Kwakọtara maka Ọdịnala na Nkwalite Nri Na Medium-Voltage Motor Site n'ụzọ Ekwupụta Coal ma gbanwee Vacuum Contactor-Fuse (VCF)

1. Tarihi na Projekt

Sistem na kofa mai taimaka 15 na motoci masu sanka ta ƙarfin wata da suka yi aiki a wurin hanyoyi. A cikin ɗaya daga cikin hanyoyi, ana iya kara mafi yawan muhimmanci ga motoci kuma haɗa sa. Don ƙarin ingantaccen gudanar da taimakawa masu kyau a lokacin da motoci ya faru, an samu fadada tsari na VCF (Vacuum Contactor-Fuse) don taimakawa masu sanka ta ƙarfin wata da 6kV. Wannan bayanin ya bayyana matsayin na fadada, muhimmanci, da kuma tushen bayanai na VCF, wanda ke taimaka waɗanda suke aiki a wurin hanyoyi na ɗaya.

2. Muhimmanci da Fadada Tsarin VCF

2.1 Na'urar Barazan da Fadada Tsarin Kwalbar

• ​Tsarin Baraza: Wannan baya ne ke amfani da VCF mai tsarin da za a iya kula da shi, a kunshi da ake kula da shi da kuma ake salo shi.
• ​Fadada Tsarin: An amfani da kompozit mai kwalbar da resin epoxy da Automatic Pressure Gelation (APG) don kwalbar, wanda ke zama da shi a kan vacuum interrupter, wanda ke zama da shi a kan resin epoxy, wanda ke zama da shi a kan kwalbar, mahimmanci, da kuma ƙarfin tsarin al'amuran.
• ​Mahimmiyar Gidajen: Mahimmiyar gidajen an yi aiki da shi da kula da shi da kuma ake kula da shi.

2.2 Ƙananan Tsarin da Muhimmancin Ingantacce

• ​Tsarin Baraza: VCF an samun tsarin mai yadda da high-voltage current-limiting fuses (wanda ke iya kara mafi yawan muhimmanci ga short-circuit currents) da VCX vacuum contactors, wanda ke iya aiki da shi har zuwa lokacin, wanda ke samun tsarin F-C.
• ​Muhimmanci: Yana da zaman lafiya mai yawa, ƙarfin tsarin, da kuma ƙarfin lafiya.
• ​Ingantacce: Ana amfani da shi a cikin power systems na thermal power plants, da kuma a cikin industries na metallurgical, petrochemical, da mining. Yana da zaman lafiya don kawo ƙarfin da kuma taimakawa masu sanka ga high-voltage motors, transformers, da induction furnaces.

2.3 Ƙarfin Ingantacce da Fadada Tsarin Lafiya

• ​Barazan na Cabinet: VCF withdrawable unit yana da tsarin da yake da circuit breaker withdrawable units a 800mm-width middle-mounted switchgear, wanda ke iya kula da shi saboda hakan.
• ​Barazan na Kula da Shiga: Tsarin withdrawable yana iya kula da shi da kuma ake kula da shi da kula da shi a kan cabinet.
• ​Barazan na Holding: Vacuum contactor zai iya amfani da electrical ko mechanical holding saboda abubuwan customer.
• ​Fadada Tsarin Phase-Loss: An amfani da phase-loss protection. Idan ana karɓe phase, fuse zai iya kula da shi da kuma ake kula da shi don kula da VCF motor circuit, wanda ke taimaka waɗanda suke aiki a wurin hanyoyi na ɗaya.

3. Muhimmanci na Fadada Tsarin (7.2kV Rating)

4. Principle na Taimakawa Masu Sanka

VCF taimakawa masu sanka an samun mafi yawan muhimmanci:

• ​Low Current Range (< 4kA)​: Vacuum contactor ke iya kula da shi don kula da shi da kuma ake kula da shi.
• ​High Current Range (> 4kA)​: High-voltage fuse ke iya kula da shi don kula da shi da kuma ake kula da shi.
• ​Curve Coordination: Protection curve na contactor an samun mafi yawan muhimmanci saboda curve na circuit breaker, wanda ke taimaka waɗanda suke aiki a wurin hanyoyi na ɗaya. Saboda hakan, an samu fadada tsarin da take da shi da kuma ake kula da shi don kula da shi.

5. Muhimmanci na VCF vs. Vacuum Circuit Breaker

Don motor loads na ƙarfin faru da kula da shi, VCF yana da muhimmanci masu yawa saboda vacuum circuit breakers:

6. Core of VCF Selection: Fuse Selection Guide

The performance of VCF hinges on correct fuse selection, considering the following factors:
Working voltage, working current, motor starting time, starts per hour, motor full-load current, and short-circuit current at the installation point.

6.1 Selection Rules and Steps

1. ​Rated Voltage: The fuse’s rated voltage must not be lower than the system working voltage (7.2kV in this case).
2. ​Rated Current Calculation:
• Use the formula: Iy=N×In×δI_y = N \times I_n \times \deltaIy​=N×In​×δ
• IyI_yIy​: Equivalent current during starting (A)
• NNN: Starting current to full-load current ratio (typically 6)
• InI_nIn​: Motor rated full-load current (A)
• δ\deltaδ: Comprehensive coefficient (based on starts per hour, n, from the table below)

1. ​Curve Matching: Plot the calculated IyI_yIy​ value and the motor’s starting time on the fuse manufacturer’s time-current characteristic curve. Select the fuse rated current corresponding to the curve immediately to the right of this point.
2. ​Additional Check: The selected fuse’s rated current must be ​**> 1.7 times the motor’s full-load current**.

6.2 Selection Example

For a 7.2kV system with a directly started 250kW high-voltage motor:
In=30AI_n = 30AIn​=30A, 16 starts per hour, starting time of 6s.

• Calculation: Iy=6×30A×2.1=378AI_y = 6 \times 30A \times 2.1 = 378AIy​=6×30A×2.1=378A
• Selection: On the fuse time-current curve, locate the curve to the right of the point (378A, 6s), corresponding to a fuse rated current of 100A.
• Verification: 100A > 1.7 × 30A (51A), meeting the requirement. Thus, a 100A or higher-rated high-voltage motor protection fuse can be selected.

7. Conclusion

From a comprehensive cost-performance analysis:

• While vacuum circuit breakers have lower procurement costs, their shorter operational life makes them unsuitable for frequent starts/stops, leading to higher long-term maintenance costs and failure risks.
• The VCF solution combines the advantages of vacuum contactors (long life, low overvoltage, suitability for frequent operation) and fuses (ultra-fast interruption of short-circuit currents), all at an economical overall cost.
• For the coal conveying system and other applications with frequent operation and heavy-load starting characteristics, VCF is an ideal solution offering high performance, reliability, and cost-effectiveness.