;
  • VIN — the abbre­vi­a­tion is not only an abbre­vi­a­tion for the name of the type of induc­tion devices (vor­tex induc­tion heaters), but also the patent­ed name of the boil­ers pro­duced by the Izhevsk com­pa­ny Alter­na­tive Ener­gy.

SAV induction heaters

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The oper­a­tion of SAV units does not require the use of an invert­er, a cur­rent with a fre­quen­cy of 50 Hz is sup­plied to the induc­tor. The elec­tro­mag­net­ic field induced by the pri­ma­ry wind­ing caus­es the for­ma­tion of vor­tex flows in the sec­ondary wind­ing, the role of which in boil­ers of this type is per­formed by a sec­tion of a closed loop of pipes with a coolant. This sec­tion of the pipe — the sec­ondary wind­ing is intense­ly heat­ed under the influ­ence of Fou­cault cur­rents and trans­fers heat to the coolant, which is forcibly cir­cu­lat­ed in the heat­ing sys­tem using a cir­cu­la­tion pump.

The device of the heat­ing sys­tem is car­ried out using radi­a­tors or in a labyrinth way, rem­i­nis­cent of base­board heat­ing, in order to increase the total area of ​​u200bu200bthe out­er sur­face (heat trans­fer) of the pipes — the heat­ing cir­cuit, at least, should not be min­i­mal in length.


SAV boil­ers are pro­duced for volt­ages of 220V and 380V. They use water as a coolant (in pure form or with antifreeze addi­tives), as well as antifreeze. The out­put of the unit at full capac­i­ty takes about 5–20 min­utes (depend­ing on the vol­ume of the coolant), the effi­cien­cy of the heaters of such devices is at least 98%. For effi­cient heat­ing of rooms up to 30 sq. m. a 2.5 kW induc­tion device is enough, the pur­chase of which, com­plete with automa­tion and con­trol sys­tems, will cost approx­i­mate­ly 300 $.

VIN-heating units

Boil­ers of this type are more per­fect in terms of the prin­ci­ple of oper­a­tion and design, which, of course, is reflect­ed in their cost. For the oper­a­tion of VIN-devices, an invert­er is required — a device for increas­ing the fre­quen­cy of the incom­ing cur­rent. The high fre­quen­cy cur­rent caus­es the for­ma­tion of an elec­tro­mag­net­ic field of high inten­si­ty, which, in turn, caus­es the occur­rence of more pow­er­ful eddy cur­rents in the sec­ondary wind­ing. In addi­tion, the heat exchang­er and the boil­er body are made of fer­ro­mag­net­ic alloys that have their own mag­net­ic field. The result of all these process­es is a high heat­ing inten­si­ty of the heat exchang­er and, of course, the coolant.

A VIN-unit with a capac­i­ty of 3 kW is suf­fi­cient for heat­ing a room with an area of ​​35–40 sq. m. (depend­ing on cli­mat­ic con­di­tions and the qual­i­ty of ther­mal insu­la­tion of exter­nal build­ing struc­tures).

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VIN units, due to their high­er pro­duc­tiv­i­ty, can be used not only in res­i­den­tial heat­ing sys­tems, but also for hot water sup­ply. To do this, addi­tion­al stor­age tanks are insert­ed into the coolant cir­cuit, equipped with pro­tec­tive automa­tion, the capac­i­ty of which is cal­cu­lat­ed depend­ing on the num­ber of hot water intake points. These con­tain­ers are pro­vid­ed with hot water by cir­cu­lat­ing it in a sys­tem with direct-flow heat­ing by an induc­tion heater.

Evaluation of marketing characteristics-statements

Many advan­tages are attrib­uted to induc­tion heat­ing boil­ers, often with­out argu­ments. We list these char­ac­ter­is­tics and give an assess­ment of the degree of con­for­mi­ty of the state­ments to the fact:

Economy

Statement

Elec­tric­i­ty con­sump­tion by induc­tion boil­ers is 20–30% less than oth­er elec­tric heaters.

