Control Voltage Selection in Roll Forming Machines (24VDC vs 110VAC Explained)

Control Voltage Selection (24VDC vs 110VAC)

Engineering Decisions for Reliable Roll Forming & Coil Processing Control Systems

Control voltage selection is one of the most important architectural decisions in a roll forming control panel.

It affects:

• Operator safety

• PLC reliability

• Sensor stability

• EMC behavior

• Fault diagnosis

• Export compatibility

• Long-term maintenance

The two most common control voltages in industrial roll forming systems are:

• 24VDC

• 110VAC (or 120VAC in North America)

Choosing incorrectly can lead to:

• Nuisance trips

• Coil burnout

• Increased shock risk

• Noise sensitivity

• Inconsistent sensor performance

This guide explains the engineering differences and when each is appropriate.

1) What Is Control Voltage?

Control voltage powers:

• PLC inputs and outputs

• Relay coils

• Contactor coils

• Solenoid valves

• Indicator lamps

• Safety relays

• Sensors

• Encoders

It is separate from main motor power.

Main motor power may be 400–480V.
Control circuits operate at much lower voltage.

2) Why Control Voltage Matters in Roll Forming Lines

Roll forming machines include:

• Vibrating mechanical systems

• High-current VFD outputs

• Long cable runs to field devices

• High-speed encoders

• Hydraulic solenoids

Control voltage must be:

• Electrically stable

• Noise-resistant

• Safe for maintenance

• Globally compatible

3) 24VDC Control Systems

24VDC is now the dominant global standard for modern machines.

Advantages

1. Low shock hazard

2. Compatible with PLC transistor outputs

3. Stable for sensors

4. Cleaner signal integration

5. Better for distributed I/O

6. Easier safety compliance

Typical Architecture

• AC Supply → Control Transformer or SMPS → 24VDC PSU →
• • PLC
• • Safety Relay
• • Relays
• • Solenoid valves
• • Sensors

4) Why 24VDC Is Preferred in Modern Roll Forming

High-speed roofing and structural lines rely heavily on:

• PLC-based automation

• High-speed counter modules

• Servo drives

• Remote diagnostics

24VDC integrates seamlessly with:

• PLC transistor outputs

• Digital inputs

• Solid-state devices

Lower voltage reduces electrical noise impact.

5) 110VAC Control Systems

110VAC control circuits were historically common in:

• Older North American systems

• Legacy contactor-based control

• Basic hydraulic systems

Advantages

• Lower current draw (for same power)

• Fewer DC power supplies required

• Direct compatibility with certain legacy devices

6) Disadvantages of 110VAC Control

In modern VFD-heavy environments:

110VAC introduces:

• Greater shock risk

• Higher arc potential

• More complex isolation

• Higher susceptibility to noise

• Reduced compatibility with PLC transistor outputs

In vibration-heavy roll forming cabinets, 110VAC relays may chatter if voltage fluctuates.

7) Safety Comparison

24VDC:

• Considered safer low voltage

• Lower arc flash severity

• Lower accidental shock risk

• Easier lockout verification

110VAC:

• Higher shock hazard

• Requires stricter isolation

• Increased PPE during troubleshooting

From safety standpoint, 24VDC is preferred.

8) EMC & Noise Considerations

In VFD-heavy cabinets:

High-frequency switching noise can affect control circuits.

24VDC:

• Better noise immunity when properly grounded

• Works well with shielded cable systems

110VAC:

• More sensitive to induced noise

• May create false triggering in long cable runs

High-speed roofing lines benefit significantly from 24VDC systems.

9) Solenoid & Coil Performance

Hydraulic solenoids are often available in:

• 24VDC

• 110VAC

24VDC solenoids:

• Faster response

• Easier PLC integration

• Better diagnostic capability

110VAC solenoids:

• Simpler wiring in older systems

• Less common in modern designs

10) Control Power Supply Architecture

24VDC systems require:

• AC to DC power supply

• Redundant PSU (optional for critical lines)

• Clean distribution blocks

• Fuse-protected outputs

Proper PSU sizing must account for:

• PLC load

• Relay coils

• Solenoid valves

• Sensors

Undersized PSU causes voltage drop and instability.

11) Voltage Drop Considerations

24VDC systems can suffer from voltage drop over long distances.

For remote I/O or long sensor runs:

• Use proper cable sizing

• Keep cable runs reasonable

• Consider distributed I/O cabinets

110VAC suffers less percentage drop but introduces higher hazard.

12) Export Considerations

When exporting roll forming machines:

• 24VDC works globally

• 110VAC may require adaptation (50Hz vs 60Hz compatibility)

• Control transformer taps must match supply

24VDC simplifies international deployment.

13) Mixed Voltage Systems (Best Practice)

Modern architecture often uses:

• 24VDC for logic and PLC

• 110VAC for specific auxiliary devices (if required)

Segregation is critical:

• Separate terminal blocks.
• Clear labeling.
• Distinct trunking.

Mixing voltages randomly increases fault risk.

14) Word-Based Control Voltage Flow Example

24VDC System:

AC → SMPS → 24VDC → Safety Relay → PLC → Relay → Solenoid

110VAC System:

AC → Control Transformer → 110VAC → Contactor Coil → Motor

Signal and power must remain clearly separated.

15) Common Control Voltage Mistakes

1. Undersized 24V power supply

2. Mixing 24V and 110VAC terminals

3. No fuse protection for 24V branches

4. Long unshielded 110VAC runs

5. No redundancy for critical lines

6. Incorrect coil voltage selection

7. No labeling distinction

8. Grounding errors in DC systems

Control voltage errors often cause intermittent faults.

16) When 110VAC Still Makes Sense

Some applications:

• Retrofit of legacy systems

• Very simple machines

• Regions with strong historical preference

• Where DC supply infrastructure is limited

However, new high-speed lines almost always benefit from 24VDC.

17) Buyer Strategy (30%)

Before purchasing or commissioning a roll forming machine, ask:

1. What control voltage is used?

2. Is 24VDC power supply sized correctly?

3. Are control circuits segregated by voltage?

4. Are safety circuits low voltage?

5. Is system compatible with export country frequency?

6. Are PLC outputs transistor or relay type?

7. Are solenoids matched to control voltage?

8. Is documentation clear on voltage classes?

Red flag:

“It uses mixed control voltage with no separation.”

Professional systems clearly define voltage architecture.

6 Frequently Asked Questions

1) Is 24VDC safer than 110VAC?

Yes. It significantly reduces shock risk and arc potential.

2) Can 110VAC cause PLC instability?

Yes, especially in noisy VFD environments.

3) Is 24VDC better for high-speed lines?

Yes. It integrates better with modern PLC and servo systems.

4) Do 24VDC systems require more components?

Yes, they require power supplies, but offer improved reliability.

5) Can both voltages be used in same panel?

Yes, but must be clearly segregated.

6) What is biggest control voltage mistake?

Undersizing 24VDC power supply and mixing voltage classes.

Final Engineering Summary

Control voltage selection in roll forming machines directly affects:

• Operator safety

• PLC reliability

• EMC stability

• Hydraulic control performance

• Export compatibility

• Maintenance efficiency

24VDC is generally the preferred modern standard for:

• High-speed roofing lines

• Structural roll forming systems

• VFD-heavy environments

• Export-ready machines

110VAC may remain in legacy or simple systems but introduces higher risk and integration complexity.

Control voltage is not a minor detail — it is a core architectural decision in industrial panel design.