RVSS Soft Starter for 3-Phase AC Motors | Solid-State Control

RVSS Soft Starters
for 3-Phase AC Motors
Title

Solid-State Control for Smooth, Jolt-Free Motor Starts – Minimizing Mechanical Stress, Eliminating Current Surges, and Extending Equipment Lifespan.

What Is a Reduced Voltage Soft Starter?

A Reduced Voltage Soft Starter is like a "gentle launch system" for electric motors. Instead of giving the motor full power immediately (which causes a stressful jolt), it gradually increases power during startup.

Think of it as the difference between flooring your car's accelerator (hard start) vs. smoothly pressing down (soft start). RVSS units are essential for protecting motors in pumps, fans, compressors and other heavy-duty equipment. Perfect for applications where you want to avoid the high cost of variable frequency drives (VFDs) but still need better protection than basic starters provide.

This smart control helps:

• Prevent sudden current spikes that can trip breakers
• Reduce mechanical stress on belts, gears and bearings
• Extend equipment lifespan significantly

Key benefits:
✓ Smoother acceleration
✓ Lower energy costs
✓ Built-in motor protection
✓ More reliable operation

Products Overview

Type

In-Line

Bypass

Integrated Bypass

Features

Continuously regulates voltage via thyristors even after startup

Uses an extra contactor to bypass thyristors after startup

Integrates the bypass contactor into the unit, saving panel space

Applications

Frequent starting and stopping (e.g. crusher, compressor)

Simple start/stop, stabilization of loads (e.g. pumps, fans)

Where space is limited or quick installation is required

Efficiency

Lower efficiency due to

continuous control.

Higher efficiency after bypassing.

Higher efficiency after bypassing.

Heat Dissipation

Generates more heat during operation.

Less heat after bypassing.

Less heat after bypassing.

Series

AVH100, ASF6K

ASF9H

ASF77H

Cost

Budget-friendly

💰

Cost-effective

💰💰

Cost-effective

💰💰

Rated Power

5.5 - 630kW

5.5 - 630kW

5.5 - 320kW

Rated Voltage

220, 380, 440V

220, 380V

380V

See More

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Where to Use

Heavy Industry

Our RVSS units protect crushers, conveyors, and compressors with controlled acceleration, reducing mechanical stress and current surges by up to 60%. Built for harsh conditions with IP54 enclosures and -30°C to +70°C operation.

Water Treatment

Our soft starters provide smooth acceleration control for pumps, fans and mixers in water treatment applications. The optimized start/stop profiles prevent water hammer in pipelines while reducing mechanical stress on equipment.

HVAC Systems

Our equipments optimize performance for chillers, cooling towers, and air handlers by reducing inrush current up to 60%. They prevent voltage dips during compressor starts while minimizing mechanical stress on fans and pumps.

FAQ

What's the difference between a soft starter and a VFD?

While both control motor starting, a VFD adjusts speed continuously, whereas an RVSS soft starter only manages startup/shutdown. Choose soft starters for simple acceleration control (cost-effective), and VFDs if you need speed regulation (more expensive).

How much starting current can RVSS limit?

Typically 200-400% of motor rated current (adjustable), compared to 600-800% with direct online starting. Exact values depend on motor size and load type.

Do I need a bypass contactor?

Only for bypass-type RVSS units. Integrated bypass models (like ASF77H series) include this internally. The in-line types operate continuously through thyristors - ideal for frequent start/stop applications.

What maintenance do RVSS starters require?

Solid-state design means:
✓ No contactors to replace
✓ Just annual dust cleaning and terminal checks

Can I use RVSS for a 50HP pump with 20 starts/hour?

Yes! Select the ASF6K-45 model (60HP rating) with "In-Line" configuration - its thyristors are rated for high cycling. Our Selection Guide details start frequency limits.

What protection functions does the soft starter provide?

✓ Overcurrent protection (adjustable 200-400% of rated current)
✓ Phase loss protection (detects missing phase in <100ms)
✓ Overheating protection (thyristor temperature monitoring)
✓ Undervoltage protection (adjustable trip point 70-90% of Vn)
✓ Motor stall prevention (automatic shutdown if acceleration fails)

✓ Current imbalance detection

✓ Ground fault protection

Why does my soft starter show "Phase Loss" error?

Most common causes:
• Loose power cable (check R/S/T connections)
• Blown fuse on one phase
• Motor winding fault
All units include 2-year warranty.

Unsure which soft starter fits your needs?

Let our technical experts guide you - contact us today for a free consultation and personalized solution recommendations!

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