MCB MCCB Selection Chart & Calculator | Motor Breaker Sizing Guide
MCB / MCCB Selection Master Calculator
Complete breaker sizing tool with FLC calculation, cable coordination, trip curve selection & PDF report download
Motor Protection
Lighting Load
Heater / Welding
PDF Download
Breaker Selection Input / Breaker Input
Calculation Results / Results
Recommended Protection / Suggested Breaker
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- Full Load Current (FLC) -- A
- Starting / Inrush Current -- A
- Safety Factor Applied --
- Calculated Rating -- A
- Standard Rating Selected -- A
- Breaking Capacity (Icu) -- kA
- Trip Curve Type --
- Selection Status --
Cable Sizing / Cable size
Minimum Required
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Recommended Size
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Voltage Drop
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Cable derating ambient & grouping ke liye already included.
Download Report / PDF
Complete calculation report with formulas download karein.
Quick Tip
Motor load ke liye hamesha starting current check karo. Type D curve DOL motor ke liye best hai.
Formulas Used / Calculation Formula
FLC = (P × 1000) / (√3 × V × PF × Î·)
Variables: P = Power in kW | V = Voltage (V) | PF = Power Factor | η = Efficiency
3-Phase: √3 (1.732) se multiply karte hain
1-Phase: Sirf V se divide karte hain, √3 nahi lagta
Starting Current: DOL mein 6x FLC, Star-Delta mein 2x, VFD mein 1.2x
3-Phase: √3 (1.732) se multiply karte hain
1-Phase: Sirf V se divide karte hain, √3 nahi lagta
Starting Current: DOL mein 6x FLC, Star-Delta mein 2x, VFD mein 1.2x
Safety Guidelines / Safety Tips
- MCB sirf overcurrent & short-circuit protection ke liye — overload ke liye OLR lagao
- Motor ke liye Type C (5-10x) ya Type D (10-20x) trip curve use karo
- Lighting ke liye Type B (3-5x) kaafi hai
- MCCB 100A se upar ke load ke liye — thermal & magnetic dono setting adjustable hoti hai
- Cable size hamesha breaker rating se zyada hona chahiye
- Industrial panel mein 10kA minimum breaking capacity rakho
MCB Trip Curve Comparison Chart
| Type | Instantaneous Trip | Best For | Applications | Starting Current |
|---|---|---|---|---|
| Type B | 3 - 5 × In | Residential / Light Commercial | Lighting, computers, TV, fans | Low inrush |
| Type C | 5 - 10 × In | Commercial / Small Industrial | Motors up to 5kW, AC, pumps, lifts | Moderate inrush |
| Type D | 10 - 20 × In | Industrial / Heavy Motor | Big motors >5kW, compressors, cranes | High inrush |
| MCCB | Adjustable | Main Distribution / Panel | DB incomer, main supply, 100A+ loads | Variable |
Standard MCB & MCCB Ratings (A)
| MCB Ratings (A) | MCCB Ratings (A) | Typical Application |
|---|---|---|
| 6, 10, 16, 20, 25 | 100, 125, 160 | Lighting, small appliances, sub-main |
| 32, 40, 50, 63 | 200, 250, 315 | Motors 1-15kW, AC units, pumps |
| 80, 100 | 400, 630, 800 | Main DB, big motors, distribution |
| - | 1000, 1250, 1600+ | Main incomer, LT panel, substation |
Quick Unit Converter / Unit Conversion
1 HP = 0.746 kW
Horsepower to Kilowatt
1 kW = 1.36 HP
Kilowatt to Horsepower
kW = kVA × PF
kVA to kW (PF needed)
1 kW = 1000 W
Watt Conversion
Live Converter / Quick Convert
HP =
kW
kVA × 0.85 =
kW
Frequently Asked Questions / Common Questions
Q1: MCB aur MCCB mein kya farq hai?
MCB (Miniature Circuit Breaker): 0.5A se 100A tak ka load handle karta hai. Ghar aur chhote commercial setup mein use hota hai. Fixed thermal-magnetic setting hoti hai.
MCCB (Molded Case Circuit Breaker): 100A se 2500A tak ka load. Industrial panels, main distribution boards mein use hota hai. Adjustable thermal & magnetic dono setting hoti hai — trip current ko precisely set kar sakte ho.
Short mein: 100A se neeche = MCB, 100A se upar = MCCB.
