This invention relates to an electric power control system, and in particular to an electric power control system in a modular format.

Electric power control systems (e.g. electric motor control systems) conventionally are custom designed and the method of designing and building such systems typically involves initially drawing a circuit for each system, incorporating the required number of control relays, auxiliary contacts, indicators and other devices such as elapsed time meters, voltmeters, power (watt) meters and power factor indicators etc, identifying each wire with a number, mounting each component, e.g. a starter, relay, indicating lamp or control switch into a starter panel and connecting the wires individually between each part of the circuit in accordance

with the drawings. This procedure is lengthy and mistakes are often made when control wires are wrongly connected or numbered leading to wasted time in fault finding, corrective work, retesting and recommissioning.

It is an object of the present invention to simplify the design and construction of electric power control systems by providing preassembled modular control units, each designed to fulfil a particular control function, and which can be connected together by means of multi-cored cables through plug and socket connections to form a control system. In so doing, the conventional practice of mounting components individually and installing and identifying control wires individually is avoided, thus making the design and construction process more efficient and reducing manufacturing time and labour.

Accordingly, the invention provides an electric power control system comprising at least one power switching device for switching power to an electric power consuming device; one or more unitary control modules for controlling the power switching device; and means for connecting the control module to the power switching device.

Examples of electric power consuming devices are fans, e.g. fans located in air handling units and ventilation units; pumps, e.g. for pumping water, oil, sewage and chemicals; industrial and marine plant, e.g. heaters, chillers, evaporators, condensers, compressors, lifts, cranes, generators and traction equipment; and process, plant such as pulleys, belts, rollers, valves and positioners.

Preferably the electric power consuming device has an electric motor, and the power switching device is arranged to switch power to the electric motor.

Each unitary control module typically comprises one or more relays, a power input, a plug/socket arrangement for connection to another module or to the power switching device, and control means for activating or deactivating the control module.

The control means may take the form of an on/off switch and/or a control input for receiving an external control signal e.g. from another control module, a remote switch or a remote microprocessor or equivalent device.

In its simplest form, the control system can comprise a single power switching unit connected via a plug/socket arrangement and multi-cored cable to a single control module. The control module can be equipped with a simple on/off switch to activate or deactivate the control module. Rather than existing as an isolated control system, the control module can be provided with an input for receiving an external control signal. The external signal input can replace the on/off switch, or the external signal input can augment the on/off switch arrangement thereby enabling the module to be activated either automatically or manually. The manual activation facility could provide a back up in case of the failure of the external control means. Typically the control module is provided with a three-way switch arrangement providing on, off and automatic modes.

It is often the case that in power consuming systems, such as for example a building air conditioning or ventilation system, one or more of the power consuming devices (e.g. fans) forming part of the system will be duplicated. This provides a back-up facility in case of failure of one of the devices, but also allows for one of the devices to be rested while the

other is operating thereby effectively providing a continuous running facility without overrunning or overheating the individual devices. In such an arrangement, each device in a pair of such devices typically would have its own power switching device and, linked thereto, its own control module. Each of the control modules typically would have a control signal input, the control signal input being linked to an external control means. The external control means preferably takes the form of a further unitary control module, hereinafter referred to as an interface module, which comprises one or more relays, a power input, a plug/socket arrangement for providing a connection via multi core cable between the interface module and each control module, and control means for activating or deactivating either control module in a desired sequence. The control means can take the form of a simple switching device (e.g. a manual switching device) for switching on either one control module or the other, or a control signal input can be provided for receiving an externally generated control signal.

Other functions of the interface module include, but are not limited to, multispeed motor control, controlling the reversing of motor rotation, and controlling standard forms of motor starting such as Star-Delta, Auto Transformer and Stator/Rotor motor starters.

