INVT DBU-055-2 - User Manual

This document describes the operation and maintenance of the INVT Dynamic Braking Unit and Energy Feedback Unit.

Dynamic Braking Unit

Function Description

The INVT dynamic braking unit is designed to rapidly slow down, position, and brake VFD-driven motors. When the VFD brakes, due to large load inertia, the kinetic energy is transformed into electrical energy during braking, causing the DC bus voltage of the VFD to rise. To prevent overvoltage protection from affecting the normal operation of the VFD, the braking unit consumes this regenerated electrical energy. The braking unit can be applied in various scenarios where the VFD drives a high-inertia load that decelerates abruptly, such as elevators, textile machines, paper machinery, centrifuges, washing machines, wire-drawing machines, winding machines, proportional linkage systems, overhead cranes, and other systems.

The main circuit terminals of the braking unit include BR1, BR2 for connecting to the external braking resistor, (+) for the positive terminal of the VFD DC bus, (-) for the negative terminal of the VFD DC bus, and PE for the grounding terminal.

The control circuit terminals include:

• RST (External reset terminal): Short connect to COM terminal for resetting when a braking unit fault occurs.
• EFI (External fault input terminal): When an external fault occurs, the braking unit outputs a fault signal.
• PI (Braking unit parallel input terminal): When multiple braking units are used in parallel, this terminal monitors the operation of other braking units.
• COM (Common terminal): Common terminal for RST, EFI, PI.
• PO1, PO2 (Braking unit parallel output terminal): When multiple braking units are used in parallel, these terminals output signals to enable other braking units to monitor the operation.
• ROA, ROB, ROC (Fault output terminal): When a braking unit fault occurs, the fault relay acts to output a fault alarm signal (ROA-ROB NC, ROA–ROC NO).

Important Technical Specifications

The braking unit's voltage threshold setting is crucial and depends on the VFD input power voltage. The manual provides a table detailing the relationship between voltage selection settings and braking starting/stopping voltages for 220V, 380V, 660V, and 1140V systems. For instance, in a 380V system, the braking starting value can range from 640V to 720V, and the stopping value from 620V to 700V, depending on the S1 selection switch settings.

Braking Resistor Calculation (100% braking torque):

• Braking current (I) is calculated based on rated motor power (P) and DC operating point (V), typically 700V, with a conversion efficiency (η) of 0.7.
• Braking resistor absorbed power (P*I) = Motor regenerative electrical energy (watt) = 1000 * P * η.
• The value of the braking resistance indirectly reflects the value of the braking torque of the system. If the braking torque is too small, the VFD still enables overvoltage protection.
• Power dissipation safety factor (ε) for the braking resistor is typically 1.4.
• Braking frequency (Kf) indicates the time proportion that the regeneration process accounts for the entire motor operation. Typical Kf values are provided for various applications:
  • Uncoiling and reeling: Kf = 50–60%
  • Oil pumping machine: Kf = 10–20%
  • Elevator: Kf = 10–15%
  • Centrifuge: Kf = 5–20%
  • Crane whose lowering height exceeds 100m: Kf = 20–40%
  • The load that brakes occasionally: Kf = 5%
  • Others: Kf = 10%

Model Selection for 380V VFDs (DC operating point 700V): The manual includes tables for various motor powers (kW) and corresponding braking unit models (DBU-055-4, DBU-160-4, DBU-220-4, DBU-315-4), adaptive braking resistor (Ω), dissipated power of braking resistor (kW) at different braking frequencies (10%, 50%, 80%), minimum resistance (Ω), and recommended resistor models. For example, for a 18.5kW motor, the DBU-055-4 unit is recommended with an adaptive braking resistor of 26.5Ω.

Model Selection for 660V VFDs (DC operating point 1120V): Similar tables are provided for 660V systems, including models like DBU-090-6, DBU-160-6, DBU-220-6, DBU-350-6. For a 75kW motor, the DBU-090-6 unit is recommended with an adaptive braking resistor of 16.73Ω.

