GB2277213A

GB2277213A - Vehicle electrical generating system

Info

Publication number: GB2277213A
Application number: GB9407403A
Authority: GB
Inventors: Alan Raymond Skelhon
Original assignee: WOODWAY ENGINEERING Ltd
Current assignee: WOODWAY ENGINEERING Ltd
Priority date: 1993-04-17
Filing date: 1994-04-14
Publication date: 1994-10-19
Also published as: GB9407403D0; GB9307970D0

Abstract

An electrical generating system has a three phase alternator which includes a stator winding (15) and a diode rectifier (14) for providing a rectified DC output voltage. A voltage regulator (22) regulates the output voltage of the stator winding (15). A transformer arrangement (33) is also provided having a primary winding (32) coupled to the stator winding by a switch (38), a first secondary winding (34) which provides a stepped up output voltage through a rectifier (40) of typically 110V or 220V DC, and a second secondary winding (36) which provides a regulating voltage for the voltage regulator (22). The latter can be switched either to the rectifier (42) or to field diodes (20) and stator winding (15) by way of a switch (28). In normal operation, the switch (38) is open and the voltage regulator (22) regulates the voltage of the stator winding (15). However, for providing a high level DC voltage, switch (38) is closed and the regulator (22) switched to the rectifier (42). The arrangement allows a simple modification to the existing regulator circuit and minor connections from the transformer arrangement to the alternator stator winding terminals to enable a conventional alternator (eg. on an emergency service vehicle) to be converted simply and quickly to provide a higher DC output voltage (eg. to power floodlighting at accident or incident scenes). <IMAGE>

Description

Electrical Generating System The present invention relates to an electrical generating system.

Vehicles such as emergency service vehicles need a provision for generating power to provide, for example, floodlighting at accident or incident scenes. Such floodlighting normally requires llOV or 240V 3KW supply and hitherto, this has been provided by a special purpose alternator on the vehicle in addition to the vehicle's normal alternator, or from a conventional vehicle alternator which has been modified by having the stator windings removed and rewound to provide the required supply.

The present invention seeks to provide an improved electrical generating system.

Accordingly, the present invention provides an electrical generating system comprising: a 3-phase alternator having: a stator winding means; and a first rectifier means coupled to said stator winding means for providing a rectified DC output; a voltage regulator for regulating the output voltage of said stator winding means in response to a first regulating voltage; and a transformer arrangement comprising: a transformer having: a primary winding means connected to said stator winding means; a first secondary winding means for providing a stepped up output voltage; and a second secondary winding means; a second rectifier means coupled to said first secondary winding means for providing a rectified DC output; and a third rectifier means coupled to said second secondary winding means for providing a second regulating voltage for said voltage regulator; and switch means coupled to said voltage regulator for switching between a first switch state for passing said first regulating voltage to said voltage regulator and a second switch state wherein said voltage regulator is coupled to said third rectifier means.

Advantageously, the alternator has field diode means for providing said first regulating voltage.

The present invention is further described hereinafter, by way of example, with reference to the accompanying drawing, which is a circuit diagram of a preferred form of electrical generating system according to the present invention.

Referring to the drawing, this shows a preferred form of electrical generating system 10 according to the present invention in which a 3-phase alternator 12 provides a rectified, output voltage for a vehicle electrical system identified here simply as a battery 13. Although the alternator is illustrated as having a star wound stator 15, it will be appreciated that the alternator is a conventional alternator and may have a delta wound stator. Rectification is provided by a 3-phase rectification circuit 14 comprising diode pairs 16, 17 and 18. The alternator 12 also has field diodes 20 for providing the output voltage for a voltage regulator 22 (although the regulator voltage may alternatively be taken from the vehicle battery). In normal operation of the alternator 12 the voltage regulator maintains the output voltage of the alternator at typically 12 or 24 volts.

The conventional alternator has been modified to include a changeover switch 28 through which the rectified output of the field diodes 20 is connected to a rotor coil 26 and an input of the voltage regulator 22. In its first switch position the switch 28 closes contacts 27 and 31 to connect the rotor coil 26 and regulator to the field diodes. In its second switch position the switch disconnects the rotor coil 26 and regulator from the field diodes and closes contacts 29 and 31.

