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Product Overview

The Schneider Electric ATS48C79Q Altistart 48 Soft Starter is an industrial motor-control device designed to manage the starting and stopping process of three-phase asynchronous motors. It is intended for industrial machinery where direct-on-line motor starting can create high starting current, mechanical shock, excessive torque, hydraulic disturbances, or unnecessary stress on the motor and driven equipment.

The ATS48C79Q is part of the Altistart 48 family and is installed as part of the motor power circuit. Its primary function is to provide controlled acceleration and deceleration rather than continuous variable-speed operation. This makes it suitable for fixed-speed motor applications where smoother starting and stopping are required.

Typical applications include large pumps, fans, compressors, conveyors, blowers, mixers, and other industrial machines with substantial motor loads or mechanical inertia.

The supplied dimensions for the ATS48C79Q are 890 × 770 × 315 mm, with a supplied weight of 115 kg. Because of its substantial physical size and weight, installation requires careful cabinet planning, structural support, lifting arrangements, ventilation, cable routing, and maintenance access.

The ATS48C79Q should always be selected according to the complete motor application. Motor rated current, supply voltage, starting duty, acceleration requirements, load inertia, starting frequency, ambient conditions, and enclosure thermal characteristics should all be evaluated before installation.

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Product Identification

Parameter	Specification
Manufacturer	Schneider Electric
Product Family	Altistart 48
Model	ATS48C79Q
Product Type	Soft Starter
Motor Type	Three-Phase Asynchronous Motor
Main Function	Controlled Motor Starting and Stopping
Starting Method	Electronic Soft Start
Stopping Method	Controlled Soft Stop
Dimensions	890 × 770 × 315 mm
Weight	115 kg
Installation	Industrial Electrical Cabinet
Typical Applications	Pumps, Fans, Compressors, Conveyors, Blowers, Mixers
Control Integration	PLC / HMI / Hardwired Control
Thermal Management	Required

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Technical Specifications

Technical Item	Specification
Brand	Schneider Electric
Series	Altistart 48
Catalog Number	ATS48C79Q
Product Category	Electronic Soft Starter
Application	Three-Phase AC Motor Control
Starting Function	Controlled Acceleration
Stopping Function	Controlled Deceleration
Dimensions	890 × 770 × 315 mm
Weight	115 kg
Mounting	Industrial Cabinet
Typical Load Types	Pumps, Fans, Compressors, Conveyors, Blowers, Mixers
Control System	PLC / HMI / Hardwired Control
Cooling Requirement	Adequate Airflow and Thermal Management
Maintenance	Electrical, Thermal, and Mechanical Inspection

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What Is the ATS48C79Q?

The ATS48C79Q is positioned in the motor-control power circuit between the electrical supply and a three-phase motor.

A simplified system arrangement is:

Three-Phase Power Supply

↓

Main Disconnect / Protection

↓

ATS48C79Q Soft Starter

↓

Three-Phase Motor

↓

Mechanical Load

The starter controls the motor during the transition from stopped to running conditions.

Instead of immediately applying the full starting condition associated with direct-on-line operation, the soft starter provides a controlled acceleration process. Depending on the application and configuration, controlled stopping can also be used to reduce abrupt deceleration.

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How the ATS48C79Q Works

A large induction motor can draw substantially higher current during startup than during normal operation. Direct starting can therefore produce electrical disturbances and mechanical stress.

A soft starter uses power electronics to regulate the electrical conditions applied to the motor during starting.

A simplified sequence is:

Motor Stopped

↓

Start Command

↓

Controlled Starting Voltage

↓

Progressive Acceleration

↓

Normal Operating Condition

During stopping:

Stop Command

↓

Controlled Deceleration

↓

Motor Stopped

The exact starting and stopping behavior must be adjusted according to the motor and mechanical load.

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Main Industrial Benefits

Controlled Motor Acceleration

The ATS48C79Q can provide a progressive acceleration process instead of an abrupt direct start.

