SD310L Open-Loop Elevator Inverter with Sensorless Vector Control

Open-Loop Control for Elevator Systems

The IFIND SD310L is an open-loop elevator inverter developed to control motor speed and torque in passenger and freight lift applications. It operates without motor-speed feedback from a shaft encoder, simplifying the drive configuration in elevator systems where sensorless control provides sufficient operating performance.

The inverter receives operating commands and speed references from the elevator controller, then regulates the connected motor during starting, acceleration, travel, deceleration and stopping.

The SD310L is a motor drive rather than a complete elevator controller. Landing logic, door control, mechanical brake management, safety circuits, limit switches and emergency functions must be handled by suitable external elevator equipment.

Sensorless Vector and V/F Control

The SD310L provides two principal motor-control modes.

Sensorless Vector Control

Sensorless vector control, or SVC, estimates motor operating conditions without requiring encoder feedback. Compared with conventional V/F control, it provides stronger low-speed torque and more controlled speed response.

SVC is intended for lift systems that require:

• Loaded starting

• Controlled low-speed movement

• Stable acceleration

• Improved response to changing car loads

• Wider speed adjustment

• Operation without a motor encoder

Correct motor nameplate data and auto-tuning procedures are important for obtaining the listed sensorless vector performance.

V/F Control

V/F control adjusts motor voltage according to output frequency. It provides a simpler control method for applications where the required torque and speed accuracy are less demanding.

The correct mode should be selected according to the motor, elevator mechanism, operating speed, load variation and required ride performance.

High Starting Torque at Low Speed

Under sensorless vector control, the SD310L provides 150% of rated torque at 0.5Hz. This low-frequency torque capability supports controlled starting when the lift car is loaded.

Low-speed torque is particularly important during the transition between standstill and movement. Insufficient torque or incorrect motor parameters may lead to slow response, current fluctuation or unstable starting.

The final result also depends on:

• Motor condition and rated current

• Gearbox and traction-machine condition

• Counterweight balance

• Mechanical brake timing

• Car load

• Acceleration settings

• Motor auto-tuning

• Drive sizing

The inverter must not be relied upon to hold the car mechanically at standstill. A correctly designed and controlled mechanical brake remains necessary.

Speed Regulation Performance

The published sensorless vector performance includes a 1:100 speed adjustment range and speed accuracy within ±0.5% of maximum speed.

This allows the elevator controller to command different operating speeds for:

• Starting

• Normal travel

• Approach

• Inspection operation

• Maintenance jogging

• Controlled stopping

The actual car-speed accuracy also depends on the traction system, motor slip, controller commands, mechanical load and commissioning quality.

Open-loop control does not provide the same direct motor-speed feedback as a closed-loop system. Applications requiring very high speed accuracy, zero-speed torque or precise position control should be evaluated separately.

Overload Capacity for Lift Duty

Elevator motors may experience short periods of high current during loaded starting and changes in operating conditions. The SD310L provides the following published overload capacity:

• 150% of rated current for 60 seconds

• 180% of rated current for 10 seconds

These ratings allow the drive to handle temporary overloads within the specified time limits. They do not mean the inverter can operate continuously above its rated current.

Drive selection should consider:

• Motor nameplate current

• Maximum car load

• Counterweight ratio

• Starts per hour

• Travel duration

• Acceleration time

• Ambient temperature

• Installation altitude

• Braking demand

Selecting only by motor power may result in an undersized drive. Rated motor current and actual elevator duty should be reviewed together.

Flexible Speed and Command Sources

The SD310L accepts speed references and operating commands from several sources:

• Built-in keypad

• Analog input

• Serial communication

• Multi-step speed settings

• PID control

• Combined command modes

Different sources can be selected or switched according to the elevator-control design.

During normal elevator service, travel commands should usually come from the elevator controller. The keypad and JOG function are more appropriate for commissioning, inspection or maintenance procedures carried out by qualified personnel.

The carrier frequency can be adjusted from 0.5kHz to 15.0kHz. Carrier-frequency selection affects motor noise, switching losses, drive temperature and cable-related electrical effects. It should be set according to the motor, cable length and installation conditions.

Multi-Step and Auxiliary Functions

Eight-Step Speed Control

Up to eight preset speeds can be configured. These settings can support different stages of elevator movement or dedicated inspection and maintenance speeds when coordinated with the main controller.

The complete speed sequence, including acceleration and stopping, must be commissioned according to the elevator mechanism and control logic.

