YBX3 Series Explosion Proof Three Phase Asynchronous Motor

Product Overview: Efficiency Meets Explosion Protection

In a petroleum refinery, a chemical mixing room, or a grain elevator, the atmosphere itself can be an explosive hazard. Every electrical device in these environments — including the motor — must be engineered so that any internal spark, arc, or hot surface cannot ignite the surrounding gas or dust mixture. The YBX3 series AC gear motor achieves this through a flameproof (Ex d) enclosure: if an explosive mixture enters the motor housing and ignites internally, the enclosure contains the explosion and cools the escaping gases below the ignition temperature of the external atmosphere.

 

What distinguishes the YBX3 from its predecessors — the YB2 and YB3 — is the step up to IE3 premium efficiency in accordance with GB18613-2012 and IEC 60034-30. This is not a minor efficiency gain: on a 30 kW motor running 6,000 hours per year, the jump from YB3 (approximately IE2) to YBX3 (IE3) saves roughly 3,600 kWh annually — approximately 2.1 tonnes of CO₂ at the Korean grid emission factor. Across a refinery running 50 such motors, the annual energy saving exceeds 180,000 kWh.

Frame sizes span H80 to H355, covering 0.55 kW to 315 kW in 2-pole, 4-pole, 6-pole, and 8-pole configurations. The explosion marking is Ex d I Gb (coal mine methane), Ex d IIA T4 Gb, and Ex d IIB T4 Gb (factory gas groups A and B, temperature class T4). IP55 ingress protection is standard. All mounting dimensions comply with IEC standards and are dimensionally identical to the YB2 and YB3 series — the YBX3 is a direct bolt-on replacement.

Technical Specifications

Gas Group and Temperature Class Reference

Before selecting any explosion-proof motor, the first engineering decision is identifying the gas group and temperature class of the hazardous area. The table below maps representative substances to their IEC/GB3836 gas groups and NEC 500 equivalents. The YBX3 standard rating of Ex d IIB T4 covers all substances in groups IIA and IIB with auto-ignition temperatures above 135 °C.

Full Performance Data

The table below provides rated output, full-load current, speed, efficiency, power factor, starting characteristics, noise level, and weight for every YBX3 model across all four pole counts. The data confirms IE3-level efficiency across the entire range. Scroll horizontally on mobile devices.

⚠ Zone Classification: Where Does the YBX3 Belong?

IEC 60079-10-1 divides hazardous areas into three zones based on how frequently an explosive gas atmosphere is expected to be present. The zone classification determines the minimum protection level (EPL) required for electrical equipment:

The YBX3 carries a Gb equipment protection level, making it suitable for both Zone 1 and Zone 2 installations. This is the most common requirement in Korean petroleum refineries and LPG storage facilities, where Zone 1 conditions exist around tank vents, valve flanges, pump seals, and loading points. Zone 0 — the interior of a storage tank, for example — does not permit motors of any type; only intrinsically safe instruments rated Ga are allowed.

For coal mine applications, the YBX3 carries the Ex d I Gb marking, certifying it for underground use where methane is the primary hazard. The distinction between Group I (mining) and Group II (factory) relates to the flameproof gap dimensions and the maximum permissible surface temperature — both are tighter for Group I due to the constant presence of methane in mines.

⚙ Flameproof Enclosure Engineering: How Ex d Works

The "d" in Ex d stands for "flameproof enclosure" — the oldest and most robust method of explosion protection for rotating machines. The principle is straightforward: the motor housing is strong enough to withstand an internal explosion, and every joint in the enclosure (the flameproof gap) is engineered to cool the escaping gases below the auto-ignition temperature of the external atmosphere before they exit the housing.

