SD3300 High-Performance Vector Frequency Inverter with High-Torque Control

Precise Motor Control

The IFIND SD3300 is a high-performance vector frequency inverter developed for speed, torque and process control of three-phase asynchronous motors. Its DSP-based control platform supports demanding industrial loads while providing flexible commissioning options for different machines.

Three principal control modes are available:

Sensorless Vector Control

Sensorless vector control, or SVC, estimates motor speed and magnetic flux without relying on a shaft encoder. It is suitable for applications that need stronger low-speed torque and more stable speed control than standard V/F operation.

V/F Control

V/F control provides straightforward frequency and voltage adjustment for pumps, fans and other applications where the load characteristic does not require high-precision torque regulation.

Torque Control

Torque control allows the drive to regulate motor output according to the process demand. It can be used in machinery where controlled pulling force, load response or torque limitation is important.

The SD3300 also integrates speed and position-related control functions. Encoder options can be configured for applications that require closed-loop feedback.

High Torque at Low Speed

The SD3300 delivers 150% starting torque at 0.5Hz under sensorless vector control. Under V/F control, the listed starting torque is 150% at 1.0Hz.

For encoder-supported closed-loop vector configurations, the product information lists torque output of up to 200% at 0Hz. This makes the series suitable for machinery that must start under load or maintain controlled torque at very low speed.

Low-speed torque performance can help in applications such as:

• Loaded conveyor starting

• Air compressor acceleration

• Textile machinery tension control

• Pumps operating under changing pressure

• Machinery with frequent speed changes

• Equipment requiring controlled low-speed movement

The motor data and vector-control parameters should be commissioned correctly to obtain the expected torque response.

Dynamic Speed Response

Industrial machines often experience sudden changes in load. The SD3300 adjusts output frequency, voltage and current to maintain controlled motor operation during acceleration, deceleration and load variation.

Key dynamic functions include:

• Rapid acceleration and deceleration response

• Rotation-speed tracking restart

• Automatic current limiting

• Automatic voltage limiting

• Slip compensation

• Torque boost

• Torque limitation

• Jump-frequency control

• Over-torque detection

• Instantaneous power-loss ride-through function

Rotation-speed tracking allows the inverter to identify the approximate speed of a rotating motor before restarting it. This is useful for fans, pumps and other equipment that may still be rotating when a restart command is issued.

Jump-frequency control can be used to avoid defined operating frequencies where the machine or mechanical structure is prone to resonance.

Built-In Process Functions

Simple PLC and Multi-Step Speed

The integrated simple PLC supports programmed operating sequences without requiring a separate controller for basic applications. Up to 16-step speed control can be configured for processes that operate at several preset speeds.

PID Control

Built-in PID control allows the inverter to adjust motor speed according to a process feedback signal. Typical examples include:

• Water-pressure regulation

• Air-pressure control

• Airflow adjustment

• Temperature-related process control

• Constant-tension applications

The required sensor and feedback signal must match the inverter’s analog input specifications.

Flexible Frequency Commands

Frequency commands can be provided through:

• Digital keypad

• Host computer

• Analog input AI1 or AI2

• High-speed pulse input

• Multi-step speed terminals

• Simple PLC program

• PID control

• RS485 communication

Different command methods can be combined or switched according to the machine-control sequence.

Programmable I/O

Programmable input and output terminals allow the inverter to interact with switches, sensors, relays, controllers and other automation devices. Available terminal functions support operating commands, status signals, frequency references and fault outputs.

The Drawing of SD3300 High Torque Vector Power Inverter

Braking and DC Bus Options

DC Braking

DC braking can be configured for controlled motor stopping. The published settings include:

• DC braking start frequency: 0–400Hz

• DC braking current: 0–150%

• DC braking time: 0–50 seconds

Actual braking settings must account for motor temperature, machine inertia and stopping frequency.

Braking Resistor

A braking resistor can dissipate regenerative energy generated during rapid deceleration or overhauling-load operation. The required resistor, braking unit and duty cycle depend on the drive power and mechanical load.

Common DC Bus

The SD3300 supports common DC bus configurations for multi-drive systems. Connecting suitable drives to a shared DC bus can allow energy generated by one decelerating motor to be used by another accelerating motor.

Common DC bus systems require coordinated protection, correct drive selection and an engineered electrical design.

