ALP UPS FEATURES & ADVANTAGES 1. True Galvanic Isolation Usually, Y-caps are installed in UPS s input & output to eliminate the electro-magnetic interference, but Y-caps will increase the ground leakage current. Together, with the parasitic capacitance of the unit itself the impedance between power lines and ground becomes very low. Therefore, the grounding quality will be affected, resulting in voltage differences between different systems, and problems will arise, such as the connection terminal sparks when plug in the communication port, or the data transmission seriously interfered. The whole LAN system will be contaminated or even computers (equipments) will be destroyed. The best way to prevent and solve this problem is to completely isolate the UPS output from the input power system. In that case, the UPS output can be tied to any ground at any potential. Not only the noise inside the UPS is stopped, and the output neutral can adapt to any voltage induced by complicated connection of the load system, but also can stop the electro-magnetic interference, surge, and spikes caused by lightning or heavy/inductive load impact/detach nearby, comes through the UPS to the load. Beside, output can remain safe even when neutral is disconnected. Now, protections against over-shoot voltage are explained below. a. Comparative System Diagram Fig 1: ALP True Galvanic Isolation Fig 2: Non-true Galvanic Isolation 1
b. Benefit Explanation (1) In case there are two or more UPSs installed in one building. When Non-isolated UPSs are installed as Fig.3 below, while Vs is the floating voltage and noise voltage between N1 & N2, there will be a considerable large voltage between the communication ports of computer1 and computer2. Therefore, there will be sparks when the two computers are being connected via communication cable. And, the two computers will interfere each other, or even when the voltage difference is strong enough the computers will be damaged. If Galvanic isolated UPSs are installed as Fig.4 below. The Vs between N1 & N2 will not exist (completely isolated) in the output of the UPSs. The phenomenon and accidents mentioned above will never happen. Fig 3:Non-true Galvanic Isolated UPS 2
Fig 4:ALP True Galvanic Isolated UPS (2) Lightning During lightning, power transmission cables are subject to attacks of lightning while very high surge voltage will exist between input L and Ground as Fig.5 below. If common UPS is installed, the input N (neutral) and output N are tied together. Therefore, the surge voltage existing at the output is exactly the size existing in the input. And the voltage is detrimental and dangerous to most of the load, or even if the load has surge protector, it leads to damaging of the load because sometimes the surge energy is larger than the internal surge absorber can endure,. But if true Galvanic isolated UPS is installed as Fig.6, since the input and output ground can be different, thus being connected to different grounds and the impedance between them is very high, the voltage between output L and ground is still zero. That is, absolutely invisible or undectable at the output, surge voltage never reaches the loads. Fig 5:Non-true Galvanic Isolated UPS 3
Fig 6:ALP True Galvanic Isolated UPS (3) Attenuation The noise attenuation of the non-isolated UPS completely relies on the filtering capability of the EMI filters (usually around 40dB to 80dB). But, with the isolation transformer of the Galvanic isolated UPS alone can contribute 120dB (or above). Together with the EMI filter inside, the noise attenuation of the UPS can achieve 200dB, that mean you can get a clean power source as well as without polluting the input. (4) Leakage current In normal power systems, the leakage current of the transmission cables, the leakage current of the UPS, and the leakage current of the load add up to a considerable large amount. If the input NFB is earth leakage current sensing type (for protection of load's faulty current to chassis), that current may force the NFB to trip. But, if Galvanic isolated UPS is used, there is no high frequency components between output neutral and load ground. Therefore, very small leakage current flows out the UPS, and the leakage current flowing into the load is very small too. As a result, the unwanted or annoying tripping of NFB can be prevented, and the load can be connected to the UPS through a long distance. Fig 7:Non-true Galvanic Isolated UPS 4
Fig 8:True Galvanic Isolated UPS (5) Faulty neutral As the figure shown above, the input neutral of the UPS is mistakenly disconnected in reserve or bypass mode, the phase with the lightest load connected will have a voltage rise up to 1.732 X line to neutral voltage (that is, the phase to phase voltage), while the phase with heaviest load will drop to a small voltage (that is, the phase to phase voltage now feed across the input line and neutral). When this condition happens, not only the surge absorber of the UPS will blow (risk of fire), but also the load will be damaged. But, in the same case, if Galvanic isolated UPS is used, the inter-core coupling characteristic of the output transformer will force the input/output neutral to the center point of the 3-phase. Even in the extreme condition of 100% unbalance load and neutral disconnected, the input/output phase to neutral voltage can be kept stably within 5%. In case the UPS output is short circuited, it will be detected and the inverter will limit the current to a safe level until the short circuited time exceed the safe margin, the inverter will automatically shut off, but differing from others, without bypassing the short circuit to mains (preventing the tripping of NFB streams up to top of power distribution, that will shutdown other critical loads!). 5
