System and method for detection of rotational direction

Abstract

A system (2) for detecting the rotational direction (β) of an electric mo- tor (8) is disclosed. The system (2) comprises: - a detection unit (24) configured to detect signals (x(t)) in a first dimension along a first axis (X) and signals (y(t)) in a second dimension along a second axis (Y) extending perpendicular to the first axis (X), wherein sad signals (x(t), y(t)) are generated by the motor (8), wherein said signals (x(t), y(t)) are indicative of the rotational direction (β) of the motor (8). The system (2) is configured to process the signals (x(t), y(t)) and hereby generate a complex vector defined as: (1) x(t) + j∙y(t). The system (2) is configured to: - carry out a Fourier transformation of the complex vector x(t) + j∙y(t) and hereby split the signals (x(t), y(t)) into a forward part and a backward part and - on the basis of the forward part and the backward part decide if: a) the rotation direction is clockwise, b) the rotation direction is counterclockwise or c) there is no rotation.

Description

[0001] System and Method for Detection of Rotational Direction

[0002] Field of invention

[0003] The present invention relates to a system for detecting the rotational direction of an electric motor. The present invention also relates to a method for detecting the rotational direction of an electric motor.

[0004] Prior art

[0005] Many rotational machines such as pumps has one way of rotor rotation direction, in which the machine has the highest capacity. A motor may operate in the wrong direction, without any operation- or service personnel is aware of this. The most typical reason for this is, that the 3- phase electric motor has two of its supply leads reversed. The machine may operate well, but it does not work optimally. Every time the motor has been removed for service and re-installed, there is a risk for making the electrical wiring wrong. Their re-installation rules may tell them, that the motor must be electrical installed and checked on the field place, but without being installed on the machine, to minimize the risk of wrong wiring - but it still may go wrong.

[0006] EP363738B1 discloses a device that comprises a holder that keeps a Hall sensor in a position, in which a magnetic field can be detected. The Hall sensor is connected to an evaluation circuit on a printed circuit board through electrical contacts that are passed through the holder. However, the holder is complicated, expensive to produce and is not suitable for being used as a clamp-on solution that can be mounted on the outside of a motor and can be retrofitted.

[0007] JPH 0221266 A discloses a system for detecting the rotational direction of an electric motor. The system discloses a sensor arranged as opposed to the outer circumference of a field magnet of a motor with a polarity P. There is a leakage of a magnetic flux varying cyclically from the motor corresponding to the number P of poles and converted with the sensor into a voltage output corresponding to a rate of change. The voltage output is converted with an A / D convertor section at each fine sampling time to be stored into a memory and a microprocessor judges a spectrum by a fast Fourier transform processing of the data. It would, however, be desirable to have an alternative way to verify if the rotation direction is clockwise, counterclockwise or if there is no rotation.

[0008] A complex number is an element of a number system that extends the real numbers with a specific element denoted i og j, called the imaginary unit and satisfying the equation:

[0009] (1) J2= -l-

[0010] A complex vector Z can be expressed as Z = a+ b - j, where a and b are real numbers, a is the real part of the complex vector and b is the imaginary part b of the complex vector. The real portion a extends along the real axis X, while the imaginary part b of the complex vector extends along the imaginary axis Y as shown in the Cartesian coordinate system shown below.

[0011] Thus, there is a need for a method and a system which reduces or even eliminates the above mentioned disadvantages of the prior art. It is an object of the invention to provide a system for detecting the rotational direction of an electric motor, which system is simple and easy to use. It is an object of the invention to provide a method for detecting the rotational direction of an electric motor, which method is simple and easy to use.

[0012] Summary of the invention

[0013] The object of the present invention can be achieved by a system as defined in claim 1 and by a method as defined in claim 12. Preferred embodiments are defined in the dependent subclaims, explained in the following description and illustrated in the accompanying drawings.