Industrial Applications

Water Pumps

With V/F, sensorless vector and PID control, the SD3300 can regulate pump speed according to pressure, flow or process demand. Sleep and wake functions can be configured for systems that operate intermittently.

Fans

Smooth speed control allows airflow to be adjusted without relying entirely on mechanical dampers. Speed tracking is useful when restarting a fan that is still rotating.

Air Compressors

High starting torque, pressure-related PID control and flexible acceleration settings support compressor applications with changing demand. Compressor unloading and safety logic must remain integrated with the original machine-control system.

Textile Machinery

Multi-step speed, torque control, programmable I/O and frequency command options can be used in textile processes requiring coordinated movement, tension control or repeatable speed changes.

Industrial Machinery

The SD3300 can also be evaluated for machinery that requires low-speed torque, programmable speed sequences, controlled braking or communication with an automation controller.

Final suitability depends on the motor type, load characteristic, duty cycle, braking demand and environmental conditions.

Protection and Communication

Drive Protection

The SD3300 provides protection for common electrical and operating faults, including:

• Overcurrent

• Overvoltage

• Undervoltage

• Overtemperature

• Input or output phase loss

• Motor and drive overload

• Short circuit

• Excessive torque conditions

Automatic current and voltage limiting help reduce repeated trips during acceleration, deceleration or changes in load. Protection parameters should still be set according to the motor nameplate and machine requirements.

RS485 Communication

Standard RS485 communication allows the inverter to exchange commands and operating data with a PLC, HMI or supervisory control system.

Communication can be used for:

• Start and stop commands

• Frequency setting

• Operating-status monitoring

• Output-frequency monitoring

• Current and voltage monitoring

• Fault-code reading

• Parameter management

The communication protocol, baud rate, station address and data format must match the connected controller.

Technical Specifications

Control Performance

Control Functions

Environmental Conditions

Installation Dimensions

A and B refer to mounting dimensions. H, W and D refer to the overall height, width and depth.

Allow adequate clearance around the inverter for wiring, ventilation and maintenance. The electrical enclosure must be sized for the heat generated by the drive and related braking or filtering components.

Motor and Drive Selection

Provide the following information before selecting an SD3300 configuration:

1. Motor rated power

2. Motor rated voltage

3. Motor rated current

4. Motor rated frequency and speed

5. Supply voltage and phase

6. Load type and operating cycle

7. Minimum and maximum speed

8. Required starting torque

9. Acceleration and stopping time

10. Braking frequency and machine inertia

11. Encoder model, when feedback is required

12. PLC or communication requirements

13. Installation altitude and temperature

14. Enclosure and ventilation conditions

The inverter should be selected primarily according to motor current, load type and overload demand rather than motor power alone.

SD3300 Inverter FAQs

Does the SD3300 require an encoder to produce 150% torque at 0.5Hz?

No. The listed 150% torque at 0.5Hz is available under sensorless vector control, which does not require a PG card or shaft encoder. Correct motor auto-tuning and parameter settings are still important.

Should the inverter be selected by motor power or motor current?

Motor rated current is the primary selection reference. Motor power is useful for initial matching, but heavy-duty loads, frequent acceleration and high ambient temperatures may require a larger drive.

Is motor auto-tuning necessary?

Auto-tuning is recommended when using sensorless vector or torque control. It allows the inverter to identify important motor parameters and improve low-speed torque and speed regulation.

When is a braking resistor required?

A braking resistor may be required when the machine stops quickly, has high inertia or produces regenerative energy. The resistor value, power rating and braking duty must be calculated for the actual load.

Can the SD3300 operate a permanent-magnet synchronous motor?

The current product information identifies the SD3300 primarily for asynchronous motors. Synchronous motor compatibility should not be assumed without confirmation of the control software and exact drive version.

Can one inverter run several motors?

One inverter may operate multiple motors only when they start and stop together and the drive is sized for their combined current. Each motor normally requires separate overload protection. Vector control performance may also be limited in a multi-motor configuration.

Can the inverter restart a motor that is already rotating?

The speed-tracking restart function is intended to detect and follow a rotating motor before resuming control. This is particularly useful for fans and pumps with long coast-down times.

Can the SD3300 be installed outdoors?

The drive should be installed in a protected indoor electrical enclosure unless a suitable outdoor cabinet is provided. It must be protected from rain, condensation, conductive dust, corrosive gas and direct sunlight.