Usage Features

• Safety Precautions: Emphasizes reading the manual carefully before installation, operation, servicing, and inspection. Warnings highlight potential for serious physical injury or equipment damage if instructions are not followed. Key safety notes include:
  • Do not use incomplete or damaged units/resistors.
  • Confirm proper setup of braking unit and resistor.
  • Avoid voltage-endurance tests.
  • Tighten screws during wiring to prevent fire/leakage.
  • Install cooling devices for parallel units.
  • Avoid touching internal components due to high voltage DC.
  • Braking resistor must have temperature protection.
  • Mount units/resistors on flame-retardant mediums.
  • Disconnect all power supplies and discharge before wiring.
  • Only professionals should perform wiring.
  • Check wiring, master/slave selection, and voltage class before operation.
  • Ensure POWER indicator is off and charging voltage is zero before adjusting/servicing.
• Installation: The braking unit should be installed in a well-ventilated indoor place. Ambient temperature should be -10°C to 40°C. Avoid electromagnetic interference, dust, oil mist, corrosive gases, direct sunlight, and vibration. Humidity should be less than 90% RH.
• Wiring: Connection cables between the VFD and braking unit, and between the braking resistor and braking unit, should be shorter than 5m and 10m respectively. The DC+ and DC- terminals inside the VFD are positive and negative, respectively. The braking unit can continuously brake up to 5 minutes at 100% braking ratio. For longer continuous braking, a larger power unit or operation at 50% braking ratio is needed.
• Parallel Operation: When using multiple braking units in parallel, one unit is designated as master and others as slaves. The master's parallel output terminals (PO1, PO2) are connected to the parallel input terminals (PI, COM) of the slave units to monitor their operation.
• Operation Panel: Features a digital display, function indicator, and unit indicator. Keys include PRG/ESC (programming/escape), DATA/ENT (confirmation), UP, DOWN, SHIFT, RUN, and STOP/RST.
  • PRG/ESC: Enter/exit level-1 menus, delete parameter.
  • DATA/ENT: Enter cascading menus, confirm parameter setting.
  • UP/DOWN: Increase/decrease data, move upward/downward.
  • SHIFT: Select display parameters, select digits for parameter setting.
  • RUN: Run VFD (keypad control).
  • STOP/RST: Stop VFD, reset fault.
• Indicators:
  • RUN/TUNE: Energy feedback unit running status (Off: stopped, On: running).
  • LOCAL/REMOT: Control mode (LED off: keypad, LED blinking: terminals, LED on: remote communication).
  • TRIP: Fault indicator (LED on: fault state, LED off: normal state).
• Function Parameters (Energy Feedback Unit):
  • P0.00 Control mode selection: 0: Keypad control, 1: Terminal control (S1: automatic, S2: manual). Default: 1.
  • P0.01 Keypad control mode: 0: Automatic, 1: Manual. Default: 0.
  • P0.02 Digital filter times: 1-10. Default: 1.
  • P0.03 Current protection threshold at power-off: 0.0-30.0%. Default: 0.0%.
  • P0.04 Voltage difference of starting feedback: 380V (40.0V), 690V (60.0V), 1140V (120.0V).
  • P0.05 Voltage difference of stopping feedback: 380V (10.0V), 690V (15.0V), 1140V (30.0V).
  • P0.06 Feedback stopping time: 0.1-10.0s. Default: 1.0s.
  • P0.07 Input power frequency: 0: 50Hz, 1: 60Hz. Default: 0.
  • P0.08 Terminal S3 function selection: 1-15 (3: External fault). Default: 3.
  • P0.09 Terminal S4 function selection: 1-15 (2: Fault reset). Default: 2.
  • P0.11 AO output: 0: DC bus voltage, 1: Output current. Default: 1.
  • P0.16 Cooling-fan running mode: 0: Run after starting, 1: Start when temperature > 45°C. Default: 1.
  • P0.18 Relay output selection: 0-15 (4: Fault output). Default: 4.
  • P0.19 Undervoltage protection: 380V (380.0V), 690V (470.0V), 1140V (1100.0V).
  • P0.20 Fault reset count: 0-3. Default: 0.
  • P0.21 Fault reset time: 0.1-10.0s. Default: 3.0s.
  • P0.23 Feedback current limit point: 100-200. Default: 165.
  • P0.25 Function parameter restoration: 0: Unchanged, 1: Restore default, 2: Clear fault records. Default: 0.
  • P0.33 Parameter locking: 0: None, 1: Lock. Default: 0.
  • P1.00 Factory password: 0-65535. Default: *****.
• Automatic Mode (Energy Feedback Unit): Operation stops automatically when the bus voltage is detected. Feedback starts when VFD bus voltage minus standard bus voltage is greater than P0.04. Feedback stops when VFD bus voltage minus standard bus voltage is less than P0.05.
• Manual Mode (Energy Feedback Unit): The feedback unit continuously feeds back when the running command is given.