[0014] The system according to the invention is a system for detecting the rotational direction of an electric motor, wherein the system comprises:

[0015] - a detection unit configured to detect signals x(t) in a first dimension along a first axis and signals y(t) in a second dimension along a second axis extending perpendicular to the first axis, wherein sad signals x(t), y(t) are generated by the motor, wherein said signals x(t), y(t) are indicative of the rotational direction of the motor, wherein the system is configured to process the signals x(t), y(t) and hereby generate a complex vector defined as:

[0016] (1) x(t) + j-y(t), wherein the system is configured to:

[0017] - carry out a Fourier transformation of the complex vector x(t) + j y(t) and hereby split the signals x(t), y(t) into a forward part and a backward part and

[0018] - on the basis of the forward part and the backward part decide if: a) the rotation direction is clockwise, b) the rotation direction is counterclockwise or c) there is no rotation.

[0019] Hereby, it is possible to reduce or even eliminate the above mentioned disadvantages of the prior art. It is possible to provide a system that is simple and easy to use. Moreover, the system may apply a clamp-on type detection unit. Accordingly, the measurements are non-invasive and requires no access to the interior of the motor hosing.

[0020] The complex vector x(t) + j-y(t) is defined in a Cartesian coordinate system having an X axis representing the real part, a Y axis representing the imaginary part and a Z axis extending along the longitudinal axis of the shaft of the motor.

[0021] The detection unit configured to detect signals x(t) in a first dimension along a first axis and signals y(t) in a second dimension along a second axis extending perpendicular to the first axis, wherein sad signals x(t), y(t) are generated by the motor, wherein said signals x(t), y(t) are indicative of the rotational direction of the motor.

[0022] In an embodiment, the detection unit comprises one or more coils arranged to generate current through induction when the magnetic field generated by the motor creates a varying magnetic flux through a region of space enclosed the one or more coils. Accordingly, the one or more coils will generate current due to the varying magnetic field caused by the motor.

[0023] In an embodiment, the detection unit comprises two or more coils, wherein the coils have different orientation relative to each other. In an embodiment, the coils extend perpendicular to each other.

[0024] In an embodiment, one of the coils is arranged in such a manner that when the detection is mounted, the coil extends a long a plane spanned by the longitudinal axis of the motor and an imaginary axis Y, wherein the imaginary axis Y extends perpendicular to the longitudinal axis of the motor.

[0025] In an embodiment, one of the coils is arranged in such a manner that when the detection is mounted, the coil extends a long a plane spanned by the longitudinal axis of the motor and a real axis X, wherein the real axis X extends perpendicular to the longitudinal axis of the motor and to the imaginary axis Y.

[0026] In an embodiment, the detection unit comprises at least one Hall effect sensor arranged to detect the magnetic field generated by the motor creates a varying magnetic flux.

[0027] The system is configured to process the signals x(t), y(t).

[0028] In an embodiment, the detection unit comprises a processing unit arranged and configured to process the signals x(t), y(t) and hereby generate a complex vector x(t) + j-y(t).

[0029] In an embodiment, the detection unit is a hand-held device.

[0030] In an embodiment, the detection unit comprises fixing structures for fixing the detection unit to a motor or a structure attached to a motor.

[0031] In an embodiment, the detection unit comprises a communication module arranged and configured to transmit data to an external receiver. In an embodiment, the communication module arranged and configured to wirelessly transmit data to an external receiver. In an embodiment, the external receiver is a processing unit. In an embodiment, the external receiver is a processing unit of a server accessible via a WEB-based service. In this embodiment, the detection device does not need to process the detected data because the data is sent to an external processing unit to be processed.

[0032] The system is configured to:

[0033] - carry out a Fourier transformation of the complex vector x(t) + j y(t) and hereby split the signals x(t), y(t) into a forward part and a backward part.

[0034] This can be done by using the equation (2):

[0035] In an embodiment, the detection unit is arranged in such a manner that the Z axis extends along the longitudinal axis of the motor.

[0036] In an embodiment, the detection unit is arranged in such a manner that the Z axis extends along the longitudinal axis of the shaft of the motor.

