كيفية استخدام ثلاثة مرحلات للحمل الزائد مع موصل واحد

عادة, one قواطع paired with one three-phase thermal overload relay is sufficient to protect a three-phase motor. However, in special scenarios where three overload relays are required (على سبيل المثال, for precise phase-by-phase monitoring or adaptation to special loads), this can be achieved by means of phase-separated series connection in the main circuit plus series connection of contacts in the control circuit. Below is the detailed implementation method, covering both installation and wiring practices:

1. Preliminary Preparation & Component Matching

– Select three overload relays of the same specification (على سبيل المثال, thermal or electronic type). Their rated current must match the rated current of the protected load (على سبيل المثال, motor). It is recommended to set the adjustable current to 1.1–1.2 times the rated current of the load. في أثناء, ensure that the rated current of the contactor’s main contacts is greater than the maximum operating current of the load, and the coil voltage is consistent with the control circuit power supply (على سبيل المثال, 220الخامس و, 380الخامس و).

– Prepare auxiliary components and tools such as circuit breakers, terminal blocks, and screwdrivers. Always cut off the main power supply before operation to avoid electric shock.

2. Phase-Separated Wiring for Main Circuit (Core: One-to-One Monitoring)

The core of the main circuit is to have the three overload relays monitor the three-phase output lines of the contactor individually. The specific steps are as follows:

1. First, connect the three live wires (L1, L2, L3) output from the circuit breaker to the incoming terminals of the three groups of main contacts of the contactor.
2. Connect the outgoing terminals of the three groups of main contacts of the contactor to the main circuit incoming terminals of the three overload relays respectively, ensuring that each overload relay is only connected in series in one phase line.
3. Then, connect the main circuit outgoing terminals of the three overload relays to the three-phase terminals of the three-phase load (على سبيل المثال, motor) correspondingly to complete the phase-separated monitoring layout of the main circuit.
4. Series Wiring for Control Circuit (Core: Interlock Protection)

The control circuit requires the protection contacts of the three overload relays to be connected in series, ensuring that the contactor power supply is cut off if any overload relay is activated. The steps are as follows:

1. Take one power supply from the control power source and connect it to one end of the stop button (مغلقة عادة). Connect the other end of the stop button to the start button (normally open).
2. Connect the other end of the start button in parallel with the auxiliary normally open contact of the contactor (to achieve self-locking function), and then connect it in series with the normally closed contacts of the three overload relays. When an overload occurs, the normally closed contacts of the overload relay will open, so the series connection realizes the function of “one overload point triggers full-circuit shutdown”.
3. After connecting the normally closed contacts of the overload relays in series, connect them to one end of the contactor coil. Connect the other end of the contactor coil back to the neutral line of the control power supply (for 220V control circuit) or another live wire (for 380V control circuit) to form a complete control circuit.
4. Installation, Fixation & Commissioning

– If the overload relays support plug-in installation (على سبيل المثال, Siemens 3RU series), they can be fixed next to the contactor via matching brackets. For conventional models, fix them independently in the distribution box with screws to ensure that the terminal blocks are free from loosening.

– During commissioning, first adjust the current value via the adjustable knob on the overload relay. Then manually press the start button and observe that the contactor pulls in and the load operates normally. Temporarily lower the adjustable current of one overload relay to simulate an overload and check whether the contactor can disconnect promptly.

– If overload alarm is required, connect the normally open contacts of the three overload relays in parallel and then access the circuit of the alarm light or audible-visual alarm. The contacts will close to trigger the alarm when an overload occurs.