Motor + Terminal Blocks (TB10·TB4) — the Panel Boundary
We've covered the panel entrance (MCCB + fuse) and the switch that drives the motor (MC). This guide reaches the destination of all that electricity — the motor — and the terminal blocks (TB) that bridge inside-panel to outside-panel.
Motor U·V·W·PE — where electricity becomes torque
- U · V · W — L1·L2·L3 arrive staggered slightly in time, creating a rotating magnetic field that drags the rotor around with it. The whole "why does a 3-phase motor spin?" answer in one line: the supply arrives staggered, and the field spins to follow.
- PE — protective bonding provides a fault-current path for protective disconnection; it is not a guarantee against shock by itself.
Terminal blocks TB10 · TB4 — the screw bridges across the boundary
A motor is too big, too hot, and too vibration-prone to live inside the panel. So it always sits *outside*, and only the wires cross the boundary. The bridge that makes that crossing clean is the terminal block (TB) — a pass-through part where each top screw is wired straight to the bottom screw below it.
If it's just a pass-through, why fit one? Two reasons.
- Mechanical isolation — the stiff single-conductor wire inside the panel and the flexible cable outside meet at one neat junction, while separate cable fixing/strain relief must handle mechanical loads.
- Serviceability — the labeled boundary makes tracing and disconnecting the motor circuit easier after safe isolation.
A TB10 has ten poles; which poles are used depends on the drawing. There is no universal rule to use only 4/5/6/7. Follow the project terminal schedule.
Terminal-block ordering — read the designated terminals
For the full terminal rules, see Wire color & terminal rules.
The path electricity takes to the motor
Press the button and current runs end-to-end in one path:
Power → TB4 (cable inlet) → TB10 (top) → MCCB → MC main → TB10 (bottom) → TB4 (motor side) → Motor (U·V·W)
- Current crosses the panel boundary twice — once on the way in (top), once on the way out (bottom).
- PE (green-yellow in the cited instructions) skips the breaker and the MC, passing straight through the four terminal blocks to reach the motor's frame.
Next
That wraps up the main-circuit parts block (protection → switch → load + boundary). Next come the parts that energize their own coils on a condition — EOCR (trips on overcurrent) and the timer (acts after a delay). See all guides →
Try it yourself
Open the practical project list →
Check your understanding
Question: Can any spare terminal be used to route a connection?
Answer: No. Confirm that it belongs to the same electrical node; a spare pole can be a different circuit.
Practice path and references
The practical project list may require sign-in. Create a project, choose a task and place the relevant components, then compare the contact/wiring paths explained here. The link does not preload a specific completed circuit.
Reference: Q-Net public-problem notice, 2025-08-04 edition, problem 14 pages 11-1 to 11-4 (work/wiring instructions) and 11-9 (component diagrams). Read the original for each task and any amendments. Site examples are distinct from general installation design requirements.