[0037] The system is configured to:

[0038] - on the basis of the forward part and the backward part decide if: a) the rotation direction is clockwise, b) the rotation direction is counterclockwise or c) there is no rotation.

[0039] In an embodiment, the system is configured to carry out a Fourier transformation and hereby determining the rotational speed (RPM) of the motor. Hereby, the rotational speed can be detected in an easy manner.

[0040] In an embodiment, the detection unit is carrying out measurements on a continuous basis. Hereby, it is possible to provide measurements on a continuous basis. In an embodiment, the system is configured to for the rotational speed (RPM) of the motor determining and comparing the length of the forward part and the length of the backward part (see equation (2) for n = RPM) and

[0041] - conclude that the rotational direction is clockwise if the length of the forward part (see equation (2)) is longer than the length of the backward part (see equation (2)) and

[0042] - conclude that the rotational direction is counterclockwise if the length of the backward part (see equation (2)) is longer than the length of the forward part (see equation (2)).

[0043] In an embodiment, the system is configured to for the rotational speed (RPM) of the motor determining and comparing the length of the forward part (see equation (2)) and the length of the backward part (see equation (2)) and conclude that the motor is not running if the length of the backward part (see equation (2)) corresponds to the length of the forward part (see equation (2)).

[0044] In an embodiment, the signals are vibration signals. The signals are processed in the same manner as the magnetic field signals.

[0045] In an embodiment, the signals are magnetic field signals from the rotating magnetic field of the motor.

[0046] In an embodiment, the system is configured to carry out a peak search and hereby identifying the rotational speed (RPM) of the motor.

[0047] In an embodiment, the detection unit comprises a communication module configured to transmit detected data to an external receiver.

[0048] In an embodiment, the detection unit comprises a communication module configured to wirelessly transmit detected data. In an embodiment, the detection unit comprises a coil assembly. Hereby, the detection is capable of measuring a magnetic field. In an embodiment, the coil assembly comprises two coils that are orientated differently relative to each other. Hereby, it is possible to use the coil assembly to detect magnetic field signals x(t) in a first dimension along a first axis and magnetic field signals y(t) in a second dimension along a second axis extending perpendicular to the first axis.

[0049] In an embodiment, the detection unit comprises a housing. The housing may comprise one or more mounting structures configured to attach the detection unit to the housing of the motor.

[0050] In an embodiment, the detection unit comprises an accelerometer. The accelerometer is arranged and configured to detect vibrations of the detection unit. Accordingly, when the detection unit is attached to the housing of the motor, the detection unit is capable of detecting vibration of the motor.

[0051] In an embodiment, the accelerometer is a multi-axis accelerometer configured to detect both the magnitude and the direction of the proper acceleration, as a vector quantity.

[0052] In an embodiment, the accelerometer is a two-axis accelerometer.

[0053] In an embodiment, the accelerometer is a three-axis accelerometer.

[0054] In an embodiment, the accelerometer is a micromachined microelectromechanical system (MEMS).

[0055] In an embodiment, the detection unit is configured to provide real time measurements of the signals x(t), y(t).

[0056] In an embodiment, the detection unit is attached to the motor or to a structure attached to the motor. Hereby, it is possible to maintain the detection unit vibrationally connected to the motor. Therefore, the detection unit will be maintained in a position, in which the detection unit can provide reliable vibration measurements indicative of the rotational direction of the motor.

[0057] In an embodiment, the detection unit is integrated in the motor.

[0058] In an embodiment, coil assembly is configured to determine the amplitude of the magnetic field of the motor.

[0059] In an embodiment, coil assembly is configured to determine the direction of the magnetic field of the motor.

[0060] In an embodiment, coil assembly is configured to determine the direction and magnitude of the magnetic field in two dimensions.

[0061] In an embodiment, coil assembly is configured to determine the direction and magnitude of the magnetic field in three dimensions.

[0062] In an embodiment, a communication module is provided in the housing.

