GB1603976A

GB1603976A - Electric motors

Info

Publication number: GB1603976A
Application number: GB9089/78A
Authority: GB
Original assignee: Holdsworth J E
Current assignee: Holdsworth J E
Priority date: 1978-03-07
Filing date: 1978-03-07
Publication date: 1981-12-02
Also published as: JPS54164208A; CA1167516A; DE2908936A1

Description

(34) ELECTRIC MOTORS (71) I, JOHN ELDRED HOLDSWORTH, a British subject, formerly of Redwell House, Foldshaw Lane, Dacre, Harrogate HC3 4AP, and now of "Sykes Grange", Lofthouse, North Yorkshire, do hereby declare the invention, for which I pray that a patent may be granted to me, and the method by which it is to be Performed, to be particularly described in and by the following statement:- This invention relates to electric motors.

Customarily it has been found necessary to apply electric motors to many types of machines. These may have been AC or DC motors and were used either for continuous operating in one direction or for reversing operation and in some cases variable speed operation in one or two directions. The method of controlling these motors has normally been through external contactors, variable speed thyristor drives, or inverter drives. The current state of the art enables AC and DC motors to be controlled through wide speed ranges in one or both directions.

This is normally accomplished by connecting to the motor supply leads which run from electronic control systems or contactor panels.

According to the present invention there is provided a motorised power module in which an electric motor and control circuitry therefor provide a single structural unit, and wherein the said control circuitry comprises programmed or programmable memory means for defining a predetermined or predeterminable operating programme for the motor.

I can provide customers with a series of motorised power modules as single units.

In a preferred embodiment each will be an AC motor complete with electronic inverter circuitry built into the same frame such that the customer may select from the shelf a power module having variable speed and variable direction control built into the motor frame. It will be merely necessary for him to connect a three phase electricity supply to the unit and close an external contact. There will be included in the control circuitry part of the unit a programming facility which will enable a read only memory to be used causing the power module for example to rotate at a defined speed through a given number of revolutions in either direction followed by a further series of speeds and directions until the programme is exhausted.It is anticipated that a single closure of an external cOntact can be used to initiate a sequence which is defined by the purchaser at tune time of pur.

chase. The programme may be entered into one or more read only memories by the manuj facturer of the device and may be easily filter changeable by virtue of a small plug-in mod ule.

An extension of this preferred embodiment will be to include a communication bus between this power module and other power modules so that special machines used for packaging, for example, with several drives on various parts of the machine will be able to communicate with each other. In this way a power module will be initiated by an external signal, it will then perform a part of tho sequence programmed into it and then deliver a signal to the communication bus which will be recognised by another power module in structing that module to perform part of its programme and then signalling either back to the first unit or on to subsequent power mod.

ules such that in this way complex sequencing arrangements of variable speeds and directions will be easily attained through softwear methods, i.e. merely by the act of the purchaser filling in programming cards at the time of purchase.

It is envisaged that although these units could be made using DC motors, special low inertia AC motors will be developed in a range of sizes.

One concept therefore, is of programmable power modules able to exist independently or as part of a team. Further more sophisticated systems, teletype terminations etc. will be provided and it will be possible to put reprogrammable random access memories into the larger units enabling programme changes to be made by customers at will by teletype terminations.

For a better undertanding of the. invention and to show how it may be pdt into effect, reference is made to the accompanying drawings in which: Figure 1 shows an axial sectional view of an embodiment of a motorised power module according to the present invention; Figure 2 is a section taken along the line I-I in Figure 1; and Figure 3 shows a perspective view showing an alternative form of control circuitry mounting.

Figure 1 shows a three-phase a.c. motorised power module comprising a cylindrical motor frame 19 and a squirrel cage rotor 1.

The latter has a winding of low resistance construction and is not required to have good mains starting characteristics because the built-in control circuitry can be adapted to the rotor to provide the good starting characteristics. The mechanical inertia of the rotor 1 is kept as low as possible, for rapid response at changes in operation, by virtue of its general geometry and also by the removal of surplus iron by providing axially extending holes 20 and 21 in the laminations of the rotor 1, which holes also provide passageways for cooling air. These holes 20 and 21 are just two of several axially-extending holes arranged about the axis of the rotor 1.

