Weekly Prog
TOMZN 1NO 1NC DIN Rail Single Phase Weekly Programmable Timer Switch
AC 220V/230V
16A Relay
7 Days Digital
Factory Direct Catalog
Featured Phase Monitoring, Timing & Intelligent Protection Relays
High-precision DIN-rail protection instruments manufactured to IEC/EN 60947 standards. Pre-calibrated for phase loss, asymmetrical voltage detection, cycle timing, and industrial telemetry.
Smart BLE
TOMZN TOS7-B Bluetooth Smart Timer Switch 40A/63A EasyCon App Remote
85-265V AC
40A / 63A
28 Timing Groups
DIN / Wall
TOS6-40 Bluetooth Time Control Switch 35mm DIN Rail & Wall Mount
AC85-265V
40A Heavy Duty
Loop Countdown
Wall Mount
TOMZN Bluetooth Smart Timer Switch 85-265VAC 10A/30A Loop Timing
EasyCon App
10A / 30A
Precision Loop
10-in-1 Multi
TORT7 10-in-1 Asymmetric Cycler Time Relay & Delay-ON/OFF Controller
0.1S-10 Days
Pulse Gen
Universal Span
New Gen
TOMZN New Type Single Phase Weekly Digital TIME SWITCH Relay
AC 220V/230V
16A Micro-prog
Anti-Jam Memory
Phase Guard
63A 3P+N Three-Phase Failure, Sequence & Voltage Monitor Relay
Phase Loss Trip
Unbalance Sensing
Auto-Reset
Dual ATS
DIN Rail 3-Phase Automatic Transfer Switch with Phase Interlock 63A-125A
3P / 4P High Amp
<50ms Transfer
Phase Safe
TÜV Rheinland Audited OEM/ODM Manufacturing Plant
Direct supply from Huabei Village, Liushi Town, Wenzhou, Zhejiang — China's low-voltage electric capital. Over 24 years of manufacturing resilience, certified ISO9001 quality management, and export verification across 100+ sovereign jurisdictions.
24+
Years In Electrical Manufacturing
5,700m²
Verified Production Floorspace
$3.3M+
Annual Audited Export Volume
100%
Full Cycle Dielectric & Trip Testing
Technical Whitepaper
Physics of Phase Failure: Negative Sequence Sensing & Motor Protection
Why conventional overcurrent relays fail to prevent catastrophic winding burnout during phase loss events, and how modern electronic phase failure relays calculate negative sequence voltage components.
In three-phase industrial power distribution networks, phase failure (also colloquially termed single-phasing) represents one of the most destructive electrical fault conditions encountered by polyphase induction motors, compressor systems, and automated production machinery. When one phase of a three-phase power feed is interrupted due to a blown high-voltage utility fuse, a mechanical contactor fault, a severed transmission conductor, or localized cable shearing, an operating three-phase induction motor does not instantly stall. Instead, the rotating machine continues to operate on the remaining two energized phases by acting as a rotary phase converter, generating a hazardous operational condition characterized by severe voltage and current asymmetry.
The Phantom Threat: Regenerated Rotor Back-EMF
A common point of engineering failure in rudimentary protection panels is relying purely on scalar voltage thresholds to detect open-phase events. When an induction motor is rotating at rated velocity while experiencing an open supply conductor, the mechanical momentum of the rotor cuts across the magnetic stator field of the two functioning phases.
This dynamic interaction induces an electromagnetic back-EMF (electromotive force) directly onto the terminal of the severed phase conductor. In motors running under partial mechanical load (30% to 70% nominal output), this regenerated phase voltage can measure up to 90% to 95% of the nominal line-to-neutral voltage. A basic electromechanical voltage sensing relay simply cannot differentiate this phantom regenerated back-EMF from a healthy utility supply line.
Meanwhile, current within the remaining functional stator coils surges to 173% to 230% of rated full-load amperage (FLA). Because the thermal time constant of winding insulation (Class F or Class H enamel) is exponentially degraded by thermal dissipation spikes according to the Arrhenius rate equation, stator core temperatures double every 8 to 10 minutes under sustained unbalance, resulting in inter-turn dielectric breakdown, short-circuit fire hazards, and catastrophic motor destruction.