[0063] The method according to the invention is a method for detecting the rotational direction of an electric motor, wherein the method comprises the step of detecting signals x(t) in a first dimension along a first axis and signals y(t) in a second dimension along a second axis extending perpendicular to the first axis, wherein said signals x(t), y(t) are generated by the motor, wherein said signals x(t), y(t) are indicative of the rotational direction of the motor, wherein the method comprises the following steps:

[0064] - processing the signals x(t), y(t) and hereby generating a complex vector defined as: x(t) + j-y(t), - carrying out a Fourier transformation of the complex vector x(t) + j y(t) and hereby splitting the signals (x(t), y(t)) into a forward part and a backward part and

[0065] - on the basis of the forward part and the backward part deciding if: a) the rotation direction is clockwise, b) the rotation direction is counterclockwise or c) there is no rotation.

[0066] Hereby, it is possible to reduce or even eliminate the above mentioned disadvantages of the prior art. It is possible to provide a method that is simple and easy to use. Moreover, the method may apply a clamp-on type detection unit. Accordingly, the measurements are non-invasive and requires no access to the interior of the motor hosing.

[0067] The method according to the invention is a method for detecting the rotational direction of an electric motor. The motor may be an electric motor of various devices. In an embodiment, the motor is an electric motor of a pump. In an embodiment, the motor is an electric motor of a conveyor belt. In an embodiment, the motor is an electric motor of a fan. In an embodiment, the motor is an electric motor of a gear.

[0068] The method comprises the step of detecting signals x(t) in a first dimension along a first axis and signals y(t) in a second dimension along a second axis extending perpendicular to the first axis. Hereby it is possible to provide sufficient information to determine the rotation direction of the motor.

[0069] The signals x(t), y(t) are generated by the motor and indicative of the rotational direction of the motor.

[0070] The method comprises the following step: processing the signals x(t), y(t) and hereby generating a complex vector defined as: x(t) + j -y(t)

[0071] The method comprises the following step:

[0072] - carrying out a Fourier transformation of the complex vector x(t) + j y(t) and hereby splitting the signals (x(t), y(t)) into a forward part and a backward part and.

[0073] The method comprises the following step:

[0074] - on the basis of the forward part and the backward part deciding if: a) the rotation direction is clockwise, b) the rotation direction is counterclockwise or c) there is no rotation.

[0075] In an embodiment, the method comprises the following step:

[0076] - carrying out a Fourier transformation and hereby determining the rotational speed (RPM) of the motor.

[0077] Hereby, the method is capable of monitoring the rotational speed of the motor.

[0078] In an embodiment, the method comprises the following step:

[0079] - for the rotational speed (RPM) of the motor determining and comparing the length of the forward part and the length of the backward part.

[0080] In an embodiment, the method comprises the following step:

[0081] - concluding that the rotational direction is clockwise if the length of the forward part is longer than the length of the backward part (for n = RPM) and

[0082] - concluding that the rotational direction is counterclockwise if the length of the backward part is longer than the length of the for- ward part (for n = RPM).

[0083] It should be noted that the length of the forward part and the length of the backward part (for n = RPM) may be very small.

[0084] In an embodiment, the method comprises the step of concluding that the motor is not running if the length of the forward part corresponds to the length of the backward part (for n = RPM).

[0085] In an embodiment, the method comprises the step of detecting signals that are vibration signals.

[0086] In an embodiment, the method comprises the step of detecting signals that are magnetic field signals from the rotating magnetic field of the motor.

[0087] In an embodiment, the method comprises the step of carrying out a peak search and hereby identifying the rotational speed (RPM) of the motor.

[0088] In an embodiment, the method comprises the step of transmitting detected data to an external receiver.

[0089] In an embodiment, the method comprises the step of wirelessly transmitting detected data.

[0090] In an embodiment, the magnetic field signals are detected by a detection unit comprising a coil assembly.

[0091] In an embodiment, the detection unit comprises a housing.

[0092] In an embodiment, the method comprises the step of applying an ac- celerometer to provide the vibration signals.

[0093] In an embodiment, the method provides real time measurements of the signals x(t), y(t).