The YBX3 achieves this through three design features. First, the housing is cast from high-strength gray cast iron with wall thicknesses significantly exceeding those of a standard motor. The end shields, terminal box, and cable entry are all part of the pressure-containing enclosure and must withstand a reference pressure of 1.5 times the maximum explosion pressure of the relevant gas group — typically 8 to 10 bar for IIB gases. Second, the flameproof gaps at the end shield joints, shaft exit, and terminal box cover are machined to tight tolerances. For Group IIB, the maximum permissible gap width is 0.2 mm with a minimum path length of 12.5 mm. The narrow, long gap path forces the hot explosion gases to travel a tortuous route, losing heat to the metal surfaces until the flame is extinguished before reaching the external atmosphere. Third, the shaft seal at the drive end uses a labyrinth or lip seal arrangement that maintains the flameproof gap integrity even as the shaft rotates.

The terminal box is a separately flameproof compartment with its own gasketed cover. Cable entry is through certified Ex d cable glands with compression seals. The entire assembly is tested to the explosion pressure test specified in GB3836.2 and IEC 60079-1 before leaving the factory.

Temperature Class: What T4 Means in Practice

The temperature class defines the maximum surface temperature the motor is permitted to reach under any operating condition — including locked rotor and overload. The YBX3 is rated T4, meaning the maximum external surface temperature must not exceed 135 °C. This covers the majority of flammable gases encountered in Korean industrial facilities:

The T4 rating means the YBX3 can safely operate in atmospheres containing any gas with an auto-ignition temperature above 135 °C. This covers propane (450 °C), ethylene (425 °C), gasoline vapor (280 °C), and most common petrochemical gases. Only a handful of specialized chemicals — notably carbon disulfide (90 °C) — fall below T4, and those environments require T5 or T6 rated equipment, which typically means non-standard motor orders.

Evolution Timeline: YB2 → YB3 → YBX3

Korean industrial plants built in the 1990s and 2000s predominantly installed YB2 explosion-proof motors. Plants built or retrofitted in the 2010s moved to YB3. The YBX3 is the current generation, and understanding the differences helps plant engineers plan replacements with confidence:

The critical point for plant engineers: the YBX3 is a direct dimensional replacement for both YB2 and YB3. Shaft diameter, mounting foot hole pattern, terminal box position, and overall height are identical within each frame size. An old YB2-200L-4 (30 kW) can be replaced with a YBX3-200L-4 without modifying the baseplate, coupling, conduit entry, or foundation bolts. The only change is a lower electricity bill and a larger thermal margin.

Application Scenarios

Petroleum Refineries and Petrochemical Plants

Cooling water pumps, fin-fan cooler motors, and compressor auxiliary drives in Zone 1 and Zone 2 areas. The YBX3-200L-4 (30 kW, 4-pole) is the most commonly specified model for horizontal centrifugal pumps in Korean refinery process units. The IE3 efficiency reduces the motor's contribution to the plant electrical load — significant when a single refinery runs hundreds of pumps.

LPG Storage and Distribution Terminals

Compressor motors, vapor recovery blowers, and loading arm hydraulic units. LPG (propane/butane) falls within gas group IIA, well within the YBX3's IIB rating. The T4 temperature class provides a substantial margin above propane's 450 °C auto-ignition temperature. Korean LPG terminals operated by major gas distributors have progressively replaced YB2 motors with YBX3 units during scheduled turnarounds.

Grain Handling and Feed Mills

Grain dust is classified as a combustible dust hazard. While the YBX3's primary certification is for gas (Group II), the Ex d I marking also covers coal mine dust applications. For grain dust specifically, the YBX3 provides robust mechanical protection (IP55) that prevents dust ingress into the motor, while the flameproof enclosure ensures that any internal fault cannot ignite external dust clouds. The YBX3-132M-4 (7.5 kW) drives bucket elevators, drag conveyors, and rotary airlocks in Korean feed processing facilities.

Paint and Solvent Manufacturing

Mixing vessels, dispersion mills, and ventilation fans in paint factories handle toluene, xylene, and MEK vapor — all Group IIA or IIB gases. The YBX3-112M-4 (4 kW) and YBX3-160M-4 (11 kW) are frequently specified for agitator drives and exhaust fan duties, paired with a helical gear reducer for speed reduction to the mixer shaft.