Mathematical Rigor: Symmetrical Component Analysis
Under Fortescue's theorem of symmetrical components, any unbalanced 3-phase system of voltages can be decomposed into three balanced vector components: Positive Sequence ($V_1$), Negative Sequence ($V_2$), and Zero Sequence ($V_0$).
$V_{unbalance} = \frac{|V_2|}{|V_1|} \times 100\%$ (IEC 60034-1 Standard Definition)
While the positive sequence voltage creates the forward-rotating magnetic flux ($+ \omega$), the negative sequence voltage ($V_2$) introduces a counter-rotating magnetic flux field ($- \omega$) rotating against the mechanical direction of the rotor at double slip frequency ($2 - s \approx 2$). This creates intense eddy-current surface heating in the rotor bars and massive parasitic braking torque, causing extreme heating with negligible shaft output.
Key Protective Functions of TMB Industrial Relays:
- Dynamic Phase Loss Trip: Instantaneous disconnect (< 100ms) upon conductor shearing, immune to rotary back-EMF.
- Reverse Phase Sequence Sensing: Immediate lockout if vector rotation switches from L1-L2-L3 to L1-L3-L2, preventing reverse machine rotation.
- True-RMS Voltage Unbalance Monitoring: User-calibrated sensitivity from 5% to 15% unbalance margins.
- Definite / Inverse Time Delays: Eliminates nuisance tripping caused by grid-switching capacitor transients.
Manufacturing Ecosystem
The Liushi Electric Cluster: Why Sourcing Directly from Wenzhou Matters
Unveiling the geographic and supply chain architecture that enables Zhejiang TMB Electric Co., Ltd. to deliver unmatched component-level traceability, engineering versatility, and factory-direct cost economics.
5-Kilometer Supply Chain Radius
Situated in Huabei Village, Liushi Town (Yueqing, Wenzhou), our manufacturing facility sits within the world's most concentrated low-voltage apparatus ecosystem. Precision bimetal elements, silver cadmium oxide (AgCdO) and silver tin oxide (AgSnO2) contact tips, halogen-free flame-retardant polyamide (PA66-V0) casings, and specialized toroidal magnetic transformers are all precision-sourced within minutes of our assembly floor.
TÜV Rheinland Third-Party Audit
Unlike pure export trading intermediaries that outsource production with volatile tolerances, Zhejiang TMB Electric Co., Ltd. operates a physical 5,700 m² verified factory with 92 staff. Independent TÜV Rheinland on-site audits verify our automated SMT pick-and-place lines, automated lead-free wave soldering, high-voltage dielectric isolation bays, and calibration benches.
Full OEM & Custom Architecture
We provide global distributors, panel builders, and switchgear brands with end-to-end customization: proprietary firmware programming for custom unbalance tolerances, customized trip response curves (0.1s to 30s), wide-range dual-frequency coils (50/60Hz, 110V to 480VAC), laser private-label engraving, and complete custom-molded distribution enclosure assemblies.
Integrated Relay Assembly & Testing Center
High-Precision Microcontroller SMT Facility
Liushi Headquarters: 5,700 m² Production Base
Product Evolution
The Generational Leap: From Bimetallic Strips to Digital DSP & IoT Telemetry
How China's premier relay manufacturers navigated the four evolutionary waves of motor protection technology, and what modern engineers must demand from current-generation hardware.
