GB2288497A

GB2288497A - DC motor control

Info

Publication number: GB2288497A
Application number: GB9506934A
Authority: GB
Inventors: Morais-Montiero Andreas De; Harald Oestmann; Martin Wichmann
Original assignee: Jungheinrich AG
Current assignee: Jungheinrich AG
Priority date: 1994-04-11
Filing date: 1995-04-04
Publication date: 1995-10-18
Anticipated expiration: 2015-04-04
Also published as: FR2718396B1; FR2718396A1; IT1273521B; DE4412407C2; ITMI950720A0; GB9506934D0; DE4412407A1; GB2288497B; ITMI950720A1

Description

1 2288497 ELECTRICAL CIRCUITRY FOR OPERATING AT LEAST A BATTERYOPERATED

ELECTRIC MOTOR MOUNTED IN AN INDUSTRIAL TRUCK The present invention relates to an electrical circuitry for the operation of at least a battery-operated electric motor mounted on an industrial truck according to the preamble of claim 1.

Conventionally, electric motors used for propelling and operating the lifting system of battery-operated industrial trucks are controlled by pulse trains. As far as tyristors are concerned, the control frequency is relatively low. When using electronic power switches, such as FET, MOSFET, transistors or IGBT etc. higher control frequences ranging between 7 to 16 kHz are preferred.

The power unit, such as of an electrical circuitry for controlling an electric motor is composed by a variety of electronical power switches, recovery diodes, capacitors and cooling components, for example. The construction of conventional power components in combination with external connections for example, provides for introducing substantial stray inductivities and thus possibly results in high excess-voltages and periodically occuring voltage peaks. Accordingly, the semi-conductor switches must be construct ed to meet these conditions. Heavy-duty capacitors usually of the electrolyte type are used to protect the circuitry against the effects of external stray inductivities, i.e. between the battery and the power unit.

The voltage peaks referred to do not only affect the power semiconductor switches, but can badly affect the function of the control circuitry which is also of the electronic type. Moreover, the voltage peaks may affect the environment, for example causing interferences in broadcasting, telephone systems or causing mal functions of other electronic components.

It is an object of the present invention to provide an electrical circuitry for the operation of at least a battery-operated electric motor mounted in an industrial truck which is constructed as a compact unit and which reduces strains and damages of high-frequency control semiconductor switches caused by voltage peaks.

According to the invention the object referred to is solved by the features of claim 1.

2 According to the invention, at least a capacitor and a semiconductor switch module is arranged on a common support member which may be formed as a cooling member according to an embodiment of the invention. Semiconductor switches of the type used are usually manufactured as modules comprising a number of chips, for example. Using the term "module" however, shall not limit the scope of the present invention. Any type of semiconductor switches having an electrically isolated mounting surface may be used.

In certain applications it is possible that a single electrolyte type capacitor is provided. However, a number of electrolyte type capacitors is usually required defining a capacitor battery.

According to the invention, a plate structure is provided atop the electrical components referred to, comprising a pair of parallel plates covering the components and an insulating layer provided therebetween. Possibly, the plates may be spaced apart from each other by insulating distance holders, wherein the insulating means is defined by air. However, a structure is preferred according to which an insulating sheet is mounted between the plates. The distance between the plates is thus extremely small,.1 mm for example. This is completely satisfactory as the nominal voltages used are such as 24 V, for example.

Each of the components referred to includes at least a terminal which is connected through the plates to a + or potential. Since the plates are to be connected to at least a terminal of the automotive battery, the terminals of the electrical components are oriented towards the plate structure for making an electrical connection to both the plates. Accordingly, the lower plate facing the components and the insulating layer are provided with openings for extending the terminals therethrough towards the outer or upper plate. When using screws, a mechanical fixing of the plates on the components or, respectively, vice versa may -be provided at the same time.

