Inovance MD330 Series Tension Control Inverter User Guide: Tension Control Principle, Parameter Settings and Fault Troubleshooting

Introduction to the MD330 Tension Control Specialized Inverter

The Inovance MD330 series is a purpose-built variable frequency drive (VFD) engineered specifically for tension control applications in winding and unwinding operations. Unlike general-purpose inverters that require complex external controllers and tension amplifiers to manage material tension, the MD330 integrates the full tension control algorithm directly into the drive firmware. This eliminates the need for a separate PLC or tension controller in many applications, reducing system cost, wiring complexity, and commissioning time while improving overall control precision.

The MD330 is widely deployed in industries such as textile manufacturing, paper converting, film extrusion, wire drawing, printing, and coating. In all of these processes, maintaining consistent material tension as the roll diameter changes is critical to product quality. The MD330 addresses this fundamental challenge through its dedicated FH parameter group, which contains over sixty parameters exclusively devoted to tension control, diameter calculation, line speed processing, tension compensation, and PID regulation.

This article provides a comprehensive technical guide to the MD330’s tension control principles, the critical parameter groups that govern its operation, and the fault troubleshooting procedures necessary to maintain reliable production.

Tension Control Principles: Winding and Unwinding

Tension control in web-handling and coil-handling applications fundamentally depends on the relationship between material line speed, roll diameter, and the torque applied by the motor. As material is wound onto a core, the roll diameter increases. If the motor speed remains constant while the diameter grows, the material line speed will increase proportionally, which causes tension to rise uncontrollably. Conversely, during unwinding, the roll diameter decreases, and a constant motor speed would cause the material tension to drop. The MD330 solves this by continuously calculating the current roll diameter and adjusting the motor output torque or speed to maintain the desired tension.

The MD330 supports multiple tension control modes, selectable through parameter FH-00. The primary modes are:

• Torque control mode (open-loop): The inverter calculates the required motor torque based on the tension setpoint and the current roll diameter. No tension feedback sensor is required. The inverter uses the formula T = F × D / 2, where T is motor torque, F is the desired tension in Newtons, and D is the current roll diameter. This mode is suitable for applications where moderate tension accuracy is acceptable and where installing a tension sensor is impractical.
• Closed-loop speed mode: A tension sensor (load cell or dancer roller) provides feedback to the inverter. The inverter uses a PID regulator to compare the actual tension with the setpoint and adjusts the motor speed to minimize the error. This mode achieves higher tension accuracy and is recommended for premium applications such as high-speed film casting and precision coating.
• Closed-loop torque mode: Combines torque control with tension feedback. The PID regulator adjusts the torque command rather than the speed command. This provides faster response and is suitable for applications with frequent acceleration and deceleration.

The selection between winding and unwinding operation is determined by the rotation direction and the tension control mode. In winding applications, the motor operates as a motor, consuming energy to pull material onto the roll. In unwinding applications, the motor typically operates in a regenerative braking mode, where the material pulls the motor and the inverter controls the braking torque to maintain tension. The MD330 handles both scenarios natively through its parameter configuration.

Tension Setting and Diameter Calculation Parameters

The core of the MD330’s tension control capability lies in its FH parameter group. Understanding these parameters is essential for proper commissioning.

Tension Setpoint Configuration

The tension setpoint defines the target tension force that the inverter maintains on the material. The MD330 provides flexible tension setting sources through parameter FH-01, which allows the tension command to come from multiple sources:

• Digital setting via FH-02 (direct numerical entry in Newtons)
• Analog input AI1, AI2, or AI3 (for external potentiometer or PLC analog signal)
• Pulse frequency input (for high-speed digital reference from a motion controller)
• Communication setting (via Modbus or CANlink protocol)

Multiple tension setpoints can be pre-configured (FH-02 through FH-04) and selected via multifunction digital input terminals, enabling automatic tension changes for different production recipes or material types without stopping the line.

Roll Diameter Calculation

Accurate roll diameter calculation is the foundation of tension control. The MD330 provides three methods for obtaining the current roll diameter, selectable through parameter FH-10:

• Line speed calculation (FH-10 = 0): The diameter is computed from the ratio of material line speed to motor rotational speed. This is the most common method and requires a line speed signal from the master (traction) drive. The formula used is D = (V × i × 60) / (π × n), where V is line speed, i is gear ratio, and n is motor RPM.
• Thickness accumulation (FH-10 = 1): The diameter is calculated by counting the number of revolutions and adding the material thickness for each layer. Parameters FH-19 (pulses per revolution) and FH-20 (turns per layer) define the counting logic. FH-21 through FH-26 configure the material thickness, which can be set digitally or via analog input. This method is particularly suited for wire drawing and metal foil applications where material thickness is well-defined.
• External diameter input (FH-10 = 2): The diameter value is provided by an external sensor (ultrasonic or laser diameter gauge) via analog input or communication.