The motor comprises a stator 2 of conventional construction made of laminated plates and fitted with slots to accommodate a stator winding 3.

In this particular embodiment a shaft 4 of the rotor 1 carries a pulse generator to act as a motor speed and/or phase indicating device.

It comprises a coded optical disc 5 to produce electronic signals from photo transistors 6 which receive light from an infra red source 7 reflected via a surface 22. These signals may be used in the control circuitry of the motor as actual values of angle in a conventional manner. The disc 5 may have patterns inscribed on it to produce incremental or absolute coded outputs.

The alternating current for the stator winding 3 of the motor is controlled in conventional manner in dependence upon control circuitry including thyristors or transistors 8 providing a controllable inverter and mounted on six heat sinks 9 which are all extruded aluminium and are arranged round the axis of the motor. The crosssection of the extrusion and the arrangement of the heat sinks 9 can be seen in Figure 2.

Each heat sink has a base and three limbs extending from the base.

The heat sinks 9 are secured by clips 23 (shown only for one heat sink 9 in Figure 2) in respective radial sectors of a plastics spider 10. The six radial arms 24 of the spider 10 are secured at their outer ends to six axially extending bar-form portions 25 of the motor frame 19. The spaces between the bar-form portions 25 allow access to the thyristors or transistors 8 from outside the frame 19, and in some cases provide room for housing other parts of the control circuitry (as will be described in more detail hereinafter).

A fan 11 rotatably mounted on the frame 19 rotates to provide a cooling air stream from holes 26 in an end plate 15 of the frame; through and around the heat sinks 9 to cool them; through holes 12 (only one of which is shown) in a bearing plate 27 of the frame 19; through the holes 20 and 21 in the rotor 1 (and also through the air gap of the motor) to cool the motor; and out through vent holes 28 near the right-hand end of the frame 19.

Another flow of air caused by the fan 11 flows through the central hole 29 of the spider 10 and out through a cone 30 attached to the spider 10 to cool the disc 5 attached to the shaft 4. This flow leaves the frame 19 via holes such as hole 31.

The fan 11 is driven at a speed independently of the speed of the rotor 1 by a relatively small three-phase motor 13, which is double wound to act as a three-phase transformer supplying low voltage three-phase to supply logic circuitry controlling the thyristors or transistors 8. An air filter 14 is provided which is easily changed by removal of the motor end-plate 15.

A sensor (not shown) measures the voltage across the frame of the fan motor 13. The fluctuation of this voltage indicates the condition of the filter. Thus, when the filter is blocked the fan 11 will speed-up and the slip frequency of the motor 13 will fall. This can be used to inhibit the drive to the main motor.

The independent drive of the fan 11 is particularly useful in providing a good stream of cooling air even when the main motor is supplying high torque and operating at low revs.

Electrical power is fed into the module via a terminal box 16. It may be A.C. or D.C.

depending upon the control circuitry.

Control logic 32 for the thyristors or transistors 8 is mounted on a printed circuit board 32a in a box 17 mounted on the frame 19. In this manner the circuit board is secured relative to the frame 19. Similarly, pulse transformers 33 on a printed circuit board are securely mounted on the frame 19 in a box 34.

The boxes 17 and 34 are made from curved extruded sections. All the remaining control circuitry for the main motor is mounted in this way, including commutation induetors 33a. In this manner a single motorised module is provided.

Figure 2 shows only two sets of boxes arranged circumferentially around the frame 19, but more could be added depending on the amount of circuitry to be housed.

The control logic 32 includes means to provide variable speed and direction for the motor. This single type of control may be achieved by a single control knob 35 mounted on the box 17. Also an electrical connector 35a could be provided giving remote speed control facilities.

In addition, the control logic includes a read-only memory 36 containing a predetermined operating programme for the motor.