The plates referred to define current distributing rails for the electrical components and, furthermore, provide for the compensation of magnetic fields as well as for a reduced input of electromagnetic radiation to adjacent components due to their arrangement. When the outer plate is connected to the -terminal for example, it forms an effecbelo tive shield against electromagnetic waves generated the plate structure which radiation thus cannot be transmitted to outside. The plate structure further makes it possible that the connections to the electrical components may be made extremely short, thus considerably reducing the stray inductivities. Furthermore, the inductivity formed by 1 1 f; A 3 the plate structure itself is extremely small because the effective surface thereof is very small. The lower stray inductivity, of course, results in remarkably reduced excess-voltages thus reducing the strain on the semiconductor switches. The semiconductor switches may be thus used up to their power limit or, respectively, their nominal power may be reduced.

The arrangement referred to further results in an extremely compact structure which is an important advantage for the application in industrial trucks.

As mentioned before, a plurality of electrolyte type capacitors is regularly arranged on the support member. According to the invention at least one row of electrolyte type capacitors is located on the support member, wherein the row is arranged in parallel with a row of semiconductor modules. According to a further aspect of the invention, the battery connections to the plates are provided at opposite ends of the capacitor row. This means that the +terminal of a capacitor for example is located very close to the battery terminal, whereas the - connection diametrally opposed is rather remote and vice versa. In this manner one obtains a symmetrical current distribution thus providing additional improvements with respect to the object underlying the invention.

Electric industrial trucks often comprise two electric motors such as for driving and for operating the lifting system. According to a further aspect of the invention. the capacitors and the semiconductor modules for both electric motors are commonly arranged on the support member, wherein all capacitors are connected in parallel. Therefore, the capacitors may be selectively used for the lifting operation or the driving operation. As a rule, while the vehicle is propelling there is no lifting or lowering and while operating the lifting system, the vehicle does not move. In this manner, the overall capacity which would be required for separate power units can be reduced.

The semiconductor modules for both power units are preferably arranged in groups on the support member.

The height of the connecting studs on the upper ends of the capacitors must be selected to be different in view of the different height of both plates of the plate structure. Since the whole pattern in the plate structure must be manufactured according to the pattern of arranging the capacitors or their terminals, the arrangement according to the invention further results in a so-called protection against a false connection. For example, when the required connection to the plates cannot be performed because of a 4 false arrangement of the capacitors, checking will reveal the error.

According to a further aspect of the invention, the upper plate of the plate structure is formed to provide an extended elevation receiving the lower plate. Then the upper plate may be mounted along the edge thereof to the modules or the capacitors by screws or similar fasteners.

According to a further feature of the invention, the structure of the power supply makes it possible to mount a circuit board including the control circuitry onto the outer plate. By the shielding mentioned before, the transmitance of electromagnetic radiation originating from the power unit to components of the control circuitry is substantially prevented. This further reduces the size of the electrical and electronical circuitry required for operating the electric motor. In most cases controlling the electric motor requires a current measurement, for example a measurement of the current flowing through the armature. According to a feature of the invention, a contact-free current sensor is located on the circuit board. The power output conductor is placed through the sensor such as an annular current sensor arranged at the lower side of the circuit board for the connection to the motor terminal. The ring-shaped current sensor can be defined to be a Hall element, for example. Then sensing the current is performed free of contact. The current sensor does not require individual service or additional interfaces.

As already mentioned, the circuitry according to the invention is of compact size and reduces all stray inductivities which are present in the circuitry. Furthermore, it is possible to assemble together both the control circuitry and the power supply for a pair of electric motors or even more as required. The arrangement of the power unit, i.e. the number of modules and electrolyte type capacitors may be varied, while the basic structure must be not changed.

The invention will be described in detail with reference to the drawings.

Fig. 3 Fig. 4 Fig. 1 is a perspective view of the power unit of a circuitry according to the invention; Fig. 2 is a view similar to Fig. 1, but the connecting screws are removed; is a view similar to Fig. 2 showing an embodiment for three-phase current; is a section view through the power unit shown in Figs. 1 through 3; Fig. 5 is a view of a circuit board for the control section to be mounted on the power unit of Fig. 1; Fig. 6 schematically shows the assembly of a power unit and a control unit according to Fig. 5; Fig. 7 is a head view of the assembly shown in Fig. 6.

