Контактор,автоматический выключатель,солнечный инвертор,электрический счетчик,солнечные батареи
Self-locking wiring for three-phase motors (also known as “self-holding wiring”) is the most commonly used motor control method in industrial field applications. Its core principle is to use the auxiliary normally open contact of the контактор to maintain continuous power supply after the start button is released. It does not require manual holding of the start button, and the control circuit can be cut off only by pressing the stop button. This solution is applicable to various types of three-phase asynchronous motors (such as pumps, фанаты, conveyors, и т. д.). The following is a highly structured and practical technical document, including core principles, wiring steps, component selection, Поиск неисправностей, и т. д..
- Core Principles and Wiring Logic
- Core Logic of Self-Locking
Start Phase: Press the start button → the control circuit is energized → the contactor coil is powered on → the main contacts close (the motor runs), and at the same time, the auxiliary normally open contacts close synchronously (replacing the start button to keep the circuit energized).
Self-Locking Phase: Release the start button → the auxiliary normally open contacts are already closed, the control circuit remains energized → the contactor keeps pulling in → the motor runs continuously.
Stop Phase: Press the stop button → the control circuit is disconnected → the contactor coil loses power → both the main contacts and auxiliary contacts open → the motor stops.
- Composition of the Wiring System
| Circuit Type | Core Components | Function Description |
| Основная схема | Three-phase power supply (Л1/Л2/Л3), автоматический выключатель (Q), contactor main contacts (KM1), thermal relay heating elements (FR), three-phase motor (U/V/W) | Provides power supply for motor operation, and realizes overload and short-circuit protection |
| Схема управления | Control power supply (например, AC220V/DC24V), stop button (SB1, нормально закрытый), start button (SB2, нормально открытый), contactor coil (KM1), contactor auxiliary normally open contact (KM1-1), thermal relay normally closed contact (FR-1) | Implements motor start, self-locking and stop control, and overload protection linkage |
- Preparations Before Wiring
- Component Selection (Matching Motor Parameters)
| Component Name | Selection Basis (Taking a 5.5kW motor as an example, 380V/50Hz, rated current ≈ 11A) | Рекомендуемые модели (Refer to the previous LS/Schneider/Chint brands) |
| AC Contactor | Rated current ≥ 1.2~1.5 times the motor rated current, AC-3 duty | LS MC-18b (18А), Schneider LC1D1201, Chint CJX2-1810 |
| Thermal Relay | Setting current range covers the motor rated current | LS GTH-22, Schneider LRD12C (6.3~10A), Chint JR36-20 |
| Автоматический выключатель (Air Switch) | Rated current ≥ 1.3 times the motor rated current, short-circuit breaking capacity ≥ 6kA | LS Metasol MCB, Schneider C65N-C16, Chint DZ47-60 C16 |
| Push Button Switch | Normally closed stop button + normally open start button (waterproof, industrial grade) | Schneider XB2-BS542 (stop) + XB2-BA511 (start), Chint NP2-BS502 |
| Wire | Main circuit: copper core wire ≥ 2.5mm² (current-carrying capacity ≥ 16A); Control circuit: copper core wire ≥ 1.0mm² | RVB/RV1.0 (control), BV2.5 (main circuit) |
- Tool and Safety Preparation
Tools: Screwdriver, wire crimping tool, multimeter (continuity/voltage range), insulating tape, wire markers.
Safety: Power off and verify no voltage (ensure the three-phase power supply has no voltage), wear insulating gloves, and keep the working area free of flammable materials.
III. Core Wiring Steps (Divided into Main Circuit + Схема управления)
- Main Circuit Wiring (Power Circuit, 380V High-Voltage Part)
| Step | Wiring Operation | Примечания |
| 1 | Connect the three-phase power supply incoming lines (Л1/Л2/Л3) to the input terminals of the circuit breaker (Q) | The circuit breaker model must match the motor power; tighten the wiring terminals to prevent overheating |
| 2 | Connect the output terminals of the circuit breaker to the input terminals of the contactor (KM1) main contacts (usually marked L1/L2/L3) | Match the main contacts with the wires and crimp firmly (avoid poor contact and ablation) |
| 3 | Connect the output terminals of the contactor main contacts to the input terminals of the thermal relay (FR) heating elements | The thermal relay must match the motor rated current; preset the setting current to the motor rated value in advance |
| 4 | Connect the output terminals of the thermal relay heating elements to the three-phase motor terminal box (U/V/W) | The motor wiring method (star/delta) must be consistent with the nameplate; the wiring sequence ensures the motor runs forward (swap any two phases if reverse rotation occurs) |
| 5 | Ground the motor housing (PE wire) | Grounding resistance ≤ 4Ω to ensure leakage protection |
- Control Circuit Wiring (Схема управления, Low-Voltage Part, Taking AC220V as an Example)
| Step | Wiring Operation | Core Logic |
| 1 | Power supply for control circuit: Lead the control wire from any phase of the main circuit (например, L1) → connect to one end of the stop button (SB1) normally closed contact | Stop button is normally closed: conducts under normal conditions, disconnects the control circuit when pressed |
| 2 | Connect the other end of the stop button (SB1) → to one end of the start button (SB2) normally open contact | Start button is normally open: conducts when pressed, disconnects when released (needs self-locking contact to replace) |
| 3 | Connect the other end of the start button (SB2) → to two branches: | The auxiliary normally open contact is connected in parallel with the start button to realize self-locking |
| ① Connect to one end of the contactor auxiliary normally open contact (KM1-1) (self-locking branch); | ||
