{"id":4241,"date":"2026-09-25T00:00:00","date_gmt":"2026-09-25T00:00:00","guid":{"rendered":"https:\/\/chac-electric.com\/?p=4241"},"modified":"2026-10-19T03:36:42","modified_gmt":"2026-10-19T03:36:42","slug":"bo-chuyen-doi-cong-suat-3-cuc-100-amp","status":"publish","type":"post","link":"https:\/\/chac-electric.com\/vi\/blog\/3-pole-100-amp-mcb\/","title":{"rendered":"B\u1ed9 ph\u1eadn MCB 3 c\u1ef1c 100 amp"},"content":{"rendered":"

A B\u1ed9 ph\u1eadn MCB 3 c\u1ef1c 100 amp<\/strong> is a three-pole miniature circuit breaker with a declared current rating of 100 A per pole under its specified conditions. It does not create a single 300 A circuit. Selection requires the line-to-line voltage, current in each phase, available fault current and the exact device configuration. A suitable current rating alone does not establish motor protection, neutral switching or compatibility with a distribution board.<\/p>\n

\"\u1ee8ng<\/p>\n

Read 100 A as a per-phase rating<\/h2>\n

Three-phase currents flow in separate conductors. If each phase carries 80 A, it is not correct to describe the breaker as carrying 240 A against a 100 A limit. Conversely, lightly loaded phases do not compensate for an overloaded phase. Review the load schedule and the most heavily loaded conductor rather than averaging the three readings to justify the selection.<\/p>\n

Power and current are also different quantities. Converting a three-phase power demand to current requires the supply voltage and relevant power-factor or efficiency assumptions. Use the equipment\u2019s input-current information where available, especially for motors and electronic loads, rather than dividing watts by a single phase voltage.<\/p>\n

Confirm the neutral and common-trip arrangement<\/h2>\n

A standard three-pole arrangement connects the three phases; it does not provide an extra neutral pole. A circuit may include a continuous neutral where permitted, but a requirement to disconnect or protect that conductor must be addressed explicitly in the design. Do not put a phase through an unprotected neutral pole as a shortcut.<\/p>\n

Specify the manufacturer\u2019s common-trip construction. Three separate single-pole devices placed next to one another are not automatically equivalent. The related three-phase miniature circuit breaker guide<\/a> explains what the linked device does and which protection functions still require separate consideration.<\/p>\n

Check the conductor, busbar and enclosure at 100 A<\/h2>\n

At this rating, terminations and assembly conditions deserve as much attention as the breaker. Verify the cable ampacity after correction factors, the terminal conductor range, approved busbar system and enclosure temperature limits. The IEC-based selection relationship in the Electrical Installation Guide remains IB \u2264 In \u2264 Iz; a 100 A label does not override a lower cable or assembly limit.<\/p>\n

For an actual product review, compare the CQB2-125 miniature circuit breaker<\/a> information with CHAC\u2019s D\u00f2ng s\u1ea3n ph\u1ea9m c\u1ee7a MCB<\/a>. Confirm the exact 100 A three-pole variant and its technical documentation. A larger catalogue family is a starting point, not evidence that every configuration is available or approved.<\/p>\n

\"S\u1ea3n<\/p>\n

Use the fault study to check breaking capacity<\/h2>\n

Ph\u1ea7n three-phase fault current<\/strong> at the board must be considered independently of the normal operating current. Verify the breaker\u2019s declared short-circuit capacity at the actual voltage and pole arrangement. If backup protection is proposed, obtain the specific tested combination and observe the applicable installation rules; do not infer protection from the upstream device\u2019s larger ampere rating.<\/p>\n

Selectivity is another separate question. Two breakers may both interrupt the fault safely yet trip together, shutting down more of the installation than intended. Use the manufacturer\u2019s coordination data and the project\u2019s continuity requirements to assess that consequence.<\/p>\n

Add motor-specific protection where the load requires it<\/h2>\n

A three-pole distribution MCB does not automatically detect phase loss, phase reversal or damaging imbalance. A motor circuit may need an overload device, a phase-monitoring function and suitable coordination with the contactor. Schneider Electric\u2019s Micrologic FAQ illustrates that even more elaborate breaker systems have model-specific limits on phase-loss detection.<\/p>\n

Choose the \u0110\u01b0\u1eddng cong chuy\u1ebfn \u0111i c\u1ee7a MCB<\/strong> from the documented starting duty and required fault-clearing performance. A C-curve is not a universal motor setting. Keep startup behavior, overload protection and short-circuit interruption as distinct checks so that a device which tolerates starting current is not mistaken for a complete motor-protection scheme.<\/p>\n

What must be confirmed for a 100 A three-pole feeder?<\/h2>\n\n\n\n\n\n\n\n\n
Decision<\/th>\nRequired check<\/th>\nSai l\u1ea7m ph\u1ed5 bi\u1ebfn<\/th>\n<\/tr>\n<\/thead>\n
Normal current<\/td>\nEach phase and corrected cable ampacity<\/td>\nAdding pole ratings to get 300 A<\/td>\n<\/tr>\n
Tr\u00e1ch nhi\u1ec7m sai s\u00f3t<\/td>\nAvailable current at the declared voltage<\/td>\nChoosing by amperes only<\/td>\n<\/tr>\n
Neutral<\/td>\nRequired switching and protection arrangement<\/td>\nAssuming a fourth pole exists<\/td>\n<\/tr>\n
Motor duty<\/td>\nStarting current, overload and phase monitoring<\/td>\nTreating common trip as phase-loss detection<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n
\n

