SUPPLY SYSTEM FOR UNINTERRUPTIBLE ELECTRIC POWER

Abstract: The invention relates to a supply system for uninterruptible electric power, comprising a back-up power unit provided with a battery serving as a storage of energy, a rectifier as well as an inverter. This back-up power unit is installed in a normal power distribution installation prior to its branching to a plurality of outlets. The system includes outletwise load decoupling switches (7) adapted to be controlled by means of a programmable control means (6), included in the system and programmed for the optimum exploitation of back-up energy.

Description: Supply system for uninterruptible electric power. The present invention relates to a supply system for un¬ interruptible electric power, comprising a back-up power unit provided with a battery serving as a source of energy, means for charging the battery, as well as an inverter between the battery and a critical load. A rectifier for charg¬ ing the batteries and said inverter can also consist of one and the same apparatus, whose operation either as a rectifier or as an inverter depends on the state of a supply mains. Computers and other modern processor-based systems often require a back-up power supply system in order to secure trouble-free operation also in cases of mains failure and i the absence of normal mains power. The supply system for uninterruptible electric power is generally known as a UPS system (Uninterruptible Power Supply) . Fig. 1 illustrates a so-called "True-UPS" system and fig. 1B shows a so-called "Stand-by UPS" system. A stand-by system can be technically resolved also in a manner that, when the mains is in proper order, power flows in an inverter from the mains to a battery. Thus, the charging of a battery proceeds through this unit and a separate rectifier is not need¬ ed (so-called tri-port system) . Such UPS systems have been commercially available roughly for as long as computers. Earlier, the stand-by source of power was provided by rotary converter, later and at present nearly exclusively by static, electronic converter. As computers and processor equipment keep developing and become more and more effective and micro-computer applications become more popular, the utilization of minor UPS units will increase e.g. in office environ¬ ment. There are several reasons for such development, the three most significant being: 1. the increase of the amount and value of information processed by even small-capacity computer units, where¬ by .the inconveniences and expenses caused even by a single malfunction of the system become significant, 2. the tendency is to link micro-computers as a local network or to otherwise operate as a part of some com¬ munications network. Thus, it is generally essential for the reliable operation of an entire network that each active point is in continuous operation and infor¬ mation is not lost or distorted at the time of unpre¬ dictable interruption in the operation of such active point, 3. as technology has developed, the UPS equipment it¬ self has become better suitable for office environment and prices of the equipment have been declining. For the above reasons a tendency at the moment is to furnish offices with rather small (less than 1 kVA) UPS units to take care of the back-up power requirement of 1 to 3 minor computers. The present development in the use of micro-computers has also introduced two mutually different demands for back-up power. The need for back-up power used to be calculated so that there was enough power available for the entire practically predictable failure (0,5 to 24 hours) . At present, however, it is more important to stop in a controllable manner the on-going actions and operations in a computer and hence to make sure that information is not lost and that re-starting is eas y . These reasons lead to a demand for providing a flexible UPS system which, e.g. in the same office environment, offers a possibility of having both long and short back¬ up periods and, on the other hand, would eliminate the service and maintenance problem that is often associated with the hardware of several different pieces of UPS equipment and the operation of such equipment. An object of the invention is to find a solution to such • a demand, i.e. to provide the above type of flexible and thus optimizable UPS system whose need of maintenance is negligible. This object is achieved by a system of the invention which is .characterized in that a back-up power unit included in the system is fitted in a normal current supply system prior to its branching to a plurality of outlets and the system is provided with outletwise load decoupling switches adapted to be controlled by means of a programmable control means, included in the sys¬ tem and programmed for the optimum exploitation of back-up energy. The invention will now be described with reference made to the accompanying drawings, in which fig. 1A shows a general block diagram for a UPS system (True-UPS) . Fig. 1B shows another general block diagram for a UPS system (Stand-by UPS) . Fig. 2 shows the disposition of components included in a UPS system of the invention in a normal current supply system. Fig. 3 shows a block diagram for a smart control unit SU (Smart Unit) included in a UPS system of the invention. Fig. 4 shows a block diagram for an outletwise active switch AS, connected with a UPS system of the invention and controlled by SU. A UPS system shown in fig. 1A includes a conventionally mains-connected rectifier/charger 1 which converts alternating current to direct current and charges a battery 2 serving as a storage of energy. An inverter 3 converts the direct current coming from charger 1 or battery 2 to alternating cur¬ rent which is supplied to a critical load 4. The supply of electric power during a mains failure can also be effected by means of a system shown in fig. 1B wherein, in a normal state, a load 4 is connected through a change-over switch 9 to the mains and a set of accumu¬ lators 2 is maintained through a lower-capacity charger 1 