DC-BANK Voltage Sag Support
Generally, the Variable Frequency Drives (VFDs) are equipped with over-voltage, under-voltage, and momentary power-off protection functions. When a VFD experiences undervoltage or a power outage, the inverter element, which uses IGBT technology, will allow the VFD to continue operating for a predefined period (td). If the undervoltage or power interruption lasts for less than td (to < td), the VFD will smoothly recover and continue running. However, if the duration exceeds td (to > td), the VFD will activate its protection mechanism and stop operation. There-fore, significant AC power fluctuations or prolonged undervoltage conditions can cause the VFD to cease operation. Currently, most common VFDs are AC-DC-AC voltage-source inverters, where the intermediate DC circuit is generated through three-phase AC rectification, resulting in a voltage of approximately 510-620V. Therefore, supplying a VFD with a DC power source in the range of 510-620V will enable the it to operate continuously. Based on this principle, we have developed the LD/DC-BANK, an uninterrupted power supply system that provides DC support for VFDs.
DC-BANK Voltage Sag Support Composition
1. Circuit breaker.
2. VFD drive module, composed of rectifier, inverter, and control unit.
3. Rectifier, composed of diodes or thyristors, filter capacitors, and control units.
4. Voltage sag protection module.
5. Energy storage unit, which is necessary to address short interruptions. Usually, it is composed of standard energy storage batteries or super capacitors.
Product Features
(1) Simple and reliable structure
When used in the VFD speed control circuit, the system does not rely on the conventional UPS to supply AC power to the VVVF, but instead uses the AVS to provide DC power to the VVVF, which eliminates the two power conversions (AC/DC and DC/AC), improves reliability and reduces system power consumption. A conventional UPS rectifier charger not only charges the battery but also supplies the rated DC power to the inverter. In contrast, an AVS charger is dedicated solely to charging the battery, consuming only about 10% of the power required by a conventional UPS, which results in significantly lower operating costs.
(2) The system includes the starting control and protection components for all motors integrated into the system, along with a VVVF inverter (please specify when placing an order).
(3) Multiple VFDs can be connected to a single system without causing circulating currents or mutual interference.
(4) The motors benefit from features such as soft start, speed control, and other VVVF capabilities, along with protections against short circuits, ground faults, overloads, etc.
(5) With freely adjusted output voltage range, the voltage regulator module can provide uninterrupted DC power for various DC loads, such as UPS, EPS, and DC motors. With our buck converter, it can supply a stable 220V (110V) DC power source for microcomputer systems, helping users save on the investment in DC screen equipment.
(6) The charging module has such functions as voltage regulation, current limiting, and temperature compensation in float charge mode.
(7) The control core system is powered by an ATMEL CPU and features a HAITEC touch panel HMI for user interaction. All parameters are digitally configured and monitored, with the ability to display various voltage and current readings. The PLC programming monitors the startup, shutdown, faults, and regular discharge of the battery to a dummy load for each motor.
(8) The modular design allows for easy maintenance and supports parallel operation.
(9) The system circuits are fully independent, ensuring that maintenance on one VVVF loop and its control protection circuits does not impact the operation of other loops.
(10) The system utilizes IGBT inverter power devices and microprocessor-based control, with main components from well-known brands, such as ABB, Siemens, LG, etc.
(11) The DC voltage regulator module employs online tracking and automatic voltage monitoring to ensure that, in the event of a power failure, the system seamlessly switches to battery power, maintaining the input motor voltage, frequency, and speed from the VFD without interruption.
Application Scope
DC-BANK provides uninterrupted power supply for motors in production lines across industries such as power, chemical engineering, chemical fiber, steel, semiconductors, pharmaceuticals, and glass production.
For example: In a chemical fiber plant, if 88 VVVF units in the short fiber production line are equipped with DC-BANK, it could ensure that the process conditions of the production line remain unaffected during grid disturbances, guaranteeing safe production with consistent quality.
For example: The ventilation fan, if equipped with DC-BANK, ensures stable environmental conditions such as temperature, humidity, positive pressure, and cleanliness, creating an optimal and compliant environment for production lines of chemical fiber, semiconductor, and pharmacy.
Data Sheet
| Electrical Parameters | |
| Wiring method | Three-phase four-wire |
| Input voltage | AC380V±10% |
| Operating frequency | 50Hz±1% |
| Product specifications | 3kW~720kW |
| Noise | 50dB during hot standby, 80dB during support. |
| Technical Features | |
| Switching devices | IGBT |
| Heat dissipation methods | Intelligent air cooling |
| Heat dissipation control | Adaptive fan speed adjustment |
| Protection functions | Short circuit, overcurrent, overtemperature, and over/under voltage protection; |
| Overvoltage, undervoltage, overload, overtemperature, and inverter-linked alarm functions; Battery management; | |
| Battery management; | |
| Product Performance | |
| Overall efficiency | ＞98% |
| Support time | 1s~2H |
| Full response time | ＜0.2ms |
| Output voltage range | DC480V (adjustable DC400V-600V) |
| DC800V (adjustable DC700V-1050V) | |
| Display Interface | |
| Display screen | 7-foot full-color touchscreen |
| Language | Chinese, English, and customizable languages |
| Battery display | Parameter control, system time log, voltage event log, event recording and data recording, waveform recording function |
| Communication interface and protocol type | RS485, Modbus protocol, system fault signal can be connected to DCS alarm |
| Environmental Conditions | |
| Operating temperature | -5℃~+40℃ |
| Relative humidity | 5%~90%, no condensation |
| Altitude | ＜1000m |
| Others | |
| Protection level | IP30 rating, other ratings available upon customization. |
| Installation method | Indoor, integrated rack-mount design. |
Q&A
What is voltage sags?
Modern industry requires higher grid availability. Voltage sags not only result in economic losses but also pose potential risks to environmental protection and safety. Therefore, managing voltage dips has become a critical concern. Voltage dips and short interruptions are generally referred to as voltage sags.
What is the definition of a voltage sag?
Voltage Dip: According to the definition in the IEEE standards and national standards of Power Quality - Voltage Dips and Short Interruptions, it refers to the phenomenon in which the power-frequency RMS voltage at a certain point in the power system temporarily drops to 10% to 90% of the rated voltage and lasts for 10 ms to 1 minute, before recovering to normal levels.
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