This can be valuable for machinery with:

• High inertia
• Long shafts
• Gearboxes
• Belt drives
• Hydraulic loads
• Large rotating assemblies

Reduced Mechanical Stress

Controlled starting can reduce sudden forces on:

• Couplings
• Gearboxes
• Shafts
• Bearings
• Belts
• Conveyor structures

Reduced Starting Disturbance

Managing the motor-starting process can help reduce the severity of electrical disturbances compared with an uncontrolled direct start.

Controlled Stopping

Where the application requires it, controlled stopping can reduce abrupt mechanical or process transitions.

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ATS48C79Q vs. Variable Frequency Drive

The ATS48C79Q is a soft starter rather than a variable frequency drive.

Function	ATS48C79Q	Variable Frequency Drive
Controlled Start	Yes	Yes
Controlled Stop	Yes	Yes
Variable Speed	No	Yes
Variable Frequency	No	Yes
Fixed-Speed Motor Operation	Excellent	Suitable
Continuous Speed Adjustment	No	Yes
Main Purpose	Motor Starting / Stopping	Speed and Torque Control
Typical Application	Fixed-Speed Industrial Motor	Variable-Speed Motor

If a machine normally operates at a fixed speed and primarily requires a controlled starting and stopping process, a soft starter may be more appropriate than a full variable-speed solution.

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Industrial Applications

Pumping Systems

Large pumps can experience hydraulic disturbances when started or stopped abruptly.

A controlled motor-starting process can help make the transition smoother.

Potential applications include:

• Industrial water systems
• Process pumping
• Cooling-water systems
• Water treatment
• Fluid transfer
• Irrigation
• Utility pumping

For pump applications, both acceleration and stopping behavior should be evaluated.

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Conveyor Systems

Large conveyors may contain significant mechanical inertia.

A direct start can produce:

• Belt shock
• Coupling stress
• Gearbox loading
• Material movement
• Vibration

Controlled acceleration can allow the conveyor to reach operating speed more gradually.

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Large Fans and Blowers

Industrial fans and blowers can have significant rotating inertia.

Typical applications include:

• Industrial ventilation
• Exhaust systems
• Cooling systems
• Dust extraction
• Air-handling equipment

A controlled starting sequence can reduce mechanical stress during acceleration.

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Compressor Applications

Compressors can present demanding starting conditions.

Before applying the ATS48C79Q, evaluate:

• Motor current
• Compressor load
• Starting conditions
• Mechanical inertia
• Acceleration time
• Starting frequency
• System pressure

The starter should be selected according to the actual application rather than simply by motor power.

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Mixers and Agitators

Large mixers may require high starting torque, especially when the vessel contains material before startup.

Controlled starting can reduce sudden mechanical loading on:

• Shafts
• Couplings
• Gearboxes
• Bearings
• Motor assemblies

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Industrial Material Handling

The ATS48C79Q can be considered for appropriately selected fixed-speed material-handling equipment.

Examples include:

• Large conveyors
• Transfer systems
• Bulk handling equipment
• Processing machines
• Industrial transport equipment

Load inertia and motor starting requirements should be evaluated carefully.

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Installation Guide

1. Verify the Model

Confirm the product identification:

Schneider Electric ATS48C79Q

Compare the model with:

• Electrical drawings
• Motor specifications
• Equipment documentation
• Existing control architecture
• Replacement records

A visually similar Altistart unit should not automatically be treated as an equivalent replacement.

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2. Pre-Installation Inspection

Inspect the unit for:

• Mechanical damage
• Damaged terminals
• Cracks
• Corrosion
• Moisture
• Dust contamination
• Loose hardware
• Signs of overheating

The equipment should be inspected carefully before being connected to the power system.

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3. Cabinet Design

The supplied dimensions are:

890 × 770 × 315 mm

These dimensions should be treated as the equipment envelope rather than the complete cabinet requirement.