at its full charging capacity. When the mains is switched off, the change-overswitch 9 transfers the supply of load from the mains through inverter 3 to batteries 2. The time taken by such change-over switching is a few milliseconds which is generally ac¬ cepted by data processing equipment making up the load. In a third embodiment, already mentioned above, there is no separate rectifier at all but, when the mains is in proper order, the power flows from the mains to a battery through an inverter. In the systems shown in figs. 1 and 1B 7 blocks 1, 2 and 3 build a static back-up power unit UPS (= Uninter- ruptible Power Supply) , indicated in fig. 2 with re¬ ference numeral 5. Associated therewith is a program- able, smart control unit SU (= Smart Unit) , indicated in fig. 2 with reference numeral 6. The programmable control unit 6 controls outletwise decoupling switches AS (= Active Switch) , indicated with reference numeral 7. Shown with a dash-and-dot line in fig. 2 is e.g.. the path of a carrier wave-based command signal be¬ tween control unit 6 and decoupling switches 7 along a current supply system. A control unit 6 (fig. 3) can be included in the moni¬ toring and control unit of a UPS apparatus or it can be separate therefrom. A central processing unit 10 (CPU) included in control unit 6 is provided with a memory and a keyboard for manual data feeding. The central processing unit 10 (CPU) is adapted to receive fed-in information about battery voltage (U, , ) , battery loading (I , ) and the state of supply system (line ON/OFF) . On the basis of a certain prog¬ ram and the information fed therein, the central pro¬ cessing unit controls decoupling switches 7, mounted at the outlets and equipped with an address. A code generator 11 included in control unit 6 develops an address code characteristic of each decoupling switch 7 according to which decoupling switch 7 a control command is intended for. Correspondingly, a decoupl¬ ing switch 7 of fig. 4 includes a code analyzing block 12 in which an address code is set. Control unit 6 and decoupling switch 7 are in communication with the transmission line through a two-way line signal receiver/ transceiver circuit 13. Such a circuit is commercially available. When decoupling switch 7 receives a signal from the line or mains, it will react to it according to its own address by switching the load ON or OFF. A decoupling switch 7 as shown in fig. 4 further in¬ cludes a load current measuring sensor 14, connected through a current limiter circuit 15 with a controller 16 which controls a switch 17 (e.g. a relay) included in the load circuit. A load current, at which said switch 17 operates for decoupling the load from the circuit, is adjustable. In addition, a current measur¬ ing signal is passed from a digitizer 18 in digital form through a signal receiver/transceiver circuit 13 into the mains, from which the control unit 6 receives this load current signal as a feedback signal into the central processing unit 10 (CPU). This is one optional mode of operation for a system of the invention but by no means mandatory. Thus, the function of control unit 6 is to investigate the state of a UPS system and, according to a desired program, to effect a controlled deloading as the charge of a battery is diminishing. Furthermore, on the basis of the current of an individual load, the control unit 6 can generate an alarm or to control the elimination of this load. The system is installed in a normal power distribution installation e.g. in an office premises, so that a UPS apparatus is coupled with those arrays of outlets which include data processing equipment or other critical loads. The UPS apparatus and control unit 6 can be fitted in the main or group centre 8 of a power distribution installation while the decoupling switches 7 are fitted in the outlets of load equipment. In some cases, said decoupling switch 7 can also be fitted in a group line including a plurality of outlets. When the normal mains supply fails, the UPS apparatus begins an uninterrupted supply of loading. At the same time, the control unit 6 through the intermediary of decoupling switches 7 cuts off the power supply ' to those loads that do not need back-up power electricity. The remaining critical loads receive electricity for a necessary period in a manner that their operations can be stopped in a controlled fashion and that the equipment requiring continuous operation are provided with an optimally long running time within the limits set by available battery capacity. The system control unit 6 communicates with outletwise or supply line wise decoupling switches 7 controlling them to open or close as necessary. In addition to that, said control unit 6 can control also other office equipment connected with the supply system and, on the other hand, it can receive information delivered from elsewhere (e.g. alarm centres of buildings) . The described novel solution is mostly competing with a decentralized UPS system. In a decentralized system there is an individual UPS apparatus for each unit to be protected. In addition to the versatility offered by the above-described control unit, the novel solut¬ ion includes following advantages: - does not require space in an office premises - more economic overall solution, since the installed UPS capacity is in optimum use and built in a single entity - the number of individual electric cable is reduced in an office premises - maintenance of a centralized system (mainly batteries) becomes easier - can be linked with other building control systems, e.g. heating, air-conditioning, alarm etc. In addition to the above qualities, the novel system offers further possibilities in equipment development e.g. by giving additional functions to decoupling switches; short-circuit current limiting, measuring of current passing through a switch etc. Similarly, the system and its components can be applied to direct- current systems, wherein especially the electronic short-circuit protection can be used to resolve present practical problems.

