• English English English en
  • Italiano Italiano Italian it
dddTel.: 0444 698877 - Fax: 0444 698759 - Mail: carbognin@carbognin.it
Carbognin
  • Home
  • Company
    • How we work
  • Products
    • Unified single-phase transformers
    • Single-phase shell transformers
    • Single-phase column transformers
    • Three-phase transformers
    • Auto-transformers for motor start-up
    • Transformers for hospital use
    • Inductors and reactors
    • Reactance coils for the start-up of motors
    • Line and converter reactors
    • Protective containers
    • Special transformers
    • Transformers for photovoltaic systems
  • Technical information
    • Regulations and standards
    • Technical notes concerning transformers
    • Technical notes concerning reactors
    • No-load currents
  • Contacts
  • Search
  • Menu

Three-phase transformers

Also produced in single quantities

  • In the three-phase transformers, the vector group acquires particular importance.
  • This choice is made according to the type of desired angular displacement between the primary and secondary and the type of load envisaged for the secondary transformer winding.
  • These transformers are manufactured in accordance with the CEI 96-1, CEI 96-2 (EN 60742) and CEI 96-3 (EN 61558-1) standards when the voltage is below 1000 V.
  • the following list indicates the vector groups most commonly used for three-phase transformers:
    (For more information click
    three-phase currents)

STAR-STAR connection, Yy0 group – Yy6 group

Reveals the drawback of instability of the neutral point voltage due to: 

a – single-phase loads connected between the line and neutral
b – differences in magnetizing currents
c – third harmonic currents

STAR-TRIANGLE connection, Dy11 group – Dy5 group

This is one of the most commonly used connections, also adopted for distribution transformers, as it offers all of the advantages relating to the presence of the secondary neutral and none of the disadvantages of the star-star connection. Furthermore, the presence of the delta connection in the primary circuit ensures correct magnetization of the core and a strictly sinusoidal secondary voltage.

TRIANGLE-TRIANGLE connection, Dd0 group – Dd6 group

This presents the disadvantage of not having the neutral in the secondary. From the operational point of view, the triangle-triangle connection offers the possibility of having free circulation of third-harmonic excitation currents without them occurring beyond the terminal block.

Primary circuit star-type connection and zig-zag secondary with neutral

This connection allows for distribution of the load of each phase over two different columns of the magnetic circuit and produces the effect of limiting voltage imbalances due to differences in load in the three phases. Another important characteristic consists in the elimination of the third harmonic from the secondary voltage.
Despite the fact the zig-zag connection, having the same voltage, requires a greater number of turns and thus involves greater cost, this is compensated by the advantage of making the transformer more suitable for withstanding unbalanced loads and the advantage of eliminating the third harmonic from the secondary star voltages.

Primary circuit triangle connection and secondary zig-zag with neutral

Together with the Dy, with neutral, this is used when accessibility of the neutral in the secondary is required and the possibility of strong load imbalances during operation is expected.
It allows for maximum voltage symmetry and the best division of the primary load
The third harmonics in the magnetizing current due to non-linearity of the core occur with a current that circulates only in the primary triangle.

MAIN CHARACTERISTICS OF THREE PHASE TRANSFORMERS

  • DESIGNED ACCORDING TO THE SPECIFICATIONS OF THE CLIENT (constructed according to any requirements in technical terms and relating to size).
  • Isolation materials of class F (155°C) and class H (180°C).
  • Compact size, thanks to the use of laminated steel presenting very low loss.
  • Class 1 (requires ground connection).
  • Degree of protection from IP00 to IP10.
  • Impregnation with oven-dried paints and resins (guarantee of perfect isolation, low-noise and reliable operation, also in humid and tropical climates)
  • The metal components are all galvanized.
  • Routine or separate type-based testing on each piece supplied. If required, a printed copy of the test certificate will be issued.
  • The three-phase transformers can be supplied, on request, with ELECTROSTATIC SHIELDS AND THERMOSTATIC SENSORS INSERTED BETWEEN THE WINDINGS.

ISOLATION TRANSFORMERS FOR PHOTOVOLTAIC SYSTEMS

For isolation transformers connected to photovoltaic systems we refer to a magnetic induction value that is lower with respect to that normally used on lines with a regular sine wave.
This is to avoid overheating the magnetic metallic sheeting and reduce no-load losses of the transformer, thereby increasing the efficiency of the equipment.

