China · Yongfan Electric Co., Ltd. (YOF®) — ISO9001 & CCC Certified OEM/ODM Manufacturer
The YFX01 Series Auto-Voltage Reducing Starting Box (Autotransformer Step-Down Starter, 10kW–320kW) is an industrial-grade electric motor starting and protection solution engineered by China · Yongfan Electric Co., Ltd. (YOF®), an established ISO9001-certified manufacturer, factory, supplier, and OEM/ODM vendor. Designed specifically for three-phase AC squirrel-cage induction motors operating on AC 50Hz, rated voltages up to 660V and below, and motor capacities of 320kW and below, this starter box is dedicated to infrequent step-down starting service.
By utilizing the tap voltage reduction characteristics of an integrated three-phase autotransformer, the YFX01 series significantly curtails the motor starting inrush current and eases mechanical shock, effectively minimizing harmful voltage dips on the power transmission network. All units are engineered and tested in rigorous accordance with Chinese national and industrial standards GB14048.4-2003 and JB/T8752-1998.
We provide complete customized manufacturing, private label, wholesale pricing, rapid quotation, strict MOQ policies, and authoritative engineering datasheets and technical specifications for global EPC contractors, switchboard builders, and industrial procurement teams.
Reduces line inrush current during startup via dedicated 65% and 80% autotransformer voltage taps, mitigating grid fluctuation and preserving electrical equipment life.
Comprehensive ratings covering 10kW up to 320kW squirrel-cage asynchronous motors at AC 50Hz, 380V/660V, supporting diverse heavy-duty industrial machinery.
Built to full conformance with GB14048.4-2003 and JB/T8752-1998 standards, featuring verified overload, under-voltage, and phase loss safety mechanisms.
| Symbol Segment | Designation | Technical Meaning & Explanation |
|---|---|---|
| YF | Enterprise Code | China · Yongfan Electric Co., Ltd. manufacturer identifier |
| X | Voltage Reducing Starting Box | Step-down reduced voltage starter enclosed box type |
| 01 | Autotransformer Series | Design number 01 indicating autotransformer starting scheme |
| □□ | Rated Power | Rated capacity of controlled electric motor in kilowatts (kW) (e.g., 14, 20, 28, 40, 55, 75, 80, 100, 115, 135, 160, 180, 200, 225, 260, 280, 300, 320kW) |
| Performance Parameter | Specified Limit / Value | Operational Requirement & Engineering Rationale |
|---|---|---|
| Maximum Starting Current | ≤ 4 × Ie | Controlled via autotransformer step-down taps to minimize grid shock during motor acceleration |
| Max Starting Time (Single / Cumulative) | ≤ 30 s | Maximum permissible energized duration for autotransformer windings during starting transition |
| Mandatory Cooling Duration | ≥ 2 Hours | Required after cumulative 30s starting time to prevent internal coil thermal relay overload trip |
| Permissible Duty Cycle | Long-Time Intermittent | Designed strictly for infrequent motor starting; not suitable for continuous cycling or high-frequency starts |
| Integrated Motor Protections | Tri-Protection System | Full coverage against motor thermal overload, electrical under-voltage, and phase loss / open phase faults |
The YFX01 series features a robust, enclosed box-type protective structure. It integrates an internal three-phase autotransformer, heavy-duty AC contactors, bimetallic thermal overload relays, intermediate relays, and high-precision adjustable time relays to form a self-contained motor control assembly.
Units rated 75kW and below operate via an automated timing sequence. Upon pressing the start button, the autotransformer contactor energizes to execute step-down starting; once the preset acceleration time elapses, the time relay automatically switches the motor over to full-voltage line operation.