Fig. 1 shows a power unit 10, for example for operating an electric motor for vehicle propelling and an electric motor for operating the lifting system of an industrial truck. The power unit includes a plate-shaped cooling block 12 having an upper surface which is formed in a stepped contour. The lower-most region thereof accomodates two rows of capacitors, for example electrolyte type capacitors, defining a capacitor battery, of which a cylindrical capacitor 14 and 16 are shown. Towards the center and somewhat elevated there is arranged a row of eight modules 18 on the cooling block 12, the modules 18 defining semiconductor power switches. All types of possible semiconductor switches, for example MOS-FET, FET, transistors IGBT or similar devices may be provided. They all are suited to be controlled with a relatively high frequency, for example between 7 and 16 kHz. Above the arrangement of circuitry components just described there is a plate structure 20 comprising an upper plate 22 extending across the capacitor battery and partly across the modules 18. Below the plate 22 there is a further plate 24 of which Fig. 1 only shows a section. The plates 22, 24 have a thickness of 1 mm, for example. The lower plate is received within an elevation 24a which is formed by downwardly bending the upper plate 22 along the edges thereof. A terminal stud 26 of the upper plate 22 defines a -terminal. A terminal stud 28 of the lower plate 24 defines the +terminal. The studs 26, 28 are fixedly secured to a plastic member which further receives the individual capacitors of the capacitor battery and which is provided with projections for securing the plates 22, 24 by means of screws. The plastic member is secured to the cooling member through pressing pins. The capacitors 14, 16 are electrically connected to the upper and lower plate 22, 24 each by means of terminal screws 30 and 32. The modules 18 as well are electrically connected to the plates 22, 24 through terminal screws 34, 36. The basic sandwich-like structure of the plate is shown in Fig. 4. It is shown that a sheet 38 of electrically insulating material is placed between the plates 22, 24. The plates are made of a relatively thin, conductive metallic sheet, for example aluminium or copper. The sheet is relatively thin, for example.1 mm. The conductors 40, 42 shown in Fig. 4 are connected to the terminals of the battery. The capacitors shown in Fig. 1 are merely illustrated in symbols in Fig. 4. One realizes that the + and terminal each are connected to one of a respective plate 22, 24. The same applies to the module 18 also illustrated as a symbol. As may be noted, the terminals of the capacitors and of the modules each must be connected to one of the respective plate 22, 24. In order to provide for a connection to the upper plate 22, the lower plate 24 as well as the sheet 38 6 must include a pattern of holes through which the conductors may be placed free of contact. Fig. 3 shows that the upper plate 22 also includes enlarged holes as shown at 38 or 40 for connecting the terminals to the lower plate 24 by means of screws 32, 36. For connecting the conductors to the upper plate 22, however, relatively small holes 42, 44 are required in which appropriate screws 30, 34 are inserted.

As shown in Figs. 1 and 2, plate-shaped rails 46, 48 are secured to the modules by screws 50, 52 wherein the rail 46 is placed across five modules and the rail 48 across three modules. For example, the five modules to which the rail 46 is connected are part of the power unit for operating a propelling motor, while the rail 48 is placed across the modules for the power unit as a lifting motor. The rails 46, 48 include lugs 52, 54 to be connected to terminal studs 56, 58 which are mechanically connected to the cooling block 12 but electrically insulated therefrom. The lugs 52, 54 may be also formed flexible. The terminal studs are connected to the propelling motor and the lifting motor, for example.

The power unit shown in Fig. 3 is different from that shown in Fig. 2 in as much as three plate-shaped rails 60, 62 and 64 are connected to the upper end of a total of 9 modules as mentioned before including lugs 66, 68, 70 to be connected to three studs 72, 74, 76. The module shown is used for a battery supplied three-phase current motor. All the remaining components are the same as shown in Fig. 2.

