FCP18-05
Asymmetry & Phase Sequence Protection Relay
Adjustable Asymmetry & Phase Protection — Without Over/Under Voltage Monitoring
The FCP18-05 is a focused three-phase monitoring relay combining two essential protection functions — adjustable voltage asymmetry (unbalance) and phase sequence/loss detection — in a single ultra-compact 18mm DIN rail module. Designed for applications where over/under voltage protection is handled separately or is not required.
The FCP18-05 offers a 5%~15% adjustable asymmetry threshold, making it ideal for protecting sensitive three-phase equipment where fine-tuning of voltage unbalance sensitivity is essential. The wide 0.1~30 second adjustable time delay ensures compatibility with both fast-trip requirements and motor-start-tolerant applications.
Quick Specifications
Why Choose the FCP18-05?
The dedicated asymmetry specialist — adjustable sensitivity for precise equipment protection.
2-in-1 Protection
Adjustable asymmetry and phase sequence/loss monitoring — focused protection without over/under voltage for cost-effective applications.
5%~15% Adjustable Asymmetry
Fine-tune the voltage unbalance trip threshold to match the exact tolerance of your sensitive equipment, from robust motors to precision CNC machines.
16A SPDT Output Relay
High-capacity SPDT output handles direct motor and contactor switching. Mechanical life 10 million cycles, electrical life 100,000 cycles.
Tool-Free Configuration
Two front-panel adjustment button (Asy, Tt) allow fast, screwdriver-free setup. No programming or software tools required.
0.1~30s Adjustable Delay
Configurable time delay from 0.1s to 30s adapts to both fast-trip requirements and motor starting conditions.
Two Protection Functions
Focused asymmetry monitoring with phase sequence/loss protection — no over/under voltage function.
The FCP18-05 monitors two fault conditions: adjustable voltage asymmetry and phase sequence/loss. The asymmetry function continuously calculates the unbalance ratio using the formula: Asy = (Umax − Umin) / Uavg × 100%. When this ratio exceeds the adjustable threshold (set between 5% and 15%), the relay trips after the configured time delay (Tt). The phase sequence function monitors the L1, L2, L3 phase order and immediately detects when any phase is interrupted or reversed.
The FCP18-05 does not include over-voltage or under-voltage monitoring. For complete voltage protection including OV/UV, see the FCP18-03 (fixed 8% asymmetry + OV/UV) or FCP18-04 (5%~15% adjustable + OV/UV).
1. Voltage Asymmetry / Unbalance Detection (Asy)
Voltage asymmetry (also called voltage unbalance) occurs when the three phase voltages are not equal in magnitude. This is one of the most common causes of three-phase motor overheating and premature failure. The FCP18-05 continuously calculates the unbalance ratio using the formula: Asy = (Umax − Umin) / Uavg × 100%. When this ratio exceeds the adjustable threshold set via the front-panel Asy setting (between 5% and 15%), the relay trips after the configured Tt delay.
- Trip threshold: 5%~15% adjustable via Asy setting (vs. fixed 8% on FCP18-03/06)
- Formula: Asy = (Umax − Umin) / Uavg × 100%
- Trip time: After Tt delay elapses (0.1s to 30s adjustable)
- Use case: Ideal when adjustable sensitivity is needed — not provided by fixed-threshold models
2. Phase Sequence & Phase Loss Protection
The FCP18-05 continuously monitors the rotational sequence of the three-phase supply (L1 → L2 → L3). If the phase sequence is reversed or any phase is interrupted (open circuit, blown fuse, or cable fault), the relay immediately detects the fault and trips. The red P LED on the front panel provides instant visual status: lit = correct sequence, flashing = fault detected.
- P LED lit (steady): All three phases present and in correct rotation sequence
- P LED flashing: Phase loss (one or more phases missing) or phase sequence reversed
- Trip behavior: Immediate — no additional time delay for phase loss/sequence faults
- Protection scope: Detects single-phase loss, two-phase loss, and reversed phase wiring errors
Technical Specifications
Full electrical and mechanical specifications for the FCP18-05 series.