Torque Control

The inverter provides multiple torque-reference sources. Torque settings can be used to limit or regulate motor output according to the operating requirement.

Torque parameters must be adjusted carefully. Incorrect limits may prevent the car from starting normally or may produce excessive current.

Speed Tracking

The speed-tracking function allows the inverter to identify and start a motor that is already rotating. It is intended to reduce the impact that may occur when control is applied to a moving motor.

This function does not replace brake sequencing, zero-speed confirmation or elevator safety logic.

PID and Traverse Functions

The SD310L also lists PID and traverse-control functions. These are general drive functions and are not necessarily required in every elevator installation. Their use should be determined by the control-system designer.

QUICK/JOG Key

The QUICK/JOG key can be assigned as a user-defined shortcut. It can simplify selected commissioning or maintenance operations when enabled by an authorized technician.

Programmable I/O

The SD310L provides programmable control terminals for connection to the elevator controller and related automation devices.

These terminals may be assigned to command, reference, operating-status or fault functions according to the parameter configuration.

Before wiring, confirm:

• Signal voltage and current type

• Common-terminal arrangement

• Input polarity

• Relay contact capacity

• Shielding and grounding

• Controller signal logic

• Fail-safe response to wire disconnection

Signal cables should be routed separately from motor and power cables where practical to reduce electrical interference.

Passenger and Freight Lift Applications

Passenger Elevators

For passenger-lift applications, the SD310L can regulate motor starting, acceleration, travel and deceleration without encoder feedback.

Ride quality depends on the complete system rather than the inverter alone. Controller commands, mechanical brake timing, traction-machine condition, guide-rail condition and parameter tuning all affect the passenger experience.

Freight and Cargo Elevators

Freight lifts can involve larger load changes and more demanding starting conditions. The SD310L’s low-frequency torque and temporary overload ratings support appropriately matched cargo-lift systems.

The drive must be sized using maximum operating current and actual load duty. Frequent heavy-load starts may require a larger current rating than a basic motor-power comparison suggests.

New Installations and Modernization Projects

The SD310L may be evaluated for new systems or modernization projects where an open-loop drive is compatible with the existing motor and controller.

For modernization work, confirm the old system’s:

• Motor nameplate

• Controller output signals

• Existing speed references

• Mechanical brake sequence

• Power supply

• Motor cable

• Fault relay logic

• Inspection controls

Do not assume that the existing terminal functions or parameter values can be transferred directly to a new inverter.

Elevator System Integration

A complete lift system normally includes an elevator controller, inverter, motor, traction mechanism, mechanical brake, door system, position devices and safety circuit.

The SD310L controls motor output, but the surrounding system must manage the elevator operating sequence and safety functions.

Integration should include coordinated control of:

1. Run direction

2. Speed reference

3. Drive enable

4. Mechanical brake release

5. Acceleration and deceleration

6. Stop command

7. Brake application

8. Drive fault feedback

9. Inspection operation

10. Emergency response

The inverter must not bypass door interlocks, final limit switches, overspeed protection, emergency-stop circuits or other mandatory lift-safety devices.

System design, installation and acceptance testing must follow the applicable lift regulations and electrical standards in the installation country.

Protection and Power-Loss Response

The product information lists up to 24 fault-protection functions. The exact fault categories, detection thresholds and reset conditions should be taken from the SD310L operating manual for the selected model.

The inverter also includes automatic voltage regulation, which helps stabilize motor-output voltage when the input supply fluctuates within the permitted operating range.

A short power-loss response function is listed for instantaneous supply interruptions. Its actual operating time depends on DC-bus voltage, motor load, inertia and parameter settings.

This function is not an emergency rescue device. It does not mean the elevator can automatically travel to a landing during an extended outage. Where automatic rescue operation is required, the complete controller, inverter and approved ARD or UPS system must be engineered and tested together.

Faults should not be reset repeatedly without identifying their cause. Qualified personnel should check the motor, brake sequence, wiring, load condition and fault history before returning the lift to service.

Technical Specifications

Control Performance

Command and Signal Functions

Electrical ratings, available power sizes and physical dimensions must be selected according to the exact SD310L model ordered.

Installation and Commissioning

The SD310L should be installed and commissioned by personnel familiar with elevator drive systems and electrical safety.

Before Power-On

Check the following items:

• Supply voltage matches the inverter rating

• Motor voltage and current match the selected drive

• Input and output terminals are not reversed

• Protective grounding is complete

• Control signals use the correct voltage

• Motor and signal cables are routed correctly

• The mechanical brake remains applied

• The safety circuit is functional

• The cabinet provides suitable ventilation

• No loose tools or conductive material remain inside the panel

Motor Setup

Enter the motor nameplate data required by the inverter and complete the applicable motor-identification procedure before evaluating sensorless vector performance.