Maintenance Features

• Routine Maintenance:
  • Confirm ambient temperature (0°C to 50°C) and humidity (20% to 95%).
  • Check for oil mist, dust, and water condensation inside the unit.
  • Verify normal heat and vibration.
  • Ensure fan runs normally without debris.
  • Confirm input power voltage and frequency are within range.
• Periodic Maintenance (within six months):
  • Check for loose external terminal screws and tighten them.
  • Completely eliminate dust and debris from the PCB board using compressed air.
  • Check for abnormal noise and vibration from the fan; clear debris or replace the fan if accumulated time exceeds 20,000 hours.
  • Check electrolytic capacitors for discoloration or unusual smell; replace if necessary.
  • Check radiator for dust and debris; completely eliminate using compressed air.
  • Check power components for dust and dirt; completely eliminate using compressed air.
• Wearing Part Replacement:
  • Fan: Replace if used for more than 20,000 hours.
  • Electrolytic capacitor: Replace if used for 30,000 to 40,000 hours.
• Troubleshooting: The manual provides a comprehensive table of fault codes, fault types, possible causes, and solutions for both Dynamic Braking Units and Energy Feedback Units.
  • OUt3 (Inverter unit fault): Possible causes include damaged IGBT module, misoperation due to interference, poor grounding. Solutions involve checking for interference, pressing STOP/RST, and seeking technical support.
  • OC3 (Overcurrent during running): Caused by feedback energy transient/exception or undersized unit. Solutions include checking wiring, selecting a larger power unit, and seeking technical support.
  • OV3 (Overvoltage during running): Caused by feedback energy exception, high voltage threshold, or insufficient unit capacity. Solutions include checking input feedback energy, reducing voltage threshold, selecting a larger power unit, and seeking technical support.
  • OL2 (Energy feedback unit overload): Caused by low energy feedback voltage threshold, feedback energy exception, or undersized unit. Solutions include resetting voltage threshold, reducing transient energy, selecting a larger power unit, and seeking technical support.
  • SPO (Input power phase loss): Caused by AC-side power failure. Solutions include detecting AC-side input power and seeking technical support.
  • OH2 (Inverter module overheat): Caused by blocked air duct/damaged fan or high ambient temperature. Solutions include ventilating air duct/replacing fan, lowering ambient temperature, checking/reconnecting, and seeking technical support.
  • EF (External fault): Caused by S3 external fault input terminal activation. Solutions include checking external device input and seeking technical support.
  • ItE (Current detection fault): Caused by poor contact of control board connector. Solutions include checking/re-plugging connector and seeking technical support.
  • EEP (EEPROM read/write fault): Caused by error in reading/writing control parameters or damaged EEPROM. Solutions include pressing STOP/RST and seeking technical support.
  • CP (Control power fault): Caused by damaged auxiliary power supply. Solution is to seek technical support.
  • PEr (Parameter setting error): No specific solution provided, implies re-checking parameter settings.