| Parameter | FCP18-05A / 05C | FCP18-05B / 05D |
|---|---|---|
| System Type | 3-Phase 3-Wire (L1-L2-L3) | 3-Phase 4-Wire (L1-L2-L3-N) |
| Voltage Range (L-L) | 173-275V AC (A) / 310-480V AC (C) | N/A for 4-wire models |
| Voltage Range (L-N) | N/A for 3-wire models | 100-160V AC (B) / 180-278V AC (D) |
| Rated Frequency | 45Hz - 65Hz | 45Hz - 65Hz |
| Voltage Tolerance | −15% to +10% | −15% to +10% |
| Over/Under Voltage | None | None |
| Asymmetry Setting | 5%~15% adjustable (front setting) | 5%~15% adjustable (front setting) |
| Time Delay (Tt) | 0.1s, 3s, 6s, 9s, 12s, 15s, 18s, 20s, 25s, 30s | 0.1s, 3s, 6s, 9s, 12s, 15s, 18s, 20s, 25s, 30s |
| Measurement Accuracy | ΔV less than ±1% | ΔV less than ±1% |
| Temperature Coefficient | 0.05%/°C at 20°C | 0.05%/°C at 20°C |
| Output Contact | 1 × SPDT (NO+NC) | 1 × SPDT (NO+NC) |
| Rated Current | 16A / 250V AC | 16A / 250V AC |
| Mechanical Life | 1 × 107 operations | 1 × 107 operations |
| Electrical Life | 1 × 105 operations | 1 × 105 operations |
| Ambient Temperature | −20°C to +60°C | −20°C to +60°C |
| Mounting | DIN Rail EN/IEC 60715 (35mm) | DIN Rail EN/IEC 60715 (35mm) |
| Dimensions (H × W × D) | 90 × 18 × 64 mm | 90 × 18 × 64 mm |
| Weight | 68g | 68g |
| IP Rating | IP20 | IP20 |
| Standards | GB/T 14048.5, IEC60947-5-1, EN61812-1 | GB/T 14048.5, IEC60947-5-1, EN61812-1 |
Voltage codes: A = 173-275V L-L (3-wire) | B = 100-160V L-N (4-wire) | C = 310-480V L-L (3-wire) | D = 180-278V L-N (4-wire). Other voltages available on request.
Terminal Connections
SPDT relay output with screw-clamp terminals for fast, reliable wiring.
FCP18-05A / 05C — 3-Phase 3-Wire (L1-L2-L3)
FCP18-05B / 05D — 3-Phase 4-Wire (L1-L2-L3-N)
- Always de-energize the panel before wiring
- Verify supply voltage matches the module rating before powering on
- Connect L1, L2, L3 (and N for 4-wire models) to the corresponding system phases
- Terminal 11 = Common, 12 = NC, 14 = NO — wire your load to the appropriate contact
- Use correct wire gauge for 16A load current (min. 1.5mm²)
- Tighten terminal screws to 0.4 N·m torque specification
- Stripping length: 7mm (AWG13-20)
Front Panel & Settings
Configure the FCP18-05 using three adjustment settings — no software or programming tools required.
| Parameter | Description | Setting Range |
|---|---|---|
Un |
Rated Input Voltage (system voltage) — the nominal voltage of the three-phase installation | See voltage code table in Models section |
Asy |
Voltage Asymmetry (unbalance) — setting to set the unbalance trip threshold for your equipment sensitivity | 5% to 15% (adjustable) |
Tt |
Time Delay before trip — the delay period the relay waits before confirming an asymmetry fault | 0.1s, 3s, 6s, 9s, 12s, 15s, 18s, 20s, 25s, 30s |
LED Indicator Panel
Un — Green LED
Lit = relay is powered on and monitoring the system
P — Red LED
Lit = correct phase sequence. Flashing = phase reversal). Off = phase loss
R — Red LED
Lit = NO contact (terminals 11-14) is closed, relay is energized
⚙ How to Set Parameters
- Enter setting mode: Press and hold the button until the LED starts flashing.
- Adjust settings: Set
Un,Asy, andTtto your desired values while the LED is flashing. - Confirm: Press and hold the button until the LED stops flashing to save your settings.
Note: When the green LED is on, add 1% to the asymmetry setting reading to get the actual trip threshold. For example, if the Asy setting reads 8% and the green LED is lit, the actual asymmetry trip point = 9%.
Models & Ordering
Choose the voltage configuration that matches your three-phase system.
| Model Code | System Type | Voltage Range (L-L) | Voltage Range (L-N) | Manual |
|---|---|---|---|---|
| FCP18-05A | 3-Phase 3-Wire | 173, 190, 198, 208, 220, 230, 240, 250, 260, 275 V | N/A | PDF ↓ |
| FCP18-05B | 3-Phase 4-Wire | N/A | 100, 110, 115, 120, 127, 133, 139, 145, 151, 160 V | PDF ↓ |
| FCP18-05C | 3-Phase 3-Wire | 310, 328, 345, 365, 380, 400, 415, 440, 460, 480 V | N/A | PDF ↓ |
| FCP18-05D | 3-Phase 4-Wire | N/A | 180, 190, 200, 210, 220, 232, 240, 255, 266, 278 V | PDF ↓ |
FCP18 Family — Model Comparison
Compare all six FCP18 series models to find the right protection configuration for your application.