This could be an interchangeable plug-in memory cooperating with a microprocessor 36a.

This memory could even be reprogrammable to enable programme changes to be made. None of the detailed circuitry of the control circuitry is illustrated or described, because it is conventional and does not form part of the present invention.

As an alternative to being housed in boxes 17 and 34 attached to the outside of the motor frame 19, the printed circuit boards could be housed around the thyristors or transistors 8. Thus, see the board 37 in Figure 2. It is attached by a hinge 38 to one of the bar portions 25, and secured by a clip 39 to the adjacent bar portion 25. In this manner the board is secured to the frame 19. If all the boxes 17 and 34 etc were removed, and covers provided for the spaces between the bars 25, a plurality of printed circuit boards mounted such as 37 and components thereon would have the general appearance as shown in Figure 3. The boards 37 could be hinged outwardly for access to the back of the boards and to the thyristors or transistors 8.

Instead of being radially inside the boards 37, the thyristors or transistors 8 could be outside.

Figure 3, for example, shows how such a motor might look externally and shows a motor 101 to the frame 101a of which are securely attached circuit boards 102, 103 and 104 carrying programmed electronic inverter control circuitry. The speed and direction of the motor is also selectable and variable by a single knob (not shown). A terminal box 105 is attached to the frame 101a of the motor for connection to an a.c. supply.

A cover 106 for the inverter circuitry is shown detached. This cover can act as a heat sink for the inverter circuitry, especially if thyristors or transistors 107 are mounted on the cover 106.

It may be advantageous for a fan to be attached to one end of the rotor of the motor to draw cooling air over the inverter circuitry.

It may assist in this case if the rotor of the motor is hollow to allow cooling air to pass through it.

It is possible for modules employing microprocessor-based logic systems to be connected together enabling speeds, angles of rotation, sequencing and relationships between large and smaller machines to be accurately specified and maintained (a simple example of this would be where one motor is instructed to accelerate to 1,000 rpm over 5 revolutions and that at the end of the 5th revolution a second motor is instructed to accelerate to 600 rpm thereafter remaining in synchronism at 06 times the speed of the first motor).

WHAT I CLAIM IS: 1. A motorised power module in which an electric motor and control circuitry therefor provide a single structural unit, and wherein said control circuitry comprises programmed or programmable memory means for defining a predetermined or predeterminable operating programme for the motor.

2. A module as claimed in claim 1, wherein said motor is an a.c. motor and said control circuitry comprises an inverter.

3. A module as claimed in claim 1 or 2, wherein said memory means is reprogrammable.

4. A module as claimed in any one of the preceding claims, wherein said control circuitry comprises thyristors or transistors mounted in at least one heat sink arranged around the axis of the motor.

5. A module as claimed in claim 4, wherein the or each heat sink is a cover in a frame of the motor.

6. A module as claimed in any one of the preceding claims, wherein some of said control circuitry is mounted on at least one circuit board arranged around the axis of the motor.

7. A module as claimed in claims 5 and 6 combined, wherein said cover is a cover for said circuit board.

8. A module as claimed in any one of the preceding claims, which is connected to at least one other such module to influence the operation thereof.

9. A module as claimed in claim 8, wherein the modules are interconnected by a communication bus, to provide a system of modules which may operate in dependence upon one another in dependence upon programming.

10. A module as claimed in any one of the preceding claims, wherein said memory means is physically interchangeable with other memory means.

11. A module as claimed in any one of the preceding claims, and comprising a cooling fan for at leat some of said control circuitry, driven by an independent small electric motor.

12. A module as claimed in any one of the preceding claims, wherein said motor comprises a low inertia rotor.

13. A module as claimed in claim 12, wherein said rotor has holes therein.

14. A module as claimed in any one of the preceding claims, wherein said motor comprises a squirrel cage rotor winding which is of low resistance construction.

