Online double conversion ups output isolation transformer based three phase
Output Isolation Transformer based UPS are most commonly used in all the critical applications where the load characteristics are non-linear, inrush, high starting current. Any critical facility using this technology gives higher reliability and rigidness.
The UPS is connected between the three-phase input power and important loads (like computer) and offers quality three-phase power to the loads. It has the following features:
• Full digitalized technology Dual-DSP control chip, advanced control technology, enhanced logic management and eliminated zero drift with analog control; convenient use of modern control technology; convenient debugging, system update and maintenance; perfect logic functions; diverse interactive data for the customers; convenient communication and network functions
• Highly reliable topological structure The rectifier adopts the most reliable thyristor phase-control technology; the inverter adopts IGBT module half-wave structure and the inverter transformer helps isolate the input and output electricity, which increases safety and shock resistance of the system; the battery is directly connected to the busbar, and the time for the electricity supply to be inverted into battery is zero, which increases the reliability of the system; the switching between inversion and bypass is controlled by a static transfer switch, and the switching time is as short as 0ms.
• Outstanding input and output features
The POWER WALK IN helps achieve gradual connection to oil engine so as to prevent unreliable start of the engine in the parallel operation system; generator power model; applicable in several voltage systems, i.e. 380V/400V/415V; 50HZ, 60HZ; meets most of the voltage systems in the world; high output power factor (0.9 lagging) which strengthens the systems load capacity and ensures sufficient overload capacity.
• Smart Battery Management
The automatic switch between equalizing charge and floating charge, prediction for the discharge time, and regular self-examination increase the service life of the battery.
• N+X parallel operation mode
It is convenient to achieve parallel operation. You only need to connect the parallel cables and set the UPS, and the host is automatically produced. In case the host breaks down, the slave automatically becomes the host, which increases the reliability of the system. The system can have at most 6 sets of UPS connected in parallel.
• LBS synchronization
LBS synchronization allows the system synchronization of two sets of UPS, which offers technical guarantee for the dual-power system.
• Perfect protection
Over-voltage protection; over-frequency protection; over-current protection; over-voltage protection for busbar; over-temperature protection; fault protection for auxiliary power supply; output overload protection; output short-circuit protection; emergency power-off
• Perfect monitoring
Support RS232 and RS485, large LCD screen display; monitoring parts help monitor the working condition of UPS, give instructions, record fault time and other local monitoring functions, and also help achieve the communication between UPS lower machine and monitoring upper computer, and control the auxiliary system.
The operating principle of the stand-alone UPS. The first AC-DC conversion adopts three-phase full-wave rectifier to convert the three-phase AC input voltage into the steady DC bus voltage.
The rectifier can also be used as a charger. The inverter takes IGBT half-wave circuit as its inversion topology. The advanced Space Vector Pulse Width Modulation (SVPWM) is used to control the system, which inverts the DC bus voltage into AC voltage output. When the AC is normal, the rectifier and the inverter work at the same time and simultaneously charge the battery. In case of abnormal AC, the rectifier stops working and the battery supplies power via the inverter. If the battery voltage drops below the cutoff voltage and the AC is not yet back to normal, the UPS shuts down (If the major circuit and the bypass circuit are not of the same source and the bypass circuit is normal, the system is powered by the bypass circuit). The cutoff voltage is preset (eg. the factory setting is 1.67V and the battery
cutoff voltage is 320Vdc). In case of abnormal AC, the battery powers the UPS until its voltage drops to the cutoff voltage. This period of time is called the “backup time”, the length of which depends on the battery’s capacity and the loads.
With the “static switch” intelligently controlling the electronic switching circuit, the loads can be powered by both the inverter and the bypass circuit. Under normal conditions, the loads are powered by the inverter whose static switch is closed. In case of overload (beyond the overload time limit) or fault with the inverter, the static switch will automatically switch to the bypass circuit.
Under normal conditions, complete synchronization of the inverter output and bypass power is a must for achieving uninterrupted switch between inverter output and bypass power. Given such requirement, when the bypass power frequency is within the locking range, the inverter output frequency in the inverter-controlled circuit is tracking the bypass power frequency. What’s more, there is also a manual maintenance bypass switch in the UPS system. When the UPS needs to be shut down for maintenance, the bypass power will directly supply power the important loads via the manual maintenance switch.
Note: When the loads are powered by bypass or maintenance bypass circuit, the power supply is not guaranteed.
When the UPS is functioning properly (i.e. when the UPS input AC is normal, the rectifier and the inverter are functioning properly), the loads are powered by the inverter, the battery switch is closed, and the battery is under the steady floating charge by the DC busbar voltage. (“1+N” parallel UPS system) Note: As the output of all the UPS stand-alone machines are connected in parallel, the system will check whether all the inverter-controlled circuits are operating synchronously, and whether the frequency and phase are in consistence with those of the bypass circuit. The output of each circuit should stay the same. The current for the loads is evenly supplied by each UPS stand-alone machine. In the course of synchronization, the UPS system will display corresponding warning message.
Only when the above requirements are met will the static switch of the stand-alone machine is closed.
In case of AC power failure or abnormality, the rectifier will automatically stop working, and the system will switch to battery inverter output, the inverting time of which depends on the loads and the battery capacity. If the AC is still not back to normal during this period of time, the inverter will automatically stop working, and the UPS operating control panel will display corresponding warning message. The interruption and recovery of the AC do not disrupt power supply to the loads.
If the AC recovers within certain time, the rectifier will automatically start (and its output power gradually increases), supply power to the loads and charge the battery, hence no interruption in the power supply.
Maintenance Bypass Circuit
There is another bypass circuit for the UPS system, i.e. the maintenance bypass circuit, which is used to provide a safe working environment for the technical staff when they are carrying out regular maintenance or repair for the UPS system, and also to provide AC power for untreated loads. The maintenance bypass circuit can be manually selected via the bypass circuit switch, and cut off when switched to “OFF”.
Output Isolation Transformer Based UPS are available from the range of 10KVA to 800KVA with an option to connect parallel units up to 8nos. Output Isolation Transformer Based UPS are widely used in Cathlab UPS, Industrial UPS, Semi Industrial UPS, UPS for the Manufacturing Facilities.