C\u00e1c c\u00e2u h\u1ecfi th\u01b0\u1eddng g\u1eb7p<\/h2>\n

M\u1ed9t c\u1ea7u ng\u1eaft \u0111i\u1ec7n 3 c\u1ef1c 100 A \u0111\u01b0\u1ee3c s\u1eed d\u1ee5ng \u1edf \u0111\u00e2u?<\/h3>\n

C\u00e1c \u1ee9ng d\u1ee5ng ph\u1ed5 bi\u1ebfn bao g\u1ed3m c\u00e1c thi\u1ebft b\u1ecb c\u1ea5p ngu\u1ed3n ba pha, b\u1ea3ng ph\u00e2n ph\u1ed1i nh\u1ecf v\u00e0 c\u00e1c m\u1ea1ch thi\u1ebft b\u1ecb trong ph\u1ea1m vi \u0111i\u1ec7n \u00e1p v\u00e0 c\u1ea5p \u0111\u1ed9 l\u1ed7i c\u1ee7a thi\u1ebft b\u1ecb. \u1ee8ng d\u1ee5ng ph\u1ea3i \u0111\u00e1p \u1ee9ng c\u00e1c quy \u0111\u1ecbnh c\u1ee7a \u0111\u1ecba ph\u01b0\u01a1ng v\u00e0 c\u00e1c gi\u1edbi h\u1ea1n c\u1ee7a nh\u00e0 s\u1ea3n xu\u1ea5t.<\/p>\n

C\u00f3 ph\u1ea3i \u0111\u01b0\u1eddng cong C lu\u00f4n ph\u00f9 h\u1ee3p v\u1edbi \u0111\u1ed9ng c\u01a1 kh\u00f4ng?<\/h3>\n

Kh\u00f4ng ph\u1ea3i l\u00fac n\u00e0o c\u0169ng v\u1eady. \u0110\u01b0\u1eddng cong C c\u00f3 th\u1ec3 ch\u1ecbu \u0111\u1ef1ng d\u00f2ng \u0111i\u1ec7n v\u00e0o v\u1eeba ph\u1ea3i, nh\u01b0ng vi\u1ec7c b\u1ea3o v\u1ec7 \u0111\u1ed9ng c\u01a1 th\u01b0\u1eddng c\u1ea7n m\u1ed9t b\u1ed9 b\u1ea3o v\u1ec7 chuy\u00ean d\u1ee5ng v\u00e0 ph\u1ed1i h\u1ee3p \u0111i\u1ec1u ch\u1ec9nh t\u1ea3i qu\u00e1 t\u1ea3i. S\u1eed d\u1ee5ng d\u00f2ng \u0111i\u1ec7n kh\u1edfi \u0111\u1ed9ng \u0111\u01b0\u1ee3c \u0111o l\u01b0\u1eddng ho\u1eb7c ghi nh\u1eadn.<\/p>\n

C\u00f3 ph\u1ea3i m\u1ed9t c\u00f4ng t\u1eafc MCB 3 c\u1ef1c c\u00f3 th\u1ec3 chuy\u1ec3n sang v\u1ecb th\u1ebf trung t\u00ednh kh\u00f4ng?<\/h3>\n

Thi\u1ebft b\u1ecb ba c\u1ef1c ti\u00eau chu\u1ea9n s\u1ebd m\u1edf c\u00e1c pha \u0111i\u1ec7n. N\u1ebfu c\u1ea7n chuy\u1ec3n \u0111\u1ed5i pha trung t\u00ednh, h\u00e3y ch\u1ec9 \u0111\u1ecbnh ki\u1ec3u k\u1ebft n\u1ed1i b\u1ed1n c\u1ef1c ho\u1eb7c k\u1ebft n\u1ed1i li\u00ean k\u1ebft ch\u00ednh x\u00e1c.<\/p>\n

C\u00e1ch l\u1eafp \u0111\u1eb7t c\u1ea7u ch\u00ec DIN-rail l\u00e0 nh\u01b0 th\u1ebf n\u00e0o?<\/h3>\n

Qualified personnel should follow the exact mounting, terminal, line\/load and tightening instructions. Perform the installation tests required by the adopted rules and commissioning plan; do not improvise a short-circuit test.<\/p>\n

Is a 3-phase breaker rating per phase?<\/h3>\n

Yes, the declared current applies to each pole under the stated conditions. A 100 A three-pole breaker is not a 300 A single-path device, and the least-loaded phase does not offset an overload on another phase.<\/p>\n

How do I calculate an MCB rating for a 3-phase circuit?<\/h3>\n

Determine the load current in each phase using the equipment input data and supply conditions. Then apply the adopted design rules, conductor correction factors, starting-duty review and fault-current check. Round-up arithmetic alone cannot establish the correct protective-device rating.<\/p>\n<\/section>\n

Tham kh\u1ea3o<\/h2>\n