WO2001088348A1

WO2001088348A1 - Power supply unit

Info

Publication number: WO2001088348A1
Application number: PCT/BE2001/000082
Authority: WO
Inventors: Guy Maria Frans Laps; Peter Louis Victorine Vanhoof
Original assignee: Atlas Copco Airpower, Naamloze Vennootschap
Priority date: 2000-05-12
Filing date: 2001-05-10
Publication date: 2001-11-22
Also published as: AU5996301A; WO2001088348A9; BE1013435A3

Abstract

The invention relates to a power supply unit which comprises an internal combustion engine (2) which is cooled by a fluid, a power generator (4) coupled to this internal combustion engine (2), a cooling circuit (7) for the cooling fluid, and a cooler (5) for cooling down the fluid, which cooler (5) comprises a radiator (6) installed in the cooling circuit (7) and a fan (8). A control device (16) is coupled to the internal combustion engine (2), which control device controls critical parameters of the internal combustion engine (2), amongst which, at least, the temperature of the cooling fluid. The fan (8) comprises an electric motor (9) with adjustable speed which, for the power supply thereof, is coupled to the outlet of the generator (4) by means of a controlling apparatus (10) which, in function of the signal from the control device (16) and, therefore, at least in function of the temperature of the cooling fluid, regulates the speed of the electric motor (9).

Description

Power supply unit.

This invention relates to a power supply unit which comprises an internal combustion engine which is cooled by a cooling fluid, a power generator coupled to this internal combustion engine, a cooling circuit for the cooling fluid which extends over the internal combustion engine, and a cooler for cooling down the fluid, which cooler is of the type comprising a radiator taken up in the cooling circuit and a fan cooperating therewith.

In many cases, such power supply units are mobile units which are used for supplying alternating current at locations without a mains supply, or as an emergency unit for supplying power when the mains supply is out of order.

These power supply units must supply power at a constant frequency, mostly 50 Hz or 60 Hz, which means that the motor, mostly a diesel engine, must have a constant number of revolutions.

However, the power consumption of the unit is not constant, and therefore the load on the motor varies, too.

The larger the load of the motor, the larger also the quantity of heat which it is producing, and the more it has to be cooled. With a maximum load, it still has to be cooled sufficiently in order to prevent a temperature rise thereof above a well-defined maximum temperature.

With known power supply units, the fan of the cooler is driven at a constant number of revolutions, mostly by means of a transmission, in most cases, a belt trans- mission, by means of the crankshaft of the internal combustion engine.

The cooler then is calculated such that it can cool this fluid in a sufficient manner even in the worst circumstances, this is with a maximum load of the internal combustion engine and at the highest environmental temperature.

The load on the internal combustion engine may vary strongly, for example, from 5% to 100%, whereas also the environmental temperature may vary strongly, for example, between -10°C and 45°C.

In that the number of revolutions of the fan remains the same and therefore its energy consumption remains the same, with a lower load of the internal combustion engine more energy than necessary is used by the fan, which has a negative influence on the energetic efficiency of the power supply unit.

An excess cooling of the motor can be avoided by means of a thermostate in the cooling circuit.

In particular with large powers, this may mean a considerable waste of fuel.

The invention aims at a power supply unit which does not show the aforementioned disadvantages and has a better energetic efficiency.

According to the invention, this aim is achieved in that a control device is coupled to the internal combustion engine, which device controls critical parameters of the internal combustion engine, amongst which at least the temperature of the cooling fluid, and whereby the fan comprises an electric motor with adjustable speed which, for its power supply, is coupled to the outlet of the generator, by means of a controlling apparatus which, in function of the signal from the control device and, thus, at least in function of the temperature of the cooling fluid regulates the speed of the electric motor.

The temperature of the cooling fluid corresponds to the temperature of the internal combustion engine and depends on the load and the environmental temperature.

The controlling apparatus regulates this number of revolutions such that it is minimum for each degree of load of the internal combustion engine and, thus, diminishes as the load diminishes, without, however, dropping below the number of revolutions at which the internal combustion engine no longer can work safely.

The controlling apparatus regulates this number of revolutions such that the maximum temperature of the cooling fluid is not exceeded. Possibly, the number of revolutions also is regulated such that the maximum temperature of another fluid having a critical maximum temperature, such as the maximum temperature of the lubricating oil of the internal combustion engine or the maximum temperature of the air suctioned by this latter, is not exceeded.

This maximum temperature of the cooling fluid depends on the type of motor, however, can be provided by the manufacturer.

The controlling apparatus can comprise a frequency transformer and therefore can be of the type which controls the speed of the electric motor by altering the frequency. With the intention of better showing the characteristics of the invention, hereafter, as an example without any limitative character, a preferred form of embodiment of a power supply unit according to the invention is described, with reference to the accompanying drawing which represents such power supply unit.

The power supply unit represented in the figure is mounted in a preferably mobile housing, of which only the basis 1 is represented, and substantially consists of a diesel engine 2, an A.C. generator or alternator 4 coupled thereto by means of a coupling 3, for example, a 400 V/50Hz alternator, a cooler 5 consisting of a radiator 6 mounted in the cooling circuit 7 of the diesel engine 2, and a fan 8 driven by an electric motor 9 with an adjustable number of revolutions which is controlled by means of a controlling apparatus 10.

To the power exit of the alternator 4, a branch is connected where the electric energy is branched off which, by means of the controlling apparatus 10, serves for driving the motor 9 of the fan 8.

In this branch, upstream of the controlling apparatus 10, further a current interrupter 11, a filter 12 and a line reactor 13 are mounted.

The motor 9 is, for example, an induction motor, the number of revolutions of which depends on the frequency of its supply.