The cabinet should provide additional room for:

• Power cables
• Motor cables
• Control wiring
• Ventilation
• Maintenance
• Inspection
• Terminal access
• Lifting and replacement

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4. Mechanical Installation

The supplied weight is:

115 kg

This is a substantial equipment load.

Installation should therefore include:

• Adequately reinforced mounting structure
• Correct mounting hardware
• Appropriate lifting equipment
• Secure mechanical fixation
• Suitable cabinet floor or mounting frame
• Safe maintenance access

Do not allow cables or conduits to support the weight of the starter.

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5. Lifting and Handling

Because the unit weighs approximately 115 kg, manual handling should be avoided where it presents a safety risk.

Use suitable mechanical handling equipment.

Before lifting:

• Confirm the lifting method.
• Secure the unit.
• Keep personnel clear of suspended loads.
• Verify cabinet structure.
• Plan the installation route.

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6. Thermal Management

The ATS48C79Q is a power electronic device and generates heat during operation.

Cabinet thermal design should consider:

• Motor current
• Starting frequency
• Ambient temperature
• Cabinet dimensions
• Other heat-generating equipment
• Fan capacity
• Airflow
• Filter condition

Insufficient cooling can cause thermal protection, intermittent operation, or reduced component life.

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7. Environmental Conditions

The installation environment should be evaluated for:

• Temperature
• Humidity
• Dust
• Oil
• Chemical contamination
• Condensation
• Vibration
• Altitude
• Ventilation

Industrial contamination can gradually affect cooling and electrical reliability.

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8. Grounding

Connect the starter to the appropriate protective grounding system.

Verify:

• Starter ground
• Cabinet ground
• Motor ground
• Ground conductor continuity
• Electrical bonding

Grounding should be checked before energizing the system.

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9. Incoming Supply

Connect the incoming three-phase power according to the approved electrical schematic.

Before energizing, verify:

• Supply voltage
• Phase arrangement
• Protective devices
• Disconnect
• Cable sizing
• Terminal identification
• Terminal tightness

---

10. Motor Connection

Connect the motor according to the actual motor nameplate and electrical design.

Verify:

• Rated voltage
• Rated current
• Frequency
• Phase configuration
• Motor grounding
• Cable insulation
• Terminal connections

Incorrect motor wiring can produce poor acceleration or abnormal current.

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11. Control Circuit

The control system may contain:

• Start command
• Stop command
• Fault reset
• Run feedback
• Fault feedback
• Interlocks
• PLC signals
• Emergency-stop logic

The exact control arrangement must follow the machine’s electrical drawings.

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PLC and Automation Integration

The ATS48C79Q can form part of an automated motor-control system.

A simplified architecture is:

PLC

↓

Start / Stop Logic

↓

ATS48C79Q

↓

Three-Phase Motor

↓

Mechanical Process

The PLC can manage the machine sequence while the soft starter handles the controlled motor-starting function.

Typical monitoring signals may include:

• Ready
• Running
• Fault
• Interlock
• Process status

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Commissioning Procedure

Step 1 — Mechanical Inspection

Verify:

• Mounting
• Mechanical support
• Cabinet clearance
• Ventilation
• Cable routing
• Grounding

---

Step 2 — Electrical Inspection

Check:

• Incoming power
• Motor connections
• Protective devices
• Grounding
• Control wiring

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Step 3 — Motor Data Verification

Confirm that all motor information used for configuration corresponds to the actual motor.

Record:

• Motor voltage
• Motor current
• Motor power
• Frequency
• Speed
• Connection
• Duty

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Step 4 — Starting Configuration

Configure the starting behavior according to:

• Motor current
• Load inertia
• Starting torque
• Acceleration requirements
• Number of starts
• Mechanical response

A heavy conveyor, large pump, and fan may require very different starting characteristics.

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Step 5 — Initial Start

Perform the initial start under controlled conditions.

Monitor:

• Motor current
• Acceleration
• Starter status
• Vibration
• Noise
• Motor temperature

If the motor fails to accelerate normally, stop the test and investigate.