Units rated 80kW and above are equipped with a door-mounted transfer switch enabling flexible selection between Manual and Automatic control modes. The high-precision time relay is field-adjustable, allowing operators to fine-tune the starting acceleration interval to match exact mechanical load inertia.
| Autotransformer Tap | Voltage Ratio (% Ue) | Starting Torque (% Tst) | Factory Setting & Application Note |
|---|---|---|---|
| Standard Tap (Default) | 65% | Approx. 42.25% | Factory Default Connection: Suitable for standard industrial loads such as centrifugal pumps, fans, and unloaders with minimal inrush impact. |
| High Torque Tap | 80% | Approx. 64.00% | Optional Connection: Easily reconnected on-site if user application requires higher starting torque (e.g. crushers, loaded conveyors, heavy mills). |
The YFX01 series auto-voltage reducing starting box is designed exclusively for indoor installation and must be operated under the following standard environmental and electrical criteria:
| Item | Environmental / Operating Parameter | Specified Operating Limits | Engineering Notes & Precautions |
|---|---|---|---|
| (1) | Altitude Limit | ≤ 2000 m | Derating required if installed above 2000m |
| (2) | Ambient Air Temperature | -5°C to +40°C (24h Average ≤ +35°C) | Minimum ambient temperature floor is -5°C |
| (3) | Atmospheric Relative Humidity | ≤ 50% at +40°C Wettest month: mean min temp ≤ +20°C, mean max RH ≤ 90% |
Higher RH allowable at lower temperatures; anti-condensation measures required if temperature fluctuates |
| (4) | Pollution Degree | Grade 3 | Standard industrial harsh electrical environment |
| (5a) | Installation Inclination | ≤ 5° from vertical/horizontal plane | Ensures proper vertical orientation of magnetic contactors |
| (5b) | Installation Category | Category II & Category III | Compatible with primary sub-distribution and branch circuits |
| (6) | Mechanical Vibration & Impact | Place without noticeable vibration or impact | Avoid direct mounting on intensely vibrating machinery frames |
| (7) | Surrounding Atmospheric Media | Non-explosive medium; free of corrosive gases & conductive dust | Must not contain gases/dust that corrode metals or impair insulation |
To ensure reliable motor thermal overload protection while preventing false nuisance tripping during autotransformer acceleration, the thermal relay setting values must be strictly configured according to the power category:
The thermal relay current dial is set directly to the full rated operational current (Ie) of the controlled motor.
The thermal relay is configured through current transformer (CT) secondary sampling. The dial setting value is calculated as Ie / K, where K represents the current transformation ratio of the matched current transformer.
| Specification Parameter | Rated Engineering Value | Standard & Compliance Notes |
|---|---|---|
| Product Series Model | YFX01 Series | Autotransformer reduced voltage starting box |
| Manufacturing Standard | GB14048.4-2003 / JB/T8752-1998 | National & machinery industry electrical standards |
| Rated Operational Frequency | AC 50 Hz | Three-phase power grid |
| Rated Operational Voltage | Up to 660V and below (380V / 660V) | Three-phase 380V standard / 660V compatible |
| Controlled Motor Capacity Range | 10 kW – 320 kW | Three-phase squirrel-cage induction motors |
| Autotransformer Voltage Taps | 65% (Factory Default) and 80% | Dual tap selection for torque/inrush matching |
| Maximum Starting Inrush Current | ≤ 4 × Ie | Peak line current during start sequence |
| Starting Duration Limitation | ≤ 30 seconds | Single start or cumulative continuous starts |
| Cooling Requirement After 30s Start | ≥ 2 Hours | Guarantees thermal safety of autotransformer core & coil |
| Operating Duty Mode | Long-Time Intermittent Starting | Strictly designed for infrequent motor startup |
| Control Mode Configuration | ≤ 75kW: Auto Control ≥ 80kW: Manual & Auto Dual Control |
Selected via transfer switch with adjustable time relay |
| Protective Functions | Overload, Under-Voltage, Phase Loss | Comprehensive protection for motor and supply grid |
As a premier China manufacturing factory, supplier, and contract fabricator, China · Yongfan Electric Co., Ltd. (YOF®) delivers full-scope OEM and ODM customized manufacturing services for international electrical distributors, panel builders, industrial wholesalers, and engineering procurement contractors.
Professional China manufacturer of BK/JBK/JMB/SBK/SG Transformers, Online & Bypass Intelligent Soft Starters & Cabinets, YFX01 Autotransformer Starting Boxes, TND/TNS/SBW/DJW/SJW Voltage Stabilizers, and TDGC2/TSGC2 Contact Voltage Regulators since 2009.
Add: Dongfeng Industrial Zone, Liushi Town, Yueqing City, Zhejiang Province, China
Tel: +86-577-27877036 | Fax: +86-577-27877037
Mobile: +86-13968736791 / +86-13868325933
Email: YOF@cnyofan.com
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