  • The tables below show the indicative dimensions of a transformer with an input voltage between 48 and 650V and an output voltage between 48 and 650V at a frequency of 50-60Hz.
  • DIMENSIONS MAY VARY, DEPENDING ON THE NUMBER OF INLETS, OUTLETS AND INTENSITY OF THE CURRENT (See Technical Notes). MORE DETAILED INFORMATION WILL BE PROVIDED ON RECEIPT OF A SPECIFIC REQUEST.
trasformatori trifase

The terminals can be mounted either on one or on two sides of the transformer, depending on the number of voltages and the value of the currents. Dimensions are expressed in mm.

Type

20.20

20.30

25.26

25.41

30.40

30.50

40.40

40.50

40.60

40.75

VA

20/50

50/90

120

250

500

800

1000

1500

2000

2500

A

120

120

150

150

180

180

240

240

240

240

B

57

67

78

93

96

106

110

120

130

145

C

115

115

147

147

175

175

242

242

242

242

D

100

100

125

125

150

150

200

200

200

200

E

46

56

56

71

76

86

80

90

100

115

G

65

75

82

97

120

130

120

130

140

155

Kg.

1.8

2.7

3.5

5.6

8.4

10.7

14.7

17.5

21

24.8

TYPE

50.50

50.60

50.70

50.80

50.90

60.70

60.90

60.120

70.80

70.90

70.100

70.120

70.140

80.80

80.90

80.100

80.110

80.130

80.150

KVA

3

4

5

5,5

6,5

8

10

12

13

15

17

20

23

22

26

30

35

42

50

A

300

300

300

300

300

360

360

360

420

420

420

420

420

480

480

480

480

480

480

B

130

140

150

160

170

170

190

220

195

205

215

235

255

200

210

220

230

250

270

C

290

290

290

290

290

345

345

345

400

400

410

410

420

480

480

480

480

500

500

D

250

250

250

250

250

325

325

325

375

375

375

375

375

425

425

425

425

425

425

E

92

102

112

122

132

135

155

185

152

162

172

192

212

160

170

180

190

210

230

G

130

140

150

170

180

150

180

250

210

215

235

275

300

240

250

260

280

300

340

Kg.

28

32

38

42

47

54

69

90

86

96

105

122

146

116

134

149

157

190

220

TIPO

10.10

10.11

10.12

10.14

10.16

KVA

50

60

70

85

100

A

600

600

600

600

600

B

235

245

255

275

295

C

600

600

600

600

600

D

550

550

550

550

550

E

190

200

210

230

250

G

270

300

330

370

420

peso Kg.

220

244

266

310

360

NOTES: INFORMATION CONCERNING SIZES IS PURELY INDICATIVE AND MAY CHANGE WITHOUT PRIOR NOTICE

THE AUTO-TRANSFORMER IS A TRANSFORMERS WITH A SOLE WINDING COMMON TO BOTH PRIMARY INPUT VOLTAGE AND OUPUT VOLTAGE, AND WITHOUT ELECTRICAL ISOLATION BETWEEN THE SAME.

The equivalent power (referred to as core power in current regulations) is provided by the formula:

Peq=Pn .( Vmax-Vmin.)

_________________

Vmax

where: Peq = actual sizing power (core power)– Pn = rated nominal power (shaft power) — Vmax = highest voltage –Vmin = owest voltage.

To establish the dimensions of the auto-transformer apply the formula to obtain an equivalent power level and then, on the basis of the power obtained, refer to the following tables.

trasformatori trifase

Contact us now for more information

    Carbognin srl

    We are suppliers of each type of industry which requires the use of electrical and electronic equipment.

    Where we are

    V. Crispi, 9 (z.a).
    36075 - Montecchio Maggiore
    Vicenza - Italy

    Contacts

    Phone: +39 0444 698877
    Fax: +39 0444 698759
    carbognin@carbognin.it

    © Copyright - Carbognin | V. Crispi, 9 (z.a) - Montecchio maggiore (VI) | P. IVA 00305730244 - R.I. di Vicenza 51179/1966 | Phone 0039 0444 698877 - Fax 0039 0444 698759 - E-mail: carbognin@carbognin.it | Cookie Policy - Policy privacy | Credits: Solutions Pubblicità e Marketing
    Single-phase column transformers Auto-transformers for motor start-up
    Scroll to top