Do not carry out rotating auto-tuning unless the lift system has been secured and the procedure is permitted by the machine manufacturer.

Initial Testing

Begin with controlled inspection operation. Verify:

• Motor direction

• Current at low speed

• Brake release and application timing

• Speed-command switching

• Acceleration and deceleration

• Stop response

• Fault relay operation

• Empty-car operation

• Loaded operation

Passenger service should begin only after the complete elevator has passed the required inspection and acceptance tests.

Manufacturing and Technical Support

IFIND was established in 2016 in Haiyan, Zhejiang. The company states that its facility covers approximately 15,000 square metres and employs more than 150 people.

Its production and service capabilities include:

• Frequency inverter manufacturing

• Elevator inverter product development

• In-house SMT production

• OEM and application-specific configuration

• Technical support from inquiry through shipment

• Remote one-to-one assistance

• Service through overseas agents

For an elevator project, IFIND engineers can review the motor nameplate, drive current, controller signals, load duty and required operating modes before the order is confirmed.

Before Selecting the SD310L

Prepare the following project information:

1. Passenger or freight-lift application

2. New installation or modernization project

3. Motor manufacturer and model

4. Motor type

5. Rated motor power

6. Rated motor voltage

7. Rated motor current

8. Rated motor frequency and speed

9. Supply voltage and frequency

10. Maximum lift load

11. Rated car speed

12. Traction and counterweight arrangement

13. Required control mode

14. Acceleration and deceleration requirements

15. Starts per hour

16. Mechanical brake-control sequence

17. Controller command and reference signals

18. Required serial communication method

19. Cabinet temperature and ventilation

20. Emergency rescue-system requirements

Providing this information helps determine whether the SD310L is suitable and which electrical rating should be selected.

SD310L Elevator Inverter FAQs

What does open-loop elevator control mean?

Open-loop control means the inverter regulates the motor without receiving continuous motor-speed feedback from a shaft encoder. The SD310L uses sensorless vector control to estimate motor conditions and improve torque and speed response.

Does the SD310L require an encoder?

The listed SVC performance does not require a motor encoder. However, the complete elevator may still use position or speed devices for other controller and safety functions.

What is the difference between open-loop and closed-loop elevator drives?

An open-loop drive estimates motor speed without encoder feedback. A closed-loop drive receives direct feedback from an encoder and is generally selected when higher speed accuracy, zero-speed torque or more demanding ride performance is required.

Can the SD310L operate a permanent-magnet synchronous motor?

The current product page does not clearly identify permanent-magnet motor compatibility. Do not connect a PMSM or gearless traction machine unless the exact SD310L version and control software have been confirmed for that motor type.

Can the SD310L be used for passenger and freight elevators?

Yes. The published application information identifies both passenger and cargo lifts. The selected inverter rating must still match the motor current, maximum load and operating duty.

Does 150% starting torque mean the inverter can hold the elevator at zero speed?

No. The published rating is 150% torque at 0.5Hz under SVC. It does not establish zero-speed holding capability and does not replace the mechanical brake.

Is the inverter also the elevator controller?

No. The SD310L controls motor speed and torque. Floor logic, door operation, position control, safety circuits and the complete lift sequence require a suitable elevator controller and related safety equipment.

Does the instantaneous power-loss function provide emergency rescue operation?

No. A short power-loss response function is not equivalent to an automatic rescue device. Emergency landing during an outage requires a compatible controller, approved ARD or UPS equipment, and a tested rescue sequence.

How should the inverter size be selected?

Use the motor rated current, maximum lift load, overload demand and operating duty as the main references. Motor power alone is not sufficient for final selection.

What should be checked if the lift starts roughly?

Review motor data, auto-tuning, low-speed torque parameters, acceleration settings, brake timing, controller commands, counterweight balance and mechanical condition. Do not compensate for a mechanical or brake problem only by increasing torque settings.

Can the SD310L run several lift motors?

A passenger or freight elevator normally requires one drive matched to one traction motor. Multi-motor operation should not be assumed because it can affect sensorless vector performance and motor protection.

Can fault protection replace the elevator safety circuit?

No. Drive protection responds to inverter and motor operating conditions. It does not replace door interlocks, overspeed protection, final limits, emergency stops or other required elevator safety devices.