Fact

All heat­ing elec­tri­cal appli­ances that do not per­form mechan­i­cal work con­vert 100% of the ener­gy of the elec­tric cur­rent into heat, their effi­cien­cy is always below 100%, but dif­fers in mag­ni­tude for dif­fer­ent devices in dif­fer­ent con­di­tions. To gen­er­ate 1 kW of ther­mal ener­gy, it is nec­es­sary to spend more than 1 kW of elec­tric­i­ty, but how much more depends on the para­me­ters of the dis­per­sion medi­um. Inside the boil­er, of course, there are also loss­es — for exam­ple, for heat­ing the coil, since any con­duc­tor mate­r­i­al has resis­tance, but all these loss­es remain indoors

Impor­tant! Old-style meters (bake­lite) will record a low­er (1.6 — 1.8 times) elec­tric­i­ty con­sump­tion than mod­ern elec­tron­ic ones, since they are not designed to take into account the reac­tive pow­er of induc­tion boil­ers.

Per­haps this fact deter­mines the state­ment about the effi­cien­cy of induc­tion boil­ers.

Durability

Statement

High reli­a­bil­i­ty and long ser­vice life of equip­ment — more than 25 years.

Fact

Indeed, the absence of mov­ing parts elim­i­nates the mechan­i­cal wear of induc­tion boil­ers. But the heat­ing sys­tem with a VIN unit includes a cir­cu­la­tion pump, the resource of which is much more mod­est. In addi­tion, the con­trol and automa­tion sys­tem includes mech­a­nisms, also con­sist­ing of many com­po­nents sub­ject to wear.

The core of the induc­tion heater oper­ates under con­di­tions of con­stant cyclic heat­ing and cool­ing, tem­per­a­ture defor­ma­tions, which are also a neg­a­tive fac­tor. There­fore, to call the resource of induc­tion boil­ers almost unlim­it­ed is an exag­ger­a­tion. How­ev­er, it is actu­al­ly many times high­er than heat­ing ele­ment heaters.

Consistency of characteristics for the entire period of operation

Statement

The absence of the for­ma­tion of scale on the inner sur­face of the pipes deter­mines the con­stant effi­cien­cy of the heater and heat exchang­er.

Fact

Scale is a deposit of salts con­tained in water (coolant). The amount of these impu­ri­ties in a lim­it­ed vol­ume of the coolant is also lim­it­ed and small, so the effect of scale on the effi­cien­cy of the heater is insignif­i­cant. And in an induc­tion boil­er, the sec­ondary wind­ing is under almost con­stant vibra­tion, and scale for­ma­tion does not occur at all. So the state­ment is true, only its sig­nif­i­cance is exag­ger­at­ed.

Noiselessness

Statement

The oper­a­tion of induc­tion heat­ing boil­ers is silent, which dis­tin­guish­es them from oth­er elec­tric heaters.

Fact

The state­ment is true, but — all elec­tric boil­ers do not make noise dur­ing oper­a­tion, since acoustic waves are not includ­ed in the range of their oscil­la­tions. Only the cir­cu­la­tion pump can make noise, but if you wish, you can choose a mod­el of silent action.

compactness

Statement

Induc­tion boil­ers are com­pact, which is con­ve­nient when choos­ing a place for their instal­la­tion.

Fact

This is true if you do not use a cas­cade of induc­tion boil­ers and do not install inter­me­di­ate tanks if there are sev­er­al points of hot water intake in the hot water sup­ply sys­tem, since an induc­tion heater is, by and large, a small piece of pipe with a wind­ing.

Safety

Statement

The safe­ty of the device is absolute.

Fact

Absolute­ly safe elec­tric heaters do not exist. Dur­ing the oper­a­tion of induc­tion devices, the pos­si­bil­i­ty of a coolant leak­age from the sys­tem is not ruled out, and the elec­tro­mag­net­ic field gen­er­a­tor will con­tin­ue to oper­ate, and the emp­ty pipe sys­tem will heat up. To pre­vent the occur­rence of such a sit­u­a­tion, the boil­er design pro­vides for an auto­mat­ic shut­down device, but it can also fail.

