{"id":22380,"date":"2021-09-16T12:47:54","date_gmt":"2021-09-16T10:47:54","guid":{"rendered":"https:\/\/comar.netechlab.it\/articolo-academy\/rifasamento-fisso-dei-trasformatori-e-dei-motori\/"},"modified":"2021-10-05T16:13:18","modified_gmt":"2021-10-05T14:13:18","slug":"fixed-pfc-of-transformers-and-motors","status":"publish","type":"articolo-academy","link":"https:\/\/www.comarcond.com\/en\/articolo-academy\/fixed-pfc-of-transformers-and-motors\/","title":{"rendered":"Fixed PFC of Transformers and Motors"},"content":{"rendered":"\n
POWER FACTOR CORRECTION OF MV\/LV TRANSFORMERS<\/h5>\n\n\n\n

The transformers for the distribution of electrical energy can be made in two different types: oil transformers, whose cooling does not require special aids and transformers insulated in resin, forced or natural cooled.
It is always advisable to provide for a fixed power factor correction of the MV \/ LV transformers<\/strong>, since even if they operate without load (for example during the night), they absorb reactive power<\/strong> that must be compensated.<\/p>\n\n\n\n

The calculation of the necessary capacitive power<\/strong> can be performed using the
approximate formula:<\/p>\n\n\n\n

\"\"
I\u2080 = no-load current (supplied by the transformer manufacturer)
Pn = rated power of the transformer<\/figcaption><\/figure><\/div>\n\n\n\n

Alternatively, if the requested data is not available, the following table can be used, differentiated by type oftransformerwith normal leakage characteristics.<\/p>\n\n\n\n

Approximately it is possible to tell that every 7 degrees of temperature increase means halfthe duration.<\/p>\n\n\n\n

REACTIVE POWER REQUIRED for the VACUUM REFUSAL of MT \/ BT TRANSFORMERS (kvar)
(indicative values)<\/strong><\/h6>\n\n\n\n
Transformer power (kVA)<\/strong><\/th>Transformers in OIL<\/th>Transformers in RESIN<\/strong><\/th><\/tr><\/thead>
100<\/td>5<\/td>2,5<\/td><\/tr>
160<\/td>7,5<\/td>5<\/td><\/tr>
200<\/td> 7,5 <\/td> 5 <\/td><\/tr>
250<\/td> 7,5 <\/td> 7,5 <\/td><\/tr>
315<\/td>10<\/td> 7,5 <\/td><\/tr>
400<\/td>10<\/td> 7,5 <\/td><\/tr>
500<\/td>12,5<\/td> 7,5 <\/td><\/tr>
630<\/td>15<\/td>10<\/td><\/tr>
800<\/td>17,5<\/td>10<\/td><\/tr>
1000<\/td>22,5<\/td>12,5<\/td><\/tr>
1250<\/td>25<\/td>15<\/td><\/tr>
1600<\/td>30<\/td>20<\/td><\/tr>
2000<\/td>35<\/td>22,5<\/td><\/tr>
2500<\/td>45<\/td>30<\/td><\/tr>
3150<\/td>55<\/td>45<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n
<\/div>\n\n\n\n
P.F.C. OF THREE-PHASE ASYNCHRONOUS MOTORS<\/h5>\n\n\n\n

One of the most common loads is the three-phase asynchronous motor, which can be rephased locally, with the advantage of having the power cable run through by a lower current.
The capacitance of the capacitors must not exceed the reactive power at no load of the motor<\/strong> due to the risk of self-excitation and resonance phenomena between the capacitor and the inductance of the machine. The following table shows the power factor correction power in the case of a cage motor. For motors with wound rotor, an increase of 5% is recommended.<\/p>\n\n\n\n

\"\"<\/a><\/figure>\n","protected":false},"excerpt":{"rendered":"

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