15. A module as claimed in claim 11, or any one of claims 12 to 14 when appended either directly or indirectly to claim 11, wherein said fan is associated with a filter,

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. 35a could be provided giving remote speed control facilities. In addition, the control logic includes a read-only memory 36 containing a predetermined operating programme for the motor. This could be an interchangeable plug-in memory cooperating with a microprocessor 36a. This memory could even be reprogrammable to enable programme changes to be made. None of the detailed circuitry of the control circuitry is illustrated or described, because it is conventional and does not form part of the present invention. As an alternative to being housed in boxes 17 and 34 attached to the outside of the motor frame 19, the printed circuit boards could be housed around the thyristors or transistors 8. Thus, see the board 37 in Figure 2. It is attached by a hinge 38 to one of the bar portions 25, and secured by a clip 39 to the adjacent bar portion 25. In this manner the board is secured to the frame 19. If all the boxes 17 and 34 etc were removed, and covers provided for the spaces between the bars 25, a plurality of printed circuit boards mounted such as 37 and components thereon would have the general appearance as shown in Figure 3. The boards 37 could be hinged outwardly for access to the back of the boards and to the thyristors or transistors 8. Instead of being radially inside the boards 37, the thyristors or transistors 8 could be outside. Figure 3, for example, shows how such a motor might look externally and shows a motor 101 to the frame 101a of which are securely attached circuit boards 102, 103 and 104 carrying programmed electronic inverter control circuitry. The speed and direction of the motor is also selectable and variable by a single knob (not shown). A terminal box 105 is attached to the frame 101a of the motor for connection to an a.c. supply. A cover 106 for the inverter circuitry is shown detached. This cover can act as a heat sink for the inverter circuitry, especially if thyristors or transistors 107 are mounted on the cover 106. It may be advantageous for a fan to be attached to one end of the rotor of the motor to draw cooling air over the inverter circuitry. It may assist in this case if the rotor of the motor is hollow to allow cooling air to pass through it. It is possible for modules employing microprocessor-based logic systems to be connected together enabling speeds, angles of rotation, sequencing and relationships between large and smaller machines to be accurately specified and maintained (a simple example of this would be where one motor is instructed to accelerate to 1,000 rpm over 5 revolutions and that at the end of the 5th revolution a second motor is instructed to accelerate to 600 rpm thereafter remaining in synchronism at 06 times the speed of the first motor). WHAT I CLAIM IS:

1. A motorised power module in which an electric motor and control circuitry therefor provide a single structural unit, and wherein said control circuitry comprises programmed or programmable memory means for defining a predetermined or predeterminable operating programme for the motor.

13. A module as claimed in claim 12, wherein said rotor has holes therein.

blocking of which filter is detected in dependence upon the slip of said independent small electric motor.

16. A module as claimed in claim 4, or any one of claims 6 and 8 to 15, excluding claims 5 and 7, when appended either directly or indirectly to claim 4, wherein the or each said heat sink is mounted in a support means of electrically insulating material.

17. A module as claimed in claim 16, wherein the or each heat sink is in the form of a member which extends substantially parallel to the axis of the motor and has a substantially triangular cross-section with an apex directed towards the axis of the motor, the support means comprising a spider having radially extending limbs.

18. A module as claimed in any one of the preceding claims, wherein some of said control circuitry is mounted in at least one box mounted on a frame of the motor.

19. A module as claimed in any one of the preceding claims, wherein an angle and/or speed and/or phase indicating device is connected to the rotor of the motor.

20. A module as claimed in claim 19, wherein the indicating device comprises a coded optical disc arranged to cooperate with photo-electric means.

21. A module as claimed in claim 6, or any one of the claims 7 to 20 when appended either directly or indirectly to claim 6, wherein the or each said circuit board is pivotably mounted.

22. A module as claimed in any one of the preceding claims, wherein said control circuitry comprises a micro-processor.

23. A motorised power module substantially as hereinbefore described with reference to Figures 1 and 2 of the accompanying drawings.

24. A motorised power module substantially as hereinbefore described with reference to Figure 3 of the accompanying drawings.