Fig. 5 is a perspective view of a circuit board 80 accomodating all control components and circuits for controling the power units shown in Fig. 1 to 4. For example, an electric motor is controlled through a socalled halfbridge which alternatively operates to be set high or low depending on the prevailing current conditions. The particular components will be not further described. However, supporting strips 82, 84 for mounting are arranged at opposite sides of the board 80, and control interfaces 86 as well as a pair of ring-shaped current sensors 88, 90 are provided. Fig. 6 is a sectional view of the control board 80 as it may be mounted on a power unit as shown in Fig. 1, for example. The arrangement of the capacitors 14 and of the semiconductor modules 18 on the cooling block 12 is shown. It can be further seen how the lug 54 of the rail 46 extends through the ring-shaped sensor 90.

The connection of the individual electrical or electronical components of the control board 80 to the semiconductor modules 18 is not shown, as is the mechanical connection of the board 80.

p 7 It should be understood that the -plate 22 may extend across the armature rail(s) but insulated therefrom.

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Claims

PATENT CLAIMS

1. An electrical circuitry for the operation of at least a batteryoperated electric motor mounted on an industrial truck, comprising at least a capacitor and a pulse control semiconductor switch, both arranged on a support member and both to be connected to a control unit, characterized in that at least a capacitor (14,16) and a semiconductor switch module (18) are arranged on a common support member (12) and that a pair of plates (22,24) made of electrically conductive material is provided at a small distance from each other above the said electrical components, at least partly covering said components, between which plates a thin insulating layer is provided, wherein one (22) of the plates is to be connected to the -terminal of a battery and the other to the +terminal thereof, and that the terminals of the electrical components are connected to a respective plate (22,24) through a terminal facing said plate structure, wherein the lower plate (24) and the insulating layer (38) are provided with openings for extending the terminals to the upper plate (22) therethrough.

2. The circuitry of claim 1, characterized in that at least a row of capacitors (14,16) is provided on the sup porting member (12) and that a plurality of semiconductor modules (18) is arranged in a row parallel thereto.

3. The circuitry of claim 2, characterized in that the battery terminal (26,28) of the plates (22,24) are located at opposite ends of the row of capacitors.

4. The circuitry of one of claims 1 to 3, characterized in that the motor terminal is also formed as a plate (46,48) extending above the module (18).

5. The circuitry of one of claims 1 to 4, characterized in that a pair of electric motors mounted in the industrial truck the respective capacitors (14,16) in semiconductor modules (18) are commonly seated on the support member (12) and are connected to the plate structure (20) wherein all capacitors (14,16) are connected in parallel.

6. The circuitry of claim 4 and 5, characterized in that both motor terminals are formed by plate-shaped rails (46, 48).

7. The circuitry of one of claims 1 to 6, characterized in that an insulating sheet (38) is disposed between the plates (22,24) made of conductive material.

A r 9

8. The circuitry of one of claims 1 to 7, characterized in that an extended elevation (24a) is formed in the upper plate (22) of the plate structure (20) for receiving the lower plate (24).

9. The circuitry of one of claims 1 to 8, characterized in that the plate (22) connected to the -terminal of the battery is arranged at the upper surface.

10. The circuitry of one of claims 1 to 9, characterized in that a circuit board (80) accomodating a control unit is disposed on the outer or upper plate (22).

11. The circuitry of claim 10, characterized in that a preferably ringshaped current sensor (88,90) is located on the side of the circuit board (80) facing the power unit and that a projection (54,56) of the motor terminal (46,48) connected to the semiconductor module (18) extends through said current sensor (88,99) towards a terminal stud (58, 56).

12. The circuitry of one of claims 1 to 11, characterized in that the support member (12) is defined as a cooling block.

13. Electrical circuitry substantially as hereinbefore described with reference to the accompanying drawings.