[0094] In an embodiment, the signals x(t), y(t) are detected by a detection unit that is attached to the motor or to a structure attached to the motor.

[0095] In an embodiment, the signals x(t), y(t) are detected by a detection unit that is integrated in the motor.

[0096] Description of the Drawings

[0097] The invention will become more fully understood from the detailed description given herein below. The accompanying drawings are given by way of illustration only, and thus, they are not limitative of the present invention. In the accompanying drawings:

[0098] Fig. 1A shows a system according to the invention comprising a pump;

[0099] Fig. IB shows a top view of the system shown in Fig. 1A;

[0100] Fig. 1C shows a perspective front view of an electric motor of a system according to the invention;

[0101] Fig. ID shows a perspective rear view of the electric motor shown in Fig. 1C;

[0102] Fig. 2 shows a schematic view of a method according to the invention;

[0103] Fig. 3 shows a system according to the invention;

[0104] Fig. 4 shows a flowchart illustrating a method according to the invention and

[0105] Fig. 5A shows a detection unit according to the invention and

[0106] Fig. 5B shows another detection unit according to the invention. Detailed description of the invention

[0107] Referring now in detail to the drawings for the purpose of illustrating preferred embodiments of the present invention, a system 2 of the present invention is illustrated in Fig. 1A.

[0108] Fig. 1A is a side view of a system 2 according to the invention. Fig. IB illustrates a top view of the system 2 shown in Fig. 1A. The system 2 is designed for detecting the rotational direction of an electric motor 8. The system 2 comprises a detection unit 24 configured to detect magnetic or vibration signals in a first dimension along a first axis X and magnetic or vibration signals in a second dimension along a second axis Y extending perpendicular to the first axis X. A Cartesian coordinate system having three axis X, Y, Z is shown in Fig. 1A.

[0109] The magnetic or vibration signals are generated by the motor 8 and the signals are indicative of the rotational direction of the motor 8.

[0110] The motor 8 is part of a pump 4 comprising a pump housing 17. The pump housing 17 has an inlet connected to an inlet pipe 12'. The pump housing 17 has an outlet connected to an outlet pipe 12. The inlet pipe 12' is provided with a flange that is attached to a corresponding flange of the inlet by means of bolts 3 and nuts 7. Likewise, the outlet pipe 12 is provided with a flange that is attached to a corresponding flange of the outlet by means of bolts 3 and nuts 7.

[0111] The motor 8 is connected to an impeller (not shown) rotatably mounted in the pump housing 17 via a coupling 9. The pump 4 rests on and is fixed to a base member 21.

[0112] The detection unit 24 is attached to the outside of the motor 8. The detection unit 24 is attached to a fixation structure 11 that is fixed to the motor 8 by means of bolts 5 that are screwed into threaded bores provided in the housing of the motor 8. Other mechanical structures may be used to attach the detection unit 24 to the outside of the motor 8. In an embodiment, the detection unit 24 is placed centrally at the top portion of the housing of the motor 8. In an embodiment, the detection unit 24 is placed centrally at a side portion of the housing of the motor 8.

[0113] In an embodiment, the detection unit 24 is detachably attached to the outside of the motor 8. In an embodiment, the detection unit 24 is arranged inside the motor 8.

[0114] The system 2 is configured to process the signals detected by the detection unit 24. In an embodiment, the detection unit 24 is configured to transmit data to an external receive, wherein the external receiver is configured to process the signals like illustrated in and explained with reference to Fig. 4.

[0115] Fig. 1C illustrates a perspective front view of an electric motor 8 of a system according to the invention. Fig. ID illustrates a perspective rear view of the electric motor 8 shown in Fig. 1C.

[0116] A detection device 24 is attached to the housing of the motor 8. The detection device 24 is arranged and configured to detect the rotational direction p of the electric motor 8. The detection unit 24 is configured to detect a magnetic field B(t) as function of time t. It can be seen that the detection unit 24 is configured to measure a first magnetic component x(t) (of the magnetic field B(t)) in a first dimension along a first axis X and a second magnetic component y(t) (of the magnetic field B(t)) in a second dimension along a second axis Y extending perpendicular to the first axis X. A Cartesian coordinate system having three axis X, Y, Z is indicated. In Fig. 1C and Fig. ID the rotational direction p of the electric motor 8 is clockwise as the rotational direction is defined as seen from the rear end of the motor 8 as illustrated in Fig. ID.