MCCB (Molded Case Circuit Breaker): 100A se 2500A tak ka load. Industrial panels, main distribution boards mein use hota hai. Adjustable thermal & magnetic dono setting hoti hai — trip current ko precisely set kar sakte ho.
Short mein: 100A se neeche = MCB, 100A se upar = MCCB.
Q2: Motor ke liye Type C ya Type D kaunsa MCB best hai?
Type C (5-10x FLC): Chhote motors ke liye — jaise 1HP se 5HP tak, jahan starting current zyada nahi hai. Agar motor DOL se start ho rahi hai aur 5kW se chhoti hai, Type C kaafi hai.
Type D (10-20x FLC): Bade motors, compressors, cranes, pumps ke liye. DOL starting mein 6-8x current hoti hai, Type D isko tolerate karta hai bina trip kiye.
Rule: Motor > 5kW + DOL = Type D. Motor < 5kW ya Star-Delta/VFD = Type C.
Type D (10-20x FLC): Bade motors, compressors, cranes, pumps ke liye. DOL starting mein 6-8x current hoti hai, Type D isko tolerate karta hai bina trip kiye.
Rule: Motor > 5kW + DOL = Type D. Motor < 5kW ya Star-Delta/VFD = Type C.
Q3: MCB ka breaking capacity (kA) kya hota hai aur kitna hona chahiye?
Breaking Capacity (Icu): Short-circuit current ki maximum value jo MCB safely break kar sakta hai bina damage ke. Agar panel mein fault current 10kA hai aur MCB ki capacity 6kA hai — toh MCB blast ho sakta hai!
Recommended:
Recommended:
- Residential: 6kA kaafi hai
- Commercial small: 10kA
- Industrial / Factory: 25kA se 50kA
- Main LT Panel: 65kA+ (fault current calculation ke baad)
Q4: Breaker rating direct motor HP se kaise nikaalein bina calculation ke?
Quick Thumb Rule for 3-Phase Motors:
- 1 HP motor → 2A FLC → 6A MCB Type C
- 3 HP motor → 4.5A → 10A MCB Type C
- 5 HP motor → 7.5A → 16A MCB Type C/D
- 7.5 HP motor → 11A → 20A MCB Type D
- 10 HP motor → 14A → 25A MCB Type D
- 15 HP motor → 21A → 32A MCB Type D
- 20 HP motor → 28A → 40A MCCB
- 30 HP motor → 42A → 63A MCCB
- 50 HP motor → 70A → 100A MCCB
Q5: Cable size aur breaker ka relation kya hai? Breaker bada aur cable chhoti kyun nahi chahiye?
Principle: Breaker ka kaam hai overload hone pe circuit ko kaatna. Agar breaker 63A ka hai aur cable sirf 4mm² (27A capacity) ki hai — toh 40A jaane pe cable garam hoke fire laga degi, breaker trip nahi hoga!
Rule of Coordination:
Rule of Coordination:
- Cable Current Capacity > Breaker Rating > Load Current
- Always: Cable size breaker se bada hona chahiye
Q6: Voltage drop ka calculation kyun dikhaya hai aur maximum kitna allowed hai?
Voltage Drop: Jab current lambe cable se jaata hai toh resistance ki wajah se voltage kam ho jaata hai. Motor pe proper voltage nahi milegi toh:
- Starting torque kam hoga — motor load se start nahi hogi
- Motor garam hogi — insulation damage hoga
- Efficiency gir jayegi — bill zyada aayega
- Lighting circuits: Max 3% voltage drop allowed
- Power / Motor circuits: Max 5% voltage drop allowed
- Main distribution: Max 2.5%
Q7: MCB ke saath OLR (Overload Relay) kyun lagate hain?
MCB: Short-circuit (instant 1000A+) aur thoda overload (1.13x to 1.45x) handle karta hai. Lekin motor ki winding 110% se zyada load pe slowly heat hokar jal sakti hai — MCB isko immediate detect nahi karta.
OLR (Overload Relay): Sirf overload ke liye bana hai. Motor current continuously monitor karta hai. Agar current set value se zyada jaati hai (jaise 105% ya 120%) — toh contactor ko trip kar deta hai.
Final Protection Setup for Motor:
OLR (Overload Relay): Sirf overload ke liye bana hai. Motor current continuously monitor karta hai. Agar current set value se zyada jaati hai (jaise 105% ya 120%) — toh contactor ko trip kar deta hai.