Where it is desired to coordinate the operation of one power consuming device, or pair of linked devices ( for example a fan or linked pair of fans at one location within a building ventilation system) with the operation of another power consuming device or pair of linked devices (for example a fan or pair of linked fans at another location in a building

ventilation system) , one or more auxiliary control modules can be employed to link the two said devices or pairs of devices. Where each of a pair of said devices is linked by an interface module, the connection between the pair of devices and the auxiliary module, and thence to another device or pair of linked devices typically is made via the interface module.

The auxiliary control module linking the interface modules of each pair of control modules will generally comprise one or more relays, a power input, a plurality of plug/socket arrangements enabling the auxiliary control unit to be connected via multi-core cable to adjacent interface modules or control modules, and control means for controlling the activation or deactivation of control module or interface module connected thereto. The auxiliary control module may therefore serve as a hub controlling the functioning of a substantial number of individual control modules. The auxiliary module may have associated therewith one or more relay modules providing additional relays, the relay modules being interposed between the auxiliary control module and the interface module.

The auxiliary control module is preferably configurable, that is to say it is constructed such that the electrical contacts within the module can be adjusted to the desired configuration prior to sealing and installation. The auxiliary control module can be provided with means for receiving an external control signal, for example from a remote microprocessor based control device.

Each control module, auxiliary control module, relay module or interface module typically comprises a printed circuit board containing the relays, as well as the power

input, plug and socket arrangement and (where appropriate) control means as hereinbefore defined. Each type of module may optionally comprise one or more other elements such as indicators and instruments for displaying the status or mode of the module.

Each module may be of fixed configuration or may comprise means for varying its configuration prior to installation. More usually, the control and interface modules will be of fixed configuration and will be arranged to perform predetermined control and interfacing functions whilst the auxiliary interface module (if such is present in the control system) will provide the variable facility.

In one embodiment, the electric motor control system comprises a pair of control modules, each control module being linked to a power switching device, and an interface module linking the pair of control modules, the interface module optionally being linked (e.g. via a relay module) to a configurable auxiliary control module.

Each module, whether it be a control module, auxiliary control module, relay module or interface module, is preferably constructed so as to fit into an electronic rack, which may for example be of a standard form or may be purpose- built, identical modules being interchangeable within the rack.

As indicated above, each module can be provided with information display means and control means, for example indicating lamps, control switches and instruments etc if required. The information display means and control means can conveniently be located on a fascia panel. The fascia panel can be either hard wired to the printed circuit board or be

constituted by a secondary printed circuit board.

Interface modules can be designed in standard fixed format for regularly used interlocking functions, or they can be individually designed in a nonstandard format for 'one-off applications. Alternatively, they can contain a number of control relays which can be used to configure non-standard functions. For such non-standard functions, relay modules (containing one or more control relays ) are provided which can be plugged into a sealable module of variable format which enables control circuits to be configured into the desired circuit arrangement. The relay modules and sealable modules can replace conventional relay sections of electric motor starter panels. Interface and relay modules can be produced using the same principles as the starter control modules with fascia panels containing any required control and indication elements. Each relay module can contain one or more control relays having coil connections and contacts connected in regular format to plug connectors forming part of the modules.

In order to effect control, a physical connection is required between the unitary control module and the power switching device, e.g. between a control module and a motor starter. Motor starter units typically comprise a contactor unit and an overload protection unit. Energising the contactor coil operates . the contactor unit which in turn provides power to an electric motor. Excess current or other fault conditions will trip the mechanism of the overload protection unit. Control and monitoring of these functions forms part of the physical connection between the starter control module and the motor starter. Where it is required to monitor or display the current drawn by electric motors for

which current transformers are installed in or around the power lines feeding the motors, the secondary circuits of the current transformers can form part of the physical connection between the control module and the motor starter.

Physical connection between the power switching device (e.g. the motor starter) and its associated control module is preferably provided by a standard plug/socket arrangement linked by, for example, a standard multicore cable assembly having a plug at one end and a socket at the other. Connections between individual control modules are also preferably provided by means of plug/socket arrangement and multicore cable.

