Pro901S-L

Professional Series (1P/1P) – TOWER
PRO 901S / PRO901L 1 KVA. Version 1.00

II. PRINCIPLE OF OPERATION
This Professional Series (1P/1P) – Tower 1KVA Online UPS system contains 4 major PCB assemblies.

They are including : 
1. PSDR : Contain major parts of
(1) DC Power Suply
(2) DC to DC converter
(3) Inverter
(4) Input and Output Circuit
(5) RS232 (communication port)

 2. CNTL : Contain major parts of 
(1) protection
(2) Signaling Circuits
(3) Regulation & control circuits of Inverter

3. CHG/ Charger : Provide 1A/5A charging current for standart models and long run models

4. PFC : Provide contant BUS Voltage to Inverter in Buck and Boost mode 

The simplified schematics in figure 1 show how the major circuits are connected and illustrate the overall system functions.

The locations of these assemblies are shown in figure 2.1

The block diagram in figure 3, shows the UPS at normal operation from left to right. Basically, this Online UPS system utilizes high frequency PWM techniques to achieve high efficient performance in battery mode. In line mode, the UPS is true double convention, and the efficiency will reach to 88%.

The sub-systems are described as below:

1.POWER STAGE (PSDR)
As shown in figure1, the power stage consists of  : 
1. DC power supply, 
2. DC-DC converter,
3. Inverter, 
4. Input and output circuits.

1-1 DC Power Supply Sub-System :
The input of the DC power supply is connected to the battery bus, i.e., the output of the charger. The output of DC power supplies provides +12 Vdc for the bias supply of IC's working voltage and the fan(s) voltage. The DC power supply works only when the 12 Vdc regulator supplies Vcc to its control IC. To have proper operation of 12 Vdc regulators, its input power is controlled by the switch as indicated in figure 5.

Figure 4:

1-2 Inverter Sub-System :
The UPS transfers DC bus voltages to the AC output voltage through an inverter of full bridge configuration in battery mode. The schematic diagram of inverter is shown in figure 5. To construct a high frequency (19.2 kHz) PWM inverter, the drivers receive switching signals from PWM generation circuit through 2 PWM ICs to trigger the four IGBT alternately. The output of IGBT' is filtered by an LC circuit to reduce the o/p voltage harmonics distortion.

1-3 The Input and Output Sub-System :
All the relays receive signals from control circuit.
The Input relay is a safety relay to switch the mains in or not. The output relay switches the output of the UPS from bypass to inverter or reverse. The input and output noise filter circuit blocks EMI noise to the loads.

1-4 DC-DC Converter Sub-System :
The major function of the UPS is to deliver accurate AC power to the loads connected to it whenever the AC line is correct or fails. In this system, the batteries release the stored energy to supply inverter immediately upon AC line fails.
Refer to figure 6, the battery voltage is transformed through a push-pull DC-DC converter to 360Vdc as DC buses for inverter. When the line fails, the 360Vdc DC sources are caught up to supply the power needed by the inverter immediately.

2. MAIN CONTROL PCB ASSEMBLIES (CNTL)
These assemblies are the control center of UPS. It is composed of three major circuits as following.
(1) Regulation & control
(2) Protection
(3) Signaling

2-1 REGULATION & CONTROL SUB-SYSTEM :
This portion can be seen as brain of the UPS. It provides the control pulses to the switching elements which deliver power to the output. The sub-system also regulates the output to ensure that the UPS is delivering constant AC voltage to the loads.
The inverter signal is sensed directly by resistor division. It is compared with a reference signal from sine wave generator. The difference of these two signals (error signal) alter the pulse widths of PWM signals which control the duty cycles of switching elements to regulate the output voltage within specification.