| Architectural Generation | Operating Principle | Phase Loss Detection Speed | Rotary Back-EMF Immunity | Harmonic Distortion Handling | Modern Application Status |
|---|---|---|---|---|---|
| Generation 1: Thermal Bimetallic Overload | Differential mechanical expansion of deflection bimetallic strips | Sluggish (30s to 180s depending on thermal mass) | Extremely Poor (Cannot detect phase loss directly; relies on secondary overcurrent) | Immune (Pure thermal reaction), but highly inaccurate | Legacy installations; high motor failure risk |
| Generation 2: Analog Solid-State Op-Amp | Discrete operational amplifier networks calculating DC rectified phase voltages | Moderate (1.0s to 3.0s) | Moderate (Trips only if back-EMF drops below 80% nominal) | Vulnerable (Susceptible to wave clipping and noise spikes) | Low-cost basic pump starters |
| Generation 3: Microcontroller True-RMS | High-speed 16-bit / 32-bit MCU computing real-time FFT symmetrical vector matrices | Ultra-Rapid (50ms to 200ms programmable) | Complete 100% Immunity (Identifies phase angle deflection and $V_2$ components) | Superior (Digital FIR filtering isolates fundamental 50/60Hz frequency) | Current Global Standard for Industrial Motor Control Centers |
| Generation 4: Connected IoT & Edge Relays | Integrated DSP with BLE, Wi-Fi, RS485 Modbus-RTU, and cloud telemetry | Real-time continuous predictive monitoring (< 20ms fault capture) | Absolute (Continuous phase vector and unbalance trend logging) | Active harmonic distortion spectrum analysis up to the 15th harmonic | Emerging Smart Microgrids, Industry 4.0, Remote Solar Hybrid Plants |
Variable Frequency Drive (VFD) Inverter Compatibility
A critical engineering consideration in modern facilities is the presence of high-order switching harmonics ($5^{\text{th}}, 7^{\text{th}}, 11^{\text{th}}, 13^{\text{th}}$) generated by PWM IGBT inverters and power factor correction capacitors. Legacy analog relays experience severe false tripping or failing-to-trip states when harmonic voltages distort zero-crossing points.
Zhejiang TMB Electric’s Gen 3 and Gen 4 DIN-rail relays utilize digital finite impulse response (FIR) filtering to process pure fundamental sinusoidal vectors, ensuring rock-solid stability even in electrically noisy industrial environments.
Dual-Function Microgrid & Generator ATS Integration
As commercial buyers combine rooftop solar PV arrays with emergency standby diesel generators, phase monitors must bridge grid-tied inverters and automatic transfer switches (ATS). An unresolved phase loss on a commercial grid line will disrupt an inverter’s synchronizing phase-locked loop (PLL).
Our 3P/4P automated systems detect grid unbalance within milliseconds, cleanly commanding ATS transfer contacts to isolate vulnerable equipment before backfeeding or rotor stalls occur.
Market Forecasting
Future Procurement Trends: How B2B Buyers Must Source Phase Failure Relays (2025–2030)
Navigating supply chain localization, total cost of ownership (TCO) modeling, micro-customization, and international compliance across European, Middle Eastern, and American procurement corridors.
Consolidated Low-Voltage BOM Procurement
Leading international EPC contractors and panel builders are discontinuing multi-vendor sourcing models in favor of unified supply chain partnerships. Sourcing your phase failure relays, miniature circuit breakers (MCBs), contactors, DC combiner boxes, and ATS units from a single verified factory like Zhejiang TMB Electric reduces shipping container fragmentation, harmonizes DIN-rail aesthetic geometry, and guarantees consistent dielectric terminal torque standards across entire control boards.
Total Cost of Ownership (TCO) Optimization
Purchasing cheap non-certified relays with inferior cadmium-poor copper alloys yields an elevated failure rate in mission-critical environments. A single unscheduled downtime event on an industrial chiller compressor or municipal irrigation pump costs thousands of dollars per hour. Sourcing verified TÜV-audited relays with certified electrical endurance of 100,000 switching operations at nominal load ensures long-term operational peace of mind.
Ultra-Flexible Minimum Order Quantities (MOQ)
Traditional state-owned Chinese manufacturing giants enforce restrictive container-load MOQs (500 to 2,000 units), stifling agile engineering distributors. TMB Electric disrupts this paradigm by offering catalog sample trial MOQs starting at 1 to 5 pieces, enabling rapid prototyping, field validation, and low-risk custom branding pilots before launching scaled volume container runs.