| Model | Over-voltage | Under-voltage | Asymmetry | Time Delay | Phase Seq. | Phase Loss | Ideal For |
|---|---|---|---|---|---|---|---|
| FCP18-01 | — | — | — | 5s fixed | ✓ | ✓ | Phase sequence/loss only, budget applications |
| FCP18-02 | ✓ | ✓ | — | 0.1~30s | ✓ | ✓ | OV/UV + phase protection — cost-effective motor & pump protection |
| FCP18-03 | ✓ | ✓ | 8% fixed | 0.1~30s | ✓ | ✓ | Full protection incl. fixed asymmetry — general motor & compressor |
| FCP18-04 | ✓ | ✓ | 5%~15% adj. | 5s fixed | ✓ | ✓ | Adjustable asymmetry + OV/UV — CNC, medical, precision equipment |
| FCP18-05 | — | — | 5%~15% adj. | 0.1~30s | ✓ | ✓ | Adjustable asymmetry + phase only — dedicated unbalance monitoring |
| FCP18-06 | 15% fixed | 15% fixed | 8% fixed | 0.1~30s | ✓ | ✓ | Fixed asymmetry + phase protection, no OV/UV adjustment |
Configuration Examples
Real-world setting examples for common three-phase system voltages.
FCP18-05A — 208V System
| Un (Voltage) | 208V |
| Asy (Adj.) | 8% (standard motor) |
| Tt (Delay) | 5s |
FCP18-05C — 400V CNC System
| Un (Voltage) | 400V |
| Asy (Adj.) | 5% (precision CNC, sensitive) |
| Tt (Delay) | 3s (fast response) |
FCP18-05B — 120V System
| Un (Voltage) | 120V |
| Asy (Adj.) | 10% |
| Tt (Delay) | 12s (motor start tolerance) |
FCP18-05D — 230V Robust Motor
| Un (Voltage) | 230V |
| Asy (Adj.) | 12% (robust industrial motor) |
| Tt (Delay) | 20s (heavy load tolerance) |
See It In Action
Watch the FCP18 series product overview and demonstration.
Typical Applications
The FCP18-05 is purpose-built for asymmetry monitoring across a wide range of industrial sectors.
CNC & Machine Tools
Precision protection for CNC machines, VFD-controlled equipment, and automated precision machinery with adjustable sensitivity.
HVAC & Compressors
Protect compressors and HVAC equipment where asymmetry monitoring with adjustable sensitivity is required.
Power Distribution
Panel-level asymmetry monitoring in LV/MV switchgear and distribution boards.
Medical Equipment
Protects sensitive medical three-phase equipment requiring precise adjustable asymmetry sensitivity.
Industrial Automation
Precision asymmetry protection for PLC-controlled systems and robotic automation equipment.
Ready to Order or Need More Details?
Download the full technical manual or contact the FIICCO team for pricing, samples, and OEM options.
Frequently Asked Questions
Common questions about the FCP18-05 asymmetry protection relay
The FCP18-05 does not include over-voltage or under-voltage monitoring — it focuses solely on asymmetry and phase sequence/loss protection. The FCP18-04 includes OV/UV protection (adjustable ±2%~20%) in addition to asymmetry and phase functions. The FCP18-05 is the right choice when you need adjustable asymmetry monitoring but handle OV/UV protection separately or do not need it at all.
Both the FCP18-05 and FCP18-06 lack over/under voltage monitoring and focus on asymmetry + phase protection. The key difference is the asymmetry threshold: the FCP18-05 has an adjustable threshold (5%~15%), while the FCP18-06 has a fixed 8% threshold. The FCP18-05 is better suited for applications where the ideal asymmetry sensitivity must be tuned to match specific equipment requirements.
A lower threshold (5-8%) provides stricter protection and is recommended for precision equipment such as CNC machines, medical devices, and variable frequency drives (VFDs) where even slight voltage unbalance can cause overheating or malfunction. A higher threshold (10-15%) is suitable for more robust industrial motors that can tolerate slight imbalance without damage.
No. The FCP18-05 is specifically designed for three-phase systems and requires three-phase input (L1, L2, L3) to operate. For single-phase voltage monitoring, consider a single-phase voltage monitoring relay from FIICCO's product range.
The time delay setting depends on your application. For fast-trip protection without motor starting conditions, use a short delay such as 0.1s or 3s. For motor protection where inrush current causes brief voltage dips during startup, use a longer delay (e.g., 12s, 20s, or 30s) to prevent nuisance tripping. The FCP18-05's 0.1~30s adjustable range covers both scenarios.
The FCP18-05 has a single SPDT (single-pole double-throw) relay contact rated 16A/250V AC. Terminal 11 is the common, 12 is normally closed (NC), and 14 is normally open (NO). Wire your load between terminal 11 and terminal 14 for normally open operation — the circuit is energized when the relay trips.
The FCP18-05 is certified to CE, RoHS, and meets the standards of IEC 60947-5-1, GB/T 14048.5, and EN 61812-1. This makes it suitable for industrial automation applications in Europe, Asia, and other global markets.
Yes. FIICCO provides OEM services including custom branding (logo, model number, color), tailored specifications, and custom packaging for orders of 100+ units. Factory-direct pricing ensures competitive costs for OEM customers. Contact us at info@fiicco.com with your requirements and quantity for a tailored quotation.