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Step 6 — Verify Rotation

Confirm the motor rotates in the correct direction.

Incorrect rotation can cause serious process problems in:

• Pumps
• Fans
• Compressors
• Conveyors
• Mixers

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Step 7 — Test Stopping

Verify the stopping sequence.

Observe:

• Motor response
• Mechanical movement
• Process behavior
• Pressure changes
• Fault status

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Step 8 — Full Load Commissioning

Gradually introduce the normal process load.

Monitor:

• Motor current
• Starter temperature
• Motor temperature
• Vibration
• Acceleration
• Stopping
• Process stability

Record abnormal behavior for further analysis.

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Troubleshooting Guide

ATS48C79Q Does Not Start

Check:

1. Incoming power
2. Start signal
3. Stop circuit
4. Interlocks
5. Control wiring
6. Starter status
7. Motor wiring
8. Configuration
9. Mechanical load

A control interlock can prevent starting even when the power section is healthy.

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No Incoming Power

Possible causes:

• Open disconnect
• Tripped circuit protection
• Missing phase
• Incorrect wiring
• Loose terminal
• Upstream electrical fault

Trace the power path systematically.

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Motor Does Not Accelerate

Possible causes include:

• Excessive mechanical load
• Insufficient starting torque
• Incorrect motor wiring
• Incorrect configuration
• Motor fault
• Mechanical obstruction
• Incorrect starter selection

Inspect both the electrical and mechanical systems.

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Motor Accelerates Too Slowly

Check:

• Starting configuration
• Motor current
• Load inertia
• Mechanical friction
• Motor condition
• Starting duty
• Starter selection

A slow acceleration problem can originate in the mechanical load.

---

Excessive Starting Current

Potential causes include:

• Heavy load
• Incorrect starting configuration
• Motor fault
• Incorrect motor data
• Incorrect starter sizing
• Supply limitations

Measure actual motor current rather than relying only on estimated values.

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Motor Starts Abruptly

If the motor does not exhibit the expected controlled acceleration, investigate:

• Starting configuration
• Control mode
• Bypass arrangement
• Contactors
• Control wiring
• Start signal

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Motor Stops Abruptly

Possible causes include:

• Incorrect stopping configuration
• Stop command
• External contactor
• PLC logic
• Mechanical load

Determine whether the stop command and actual starter response correspond correctly.

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Starter Overheats

Check:

• Motor current
• Starting frequency
• Ambient temperature
• Cabinet airflow
• Cooling fans
• Filters
• Ventilation openings
• Application sizing

Because the ATS48C79Q is installed in a large industrial system, cabinet thermal management should be evaluated as part of the complete installation.

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Motor Overheats

Possible causes:

• Excessive load
• Frequent starts
• Long acceleration
• Mechanical friction
• Motor cooling problem
• Incorrect motor configuration
• Motor degradation

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Phase-Loss Problem

Potential symptoms include:

• Poor acceleration
• Excessive current
• Motor heating
• Protective trips
• Abnormal operation

Inspect the entire power path, including supply, terminals, cables, starter connections, and motor connections.

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Pump Pressure Fluctuation

If the pump system experiences excessive pressure variation:

• Review starting behavior.
• Review stopping behavior.
• Inspect valves.
• Check piping.
• Inspect the pump.
• Evaluate hydraulic conditions.

Soft-starter settings should be coordinated with the actual pumping system.

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Conveyor Starting Shock

If the conveyor continues to experience excessive mechanical shock:

• Review acceleration.
• Inspect belt tension.
• Check couplings.
• Inspect gearbox.
• Verify alignment.
• Evaluate load distribution.

Mechanical problems cannot be solved solely through starter configuration.

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PLC Start Command Fails

Check:

• PLC output
• Control voltage
• Start input
• Stop input
• Interlocks
• Fault state
• PLC logic
• Control wiring

Trace the signal from the PLC through the complete control circuit.