The invention will now be illustrated in more detail by reference to the specific embodiments shown in the accompanying drawings of which:

Figure 1 is schematic view of an electric motor control system in accordance with one embodiment of the invention;

Figure 2 is a more detailed schematic view of a control system in accordance with a second embodiment of the invention;

Figure 2a illustrates schematically the layout of one starter control module shown in Figure 2;

Figure 2b illustrates schematically the layout of an interface module shown in Figure 2;

Figure 2c illustrates schematically the layout of a second starter control module shown in Figure 2;

Figure 3 is a schematic view illustrating the arrangement of a number of motor starters and control modules within a containing cabinet;

Figure 4 is a front elevation of a starter control

module ;

Figure 5 is a side elevation from direction A in Figure 4;

Figure 6 is a circuit diagram for the starter control module shown in Figures 4 and 5;

Figure 7 is a wiring diagram for the circuit shown in Figure 6;

Figure 8 is a front elevation of an interface module;

Figure 9 is a side elevation from direction B in Figure 8;

Figure 10 is a circuit diagram for the interface module shown i Figures 8 and 9; and

Figure 11 is a wiring diagram for the circuit diagram shown in Figure 10.

Referring now to the drawings it can be seen that a power control system in accordance with one embodiment of the present invention comprises a power switching device which, in this instance, is an electric motor starter unit 1 containing the usual contactor units and overload protection unit. The motor starter unit may be, for example, connected to the motor of a fan in an air-conditioning system. The contactor is provided with a plug or socket arrangement 2 into which is plugged a corresponding socket or plug end of a multicore cable 3, of conventional- type. Multicore signal cable 3 is connected at its other end 4 by means of another plug and socket arrangement to the unitary control module 5, hereinafter referred to as the motor starter control module 5. Motor starter control module 5 is provided with plug/socket means from which a cable 7 extends to the terminal rail 8. Motor starter control module 5 is also provided with

plug/socket means 9 for connection via multicore signal cable 10 and plug/socket assembly 11 to interface module 12. Interface module 12 is connected via plug/socket arrangement 13 and multicore signal cable arrangement 14 to terminal rail 8 and is also connected via plug/socket arrangement 14 to an additional motor starter control module (not shown in Figure 1), which controls the operation of a second fan operating in tandem with the aforementioned fan. Interface module 12 is connected via plug/socket arrangement 16, signal cable 17 and plug/socket arrangement 18 to relay module 19. Relay module 19 is connected in turn by plug/socket arrangement 20, multicore signal cable 21 and plug/socket arrangement 22 to the auxiliary module 23 which is of configurable format. Whereas the motor starter control module 5 and interface module 12 are of fixed configuration, the auxiliary control module 23 is designed to be variable, the user adjusting the parameters of this unit to the desired configuration before sealing the unit and installing it.

Figures 2, 2a, 2b and 2c illustrate in schematic form, but in more detail than Figure 1, the arrangement of a system comprising motor starter units 201 and 202, motor starter control modules 203 and 204 and interface module 205.

The motor starters and control modules can be be grouped together and located inside a single cabinet as shown in Figure 3. The arrangements shown in Figure 3 are by way of example only and other arrangements are possible.

In Figures 4 to 7, there is shown the typical construction and layout of a motor starter control module 401. Thus, module 401 comprises a fascia plate 402 which can be secured by means of screws 403 to an appropriate rack. Handles

404 and 405 are provided to assist withdrawal of the module from the rack. Set into the fascia plate 402 are indicator lamps 406, 407 and 408 which are respectively green, amber and red in colour, green indicating that the motor starter has been energised or that the motor is running, dependant upon the feedback source; amber indicating that the control circuit is live, and red indicating that the overload unit has tripped. Also set into the fascia plate 402 is an ammeter 409 which shows the value of the current being drawn, and a control knob 410 linked to a three-position selector switch 411 which selects the mode of the control circuit.