Engineering Matrix
B2B Device Selection Guide: Matching Phase & Timing Relays to Load Types
Use this definitive application matrix to engineer correct protection topologies across HVAC chillers, submersible pumps, heavy industrial conveyors, and automated standby generators.
| Target Industrial Load | Critical Threat Mechanism | Recommended Relay Topology | Configurable Delay Window | Standard Auxiliary Contacts |
|---|---|---|---|---|
| Centrifugal Water Pumps & Submersibles | Reverse motor spinning caused by phase sequence inversion; dry-run overheating | Phase Failure + Phase Sequence + Under-Current Relay | 0.5s – 10s Adjustable Delay | 1 NO / 1 NC (5A 250VAC) |
| Hermetic HVAC Scroll & Screw Compressors | Rapid winding failure under phase loss; high back-EMF masking fault | Negative Sequence Voltage Unbalance Relay (Adjustable 5%-15%) | < 0.2s Trip; 3-5min Reconnection Lockout | 2 CO (Changeover) |
| Overhead Cranes, Elevators & Hoists | Phase reversal causing hoist to drop rather than lift; catastrophic safety hazard | Instantaneous Phase Sequence & Phase Loss Interlock Relay | Instantaneous (< 0.1s definite trip) | Mechanically Interlocked Dual Outputs |
| Automatic Standby Diesel Generator Sets | Utility grid brownouts, floating neutral displacement, and single-phasing | 3-Phase 4-Wire (3P+N) Over/Under Voltage + Phase Monitor | 1s – 30s Start Signal Delay; 60s Cool-down | Isolated Dry Voltage-Free Contacts |
| Industrial Automation Cyclers & Mixers | Uneven duty cycle heating; asynchronous dosing cycle drift | TORT7 Series 10-in-1 Asymmetric Cycler / Time Relay | 0.1s to 10 Days Independent On/Off Times | 1 CO / 2 CO Silver Alloy Pins |
Quality Assurance
Inside Zhejiang TMB Electric: 6-Tier Zero-Defect Manufacturing Protocol
Every phase failure relay, digital timer switch, and modular circuit protection device produced at our Wenzhou base undergoes rigorous inspection checkpoints before customs clearance.
01
Incoming Material Spectrometry
Metallurgical composition testing of high-conductivity electrolytic copper busbars, verification of silver alloy contact percentage (minimum 85% Ag content), and thermal deflagration testing of polycarbonate/PA66 engineering resins (UL94 V-0 flame rating verification).
02
Automated SMT & Optical Inspection
High-speed surface-mount technology (SMT) component placement for internal microcontroller motherboards, followed by Automated Optical Inspection (AOI) to detect micro-bridging, missing components, or solder voids on critical SMD trace resistors.
03
Precision Phase-Angle Calibration
Programmable 3-phase AC power calibrators inject deliberate voltage asymmetry (3% to 20%), phase vector shift (180° inversion), and harmonic distortion into every batch to ensure tripping thresholds match faceplate scales within ±1.5% accuracy.
04
High-Voltage Dielectric Withstand
Testing phase-to-phase and phase-to-enclosure dielectric insulation resistance at 2.5kV AC for 60 seconds according to IEC 60947-1, ensuring absolute galvanic isolation between sensing terminals, auxiliary output contacts, and front user-accessible interfaces.
05
Thermal & Accelerated Aging Cycling
Sample lots from every production shift undergo 72 hours of continuous energized operation inside temperature-controlled environmental chambers (-25°C to +70°C) at 95% relative humidity to purge latent solder joint thermal stress faults.
06
Final Pre-Shipment Audit & Packaging
Auditing laser markings, terminal thread torque compliance, user instruction leaflet accuracy in English, Spanish, or Russian, custom client barcoding, and impact-resistant double-corrugated master carton palletization before container sealing.
International Compliance & Factory Verification Documents
All production models carry CE mark compliance; official factory test reports, material safety declarations, and the full TÜV Rheinland assessment report are delivered upon request.
Procurement Knowledge Base
Frequently Asked Questions (FAQ) for Global B2B Buyers
Comprehensive technical, commercial, and logistical answers compiled by our chief electrical engineering team to facilitate seamless imports.
1. What is the fundamental difference between a Phase Failure Relay and a standard Thermal Overload Relay?
A thermal overload relay relies purely on the heating effect ($I^2t$) of current passing through internal bimetallic strips. During a single-phasing event on a motor operating under moderate mechanical load, current rise can be sluggish, requiring anywhere from 30 seconds to several minutes before tripping. During this interval, severe negative-sequence currents destroy winding insulation. A dedicated electronic Phase Failure Relay monitors phase vector symmetry directly at the line terminals and trips within 50 to 100 milliseconds, arresting rotor counter-torque and back-EMF destruction before any thermal accumulation occurs.