| ② Connect to one end of the contactor coil (KM1) | ||
| 4 | Connect the other end of the contactor auxiliary normally open contact (KM1-1) → to converge with the other end of the start button (merge the two branches) | Ensure that the auxiliary contact keeps the control circuit energized after releasing the start button |
| 5 | Connect the other end of the contactor coil (KM1) → to one end of the thermal relay normally closed contact (FR-1) | When the thermal relay is overloaded, the normally closed contact disconnects to cut off the control circuit and protect the motor |
| 6 | Connect the other end of the thermal relay normally closed contact (FR-1) → to the neutral line (Н) or another phase (например, L2) of the control power supply to form a complete circuit | The control voltage must match the coil rated voltage (например, AC220V needs to be connected to L+N, DC24V needs to be connected to positive and negative poles) |
- Standard Wiring Diagram (Simplified Illustration)
Основная схема: L1/L2/L3 → Circuit Breaker Q → Contactor KM1 Main Contacts → Thermal Relay FR → Motor U/V/W
Схема управления: L1 → Stop Button SB1 (Нормально закрытый) → Start Button SB2 (Нормально открытый) → Contactor Auxiliary Normally Open KM1-1 (Parallel with SB2) → Contactor Coil KM1 → Thermal Relay FR-1 (Нормально закрытый) → N
- Self-Locking Function Testing and Verification
| Test Step | Метод работы | Expected Result |
| 1 | Pre-power-on inspection | Use a multimeter to measure that the control circuit has no short circuit, and the main circuit insulation resistance ≥ 1MΩ |
| 2 | Close the circuit breaker and supply power | The circuit breaker is closed, and the control power indicator light is on (if equipped) |
| 3 | Start test | Press SB2 (start) → KM1 pulls in (audible pull-in sound), the motor runs; release SB2 → the motor continues to run (self-locking successful) |
| 4 | Stop test | Press SB1 (stop) → KM1 loses power, the motor stops; release SB1 → the motor does not restart |
| 5 | Overload protection test | Manually simulate overload (например, jam the motor shaft) → the thermal relay FR operates, KM1 loses power, the motor stops |
- Common Troubleshooting (Related to Self-Locking)
| mon Troubleshooting (Related to Self-Locking) | ||
| Fault Phenomenon | Possible Causes | Solutions |
| 1. The motor runs when the start button is pressed, but stops immediately when released | ① The contactor auxiliary normally open contact (KM1-1) is not connected or has poor contact; | ① Check if the auxiliary contact wiring is correct (connected in parallel across SB2); |
| ② The auxiliary contact is oxidized or ablated; | ② Use a multimeter continuity range to test the auxiliary contact, polish the oxide layer with fine sandpaper, and replace the contact if severely damaged; | |
| ③ The wiring of the self-locking branch is loose | ③ Tighten the wiring terminals of the self-locking branch | |
| 2. No response when the start button is pressed, KM1 does not pull in | ① The control power supply is not connected (например, N line is not connected); | ① Measure the control power supply voltage (например, 220 В переменного тока), check the N line wiring; |
| ② The stop button SB1 (нормально закрытый) is open-circuited; | ② Use a multimeter to test SB1 and replace the damaged button; | |
| ③ The coil is burned out or the coil voltage does not match; | ③ Measure the coil resistance (normally several hundred to several thousand ohms) and replace the coil with the same voltage specification; | |
| ④ The thermal relay FR-1 (нормально закрытый) has operated and not reset | ④ Press the thermal relay reset button and check the cause of overload | |
| 3. The contactor jitters and makes abnormal noise after pulling in, and self-locking is unstable | ① The control voltage is too low (lower than 80% of the coil rated voltage); | ① Measure the control voltage and adjust it to the allowable range of the coil; |
| ② Poor contact of the auxiliary contact; | ② Clean or replace the auxiliary contact; | |
| ③ Loose installation leading to vibration | ③ Tighten the contactor mounting screws to reduce vibration | |
| 4. Unable to stop the motor | ① The stop button SB1 (нормально закрытый) is stuck; | ① Replace the SB1 button; |
| ② The contactor main contacts are stuck; | ② Power off and check the main contacts, replace the contactor if stuck; | |
| ③ The self-locking branch is short-circuited | ③ Check the wires of the self-locking branch for short circuits and repair the insulation |
- Wiring Specifications and Safety Points
- Wire Number Marking: Each wire in the control circuit must be marked with a wire number (например, L1 → wire No.1, both ends of SB1 → wire No.1/2) for easy maintenance.
- Terminal Tightening: All wiring terminals must be tightened firmly to avoid overheating and poor contact caused by large currents (especially important for the main circuit).
- Coil Protection: An RC surge suppressor can be connected in parallel with AC coils, and a freewheeling diode can be connected in parallel with DC coils to extend the coil service life.
- Dual Protection: A thermal relay (защита от перегрузки) and a circuit breaker (защита от короткого замыкания) must be equipped; they are not allowed to be omitted.
- Характеристики проводки: Separate the main circuit and control circuit during wiring (main circuit on top, control circuit at the bottom) to avoid electromagnetic interference; the wire bending radius ≥ 10 times the wire diameter, and the insulation layer must not be damaged.
VII. Типичные сценарии применения
Three-phase motors that run continuously: например, водяные насосы, фанаты, conveyors, machine tool spindles, и т. д..
Unattended automation equipment: such as production line conveyors, packaging machinery, и т. д..
Compatible with various AC contactors mentioned earlier, such as LS MC-10b contactor (for controlling motors ≤ 5.5kW), Серия Шнайдер LC1D, Chint CJX2 series, и т. д..