Claims: Claims 1. A supply system for uninterruptible electric power for critical loads such as computers, said system com¬ prising a back-up power unit provided with a battery (2) serving as a storage of energy and means (1) for charging the battery, said back-up power unit being installed in a normal power distribution installation prior to its branching to a plurality of outlets, c h a r a c t e r i z e d in that the system includes outletwise load decoupling switches (7) adapted to be controlled by means of a programmable control means (6) , included in the system and programmed for switching off loads in a predetermined priority order on the basis of the measured or calculated rating of the charging state of said battery for the optimum exploitation of back-up energy. 2. A system as set forth in claim 1, c h a r a c t e r ¬ i z e d in that said back-up power unit includes an inverter (3) fitted between the battery and a critical load in a normal power distribution installation prior to its branching to a plurality of outlets. 3. A system as set forth in claim 1 or 2, c h a r a c ¬ t e r i z e d in that the outletwise decoupling switch¬ es (7) are fitted with a load current measuring sensor (14) . 4. A system as set forth in claim 3, c h a r a c t e r ¬ i z e d in that the outletwise decoupling switches (7) are fitted with a current limiter means (15) linked with the load current measuring sensor (14) for con¬ trolling a switch (17) included in the load current supply circuit. 5. A system as set forth in claim 3, c h a r a c t e r ¬ i z e d in that the information provided by load current measuring sensor (14) is adapted to be transmitted to a central processing unit (10) included in said program- able control means (6) , wherein this information is adapted to be forwarded into a program controlling said decoupling switches (7) . 6. A system as set forth in claim 1 or 2, c h a r a c ¬ t e r i z e d in that said programmable control means (6) is fitted in the main or group centre (8) of a power supply installation and-at least some of the decoupling switches (7) are fitted immediately adjacent to load equipment. 7. A system as set forth in claim 6, c h a r a c t e r ¬ i z e d in that at least some of the decoupling switch¬ es (7) are fitted in load equipment outlets. 8. A system as set forth in claim 1 or 6, c h a r a c ¬ t e r i z e d in that said control means (6) includes a code generator (11) and said decoupling switches (7) include a code analyzing circuit (12) . 9. A system as set forth in claim 1, c h a r a c t e r ¬ i e d in that the central processing unit (10) of said programmable control means (6) is provided with a memory and a keyboard for programming and manual data input, in addition to which the central processing unit (10) is linked for data communication with means measuring battery voltage (U, .. ) and battery loading (I , ) as well as with means sensing the state of a supply mains (line ON/OFF) .

Inventors: KUJALA ANSSI VEIKKO, POKKINEN KIMMO KALERVO, TUCKER TOMMY NORRIS, VAELIMAEKI PEKKA MATIAS, KUJALA, ANSSI, VEIKKO, POKKINEN, KIMMO, KALERVO, TUCKER, TOMMY, NORRIS, VAELIMAEKI, PEKKA, MATIAS
Applicants: FISKARS AB OY, FISKARS OY AB
Application year: 1988
Main classification: H02J9
IPC codes: H02J9