2-2 PROTECTION SUB-SYSTEM:
The UPS provides the following protection circuits:
1. Overload protection. 
The load detector senses the load current. i.e. the inverter current, and sends the signal by two paths. The UPS will go to failure mode if overload condition happened. The panel will indicate the fault condition. 
There are two kinds of protection in our UPS :
a. Overload Protection: The UPS collects the continuous overload signals through CPU switch the output relay.
In Line Mode :
- if the output load is higher than 103% and lower than 110% of rated load (VA, or Wattage) the UPS will warning, after 5 minutes go to fault mode. 
- If the output load is between 110% and 130% of rated load (VA, or Wattage) the UPS will warning, after 10seconds go to fault mode.. 
- If the output load is higher than 130% of rated load, the UPS will go to fault mode after 1second.

In battery mode : 
- if the output load is higher than 110% and lower than 120% of rated load (VA, or   
  Wattage) the UPS will warning, after 0.5minutes go to fault mode. 
- If the output load is between 120% and 130% of rated load (VA, or Wattage) the UPS will   warning, after 10seconds go to fault mode.. 
- If the output load is higher than 130% of rated load, the UPS will go to fault mode after
1second.

b. Cycle by Cycle Current Limit :
When output loads sink a high surge current for a short time, a high inverter current is detected and the inverter switches, i.e. the IGBT's, are turned off pulse by pulse to protect themselves from thermal runaway. The output relay stays at inverter output
position unless a continuous overload is detected or an abnormal inverter operation occurs.


2. Battery over or under shut down
Upon the battery voltage declines to battery-under/over level, the UPS will warn and the LCD will display the fault code, and then shut down. In case of the battery voltage is high voltage, the UPS will warn and the LCD will display the fault code.

3. Inverter output abnormal protection
The inverter failure signal shuts down the inverter immediately, makes the buzzer a continuousalarm, and the LCD displays the fault code.“The failure signal latches itself unless SW off or battery is empty".

4. Over temperature protection
The thermal switch detects the temperature of PSDR heat sink. The thermal switch is electrically connected to the CPU. An opened thermal switch is thought as temperature failure by the UPS. The LCD will display the fault code.

5. Bus over/under protection
To protect any BUS over/under condition. The LCD will display the fault code.

2-3 Signaling Sub-System:
When the AC line is unable to supply, the batteries release energy inside to supply the inverter immediately. At the same time, the buzzer beeps every 4 seconds.
Upon the batteries are discharged to battery-low level, the battery-low signal is activated and the buzzer beeps every 1 second. Remote shutdown signal is enabled only when the line fails.

3. Charger Sub-System
The purpose of charger is to charge and to maintain the batteries at fully charged condition. Refer to figure 7, the voltage flyback switching power supply provides a constant DC voltage (27.4 Vdc) for batteries. Besides providing constant voltage, the  power supply also limits the current flowing into batteries and therefore protects and prolongs the life time of charged batteries.

4. Input Power Factor Correction Sub-System :
The purpose of power factor correction (P.F.C.) circuit is to make a constant bus for Inverter in Buck and Boost mode. The schematic is indicated in figure 8.
When the input AC power cord is plugged in, the AC relay is activated and the AC power goes through noise filter to the charger and to the line detector. Both DC buses present voltages at about 1.4 times of input RMS voltage. When the UPS is in Buck or Boost mode, the P.F.C. circuit is enabled and the DC bus is regulated at 360 Vdc.

5. Front Panel :
The front panel consists 2 parts: push button and display LCD set. The push button is used to turn on and off the UPS. LCD display indicates the load level, the battery voltage level  and operation  status of the UPS. Besides, when the system works abnormally, The LCD will display the fault code.

Battery Mode

Line Mode/ AC Mode

 
IV. ALIGNMENTS
List below are some test points and procedures when a qualified service person wants to check whether EUT (Equipment under Test) will works properly. Before beginning following procedures, please make sure that EUT is OFF and disconnected from Utility.

V. TROUBLE SHOOTING
Due to careful design and strict tests of our products, fail of UPS seldom occurs. However, once they do fail in some situations, please check them according to Trouble Shooting Chart, which will help you solve the most problems on UPS.

PANEL LCD DISPLAY EXPLANATION