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Intermittent Faults

For intermittent faults, record:

• Fault occurrence time
• Motor current
• Ambient temperature
• Motor temperature
• Number of starts
• Process load
• Supply conditions
• Cabinet temperature

Patterns often help distinguish between thermal, electrical, mechanical, and process-related problems.

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Preventive Maintenance

Electrical Inspection

Inspect:

• Incoming power terminals
• Motor terminals
• Ground connections
• Control wiring
• Protection devices

Look for:

• Loose connections
• Heat discoloration
• Burn marks
• Corrosion
• Damaged insulation

---

Thermal Inspection

Inspect:

• Cooling fans
• Cabinet ventilation
• Air filters
• Air passages
• Dust accumulation
• Cabinet temperature

A gradual reduction in airflow can eventually cause thermal faults.

---

Motor Inspection

Inspect:

• Bearings
• Couplings
• Shaft
• Cooling
• Vibration
• Insulation
• Operating current

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Mechanical Load Inspection

Inspect the driven equipment for:

• Bearing wear
• Gearbox problems
• Belt tension
• Coupling condition
• Pump resistance
• Fan condition
• Shaft alignment
• Mechanical obstruction

Increased mechanical resistance can increase motor current and starter loading.

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Configuration Backup

After commissioning, maintain a record of the final configuration.

Recommended information includes:

• ATS48C79Q model
• Motor nameplate data
• Starting parameters
• Stopping parameters
• Control wiring
• PLC interface
• Application type
• Commissioning date
• Maintenance records

This documentation can significantly simplify future troubleshooting and replacement.

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Replacement Selection Guide

When selecting a replacement for the ATS48C79Q, verify the complete application.

Selection Factor	Verification
Motor Voltage	Required
Motor Current	Required
Motor Power	Required
Starting Duty	Required
Number of Starts	Required
Acceleration Time	Required
Load Inertia	Required
Control Voltage	Required
I/O Requirements	Required
Communication	Required
Cabinet Dimensions	Required
Cooling	Required
Environmental Conditions	Required
Mounting	Required
Mechanical Support	Required

A replacement should not be selected solely because its physical appearance or product family is similar.

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Compatible System Components

Component	Typical Function
Schneider PLC	Machine control
HMI	Operator interface
Circuit Breaker	Power protection
Disconnect Switch	Electrical isolation
Contactor	Switching / bypass
Three-Phase Motor	Mechanical power
Motor Protection Device	Motor protection
Sensors	Process feedback
Control Relay	Interlocking
Industrial Cabinet	Equipment enclosure
Cooling System	Thermal management

Actual component selection depends on the complete machine design.

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Key Advantages

Controlled Acceleration

The ATS48C79Q provides a controlled motor-starting process that can reduce the abrupt electrical and mechanical effects associated with direct starting.

Reduced Mechanical Stress

Controlled acceleration can help reduce stress on:

• Gearboxes
• Couplings
• Belts
• Shafts
• Bearings
• Conveyor systems

Controlled Stopping

Controlled deceleration can help reduce sudden process and mechanical transitions.

Suitable for Large Industrial Equipment

The supplied 890 × 770 × 315 mm dimensions and 115 kg weight indicate a substantial industrial installation requiring appropriate structural support and handling procedures.

Fixed-Speed Motor Applications

A soft starter is particularly suitable where the motor normally operates at a fixed speed and the primary requirement is controlled starting and stopping.

Automation Integration

The ATS48C79Q can be incorporated into PLC-based industrial motor-control architectures.

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Technical FAQs

What is the Schneider ATS48C79Q?

The ATS48C79Q is a Schneider Electric Altistart 48 electronic soft starter intended for three-phase asynchronous motor applications.

What does the ATS48C79Q do?

It controls the motor’s starting and stopping process to reduce abrupt electrical and mechanical transitions.

What are the dimensions of ATS48C79Q?

The supplied dimensions are:

890 × 770 × 315 mm

What is the weight of ATS48C79Q?

The supplied weight is:

115 kg

Is ATS48C79Q a variable frequency drive?