2. Software and Hardware Redundant Design The UPS employs both hardware and software redundant design, especially in protection circuitry, as the figure above, to ensure safety. The characteristic of CPU control is step by step execution of each program lines. But if one or more lines are jumped over during execution, the following execution may run out of order due to incorrect value inherit from the previous steps. It is very dangerous if short circuit happens when the CPU is not working correctly. Therefore, we add extra hardware circuitry to ensure protection action is taken so as to improve the UPS's reliability and load safety. 3. Component Reliability There are approximately 5,000 components used in one mid-power UPS. The average failure rate of electronic components is 2 PPM. Therefore, excluding the factor of design fault, the failure rate of a UPS caused by components is around (5,000X2/1,000,000)X100%=1%. But our ALP series UPSs employ the quality scheme by a research bureau, for example, sorting the components by 1.5 X rated value, the failure rate of components will drop to 0.2 PPM. Then, the failure rate caused by components is (5000X0.2/1,000,000)X100%=0.1%. That is, only one out of one thousand our UPSs may break down because of component defects. 4. No Harms If Incorrect Operation Different from other UPSs (must follow the specified operation procedures, or else the operator is responsible to the destruction of UPS and loss of user due to power failure), our UPS will not be damaged by any incorrect operation. For example, turning on the bypass breaker of a UPS under inverter operating mode is hazardous to UPS (the inverter is directly shorted to the mains, and unlimited energy will flow either from inverter to mains or from mains to inverter, battery & loads, causing damage of the inverter or high DC voltage damage the connected capacitors or battery. 6
But, our ALP UPSs continuously detect the switches, when the above condition happens, the inverter will shutdown immediately, and transfer the load to the mains. Once the bypass breaker is turned off again, the UPS will perceive and automatically restart and run in inverter mode again. For other breakers and switches, no priority is critical or strictly specified. According to the field statistics, 15% of the UPS failure is caused by incorrect operation; therefore this feature should put in the consideration of UPS design. Non-true Galvanic Isolation ALP True Galvanic Isolation 7
5. Battery Start Usually battery is directly connected to the DC bus, so the inverter cannot be switched on without AC mains because if you close the battery NFB/switch, either someone want to start the UPS with battery only or mistakenly, the current flowing from battery to the empty capacitor is unlimited, the DC capacitor may blow due to very large surge current. But, we put a magnetic switch to limit the current. Therefore, the battery can connect to the DC bus smoothly without AC mains. 6. Input Protection A frequently happen field problem of power system is that (refer to the figure below) the power cable is too long that the inductance is not negligible, when the load change abruptly (switch on/off of adjacent load) the energy stored in the cable (1/2xIxIxL) can not be released, will induced a high voltage between phase and neutral (where V=Lxdi/dt), the UPS (surge absorber or inner semi-conductor) or even all the connected load will be damaged. Therefore, we put a dedicated protection device at the input to release the energy of transmission cable induced by abrupt change of load, preventing any high voltage that threat to all the connected devices. 8
7. Intelligent Charger and Battery Tester There is a big capacity, programmable (as the following LCD Menu), temperature compensated charger inside the UPS. The period and amount of the periodic boost charge is programmable, therefore the life expectancy of battery is prolonged, and can quickly charge up large battery bank. < B O O S T C H A R G E S E T T I N G > A U T O - B O O S T ( M O N T H ) = 0 4 0 8 1 2 1 6 2 0 2 4 A U T O - B O O S T ( B A T T L OW ) = 0 4 0 8 1 2 1 6 2 0 2 4 C H A R G E C U R R E N T = L O M E H I E X I T Beside, there is a safe, intelligent battery tester to periodically, safely test the battery without the risk of affecting the UPS output. Other battery bank problem, such as battery fluid leakage and battery cabinet improper grounded, can also be detected and sent warning message to user. 8. Plug & Play Modular Design The power section of our UPS are divided in several detachable heat-sink modules, (plug & play modules), so as to enable quick debug and repair, in return save cost and minimize the loss of the user. That is, if the users keep one set of the spare part, the MTTR will be shortened to 30 min. 9
9. Features of Parallel Operation a. Can parallel several units together. b. Employ most advanced technology. c. Use high-speed digital signal processors (DSP) to calculate the control signal. Some of the superior features are listed below: (1) No adjustments to be done on the site (all adjustments are done in factory), while most of the products in the market need complicated or difficult adjustments on the site. (2) The difference of power sharing between each unit is smaller than 0.5% under any kind of load. (3) Completely no circulation current between each unit. (4) No extra parallel cabinet needed. (5) Switch on/off procedures are not critical, incorrect operation has no harm to the units. (6) Can endure wide dynamic variations of the input voltage and frequency, no other products in the market can compare. (7) The safety and reliability of the power system is highly increased. 10
10. Variety of Accessories / Options a. UPSCAN TM - Remote Control Penal A hand held display module with LCD and LED can monitor 1 99 UPSs with RS-485 connected in series from distance < 1000M. Size: W*H*D=22*12.3*4.5cm, 0.45kg b. Emergency Stop Switch Be installed outside or nearby the UPS for stopping the UPS output in case of emergency. c. UPSCOM TM - PC Monitoring Software Can provide real-time three phases information of UPS connected on the line and monitor several UPSs with one PC. 11
(a) UPSCOM monitoring 1UPS. RS232 PC CNR21 in 3R PCB (b) UPSCOM monitoring multiple UPS (up to 31 units) RS485 CNR10 in 3R PCB Adapter RS485 RS232 PC RS485 CNR10 in 3R PCB RS485 CNR10 in 3R PCB 12
d. SNMP/HTTP agent Can monitor and manage the UPS through Web browser and Java applet, providing simultaneously three phases data acquisition. 13
10. Low UPS Maintenance Cost Being high reliability and support of quick maintenance, In addition to guaranty period the maintenance charge of ALP series will be assured less than 5% of the UPS sale price in the second year usage and less than 10% in the third year. 14