The initial roll diameter must be set correctly before starting production. The MD330 provides three initial diameter presets (FH-13, FH-14, FH-15) that can be selected via digital input terminals, allowing the operator to quickly switch between different core sizes. Parameter FH-17 provides a diameter filter time constant (0.0 to 100.0 seconds, default 1.0s) to smooth out diameter calculation fluctuations caused by signal noise or mechanical vibration.

Parameter FH-18 displays the current roll diameter in real-time and can also be manually modified to set the starting diameter. This is useful when resuming production after a roll change where the exact diameter is known.

Taper Tension Control

For winding applications, taper tension (also known as taper tension control) is a critical feature that gradually reduces the tension as the roll diameter increases. This prevents the inner layers from being compressed too tightly, which can cause material deformation, telescoping, or blocking. The MD330 provides comprehensive taper control through parameters FH-48 through FH-65:

• FH-48 selects the taper tension source (digital setting or analog input)
• FH-57 sets the taper tension ratio (0.0% to 200.0%, default 50.0%)
• FH-61 and FH-63 define taper breakpoints (in mm) where the taper ratio changes
• FH-62 and FH-64 set the taper percentages at each breakpoint
• FH-65 selects the taper mode: curve taper (0) for smooth continuous reduction, or linear taper (1) for step-wise reduction

The taper function is particularly important in paper winding and film converting, where a constant tension throughout the roll would result in a hard center and soft outside, or vice versa. By programming appropriate taper breakpoints, operators can achieve a roll structure with consistent density from core to outer layer.

Line Speed Input and Tension Compensation

The line speed signal is essential for both diameter calculation (when using line speed mode) and closed-loop speed tension control. The MD330 accepts line speed input from multiple sources through parameter FH-27:

• No input (0) — used when diameter is obtained via thickness accumulation or external sensor
• AI1, AI2, or AI3 analog input (1, 2, 3) — typically the most convenient method, obtained from the master drive’s frequency analog output
• Pulse frequency input (4) — for high-precision applications where digital line speed signal is available
• Communication setting (5) — line speed value transmitted via Modbus or CANlink

Parameter FH-28 defines the maximum line speed, which corresponds to the maximum frequency of the traction (master) drive. This calibration ensures that the line speed analog signal is correctly scaled. For example, if the traction drive outputs 10V at 50Hz, and the corresponding line speed is 300 meters per minute, then FH-28 should be set to 300 m/min.

The MD330 also provides pre-drive (预驱动) functionality for automatic roll change operations. Parameters FH-45 through FH-56 configure the pre-drive speed gain, torque limit, and diameter calculation behavior during the splice operation. The pre-drive function accelerates the new core to match the current line speed before the splice is made, ensuring that the tension disturbance during roll change is minimized.

High-Speed Torque Compensation

At high operating speeds, mechanical losses such as bearing friction and air drag increase significantly. Without compensation, these losses cause the actual tension to deviate from the setpoint. The MD330 addresses this through parameter FH-51 (high-speed torque compensation coefficient, -50.0% to +50.0%) and FH-52 (compensation basis: frequency or line speed). The compensation is automatically applied as a function of the selected variable, ensuring consistent tension across the entire speed range.

PID Parameters and Control Mode Selection

For closed-loop tension control, the MD330 implements a PID (Proportional-Integral-Derivative) regulator that continuously adjusts the motor torque or speed based on the tension feedback error. The PID parameters are configured through FH-41, FH-42, and FH-43:

Parameter	Name	Range	Default	Description
FH-41	Proportional gain (Kp)	0.0-100.0	—	Determines the immediate response to tension error. Higher values produce faster correction but may cause oscillation if set too high.
FH-42	Integral gain (Ki)	0.0-100.0	—	Eliminates steady-state tension error. Higher values reduce the residual error faster but increase the risk of overshoot.
FH-43	Differential gain (Kd)	0.0-100.0	—	Anticipates tension changes based on the rate of error change. Useful for applications with rapid tension disturbances but amplifies noise.

Parameter FH-44 provides automatic PID parameter adjustment, which can adapt the PID gains based on operating conditions:

• 0: Use only the first set of PID parameters (fixed gains)
• 1: Adjust PID parameters based on roll diameter — as the diameter changes, the system dynamics change, and the PID gains are automatically scaled to maintain stability
• 2: Adjust based on running frequency — suitable for applications with wide speed ranges
• 3: Adjust based on line speed — provides optimal response across different production speeds

The automatic PID adjustment feature is particularly valuable in winding applications where the roll diameter can change by a factor of 10 or more from core to full roll. A fixed set of PID parameters that provides stable control at the core diameter may cause oscillation at full roll, or vice versa. By enabling diameter-based adjustment (FH-44 = 1), the MD330 automatically scales the gains to maintain consistent control performance throughout the winding cycle.