2. How do TMB phase failure relays solve the rotary back-EMF masking issue in running induction motors?
Traditional scalar relays measure root-mean-square amplitude between line pairs. If a motor generates a 90% phantom back-EMF on the lost phase, a scalar relay assumes voltage is normal. TMB’s microcontroller-based relays decompose the three input phases into Fortescue symmetrical components in real-time. Even if back-EMF magnitude remains high, its phase angle shifts drastically from the ideal 120° displacement. This phase angle deviation instantly generates a large Negative Sequence Voltage component ($V_2$), which triggers the relay's trip threshold regardless of scalar voltage magnitude.
3. Can your 3-phase protection relays be used upstream or downstream of Variable Frequency Drives (VFDs)?
Phase monitoring relays must always be installed upstream (on the line input side) of a VFD to protect the inverter's front-end diode rectifier bridge against unbalanced thermal stress and DC-bus ripple damage. They must never be installed downstream between the inverter and the motor, because the high dV/dt pulse-width modulation (PWM) square-wave output and variable carrier frequencies (2kHz to 16kHz) will prevent microcontroller phase measurement and induce false trips. For downstream motor protection, thermal models integrated within the drive firmware or motor-embedded PTC thermistors should be utilized.
4. Is Zhejiang TMB Electric Co., Ltd. a direct factory or an export broker?
We are an on-site verified manufacturer with an integrated export engineering team. Our manufacturing plant is situated in Huabei Village, Liushi Town, Wenzhou, Zhejiang, China, spanning approximately 5,700 m² of verified industrial production area with 92 full-time staff. Our physical production lines, component testing benches, and quality control systems have been audited on-site by TÜV Rheinland, with verified annual exports exceeding US$ 3.3 million.
5. What are the minimum order quantities (MOQ) and sample lead times for OEM private-label production?
For standard catalog models, our trial MOQ starts from just 5 pieces (and selected timer switches from 1 piece), allowing distributors and engineering panels to validate samples before mass ordering. For full private-label OEM production (custom laser faceplate branding, custom multi-language user manuals, and customized gift-box packaging), the typical MOQ is 500 to 1,000 units per model. Standard off-the-shelf samples ship within 48 to 72 hours; customized OEM production batches ship within 15 to 25 business days.
6. What is the difference between 3-Wire (3P) and 4-Wire (3P+N) phase monitoring relays?
A 3-Wire (3P) relay monitors line-to-line voltages (L1-L2, L2-L3, L3-L1) and is ideal for delta-connected loads, three-phase motors, and systems without a neutral conductor. A 4-Wire (3P+N) relay monitors line-to-neutral voltages (L1-N, L2-N, L3-N) in addition to line-to-line vectors. This is essential in four-wire wye distribution boards feeding single-phase branch circuits, where a severed or high-impedance floating neutral can cause extreme line-to-neutral voltage fluctuations (surging to 380V on lightly loaded phases while sagging to 100V on heavily loaded phases), destroying connected electronics.
7. How should buyers configure the trip time delay setting on a phase failure relay?
Phase sequence reversal and total phase loss should always be configured with minimum time delay (< 0.1s to 0.2s) because there is no legitimate operational condition where reverse rotation or complete phase loss should be tolerated. However, voltage unbalance, undervoltage, and overvoltage trips should typically be calibrated with a 1.0s to 5.0s delay. This intentional delay prevents nuisance tripping caused by momentary inrush currents from large neighboring motor starts, network utility grid switching, or transient lightning surge suppressions.
8. What certifications and international documentation do you provide for customs clearance?
Our protection relays, timer switches, ATS units, and circuit breakers carry CE conformity marking complying with the Low Voltage Directive (LVD 2014/35/EU) and Electromagnetic Compatibility Directive (EMC 2014/30/EU). In addition, we supply complete factory test reports, certificates of origin (Form A, Form E, CO), RoHS material compliance declarations, and verified on-site inspection reports from TÜV Rheinland to ensure rapid customs processing in the EU, Americas, Southeast Asia, and Middle East.
Looking for Factory-Direct Phase Failure & Protection Relays?
Submit your electrical specifications, system schematics, or target distribution bill of materials. Our Liushi engineering team provides detailed model mapping, compliance documentation, and wholesale FOB/CIF price quotations within 24 hours.