No. The ATS48C79Q is a soft starter. It is designed primarily for controlled motor starting and stopping rather than continuous variable-speed operation.

Can ATS48C79Q be used for pumps?

Yes. Pump systems can benefit from controlled acceleration and stopping when the starter is correctly selected for the motor and hydraulic application.

Can it be used with conveyors?

Yes. Controlled acceleration can reduce mechanical shock in suitable conveyor applications.

Why does the motor fail to start?

Check incoming power, control signals, interlocks, starter status, motor wiring, configuration, motor condition, and mechanical load.

Why is motor acceleration too slow?

Possible causes include excessive load, insufficient starting torque, unsuitable starting parameters, mechanical friction, or incorrect starter sizing.

Why does the ATS48C79Q overheat?

Potential causes include excessive current, frequent starting, high ambient temperature, inadequate cabinet ventilation, blocked airflow, or incorrect application sizing.

Why does the motor overheat?

Possible causes include excessive mechanical load, frequent starts, long acceleration, mechanical friction, poor motor cooling, incorrect configuration, or motor degradation.

Can the ATS48C79Q be controlled by a PLC?

Yes. It can be integrated into an industrial PLC control system through the appropriate control interface.

What should be checked before replacement?

Verify motor voltage, motor current, power, starting duty, number of starts, acceleration requirements, control architecture, cabinet dimensions, thermal requirements, and environmental conditions.

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Installation Checklist

Item	Verification
Manufacturer	Schneider Electric
Product Family	Altistart 48
Model	ATS48C79Q
Product Type	Soft Starter
Dimensions	890 × 770 × 315 mm
Weight	115 kg
Motor Voltage	Verified
Motor Current	Verified
Motor Power	Verified
Cabinet Space	Verified
Mechanical Support	Verified
Lifting Arrangement	Verified
Ventilation	Verified
Grounding	Verified
Incoming Power	Verified
Motor Wiring	Verified
Control Wiring	Verified
PLC Interface	Verified
Starting Parameters	Configured
Stopping Parameters	Configured
Motor Rotation	Tested
Initial Start	Completed
Full Load Test	Completed
Configuration Backup	Completed

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Troubleshooting Decision Flow

For systematic diagnosis, follow this sequence:

Check Incoming Power

↓

Check Start / Stop Signals

↓

Check Interlocks

↓

Check Starter Status

↓

Check Motor Wiring

↓

Measure Motor Current

↓

Review Starting Configuration

↓

Inspect Mechanical Load

↓

Check Cabinet Cooling

↓

Inspect Motor Condition

↓

Perform Controlled Retest

This approach helps separate soft-starter faults from problems involving the electrical supply, PLC, motor, mechanical load, or installation environment.

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Conclusion

The Schneider Electric ATS48C79Q Altistart 48 Soft Starter is designed for controlled starting and stopping of three-phase asynchronous motors in demanding industrial applications. It is particularly useful when direct-on-line starting produces excessive electrical current, mechanical shock, hydraulic disturbances, or unnecessary stress on the machine.

With supplied dimensions of 890 × 770 × 315 mm and a supplied weight of 115 kg, the ATS48C79Q requires careful consideration of cabinet construction, mechanical support, lifting, cable routing, ventilation, and service access.

Successful commissioning begins with correct application selection and verification of the actual motor and load characteristics. Motor voltage, rated current, starting duty, acceleration requirements, starting frequency, mechanical inertia, and environmental conditions should be considered before operation.

When troubleshooting the ATS48C79Q, the complete motor-control system should be examined rather than treating the soft starter as an isolated component. Starting failures, excessive current, overheating, phase-loss conditions, abnormal acceleration, and intermittent faults may originate from the starter, power supply, control system, motor, or driven machinery.

Proper installation, configuration, cooling, preventive maintenance, and systematic troubleshooting can help the ATS48C79Q deliver reliable controlled motor starting and stopping in large industrial motor-control systems.