The controlling apparatus 10 comprises a frequency transformer 14 which can vary the frequency between, for example, 0 and 100 Hz, which, by means of a signal transformer 15, is coupled to a control device 16 which is coupled to the diesel engine 2 and which observes one or more critical parameters of this diesel engine 2.

This control device 16 observes at least the temperature of the cooling fluid, to wit, the cooling water, which is pumped through the cooling circuit 7 , and therefore comprises a thermometer 16A which is provided at the exit or downstream of the internal combustion engine in or at this cooling circuit 7.

This temperature is equal to the temperature of the diesel engine 2 which is a function of the load and the temperature of the environment.

The controlling apparatus 10 regulates the number of revolutions of the motor 9 such that the maximum temperature of the cooling fluid and, thus, the maximum temperature of the diesel engine 2 is not exceeded.

Preferably, the control device 16 also observes other critical parameters of the diesel engine 2, such as the temperature of the lubricating oil in the carter of the motor and the temperature of the air suctioned by the diesel engine for combustion, and thus comprises a thermometer 16B in the carter and a thermometer 16C in the air inlet 17 of the diesel engine 2.

The controlling apparatus 10 controls the motor 9 such that the temperature of another fluid with critical maximum temperature, such as the temperature of the lubricating oil of the diesel engine 2, or the temperature of the air suctioned by this latter, do not exceed their allowed maximum.

Possibly, also the fuel temperature can be measured.

If the diesel engine 2 is of the type provided with a turbo and intermediate cooler, the control device also can comprise a thermometer measuring the temperature of the intermediate cooler.

This intermediate cooler also may comprise a radiator which can be mounted next to the radiator 6 of the cooler 5 and, thus, is cooled by said fan 8, driven by motor 9.

This signal then is transformed in the signal transformer 15 to a current controlling the frequency transformer 14, such that the speed of the motor 9 of the fan 8 is minimum, without the danger that the operation of the diesel engine 2 is not safe.

Normally, thus, the frequency of the motor 9 will be reduced when the load and, thus, the temperature of the cooling fluid in the cooling circuit 7 is reduced.

If other temperatures are observed, too, the control can take these temperatures into account by means of the controlling apparatus 10, such that the diesel engine 2 remains working safely.

So, if, for any reason, the temperature of the lubrica- ting oil in the carter becomes too high, the reduction of the number of revolutions of the motor 9 can take place less fast or even not at all.

The lubricating oil itself can be cooled and be pumped through a circuit in which a cooling radiator is mounted and which also is mounted opposite to said fan 8 driven by the motor 9.

It can be noted that diesel engines already are known in which a controle device 16 is built-in which measures the parameters of the diesel engine 2 and provides an output signal.

After transformation in the transformer 20, this signal can be used for regulating the speed of the motor 9 of the fan 8.

Tests have shown that for a diesel engine-alternator unit of 1000 kVA, a diesel economization of more than 10 1/h can be obtained. At the same time, an average noise reduction of 2 dB(A) has been obtained.

The number of revolutions of the motor 9 of the fan 8 does not necessarily have to be adjusted by means of a frequency transformer. Other electronically adjustable motors are known, the speed of which can be regulated in other ways than by regulating the frequency.

The invention is in no way limited to the form of embodiment described in the aforegoing or represented in the drawing appended hereto, however, such power supply unit can be realized in different variants without leaving the scope of the invention.

Claims

Claims,

1.- Power supply unit comprising an internal combustion engine (2) cooled by a fluid, a power generator (4) coupled to this internal combustion engine (2), a cooling circuit (7) for the cooling fluid which extends over the internal combustion engine (2), and a cooler (5) for cooling down the fluid, which cooler (5) is of the type comprising a radiator (6) taken up in the cooling circuit (7) and a fan (8) cooperating therewith, characterized in that a control device (16) is coupled to the internal combustion engine ( 2) , which device controls critical parameters of the internal combustion engine ( 2) , amongst which at least the temperature of the cooling fluid, and that the fan (8) comprises an electric motor (9) with adjustable speed which, for its power supply, is coupled to the outlet of the generator (4) by means of a controlling apparatus (10) which, in function of the signal from control device (16) and, thus, at least in function of the temperature of the cooling fluid, regulates the speed of the electric motor ( 9) .

2.- Power supply unit according to claim 1, characterized in that the controlling apparatus (10) is of the type regulating the number of revolutions in such a manner that it is minimum for each degree of load of the internal combustion engine (2) and, therefore, diminishes as the load diminishes, without, however, dropping below a number of revolutions at which the internal combustion engine (2) could not work safely.

3.- Power supply unit according to claim 2, characterized in that the controlling apparatus (10) regulates the number of revolutions of the motor (9) of the fan (8) in such a manner that the maximum temperature of the cooling fluid is not exceeded.

4.- Power supply unit according to claim 3, characterized in that the control device (16) also measures other critical parameters of the internal combustion engine (2) and that the controlling apparatus (10) regulates the motor ( 9 ) of the fan (8) , taking into account the measuring of these other parameters.

5.- Power supply unit according to claim 4, characterized in that the controlling apparatus (10) regulates the motor (9) of the fan (8) without exceeding the maximum temperature of another fluid with critical maximum temperature as well, such as the maximum allowed temperature of the lubricating oil of the internal combustion engine (2) or the maximum allowed temperature of the air suctioned by this latter.

6. - Power supply unit according to any of the preceding claims, characterized in that the controlling apparatus

(10) comprises a frequency transformer (14) and therefore is of the type controlling the speed of the electric motor (9) of the fan (8) by means of altering the frequency.

7. - Power supply unit according to any of the preceding claims, characterized in that the power generator (4) is an alternator.

8.- Power supply unit according to any of the preceding claims, characterized in that the internal combustion engine (2) is a diesel engine.