[0117] Fig. 2 illustrates a schematic view of the steps of a method according to the invention. A detection unit 24 is attached to an electric motor 8. The detection unit 24 is arranged and configured in a first step I to measure a first magnetic component x(t) of the magnetic field of the motor 8 in a first dimension along a first axis X and a second magnetic component y(t) of the magnetic field of the motor 8 in a second dimension along a second axis Y extending perpendicular to the first axis X.

[0118] In a second step II a complex vector p(t) is generated from the first magnetic component x(t) and the second magnetic component y(t). The complex vector p(t) is defined in the following equation (1):

[0119] (1) p(t) = x(t) + j-y(t), where j is the imaginary unit satisfying the equation : j2= -1.

[0120] In a third step III a Fourier transformation of the complex vector x(t) + j y(t) is carried out to split the signal x(t), j y(t) into a forward part rn(RPM)fand a backward rn(RPM)bpart as defined in the following equation (2) :

[0121] Here Xn* is the conjugate of the complex number Xn, onis the frequency step by which the signal is constructed and Xnis the Fourier series coefficient from the Fourier transformation.

[0122] In another step IV a Fast Fourier Transformation (FFT) is carried out on the first magnetic component x(t) and / or the second magnetic component y(t) to find the dominant frequency. The dominant frequency is defined as the rotational speed RPM of the motor 8.

[0123] When the rotational speed RPM of the motor 8 is determined, the peak lrbRpMl (backward part) and the peak Ir il (forward part) are identified (as shown in step V).

[0124] The detected frequency (rotational speed RPM) of the motor 8 is applied to carry out a search for the corresponding forward part rfRpMand a backward rRPMbpart for this frequency (rotational speed RPM).

[0125] In the last step VI a comparison of the forward part rfRPMand the backward rbRPMpart is carried out. Based on the comparison it is concluded that: a) the rotation direction is clockwise when rfRPM> rbRPM, b) the rotation direction is counterclockwise when rfRPM< rbRPMand c) there is no rotation when rfRPM= rbRPM.

[0126] The spectrum is defined by the following equation (3):

[0127] (3) (co

[0128] The power spectrum is defined by the following equation (4):

[0129] Where ro = Xo + J ■ Yo and co is the rotation frequency, f is the forward part and b is the backward part, 8 is the Dirac delta distribution and con is the frequency step in the Fourier transformation and n is an index number.

[0130] Fig. 3 illustrates a system 2 according to the invention. The system 2 comprises a rotatory machine 4 that is mechanically connected to a floor 34. The rotatory machine is a pump 4 comprises a motor 8 provided with a motor shaft 22. The motor 8 is arranged and configured to rotate a pump shaft 15 of the pump 4.

[0131] The pump shaft 15 is connected to the motor 8 via a coupling 9.

[0132] The system 2 comprises a detection unit 24 placed on the motor 8 of the first rotatory machine 4. The detection unit 24 is configured to be attached to and hereby detect data 28 of the rotatory machine 4. In an embodiment, the data 28 includes measurements of one or more magnetic fields. In an embodiment, the data 28 includes measurements of vibration of the motor 8.

[0133] In an embodiment, the detection unit 24 is configured to measure a first magnetic component of the magnetic field of the motor 8 in a first dimension along a first axis and a second magnetic component of the magnetic field of the motor 8 in a second dimension along a second axis extending perpendicular to the first axis.

[0134] The system 2 comprises a processing unit 32 configured to receive and process said data 28. The processing unit 32 may be contained in a web-based server accessible via the Internet 30. In an embodiment, the processing unit 32 is integrated in the detection unit 24. In an embodiment, the processing unit 32 is integrated in an external device (e.g. a laptop computer or a tablet that is communicatively connected to the detection unit 24).