Parameters FH-49 and FH-50 provide closed-loop tension control regulation limits. FH-49 sets the regulation limit (0.0% to 100.0%, default 50.0%), which caps the maximum PID output adjustment as a percentage of the tension setpoint. FH-50 sets the regulation limit offset (0.0% to 100.0%, default 0.0%), which provides a bias to the limit. These parameters prevent the PID regulator from making excessive corrections that could damage the material or cause machine instability.

Automatic Roll Change (Splice) Function

In continuous production lines, roll changes must be performed without stopping the machine. The MD330 provides a comprehensive automatic roll change function through parameters FH-45 through FH-56. The sequence typically operates as follows:

1. The pre-drive function is activated, accelerating the new core to match the current line speed. FH-45 (pre-drive speed gain, -50.0% to +50.0%) fine-tunes the pre-drive speed matching.
2. FH-46 selects the pre-drive torque limit source: either the standard torque limit (F2-09) or a limit calculated from the tension setpoint. Using the tension-based limit ensures that the pre-drive does not apply excessive torque to the new core.
3. FH-47 (pre-drive torque gain, -50.0% to +50.0%) adjusts the torque during the pre-drive phase.
4. After the splice is completed, FH-55 controls whether the diameter calculation resumes immediately (0) or is held (1). FH-56 sets a delay time (0.0 to 10.0s, default 5.0s) before diameter calculation resumes after the pre-drive ends, allowing the system to stabilize.

This automatic roll change capability is one of the key differentiators of the MD330 compared to general-purpose inverters, which would require extensive external logic to achieve the same functionality.

Fault Codes and Troubleshooting

The MD330 inherits the comprehensive fault protection system from the Inovance drive platform. The following table lists the most commonly encountered fault codes, their causes, and recommended troubleshooting actions.

Fault Code	Fault Name	Possible Cause	Solution
Err02	Acceleration overcurrent	Output short circuit or ground fault; acceleration time too short; motor parameters not tuned; manual torque boost too high	Check motor and cable insulation; increase acceleration time (F0-17); perform motor parameter auto-tuning; reduce torque boost
Err03	Deceleration overcurrent	Output short circuit; deceleration time too short; no brake resistor installed; overcurrent stall suppression improperly set	Check motor wiring; increase deceleration time (F0-18); install brake resistor; verify F3-18/F3-19/F3-20 settings
Err04	Constant speed overcurrent	Output short circuit; sudden load change; inverter undersized; external interference	Check for mechanical jams; verify inverter sizing; check fault record current value vs. F3-18 threshold
Err05	Acceleration overvoltage	Input voltage too high; external force driving motor during acceleration; overvoltage suppression improperly configured	Measure input voltage; install brake resistor; adjust F3-22 (action voltage 770V-700V range) and F3-24 (gain 30-50)
Err06	Deceleration overvoltage	Deceleration time too short; high inertia load; no brake resistor; overvoltage suppression not enabled	Increase deceleration time; install brake unit and resistor; enable overvoltage suppression (F3-23); adjust F3-22 and F3-24
Err07	Constant speed overvoltage	Input voltage too high; external force driving motor; load inertia too large	Reduce input voltage; install brake resistor; enable overvoltage suppression
Err09	Undervoltage	Input voltage too low; phase loss; power supply capacity insufficient; contactor failure	Check power supply voltage; check for phase loss; verify power supply capacity; check contactor operation
Err10	Inverter overload	Load exceeds inverter rated current for extended period; insufficient ventilation; ambient temperature too high	Reduce load; improve ventilation; lower ambient temperature; verify inverter sizing
Err11	Motor overload	Motor overloaded; F9-01 (motor overload protection gain) set incorrectly; motor parameters wrong	Reduce load; verify F9-01 matches motor rated current; check F1-00 through F1-05 motor parameters
Err12	Input phase loss	Input phase lost; input wiring loose; contactor contact poor	Check input wiring; check contactor contacts; check F9-12 input phase loss protection setting
Err13	Output phase loss	Output wiring loose; motor winding open; output contactor faulty	Check output wiring and motor continuity; check output contactor
Err14	Module overheat	Inverter散热器 temperature exceeded limit; cooling fan failed; airway blocked; ambient temperature too high	Clean airway; replace cooling fan; reduce ambient temperature; reduce load or duty cycle
Err15	External fault	External fault signal input via DI terminal; external protection device triggered	Check external fault source; verify external protection circuit
Err16	Communication fault	Communication cable disconnected; communication parameter mismatch; communication timeout	Check communication cable; verify baud rate and address settings; check Fd-04 communication timeout setting
Err20	Encoder/PG card fault	Encoder wiring incorrect or broken; PG card not installed properly; encoder type mismatch	Check encoder wiring; verify PG card installation; confirm F1-27 through F1-30 encoder parameters
Err21	Parameter read/write fault	EEPROM failure; parameter copy interrupted; control board hardware fault	Power cycle the inverter; re-attempt parameter initialization; contact technical support if persistent
Err42	Speed deviation too large	Load too heavy; acceleration/deceleration time too short; speed feedback signal unstable; PID parameters improper	Reduce load; increase accel/decel time; check encoder signal quality; adjust F9-69 (deviation threshold) and F9-70 (detection time)
Err43	Motor overspeed	External force driving motor beyond overspeed threshold; speed feedback signal noise; F9-67 setting too low	Check for external driving force; verify encoder signal; adjust F9-67 (overspeed detection value) and F9-68 (detection time)