Final Protection Setup for Motor:
- MCCB/MCB: Short-circuit + moderate overload
- Contactor: Switching control
- OLR: Thermal overload protection
- SPD: Surge protection (optional)
Q8: Star-Delta starter ke liye breaker kaise select karein? 3 breakers lagte hain na?
Yes! Star-Delta mein 3 contactors hain: Main, Star, aur Delta. Breaker sirf ek incoming MCCB/MCB lagta hai jo pura circuit protect kare.
Breaker Selection for Star-Delta:
FLC = 28A → Breaker = 32A or 40A Type C MCCB
Cable = 16mm² (68A capacity) minimum
Breaker Selection for Star-Delta:
- Star-Delta mein starting current only 2x FLC hoti hai (vs 6x in DOL)
- Isliye Type C breaker kaafi hai, Type D ki zaroorat kam hai
- Breaker rating = 1.25 × Motor FLC
FLC = 28A → Breaker = 32A or 40A Type C MCCB
Cable = 16mm² (68A capacity) minimum
Q9: 1-Phase MCB selection ka formula alag hai?
Haan, 1-Phase mein √3 (1.732) nahi lagta!
1-Phase Formula:
Current (A) = Power (W) / Voltage (V)
Example: 2kW, Single Phase geyser
Current = 2000W / 230V = 8.7A
Safety factor 1.25x → 10.8A
Recommended: 16A Type B MCB (next standard size)
Common 1-Phase Loads:
1-Phase Formula:
Current (A) = Power (W) / Voltage (V)
Example: 2kW, Single Phase geyser
Current = 2000W / 230V = 8.7A
Safety factor 1.25x → 10.8A
Recommended: 16A Type B MCB (next standard size)
Common 1-Phase Loads:
- Geyser 2kW → 16A MCB
- AC 1.5 Ton → 10A-16A Type C
- Refrigerator → 6A Type B
- Washing machine → 10A Type C
- Home main (3kW total) → 32A/40A MCB
Q10: Generator ke output breaker ka size kaise calculate karein?
Generator Breaker Formula:
Current = kVA / (√3 × V) for 3-Phase
Current = kVA / V for 1-Phase
Example: 62.5 kVA, 3-Phase Generator
Current = 62500 / (1.732 × 415) = 87A
Safety factor 1.2x → 104A
Recommended: 125A MCCB (next standard)
Breaking capacity: Minimum 25kA
Tips:
Current = kVA / (√3 × V) for 3-Phase
Current = kVA / V for 1-Phase
Example: 62.5 kVA, 3-Phase Generator
Current = 62500 / (1.732 × 415) = 87A
Safety factor 1.2x → 104A
Recommended: 125A MCCB (next standard)
Breaking capacity: Minimum 25kA
Tips:
- Generator breaker hamesha 1.25x rated current se zyada ka ho
- AVR failure pe overvoltage protection bhi rakho
- Earth leakage protection (ELCB) must hai DG set ke liye
Cable Current Capacity Reference (PVC Insulated)
| Cable Size (mm²) | 1-Phase Current (A) | 3-Phase Current (A) | Motor Capacity (Approx) |
|---|---|---|---|
| 1.5 | 15 | 13 | Up to 1 HP |
| 2.5 | 20 | 18 | Up to 2 HP |
| 4 | 27 | 24 | Up to 3 HP |
| 6 | 36 | 32 | Up to 5 HP |
| 10 | 50 | 45 | Up to 7.5 HP |
| 16 | 68 | 60 | Up to 15 HP |
| 25 | 91 | 80 | Up to 20 HP |
| 35 | 115 | 100 | Up to 25 HP |
| 50 | 145 | 125 | Up to 40 HP |
| 70 | 185 | 160 | Up to 50 HP |
| 95 | 225 | 195 | Up to 60 HP |
| 120 | 260 | 225 | Up to 75 HP |
| 150 | 300 | 260 | Up to 100 HP |
| 185 | 345 | 300 | Up to 125 HP |
| 240 | 410 | 355 | Up to 150 HP |
Values are approximate for PVC insulated copper cable at 35°C ambient. For armoured / XLPE cables, capacity 15-20% higher. Always refer to manufacturer catalogue for exact values.
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