🔧 Hazardous Area Maintenance: What Makes Ex d Different

Maintaining an explosion-proof motor is fundamentally different from maintaining a standard motor. The flameproof enclosure is a safety device — any damage to the enclosure, flameproof gaps, or cable glands can compromise the motor's ability to contain an internal explosion. The following rules apply to all Ex d motors including the YBX3:

1. Never open the terminal box in a live, hazardous atmosphere. A gas-free certificate or hot work permit is required before removing any enclosure cover in Zone 1 or Zone 2.
2. Inspect flameproof surfaces during every motor removal. The machined mating faces of the end shields and terminal box must be free of scratches, dents, and corrosion. Any surface damage deeper than 0.05 mm requires professional re-machining or motor replacement.
3. Use only certified cable glands. The cable entry into the terminal box must use Ex d certified glands that match the motor's gas group and temperature class. Substituting non-certified glands invalidates the motor's explosion protection.
4. Apply anti-corrosion grease to flameproof surfaces. Before reassembly, coat all machined flameproof gaps with a thin layer of silicone-based anti-corrosion grease. This prevents corrosion from narrowing the effective gap path and maintains the seal integrity.
5. Check bearing condition by vibration measurement. Bearing failure in an Ex d motor generates heat that can raise the external surface temperature above the T4 limit. Vibration monitoring (quarterly, ISO 10816) catches bearing degradation before it becomes a thermal hazard.
6. Do not weld, drill, or machine the enclosure in the field. Any modification to the flameproof housing invalidates the Ex certification permanently. Repairs must be performed by the manufacturer or a certified Ex repair facility.

For frame sizes H160 and above, the YBX3 is equipped with grease nipples and drain plugs that allow bearing re-greasing without stopping the motor or opening the enclosure. This non-stop lubrication feature is particularly valuable in continuous-process plants (refineries, chemical plants) where motor shutdowns are costly.

Related and Complementary Products

In many hazardous area applications, the YBX3 motor drives a load through a speed reducer. The choice of reducer matters for two reasons: efficiency (which affects motor loading and temperature rise) and mechanical suitability for the environment. A worm gear reducer offers compact right-angle output and high reduction ratios (5:1 to 60:1), making it suitable for fan drives and slow-speed agitators. However, worm gear efficiency (75–90%) means more heat is generated in the drive train — a consideration in hot refinery environments where ambient temperatures already approach 40 °C.

For pump drives requiring direct coupling, the YBX3 often connects through a flexible coupling to a centrifugal pump. In VFD-driven applications where the motor runs at variable speed, the YBBP explosion proof variable frequency motor with independent cooling (IC416) is the more appropriate choice — the YBX3's shaft-mounted fan (IC411) loses cooling effectiveness at low speeds.

Same-Series Alternatives: The YBX4 offers IE4 super-premium efficiency for applications where energy cost justifies the premium. The YBK3 is the mining-specific variant with a steel housing instead of cast iron, mandated for underground coal face equipment in Korea. The YFB3 dust explosion-proof motor carries Ex tD certification specifically for combustible dust environments where the gas-rated YBX3 may not be the optimal regulatory fit.

Energy Savings: The IE3 Advantage in Hazardous Areas

Explosion-proof motors historically lagged behind standard motors in efficiency because the heavy flameproof enclosure constrains the electromagnetic design — thicker housing walls limit airflow, and the robust construction adds weight that increases bearing losses. The YBX3 closes this gap through optimized stator and rotor lamination geometry, higher-grade silicon steel, and improved cooling fin design.