A transformer unit 33 is preferably mounted in its own housing. The transformer unit 33 has a transformer 30 which has a set of 3-phase primary windings 32. These are connected as shown through a switch 38 to the junctions of the diode pairs 16, 17, 18 in the rectification circuit 14 of the alternator.

The transformer 30 has two sets of 3-phase secondary windings 34, 36. The windings 34 are centre tapped to the vehicle chassis and are coupled through a 3-phase rectification circuit 40 to provide a DC output of typically 110 volts DC or 220 volts DC.

The second series of windings 36 is also connected through a 3-phase rectifier circuit 42 to contact 29 of the switch 28 for voltage regulation when the switch 28 is switched into its second switched state, closing contacts 29, 31. The winding ratio between the transformer primary windings 32 and the secondary windings 36 is such that when the voltage output from the rectifier circuit 42 is 24 volts for regulation (or 12 volts on a 12v vehicle), the stator windings of the alternator are providing a resulting 48 volts DC (24v DC).

The effect, therefore, is to enhance the output of the alternator.

A 100A solenoid switch 50 connects the battery 13 to the rectification circuit 14.

In operation, when the alternator 12 is required to provide power to charge the battery 13 and for the vehicle electrics only, switch 28 is switched into its first switched state closing contacts 27, 31, switch 38 is open and solenoid 50 is closed. Power is therefore supplied to the vehicle electrics and to the vehicle battery 13 for charging and the regulator 22 monitors the voltage from the field diodes 20 through the switch 28 to regulate the alternator output voltage in the conventional manner. There is no output voltage from the rectifier circuit 40 since switch 38 is open.

When the alternator 12 is required to provide a high output voltage (e.g. 110 volts DC) for, for example, external floodlighting, switch 28 is switched into its second switched state to close contacts 29, 31 so that the regulator 22 monitors the voltage output of the rectifier circuit 42 coupled to the transformer secondary windings 36. As a result of this, the DC output voltage of the alternator 12 is allowed to rise to 48 volts. Switch 50 is also opened and switch 38 is closed. As a result, the output of the secondary windings 34 is rectified by the rectifier circuit 40 to provide the required higher output voltage. The switches 28, 38 and 50 are ganged so as to be operable together with switch 50 being in the opposite state to switches 28 and 38.

A typical 24V 60A alternator provides 3KW at llOV DC.

It will be appreciated that the electrical generating system described with reference to the drawing requires only three connections from the transformer to the alternator stator winding terminals and a simple modification to the existing regulator circuit. Thus a conventional alternator can be simply and quickly converted to provide the higher output voltage required at minimal expense.

Claims

1. An electrical generating system comprising: a 3-phase alternator having: a stator winding means; and a first rectifier means coupled to said stator winding means for providing a rectified DC output; a voltage regulator for regulating the output voltage of said stator winding means in response to a first regulating voltage; and a transformer arrangement comprising: a transformer having: a primary winding means connected to said stator winding means; a first secondary winding means for providing a stepped up output voltage; a second secondary winding means; a second rectifier means coupled to said first secondary winding means for providing a rectified DC output; a third rectifier means coupled to said second secondary winding means for providing a second regulating voltage for said voltage regulator; and switch means coupled to said voltage regulator for switching between a first switch state for passing said first regulating voltage to said voltage regulator and a second switch state wherein said voltage regulator is coupled to said third rectifier means.

2. An electrical generating system as claimed in claim 1 wherein the alternator has field diode means for providing said first regulating voltage.

3. An electrical generating system as claimed in claim 1 or 2 wherein said switch means and said transformer arrangement are located outside a housing of said alternator.

4. An electrical generating system as claimed in claim 1, 2 or 3 wherein said second secondary winding means and said third rectifier means are operable to provide a regulating voltage of 12 volts or 24 volts.

5. An electrical generating system as claimed in any of the preceding claims wherein said first secondary winding means and said second rectifier means are operable to provide an output voltage of between 110 volts and 220 volts DC.

6. An electrical generating system as claimed in any of the preceding claims wherein said primary winding means is coupled to said stator means by second switch means.

7. An electrical generating system as claimed in claim 6 wherein said switch means are operable in unison.

8. An electrical generating system substantially as hereinbefore described with reference to the accompanying drawing.