Figure 5 is a side elevation from direction A in Figure 4 and shows the internal layout of the modular unit. Referring to Figure 5, it can be seen that a printed circuit board 412 is attached to the fascia plate 402. Secured to the rear end of the printed circuit board are a 15-way connector socket 413, a 9-way connector plug 414 and a 15-way connector plug 415. Connected to the circuit board are 4Amp and 2Amp fuses 416 and 417, a 1-pole relay 418, two 4-pole relays 419 and 420, a rectifier circuit 421, resistors 422, removable links 423 and diodes 424. The connections between the aforementioned components are shown in Figures 6 and 7. In Figure 6, the components forming part of the module are enclosed within the dotted line L, the 15-way socket 413 is represented by symbols A1-A15, the connector plug 414 is represented by symbols B1-B9 and the 15-way connector plug 415 is represented by symbols C1-C15. Table 1 below provides a correlation between the reference numbers used in Figure 5 and the symbols used for the same components in Figure 6.

TABLE 1

Figures 8 to 11 illustrate an interface module in accordance with one embodiment of the invention. Thus, the interface module 801 comprises a fascia plate 802 which can be secured by means of screws 803 to an appropriate rack. Set into the fascia plate 802 are indicating lamps 804 and 805, handles 806 and 807, and 3-position selector switch, the functions of which correspond to or are analogous to the equivalent components of the starter control module illustrated in Figures 4 to 7. Secured to the fascia plate 802 is printed circuit board 809 upon which are mounted the components listed in Table 2 below. The connections between

the components are shown in more detail in Figure 10 and the wiring diagram for the circuit is shown in Figure 11. The components of the circuit have been numbered differently in Figure 10 and Table 2 below provides a correlation between the two. TABLE 2

The starter control module shown in Figures 4 to 8, and the interface unit shown in Figures 9 to 11 correspond to the starter control module 5 and the interface module 12 respectively shown in Figure 1. As indicated above interface module 12 has connected thereto another starter control module and another electric motor starter unit. The two motor starter units can, for example be connected to a pair of air- conditioning fans (or other power consuming devices) operating in tandem. In use, each fan can be controlled individually by means of the "off" and "hand"(on) settings on the control knob/switch 410/411. However, if the control knob is switched to "automatic", then control of the functioning of the motor starter is effected by means of a control signal received from the interface module 12.

As can be seen from Figure 8, control knob C on the fascia 802 of the interface module has three settings, namely the "No. 1", "No. 2" and "BMS" settings. Manual control of the two starter control modules can be effected using the "No. 1" and "No. 2 " switch positions whilst the operation of the control modules and their associated motor starter units and fans can be brought under the control of an external control means such as a building management system or energy management system by switching the knob C to the "BMS" position. Thus the operation of the two fans (or other power consuming devices) associated with the motor starters can be alternated, either manually or automatically, for example to

prevent overheating. The control system is designed such that if a fault signal is received indicating a fault with either the No. 1 or the No. 2 power consuming devices (e.g. fans), the non-functioning device is de-energised and the other device is energised. This happens in either the manual or automatic mode: thus if No. 1 is manually selected and a fault signal is received, the interface module automatically switches to No. 2 and vice versa.

In addition to providing control for each of its associated starter control modules by either manual means or remote means such as a building or energy management system, the interface module can be set up to provide any required system buffer such as a time delay between de-energisation of one of its associated starter control modules and energisation of the other.

The circuits described above and illustrated in the drawings are of course merely exemplary and it will readily be appreciated that numerous alterations and modifications could be made in order to change the function of each modular unit in a desire manner. All such modifications and alterations are intended to be embraced by this application.

The advantage of the modular system of the present invention is that it avoids the need to design the circuitry for a given control system from scratch. Instead, standard control elements can be introduced by use of an appropriate control module of a preset standard form, unusual or new

functions being catered for by means of a configurable or variable unit. Thus, rather than a control cabinet containing a mass of wires, thereby leading to the potential for wires being connected up wrongly, adjacent modular control units are linked by a single multicore signal cable and standard multicore cable plugs and sockets.