[0135] The rotatory machine 4 is mechanically connected to a base member 21 that is placed on a floor 34.

[0136] The pump 4 comprises a housing 17 that is connected to and receives a media to be pumped via an inlet pipe 12'. The pump housing 17 is connected to and pumps the media out through an outlet pipe 12.

[0137] It is important to underline that the pump 4 may be different from the ones shown in Fig. 1. In an embodiment, the rotatory machine(s) are pumps, wherein the motor and the pump are joint (built together or integrated). In an embodiment, the rotatory machine(s) are pumps, wherein the motor of the pump is fixed the pump housing of the pump.

[0138] The detection unit 24 may be attached to any suitable structure of the motor 8. The attachment may be established by using any suitable mechanical fastening structures including bolts, a hose clamp, or a mounting bracket.

[0139] Fig. 4 illustrates a flowchart illustrating a method according to the invention. In a first step I of the method the magnetic field of the motor 8 is detected, wherein the magnetic field is detected as signals (x(t)) in a first dimension along a first axis (X) and signals (y(t)) in a second dimension along a second axis (Y) extending perpendicular to the first axis (X).

[0140] In a second step II of the method a complex vector is generated. The complex vector is defined as: x(t) + j-y(t).

[0141] In a third step III of the method a Fourier transformation of the complex vector x(t) + j-y(t) is carried out and hereby the signals (x(t), y(t)) are slit into a forward part and a backward part. Accordingly, a series of components of the forward part and a backward part (as shown in and explained with reference to Fig. 2) are determined. A Fast Fourier Transformation (FFT) is carried out on the first magnetic component x(t) and / or the second magnetic component y(t) to find the dominant frequency defining the rotational speed of the motor 8.

[0142] When the rotational speed of the motor 8 is determined, peaks for the forward part and a backward part are indexed.

[0143] The detected frequency (rotational speed) of the motor 8 is applied to carry out a search for the corresponding forward part rfRpMand a backward rbRPMpart for this frequency (rotational speed a). In the last step IV a comparison of the forward part rfRPMand the backward rbRPMpart is carried out. Based on the comparison it is concluded that: a) the rotation direction is clockwise (when rfRPM> rbRPM), b) the rotation direction is counterclockwise when (rfRPM< rbRPM) and c) there is no rotation when (rfRPM= rbRPM).

[0144] Fig. 5A illustrates a detection unit 24 according to the invention. The detection unit 24 comprises a housing 40 configured to be attached to a motor of a pump. The detection unit 24 comprises a battery 42 for providing electrical power to the detection unit 24. The detection unit 24 comprises a printed circuit board 44 provided with a communication module 36. The communication module 36 is configured to communicate wirelessly with an external device (e.g. via a local network). In an embodiment, the detection unit 24 comprises a modem configured for sending digital data wirelessly. In an embodiment, detection unit 24 comprises a Bluetooth radio module with built-in antenna.

[0145] The detection unit 24 comprises an accelerometer 38 arranged and configured to detect vibrations of the detection unit 24. Accordingly, when the detection unit 24 is attached to a motor, the accelerometer 38 is capable of detecting the vibrations of the motor. In an embodiment, the accelerometer 38 is a multi-axis accelerometer configured to detect both the magnitude and the direction of the proper acceleration, as a vector quantity. In an embodiment, the accelerometer 38 is a two-axis accelerometer. In an embodiment, the accelerometer 38 is a three-axis accelerometer. In an embodiment, the accelerometer 38 is a single-axis accelerometer 38.

[0146] In an embodiment, the accelerometer 38 is a micromachined microelectromechanical systems (MEMS).

[0147] In an embodiment, the detection unit 24 comprises a control unit. In an embodiment, the control unit comprises a processing unit.