The practical savings are significant. Consider a YBX3-160L-4 (15 kW) replacing a YB2-160L-4 on a refinery cooling water pump running 8,000 hours per year at 75% average load:

Across a Korean refinery operating 200 explosion-proof motors with an average rating of 15 kW, the annual energy saving from migrating the fleet from YB2 to YBX3 exceeds 800,000 kWh — equivalent to approximately ₩96 million per year and a CO₂ reduction of over 460 tonnes. Korean government incentives under the K-ETS (Korea Emissions Trading Scheme) may provide additional financial benefit for verified energy efficiency improvements in ETS-covered facilities.

Frequently Asked Questions

Can the YBX3 be paired with a VFD?
The standard YBX3 uses IC411 shaft-mounted fan cooling. At reduced speed, the fan delivers less airflow and the motor's thermal capacity decreases. For sustained VFD operation below 25 Hz, the YBBP series variable frequency explosion proof motor with IC416 independent forced cooling is the correct choice. The YBBP maintains full cooling at any speed from 3 Hz to 100 Hz.

What gas groups does the YBX3 cover?
Standard marking is Ex d IIB T4, which covers gas groups IIA and IIB. Group IIC (hydrogen, acetylene) requires a motor with tighter flameproof gap tolerances — the YBX3 is not certified for IIC in standard production. IIC-rated motors are available as a special order with longer lead time.

How do I identify the correct YBX3 replacement for my old YB2?
Send us the old motor nameplate data — frame size, kW rating, pole count, and voltage. In most cases the YBX3 frame size is identical. We will confirm the dimensional match and provide a cross-reference datasheet before shipment.

What is the delivery time?
Standard 380 V models in commonly stocked frame sizes (80–200) ship within 10 to 20 working days. Non-standard voltages (660 V, 440 V) and large frames (250–355) typically add 5 to 10 working days.

Does the YBX3 carry KCs certification for the Korean market?
Standard production carries CCC and Ex d certification per GB3836. Korean KCs marking is arranged upon request — typical lead time is 4 to 6 weeks for the certification process. We handle all documentation and testing coordination.

What is the altitude derating for the YBX3?
Standard rating applies at altitudes up to 1,000 meters above sea level. Above 1,000 m, the thinner air reduces cooling effectiveness. Derating is approximately 1% per 100 m above 1,000 m. For installations above 2,000 m, contact our engineering team for a motor with enhanced cooling or oversized frame selection.

Customer Reviews

Hwang Dae-ho, Safety Manager, Gyeongsang-do (early 2025)
"Replaced 10 old YB2 motors at our LPG terminal during the annual turnaround. Bolt pattern matched perfectly — no baseplate modifications needed. The safety audit accepted the Ex d IIB T4 documentation without issues. Energy monitoring shows consumption dropped by an estimated 8% across the replaced units."

---

Kim Seung-ho, Plant Engineer, Ulsan (mid 2024)
"The YBX3-200L-4 has been running a cooling water pump in our refinery process unit for 14 months without a single unplanned stop. Vibration readings are consistently lower than the YB3 it replaced. The temperature rise margin is noticeably better — surface temperature runs about 15 °C cooler under the same load."

---

Jang Min-ah, Procurement Manager, Incheon (late 2024)
"Ordered 6 units for a coal handling facility. Delivery was 15 days. Packaging was excellent — wooden crate with anti-moisture wrap. Certification documents arrived digitally before the motors shipped. 11 months in service with zero unplanned downtime."

---

Seo Tae-jin, Equipment Director, Busan (mid 2025)
"The 6-pole option (YBX3-160M-6, 7.5 kW) lets us direct-drive a slow-speed chemical agitator at 970 rpm without a gearbox, removing one potential ignition source from the hazardous zone. Fewer components in the Ex area means fewer things to certify and maintain."

---

Park Ji-won, Maintenance Engineer, Daejeon (early 2025)
"We are midway through a 3-year plan to replace all YB2 motors in our paint manufacturing facility. So far 14 YBX3 units installed. The non-stop grease lubrication on the H160 and larger frames is a real time-saver — no need to pull the motor off-line for bearing service."

Packing and Shipping