Marble Factory Switchgear Sizing Guide Pakistan 2026 — Cutter, Polisher, Compressor BoM
What switchgear does a Pakistani marble factory need?
A typical 50–200 kW Pakistani marble-processing factory needs: ACB or MCCB main incoming (sized 1.25× total connected load), per-motor MCCB+contactor+overload starter for each cutter / polisher / compressor / dust-collector, capacitor bank for power-factor correction (eliminates Rs. 200-400/kW NEPRA MD penalty), ATS for backup-generator transfer, and Type 2 AC SPDs at main + sub-DB. Built to IEC 60947-2 (MCCB), IEC 60947-4-1 (contactor + overload), IEC 60831-1 (PFC capacitor), and IEC 60947-6-1 (transfer switching). Total switchgear investment: PKR 500K–2.5M depending on factory size.
Typical Pakistani marble factory load profile
| Equipment | Typical kW | FLA (400V 3φ) | Quantity per factory |
|---|---|---|---|
| Block cutter (gang saw) | 75 kW | ~145 A | 1–2 |
| Bridge cutter | 22 kW | ~42 A | 2–4 |
| Edge polisher (line) | 15 kW | ~29 A | 1–3 |
| Air compressor (screw) | 37 kW | ~70 A | 1 |
| Dust-collection fan | 7.5 kW | ~14 A | 1–2 |
| Water-recycling pump | 5.5 kW | ~11 A | 1–2 |
| Office / lighting load | 10–15 kW | ~20–30 A | 1 panel |
Mid-size factory (100 kW connected) — switchgear BoM
| Component | Spec | CNC SKU | PKR |
|---|---|---|---|
| Main incoming MCCB | 4P 250A 35kA | YCM7-250 4P | 14,300 |
| Bridge cutter starter (each) | 3P MCCB 63A + CJX2 50A + JR28S | YCM1-100 + CJX2i-50A + JR28S | 15,000 × 2 |
| Edge polisher starter (each) | 3P MCCB 40A + CJX2 32A + JR28S | YCM1-100 + CJX2i-32A + JR28S | 10,500 × 2 |
| Air compressor starter | 3P MCCB 100A + CJX2 80A + JR28S | YCM7-100 + CJX2i-80A + JR28S | 25,000 |
| Dust + water pump starters | 3P MCB 20-32A + CJX2 18A + JR28S each | YCB7 3P + CJX2i-18A + JR28S | 8,000 × 2 |
| Lighting/office sub-DB | 4P RCBO 63A 30mA + 8× 1P MCBs | YCB6HLN 4P + YCB7 1P | 12,000 |
| PFC capacitor bank | 3-step automatic 90 kvar (1×50 + 1×25 + 1×15) + JKW5C | BSMJ0.44 + JKW5C | 42,000 |
| ATS (grid → 100 kVA generator) | 4P motorised 200A | YCQ6 4P 200A | 38,000 |
| Type 2 AC SPD at main + each sub-DB | 4P 40kA 385V × 3 | YCS6-B | 15,000 |
| DB enclosures (main + 3 sub) | Steel YCX6 24-way + 3× 16-way | YCX6 | 23,400 |
| Subtotal switchgear | ~226,200 |
Plus cabling (~PKR 80,000), labour (~PKR 50,000), panel fabrication (~PKR 60,000) = total ~PKR 420,000 for a 100kW marble factory installation.
Why PFC is mandatory in a marble factory
Marble cutters and polishers run at poor power factor (0.65–0.75) due to induction motors. Without correction, NEPRA / DISCO penalises commercial sites at PF < 0.90:
- 100 kW connected load at PF 0.70: kVA = 100/0.70 = 142.8 kVA
- Reactive load Q = √(142.8² − 100²) = 102 kvar
- To reach PF 0.95: target Q = 100 × tan(arccos 0.95) = 32.9 kvar; need to absorb 102 − 33 = 69 kvar
- Install 70 kvar bank (1×50 + 1×15 + 1×5 or 1×25+1×25+1×15+1×5) in 3-4 steps for automatic load matching
- NEPRA penalty avoided: ~Rs. 20,000-40,000/month saved
- Payback: 3-5 months on the capacitor bank cost
Common Pakistani marble-factory installer mistakes
- Direct-online start of 75 kW gang saw — LRA 500+ A causes voltage dips on the rest of the factory. Use star-delta or soft-starter to limit inrush.
- Skipping dust-collector earth bonding — marble-dust static buildup ignites in the duct. Bond all metal ductwork to factory earth.
- Single-frame MCCB for all motors — uses 250A frame everywhere. Right-size each motor: 25/63/100A frames. Saves PKR 50K+ on a mid-factory.
- No discrimination between main + sub-DB MCCBs — a small motor short-circuit trips the entire factory. Cascade: main 250A 35kA → sub 100A 25kA → motor 32-63A.
- Capacitor bank without de-tuned reactor — cutter VFDs inject 5th, 7th harmonics that resonate with the cap bank and blow it open. Install 7% de-tuned reactor (mandatory if any VFD on site).
- PFC controller programmed for fixed PF target — light-load nights overcorrect to leading PF (also penalised). Use a JKW5C controller with min-step and dead-band settings.
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