The present invention relates to a system for linking and coordinated operation of electronically controlled motors, said system being of the kind set forth in the preamble of claim 1.

Especially in connection with pumps and ventilators, there is a need for such linking and coordinated operation of the electronically controlled drive motors, with the aim to achieve an output characteristic having a wide operating range for the whole system, particularly in connection with a great variation in the desired output.

Such systems are known, in which the control-related interlinking of the motors takes place via a central control panel, the latter being a separate unit in relation to the individual electronically controlled motors and providing the coordination of the individual electronic control arrangements necessary to achieve the desired characteristic for the output provided by the motors. Such a system requires a control connection from the central control panel to each and every electronically controlled motor. The control connections are usually provided by means of wiring connections, leading to a great amount of work with installing these wiring connections, a risk of noise being radiated-in via the wiring connections, and galvanic connection between the individual control arrangements and the control panel.

DE-4128390-C1 discloses such a system comprising a separate central control panel, a number of motor controllers with associated frequency converters, and a common sensor for detecting the desired output, wherein the central control panel appoints one of the motor controllers to be a pilot controller controlling based on the sensor signal and the other motor controllers being bypassed and the associated frequency converters being controlled from the central control panel by af frequency setting signal. The redundancy, which by the present invention is achieved by any of the involved motor controllers being appointable to govern the superior control of the system, cannot be achieved by this system.

EP-0 735 273-A1 (filed before but published after the priority date of the present application) discloses a double-pump provided with a superior controller formed as a separate unit which is able to independently set the speed of the two motors in the double-pump. Furthermore the possibility of connecting the superior controller to control further single- or double-pumps is mentioned. However the present invention is not concerned with double-pumps.

In addition to this it is known for controlling single individual motors to use a microprocessor circuit to provide a control aimed at achieving the desired characteristic for the output provided by the motor, the microprocessor circuit being connected to a motor-control electronic circuit for controlling the motor and providing the measurement data necessary for the control, as well as with a memory circuit for containing a program and data for the operation of the microprocessor circuit. The reading-in of the program in the memory circuit can possibly be carried out via a keyboard and display connected by a plug-and-socket connection.

It is on the basis of this known technology the intention with the invention to provide a system that in a simple manner interconnects a number of electronically controlled motors to provide a desired characteristic for the output provided jointly by the motors.

This is achieved by means of the measures set forth in the characterizing clause of claim 1. Via the communication interface, the microprocessors in the motor control arrangements can transmit data for controlling the remaining motors involved, so that the total output provided conrresponds to the desired characteristic for this output.

With the measures set forth in claim 2 it is achieved that one of the motor control arrangements is appointed to be responsible for the superior governing of the motor control arrangements involved.

By constructing the interface as a fibre-optical interface as set forth in claim 3, a galvanic separation between the individual motor control arrangements is achieved, with consequent advantageous noise immunity for the data transmission between the control arrangements.

As set forth in claim 4, the fibre-optical interface can be used in connection with a central control panel provided with a corresponding fibre-optical interface, so that this system as well achieves the advantages described above. In this system, the central control panel functions as the superior or commanding control arrangement.

By constructing this fibre-optical interface as a fibre-optical transmitter and a fibre-optical receiver in each of the motor control arrangements, interconnected in a fibre-optical ring system, it is achieved that the motor control arrangement emitting data can verify the correct reception of these data, identical data being received in return on the fibre-optical receiver.

In addition to this, the fibre-optical ring connection between the individual motor control arrangements provides an advantage with regard to installation, as the fibre-optical ring connection can be installed in a simple manner, the optical fibre being cut to suitable lengths and connected to the transmitter output terminal on one motor control arrangement and the receiver input terminal on the next motor control arrangement in the row.

Preferred areas of application are set forth in claims 6 to 8, these being motor control arrangements in connection with the transportation of fluids, particularly liquid in a liquid-circulation system or air in a ventilation system, in which the motors are preferably electric motors as indicated in claims 9 to 10, especially asynchronous motors, and in which the motor control electronics preferably comprises a frequency converter as indicated in claim 11.

The invention will be explained in more detail below with the aid of a non-limiting example and referring to the drawing, in which

• Figure 1 shows a block diagram of a motor control arrangement according to one embodiment of the invention, and
• Figure 2 shows the control-wise interconnection of a number of motor control arrangements via a fibre-optical ring system.

The embodiment of the motor-control arrangement according to the invention shown in Figure 1 comprises a motor-electronics unit 1 for controlling the motor 2 and providing measurement data for use in controlling the motor, a microprocessor circuit 3 to govern the control of the motor via the motor-electronics 1, the microprocessor circuit 3 basing its governing of the control on said measurement data. To enable the microprocessor circuit 3 to govern the control process, the motor control unit comprises a memory circuit 4, e.g. in the form of RAM, ROM, E-PROM, E²-PROM etc. for containing programs and data. A keyboard 5 and a display 6 for use when programming the desired control procedure can be connected to the microprocessor circuit 3, e.g. with a plug-and-socket connection. With a suitable programming of the operation of the microprocessor circuit 3, the motor control unit shown will be capable of controlling the motor to provide a desired characteristic curve for the output provided by the motor, e.g. a characteristic curve for pressure as a function of flow in connection with a pump or a blower.

In order to make it possible for the motor control arrangement shown in Figure 1 to be linked control-wise to further motor control arrangements of a similar kind, the microprocessor circuit 3 shown is connected to a fibre-optical transmitter 7 and a fibre-optical receiver 8. The motor control arrangement can communicate data and control signals via this fibre-optical interface to other similar motor control arrangements, e.g. by interconnecting a number of motor control arrangement in a ring system as shown in Figure 2.

In the system shown in Figure 2, e.g. the motor control unit 1 has been designated to be the superior or commanding motor control unit. Via the fibre-optical transmitter and a optical fibre, the latter is connected to the fibre-optical receiver 8 on a motor control unit II and so forth, the last motor control unit IV in the row having its fibre-optical transmitter 7 connected via an optical fibre to the fibre-optical receiver 8 on the motor control unit I.

The commanding control unit I can communicate with the remaining control units via the optical fibres in the ring connection linking the transmitter and receiver components 7 og 8, respectively, of the individual control units. Thus, data being emitted from one control unit will be transmitted around the ring with the individual control units as link module, and when the sender identifies its transmission on the incoming fibre channel, it can be verified that data has been received and processed without error in all control units involved. Each of the control units is identified, e.g. by means of an address code, so that the individual control units may be controlled separately.

The above-mentioned measurement data provided by the motor-electronics unit may e.g. comprise the current drawn by an asynchronous motor, the frequency provided by a frequency converter possibly being present, the voltage applied to the electric motor etc., these measurement data merely having to be sufficient for the microprocessor circuit 3 to be capable on the basis of these measurement data of governing the control of the motor 2 via the motor-electronics unit 1 in such a manner, that the desired characteristic curve for the output provided by the motors is achieved.

Even though the above motors are described as having substantially the same function, e.g. pump motors or blower motors respectively, it is conceivable that certain of the motors have special functions, such as damper motors for motor-driven dampers in ventilating plants for providing opening and closing functions in connection with starting and stopping of ventilators, or valve motors for motor-operated valves in liquid-circulating plants, respectively, for providing opening and closing functions in connection with starting and stopping of pumps. Other corresponding functions are conceivable in connection with other areas of application.