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Motor Starters
4 Series · 55 Models
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Motor Starters Overview
Motor starters control three-phase motor energization with reduced-voltage methods that limit inrush current and mechanical stress. QDTB cabinets offer star-delta (Y-delta), auto-transformer, and electronic soft starting for motors from 2.2 kW to hundreds of kilowatts at 380 V/440 V/660 V. Series QX4 (star-delta), JJ01 (auto-transformer), and RS/RC (soft start) reduce starting current 3-5 times with overload, phase-loss, and short-circuit protection for pumps, fans, compressors, conveyors, and crushers.
Available Series
QX4 Series
The QX4 series motor starting control cabinets provide complete motor starting solutions including direct-on-line, star-delta, and auto-transformer starting methods.
JJ01 Series
The JJ01 series liquid resistance motor starters provide smooth, stepless starting for large slip-ring induction motors using liquid rheostat technology.
RS Series
The RS series electronic soft starters use thyristor technology for smooth, controlled acceleration of three-phase induction motors with reduced mechanical stress.
RC Series
The RC series motor running control cabinets provide complete motor control and protection solutions including speed control, reversing, and multi-motor coordination.
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Application Scenarios
Pumps & Water Systems
Reduced-voltage starting protects pumps from mechanical and electrical shock.
Large Fans & Blowers
Soft starting for HVAC and industrial fans with high inertia.
Air Compressors
Cuts starting current and mechanical stress on compressor motors.
Conveyors & Material Handling
Smooth starts for conveyors, avoiding belt slip and load shock.
Crushers & Mills
Handles high-inertia, heavy-starting loads in mining and aggregates.
HVAC Systems
Reduced inrush for chillers, compressors and pumps in buildings.
Technical Advantages
Multiple Starting Methods
Star-delta, auto-transformer and electronic soft-start from one supplier.
Reduced Starting Current
Cuts starting current 3-5x, protecting the motor and supply network.
Comprehensive Protection
Overload, phase-loss, short-circuit and under-voltage protection.
Wide Power Range
From 2.2 kW to hundreds of kW across the product families.
FAQ - Motor Starters
What is the difference between star-delta and soft start?
When should I use a soft starter?
Can it start heavy loads?
What capacity and voltage range is available for Motor Starters?
What is the minimum order quantity (MOQ) for Motor Starters?
What is the delivery time for Motor Starters?
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Star-Delta vs Auto-Transformer vs Soft Starter: How to Choose
| Star-Delta (QX4) | Auto-Transformer (JJ01) | Electronic Soft Starter (RS/RC) | |
|---|---|---|---|
| Starting current | Cut to roughly a third of the direct-on-line value | Set by the tap chosen on the transformer | Ramped smoothly from a set initial value |
| Starting torque | Also cut to about a third, which is the limitation | Higher than star-delta at the same current | Adjustable, so torque follows the load |
| Torque transition | Torque step at the star-delta changeover | Step at each tap change | No step, because the ramp is continuous |
| Cost | Lowest of the three | Higher, because of the transformer | Highest, driven by the thyristor stage |
| Panel size | Compact | Bulky, dominated by the transformer | Compact, with heat to manage |
| Load suitability | Fans, pumps and loads that start unloaded | Large motors on a supply that cannot take the inrush | Pumps and conveyors where water hammer or belt slip matters |
| Typical application | Pumps, blowers and compressors | Crushers and mills on weak supplies | HVAC, conveyors and process lines |
Where QDTB® Motor Starters Are Specified
Motor starters are specified wherever a three-phase motor is too large to start direct-on-line on the supply available: pumps and water systems, large fans and blowers, air compressors, conveyors and crushers. The starter limits inrush and mechanical stress at the same time, so it protects the network and the driven machine together.
Star-delta remains the default on loads that start unloaded, because it is the lowest-cost way to cut starting current. Auto-transformer starting is chosen where the motor still needs torque at start-up, and soft starters where a smooth ramp removes water hammer, belt slip or product damage on the line.
HVAC and process plants use soft starters on fans and conveyors where the ramp profile has to match the load. The bypass contactor sits in the same cabinet, so the thyristor stage drops out of circuit once the motor is up to speed.
Cabinets cover 14 kW to 320 kW at the common three-phase supply voltages. Overload, phase-loss and short-circuit protection are included to GB/T 14048.4 and IEC 60947-4-1, and the starting method is selected from the load torque curve.
Frequently Asked Questions
What is the difference between star-delta and soft start?
Star-delta switches winding configuration to reduce starting current but causes a torque step. A soft starter ramps voltage smoothly for a gentler, more controllable start.
When should I use a soft starter?
For pumps, fans and compressors where a smooth start reduces water hammer, belt slip and mechanical wear, or when the supply is weak.
Can it start heavy loads?
Yes. Select the starting method and rating for the load's inertia and required starting torque.
What capacity and voltage range is available for Motor Starters?
QDTB® supplies Motor Starters from 14 to 320 kW.
What is the minimum order quantity (MOQ) for Motor Starters?
One unit for standard products. Custom-designed equipment is quoted on specifications — send your parameters or drawings and our sales team will confirm the MOQ for your configuration.
What is the delivery time for Motor Starters?
Standard units are delivered in 30-45 days. Custom or large-capacity units follow a project-specific schedule confirmed at quotation. Rush orders can be accommodated for urgent projects.