There­fore, induc­tion heaters, while out­per­form­ing rivals in some safe­ty cri­te­ria, are not com­plete­ly safe.

Disadvantages of induction heaters

  • The high cost of devices.
  • Sig­nif­i­cant weight with com­pact­ness.
  • The pres­ence of a fac­tor in the influ­ence of the elec­tro­mag­net­ic field on the body and devices.

Let’s take a clos­er look at the last point.

The elec­tro­mag­net­ic field affects liv­ing organ­isms in much the same way as food in a microwave oven — it warms them up to a cer­tain depth, and this can have con­se­quences. The inten­si­ty of the impact of the field, includ­ing on a per­son, is deter­mined by such an indi­ca­tor as the ener­gy flux den­si­ty (PEF), which grows with an increase in the fre­quen­cy of the cur­rent sup­plied to the pri­ma­ry wind­ing. When oper­at­ing induc­tion heaters, it is nec­es­sary to com­ply with the san­i­tary lim­it val­ue of the PES, which is estab­lished in San­PiN 2.2.4 / 2.1.8.055–96, depends on the dura­tion of the field expo­sure and is, for exam­ple, for an 8‑hour expo­sure — 25 μW / sq. cm, one-hour — 200 μW / sq. cm.

In addi­tion, the radi­a­tion of the induc­tor adverse­ly affects the elec­tron­ics and radio equip­ment locat­ed near­by, cre­at­ing inter­fer­ence dur­ing oper­a­tion.

Impor­tant! To pro­tect your­self from the effects of an elec­tro­mag­net­ic field, you can sur­round the boil­er with a fine-mesh (1x1, 2x2 mm) met­al mesh (Fara­day cage), which is not in con­tact with the boil­er body and is ground­ed.

Operating rules

The safe oper­a­tion of induc­tion heat­ing boil­ers, like any oth­er tech­ni­cal devices, is ensured by the imple­men­ta­tion of a num­ber of rules regard­ing both their instal­la­tion and use after instal­la­tion:

  • The boil­er must be earth­ed.
  • The dis­tance from the device to the walls on the sides must be at least 30 cm, from the bot­tom point of the boil­er to the floor — 80 cm, from its top point to the ceil­ing — 80 cm.
  • Induc­tion boil­ers are installed only in a closed cir­cuit with a mem­brane-type expan­sion tank.
  • The sys­tem must include a block of safe­ty devices (pres­sure gauge, air valve, over­pres­sure relief valve, auto­mat­ic over­heat shut­down sys­tem).

Overview of well-known manufacturers

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  • Edi­son — induc­tion-type heaters with a capac­i­ty of 4.7 to 500 kW, pro­duced by the of the world plant “SibTech­no­Mash”, for domes­tic and indus­tri­al needs;
  • Mira­tron — prod­ucts of the Euro­pean man­u­fac­tur­er of induc­tion heat­ing equip­ment NPK Mira­tron for domes­tic use, fea­tur­ing an advanced design that allows you to use the equip­ment with­out dam­ag­ing the inte­ri­or of the room;
  • Teco-House — induc­tion heat­ing boil­ers with a unique con­trol sys­tem, pro­duced by the Ukrain­ian com­pa­ny of the same name accord­ing to the stan­dards of the EU and the EU.

Conclusion

The mod­ern mar­ket of boil­ers for the instal­la­tion of autonomous heat­ing sys­tems is rep­re­sent­ed by hun­dreds of mod­els of var­i­ous types of units. The objec­tiv­i­ty of the price / qual­i­ty cri­te­ri­on of each vari­ety is dif­fer­ent. The choice in favor of induc­tion heat­ing devices in terms of the risk of sub­se­quent dis­ap­point­ment in the pur­chase is the most rea­son­able.

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