Fault Record and Diagnosis

The MD330 stores the three most recent fault records, accessible through parameters F9-14 through F9-44. For each fault occurrence, the inverter records the fault type, the operating frequency at the time of fault, the output current, the DC bus voltage, the digital input terminal states, the digital output terminal states, the inverter status, the cumulative power-on time, and the cumulative running time. This comprehensive fault logging enables maintenance personnel to perform root cause analysis long after the fault occurred.

Parameters F9-47 through F9-50 allow configuration of fault protection actions for different fault types. For each fault, the user can select from the following responses:

• 0: Free coast to stop (default for most faults)
• 1: Decelerate to stop according to the configured deceleration time
• 2: Continue running (fault is logged but drive does not stop — use with caution)
• 3: Electromagnetic star-delta braking (for specific motor configurations)
• 4: Warning only (DO output signals the fault but drive continues)
• 5: Cancel (fault detection is disabled)

This granular fault response configuration allows production managers to balance equipment protection against production continuity. For example, a minor communication timeout (Err16) might be configured as a warning rather than a stop, while a motor overload (Err11) would always trigger a stop.

Commissioning Recommendations

When commissioning the MD330 for a new tension control application, the following procedure is recommended:

1. Configure motor parameters: Set F1-00 through F1-05 according to the motor nameplate. Perform motor parameter auto-tuning (F1-37) if possible, as accurate motor parameters are essential for torque control accuracy.
2. Set tension control mode: Select the appropriate mode in FH-00 based on whether a tension sensor is available and whether torque or speed control is preferred.
3. Configure diameter calculation: Set FH-10 to the appropriate diameter calculation method. For line speed calculation, configure FH-27 (line speed source) and FH-28 (maximum line speed). For thickness accumulation, configure FH-19 through FH-26.
4. Set initial diameter: Enter the correct core diameter in FH-13 (or FH-14/FH-15 if multiple cores are used).
5. Set tension setpoint: Configure FH-01 and FH-02 (or analog input) with the desired tension value in Newtons.
6. Tune PID parameters: If using closed-loop control, start with conservative PID values and gradually increase. Enable FH-44 = 1 for diameter-based auto-adjustment.
7. Configure taper tension: For winding applications, set FH-48 through FH-65 to achieve the desired roll structure.
8. Test at low speed: Run the line at reduced speed and verify that tension is maintained correctly. Check the diameter display (FH-18) for accuracy.
9. Gradually increase speed: Once stable operation is confirmed at low speed, gradually increase to production speed, monitoring for oscillation or instability.
10. Set fault protection: Configure F9-47 through F9-50 for appropriate fault responses based on the application’s tolerance for downtime.

Conclusion

The Inovance MD330 series tension control inverter represents a specialized solution that integrates sophisticated tension control algorithms directly into the drive hardware. Its FH parameter group provides over sixty dedicated parameters covering every aspect of tension control, from basic torque calculation to advanced taper tension, automatic roll change, and adaptive PID regulation. By eliminating the need for external tension controllers and simplifying the system architecture, the MD330 reduces cost, improves reliability, and shortens commissioning time for winding and unwinding applications across diverse industries including textiles, paper, film, and wire manufacturing.

Successful deployment requires careful attention to diameter calculation method selection, tension setpoint configuration, PID parameter tuning, and fault protection setup. The comprehensive fault diagnostic system with three-level fault recording ensures that any production interruption can be quickly analyzed and resolved. For operations that demand precise, reliable tension control without the complexity of a multi-component control system, the MD330 offers a compelling, purpose-built solution.