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The problem
Three-phase supply faults are among the most common causes of motor damage in industry: a reversed phase sequence can spin a motor backward into mechanical damage, and a lost phase (single-phasing) overheats the remaining windings within minutes. Protection practice therefore relies on two ideas every electrical engineer must internalize — sequence detection and phase-failure monitoring — yet in college labs both are taught only as theory. This project closes that gap with a safe low-voltage demonstration panel: a 24 V 3-phase equivalent supply feeds a rotating-lamp phase-sequence indicator (R-Y-B vs R-B-Y), and a phase-failure relay supervises the same supply and trips a contactor when any phase is lost or badly unbalanced, cutting a small demo load while lighting an alarm lamp. Selector switches let the demonstrator deliberately swap two phases or drop one phase and watch the protection respond. Everything runs at extra-low voltage behind clearly labeled terminals, so the panel is safe to demonstrate live in a classroom or viva.
Low-voltage 3-phase trainer supply, isolated and fused for safe live demos.
Follow the working sequence
How it works
- A low-voltage 3-phase supply (approximately 24 V AC line-to-line equivalent, isolated and fused) feeds the panel input terminals.
- The phase-sequence indicator circuit connects three lamps so that with correct R-Y-B sequence they light in rotating order (clockwise chase); with any two phases swapped the rotation reverses (counter-clockwise).
- The phase-failure relay continuously supervises all three phases for loss, severe voltage unbalance and phase reversal, driving front-panel status LEDs.
- When the relay detects a fault it opens its output contact after its set trip delay (approximately 1–5 s), dropping the contactor coil.
- The contactor's main contacts open and disconnect the demo load (a small lamp/motor model), while an auxiliary contact lights the trip lamp and sounds the buzzer.
- Using the selector switches the demonstrator can introduce a swapped sequence or a dropped phase; pressing the reset push button restores normal operation once the selector is returned to healthy.
Tech stack:
- 24 V AC 3-phase equivalent supply (isolated, fused)
- Phase sequence indicator module (rotating-lamp type)
- Phase-failure / single-phasing relay with trip delay
- 3-pole contactor with auxiliary contacts
- Panel-mount selector switches and push buttons
- Indicating lamps (red/yellow/blue + trip lamp), buzzer
- DIN rail, terminal strips, panel enclosure
| Parameter | Value |
|---|---|
| Supply | 24 V AC 3-phase equivalent, isolated (design target) |
| Sequence indication | Lamp rotation; CW = R-Y-B, CCW = R-B-Y |
| Relay supervision | Phase loss, unbalance, reversal (module dependent) |
| Trip delay | Approximately 1–5 s, adjustable (design target) |
| Contactor | 3-pole, coil matched to trainer supply (approximate) |
| Demo load | Low-voltage lamp / small motor model (approximate) |
| Panel size | Approximately 450 × 350 × 120 mm (design target) |
| Safety | ELV throughout; fused supply; labeled terminals |
| Alarm | Trip lamp + buzzer, manual reset |
Project features
- [Rotating-lamp sequence indicator] Three phase lamps wired in sequence-detection order that visually chase clockwise for R-Y-B and counter-clockwise for R-B-Y, making correct vs reversed sequence instantly readable.
- [Phase-failure / single-phasing relay] A dedicated supervision relay that detects phase loss, severe unbalance and (on supported modules) phase reversal, with adjustable trip delay and LED status indication.
- [Contactor trip demonstration] The relay's output contact drops a 3-pole contactor that switches the demo load, so tripping is a real power-circuit interruption — not a simulation on a microcontroller pin.
- [Deliberate-fault selector switches] Panel-mounted selectors let the demonstrator swap two phases or drop any single phase at will, so sequence reversal and single-phasing can be reproduced repeatably for an audience.
- [Low-voltage safe trainer] Runs on an extra-low-voltage 3-phase equivalent (approximately 24 V AC) with a fused, isolated supply and clearly labeled terminals — safe to operate live in a lab or viva hall.
- [Alarm and status indication] Separate trip/alarm lamp plus buzzer annunciate the fault, with a reset push button that restores the contactor once the fault is cleared.
- [Hand-wired panel construction] DIN-rail mounted components with marked terminal strips and a wiring diagram in the documentation, so the build itself demonstrates standard panel-wiring practice.
What is included
- Assembled and wired demonstration panel (relay, contactor, lamps, selectors)
- Isolated low-voltage 3-phase trainer supply
- Wiring diagram and terminal chart
- Project report PDF (theory: sequence, protection, build, demonstration procedure)
- PPT presentation for final review
- Viva Q&A preparation document (sequence vs reversal, single-phasing effects, relay settings)
- Operating and fault-injection procedure sheet
Limitations & prerequisites
- Extra-low-voltage trainer only — it does not connect to 230/415 V mains and cannot demonstrate real mains-level protection behavior; sequence detection is shown at approximately 24 V AC.
- The demo uses a lamp/motor model as load, not a real 3-phase induction motor; effects like actual motor heating during single-phasing are explained in the report, not reproduced.
- Relay trip characteristics are those of the supplied protection module — timing and unbalance thresholds are approximate module ratings, not calibrated measurements.
- The exact unbalance level that triggers a trip depends on the module; very small voltage dips may not trip it — this is a module limit, stated in the documentation.
- The panel demonstrates protection logic; it is not a certified protection device and must never be wired into a real installation.
Frequently Asked Questions
How does the lamp rotation show phase sequence?
The three lamps are wired so that with R-Y-B sequence they chase in clockwise order; swapping any two phases reverses the rotation to counter-clockwise. It is the classic electrical-trade sequence test rendered as a visible demo.
What faults does the relay demonstrate?
Phase loss (single-phasing), severe voltage unbalance, and phase reversal on modules that support it — each drops the contactor and raises the trip alarm after the set delay.
Is it safe to demonstrate live?
Yes — the entire panel runs at extra-low voltage (approximately 24 V AC) from an isolated, fused supply with labeled terminals. It never connects to mains.
Can it run a real 3-phase motor?
No — the load side is a low-voltage lamp/motor model. The panel demonstrates detection and tripping logic; motor behavior under faults is covered in the report's theory section.
What is single-phasing and why does it matter?
Losing one phase of a 3-phase supply forces the remaining two to carry the load, overheating motor windings — one of the most common causes of industrial motor burnout, which is exactly why phase-failure relays are standard protection.
Is this project suitable for a final-year project?
Yes — for Electrical Engineering programs. It covers 3-phase fundamentals, sequence, unbalance, protection relaying and panel wiring, with a live, repeatable demonstration. Suitable for B.E./B.Tech final-year projects in Electrical Engineering.
Components & software requirements
- 24 V AC 3-phase equivalent supply (isolated, fused)
- Phase sequence indicator module (rotating-lamp type)
- Phase-failure / single-phasing relay with trip delay
- 3-pole contactor with auxiliary contacts
- Panel-mount selector switches and push buttons
- Indicating lamps (red/yellow/blue + trip lamp), buzzer
- DIN rail, terminal strips, panel enclosure
Delivery information
Built-to-order project. Delivery timeline is shared after order confirmation based on current queue.
Support terms
Complete documentation, setup guide, and viva preparation included. Support for setup and explanation provided.
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