CONTROL TECHNIQUE VFD

Product Description

 VFD Control Technique Specifications

1 VF Control Scalar Control

Description

Maintains a fixed voltagetofrequency ratio to control speed

Typical Specification Parameters

Parameter Typical Value  Range

Speed Regulation Accuracy 2 to 5

Torque Capability 100 rated torque above base speed reduced at low speed

Stability Good for constant load

Control Type Open loop

Feedback Not required

Suitable Motor Standard induction

Primary Use Fans pumps blowers

Response Time Slowmoderate

Key Notes

Easy to configure

Cheapest option

Poor dynamic and transient response

2 Sensorless Vector Control SVC  OpenLoop Vector

Description

Estimates rotor flux and torque without encoder  better torque at low speed

Typical Specification Parameters

Parameter Typical Value  Range

Speed Regulation Accuracy 1 to 3

Starting Torque 150200 of rated

Control Type Open loop

Feedback Optional current  voltage sensors

Motor Type Induction

Torque Control Good

Response Time Moderate

Key Notes

Doesnt require encoder

Much better lowspeed performance than VF

3 ClosedLoop Vector Control FOC  FieldOriented Control

Description

Uses feedback encoder resolver for precise motor control and full torque at very low speed

Typical Specification Parameters

Parameter Typical Value  Range

Speed Regulation Accuracy 01 to 1

Starting Torque 200 of rated

Control Type Closed loop

Feedback Encoder  Resolver

Motor Type Induction  Synchronous

Torque Control Excellent

Response Time Fast

Key Notes

Maintains torque at standstill

High cost and configuration complexity

4 Direct Torque Control DTC

Description

Directly controls motor torque and flux using instantaneous values

Typical Specification Parameters

Parameter Typical Value  Range

Speed Regulation Accuracy 05 to 15

Torque Ripple Moderate

Control Type Open or closed loop

Feedback Optional

Motor Type Induction

Response Time Very fast

Key Notes

Fast dynamic response

Some torque ripple and acoustic noise

Works without encoder in many VFDs

5 PID Control Process Control in VFD

Description

Uses feedback from process pressureflowtemperaturelevel to adjust motor speed

Typical Specification Parameters

Parameter Typical Value  Range

Control Loop Standard PID PID adjustable

Feedback Types Analog 420 mA 010 V Digital

Update Rate 10100 ms

Tuning Auto or Manual

External Sensor Required

Key Notes

Not a motor control method but integrates with VFD for process loops

Saves energy

6 Servo  PMSM Control

Description

Highprecision control for permanent magnet synchronous motors

Typical Specification Parameters

Parameter Typical Value  Range

Speed Regulation 001 or better

Torque Capability High with feedback

Control Type Closed loop vector

Feedback Encoder  Resolver

Dynamic Response Extremely fast

Application Focus Robotics CNC automation

Key Notes

Designed for motion profiling

Needs advanced feedback and tuning

 Comparison Summary

Feature VF SVC FOC DTC PMSMServo

Encoder Required No No Yes Optional Yes

LowSpeed Torque Poor Good Excellent Very good Excellent

Dynamic Response Low Medium High Very high Very high

Complexity Low Medium High High Very high

Cost Low Mid High High Highest

 Typical VFD Datasheet Values

When you read a VFD spec sheet youll see control techniques listed alongside

 Control Modes Supported VF SVC Vector DTC

 Speed Control Accuracy x

 Torque Capability  of rated torque at low speed

 Feedback Support EncoderResolver

 Communication Modbus CANopen Profibus etc

 IO Analog and digital inputsoutputs

 Example Use Cases

Fans  Pumps VF

Conveyors SVC

CNC Machines FOC or DTC

HighPerformance Robotics PMSMServo

Process Control Systems VFD  PID loop

If you want I can tailor this spec table for a specific VFD model eg INVT Control Techniques Schneider ABB or help you choose the right control technique for your machine