What Are Variable Frequency Drives?

Variable frequency drives, also known as VFDs, control motor speed by adjusting the frequency and voltage supplied to a compatible electric motor.

They are used for motor control, variable-load energy management, controlled starting and stopping, process stability and flow regulation in fan and pump systems.

How Does a VFD Work?

A VFD first converts the incoming alternating current into direct current. Its inverter stage then produces a controlled AC output at the frequency and voltage required by the motor and application.

This allows the motor speed to be adjusted continuously. In suitable fan and pump applications, reducing motor speed during partial demand can lower energy consumption.

Application Areas

• HVAC and mechanical building systems
• Air-handling unit fans
• Extract, exhaust and outside-air fans
• Pumping and pressure-boosting systems
• Chillers, boilers and cooling systems
• Dust collection and filtration systems
• Industrial process lines
• Conveyors and material-handling systems
• Pressure, flow and airflow control
• Automation panels and building management systems

Technical Features

• Single-phase and three-phase supply options
• Capacity alternatives for different motor ratings
• 0–10 V, 4–20 mA and digital-input control
• Relay, analogue and digital output options
• PID functions for pressure, flow or temperature control
• Controlled acceleration and deceleration
• Overcurrent, overvoltage, undervoltage and motor-protection functions
• Models supporting Modbus, BACnet and other communication protocols
• Options for panel installation and protected field applications

System Advantages

• Regulates motor speed according to operating demand.
• Can reduce energy use in suitable variable-load fan and pump systems.
• Limits motor starting current and electrical stress.
• Reduces sudden mechanical loading and shock.
• Enables more accurate pressure, flow and airflow control.
• Can integrate with compatible automation systems.
• May support longer equipment life and lower maintenance requirements.

Variable Frequency Drive Selection Criteria

Selecting variable frequency drives requires more than matching motor power. The application, motor nameplate current, load characteristic, supply, control method, ambient conditions, panel design and communication requirements must be evaluated together.

• Motor power and rated current
• Single-phase or three-phase supply
• Fan, pump, compressor or conveyor application
• Variable-torque or constant-torque duty
• Analogue, digital or networked control
• Panel-mounted or protected field installation
• Ambient temperature, humidity, altitude and dust
• EMC, harmonics and electrical protection requirements
• PLC, BMS or SCADA integration

Use in HVAC Systems

In HVAC systems, VFDs regulate fan and pump speed according to actual demand. They can control outside air, exhaust air, pressurisation, chilled-water and hot-water systems.

Fan speed can be adjusted using airflow, duct pressure or zone demand. When the application and control strategy are suitable, this can improve system balance and reduce energy use.

Use in Pump and Process Systems

In pumping systems, a VFD adjusts motor speed according to pressure or flow demand. For suitable variable-flow applications, this can be more efficient than controlling flow only by throttling a valve.

In process lines, speed can be matched to production requirements. Controlled acceleration and deceleration can also reduce mechanical shock and support process stability.

Automation Integration

VFDs can operate with PLCs, building management systems, automation panels, sensors and controllers. Pressure, flow, temperature and level signals can be used for automatic speed control.

Analogue signals, digital commands, relay outputs and supported communication protocols allow the drive to be integrated into a central automation system.

Energy Efficiency and Operating Costs

Fans and pumps do not always need to operate continuously at full capacity. A correctly applied VFD can reduce motor speed during periods of lower demand and may therefore reduce electricity consumption.

Actual savings depend on the load profile, control strategy, motor-drive compatibility, operating hours and overall system design. Performance should be assessed at system level rather than from the drive alone.

The European Commission provides official information about efficiency requirements for electric motors and variable speed drives.

Maintenance and Commissioning

Safe and efficient operation requires correct wiring, motor nameplate data, parameters, speed limits, acceleration and deceleration ramps, protection settings and control signals.

After commissioning, operating current, motor direction, frequency range, alarms, communications and cooling conditions should be checked. Installation and electrical work must be performed by qualified personnel in accordance with the manufacturer’s instructions and applicable requirements.

Airtes Variable Frequency Drive Solutions

Airtes supports the selection of variable frequency drives for HVAC, mechanical services, dust collection, process ventilation, pump and fan systems.

Drive solutions for new installations and system upgrades are evaluated according to motor data, field conditions, energy objectives and process-control requirements.

Why Choose Airtes?

• Drive selection based on motor data and application
• Technical experience in HVAC, fan, pump and process systems
• Solutions focused on system efficiency and operating requirements
• Selection support for PLC, BMS and automation integration
• Technical contribution to panel, installation and commissioning processes
• Project-specific surveys, analysis and quotation support

Frequently Asked Questions

What do variable frequency drives do?

They control the speed of compatible electric motors so that fans, pumps and process equipment can operate according to demand.

Can a VFD save energy?

Yes, in suitable variable-load applications. Savings depend on motor speed, load profile, control method, operating hours and system design.

Which motors can be used with a VFD?

Many compatible induction and purpose-designed motors can be used when voltage, current, insulation, cooling, speed range and application requirements are correctly evaluated.

How should a VFD be selected?

Selection should consider motor power and current, supply voltage, load type, duty, control strategy, environmental conditions and automation requirements.

Contact Airtes for Variable Frequency Drives

Motor data, fan or pump duty, supply voltage, control strategy, communication infrastructure, panel design and site conditions should be analysed before selecting a drive. The Airtes technical team provides project-specific support.

Contact us for detailed information, a technical survey and a project-specific quotation.