[0148] The detection unit 24 comprises a coil assembly 60 arranged and configured to detect the magnetic field of a motor to which the detection device is attached. In an embodiment, the coil assembly 60 comprise one or more coils arranged and configured to detect the direction and magnitude of the magnetic field of the motor. In an embodiment, the coil assembly 60 comprise two coils arranged and configured to detect the direction and magnitude of the magnetic field of the motor. In an embodiment, the coil assembly 60 comprise three coils arranged and configured to detect the direction and magnitude of the magnetic field of the motor.

[0149] Fig. 5B illustrates another detection unit according to the invention. The detection unit 24 comprises a housing 40 configured to be attached to a rotatory machine such as a pump, a conveyor belt, a gear or another machine having an electric motor. The detection unit 24 comprises a power supply 46 connected to a power cable 48 protruding from the housing 40.

[0150] The detection unit 24 comprises a printed circuit board 44 provided with a communication module 36. The communication module 36 is connected to an external device by means of a data cable 52. The data cable 52 may be electronically connected to a control box of rotatory machine (e.g. a pump, a conveyor belt, a gear or another machine having an electric motor)). In an embodiment, the detection unit 24 comprises no communication module but is electrically connected to an external communication module (e.g. built into an external device such as a control box of a pump or a motor).

[0151] The detection unit 24 comprises an accelerometer 38 corresponding to the one shown and explained with reference to Fig. 5A. In an embodiment, the detection unit 24 comprises a control unit. In an embodiment, the control unit comprises a processing unit. The detection unit 24 comprises a coil assembly 60 arranged and configured to detect the magnetic field of a motor to which the detection device is attached. In an embodiment, the coil assembly 60 comprise one or more coils arranged and configured to detect the direction and magnitude of the magnetic field of the motor. In an embodiment, the coil assembly 60 comprise two coils arranged and configured to detect the direction and magnitude of the magnetic field of the motor. In an embodiment, the coil assembly 60 comprise three coils arranged and configured to detect the direction and magnitude of the magnetic field of the motor.

[0152] In an embodiment, the detection units 24 shown in Fig. 5A and in Fig. 5B, the accelerometer 38 is removed. In these embodiments, the coil assembly 60 is arranged and configured to detect the direction and magnitude of the magnetic field of the motor. List of reference numerals

[0153] 2 System

[0154] 3 Bolt

[0155] 4 Pump

[0156] Bolt

[0157] 7 Nut

[0158] 8 Motor

[0159] 9 Coupling

[0160] Fixation structure

[0161] 12 Outlet pipe

[0162] 12' Inlet pipe

[0163] 15 Pump shaft

[0164] 17 Pump housing

[0165] 21 Base member

[0166] 22 Motor shaft

[0167] 24 Detection unit

[0168] 28 Data

[0169] 30 Internet

[0170] 32 Processing unit

[0171] 34 Floor

[0172] 36 Communication module

[0173] 38 Accelerometer

[0174] 40 Housing

[0175] 42 Battery

[0176] 44 Printed circuit board

[0177] 46 Power supply

[0178] 48 Power cable

[0179] 52 Data cable

[0180] 60 Coil assembly

[0181] Rotational direction RPM Rotational speed

[0182] X, Y, Z Axis

[0183] I, II, III, IV Step

[0184] V, VI Step 5 The Dirac delta distribution

[0185] O n Frequency step in a Fourier transformation n Index number.

[0186] Xn The nthFourier series coefficient t Time v(t) Time dependent vector

Claims

Claims1. System (2) for detecting the rotational direction (p) of an electric motor (8), wherein the system (2) comprises:- a detection unit (24) configured to detect signals (x(t)) in a first dimension along a first axis (X) and signals (y(t)) in a second dimension along a second axis (Y) extending perpendicular to the first axis (X), wherein sad signals (x(t), y(t)) are generated by the motor (8), wherein said signals (x(t), y(t)) are indicative of the rotational direction (p) of the motor (8), characterised in that the system (2) is configured to process the signals (x(t), y(t)) and hereby generate a complex vector defined as: (1) x(t) + j-y(t), wherein the system (2) is configured to:- carry out a Fourier transformation of the complex vector x(t) + j y(t) and hereby split the signals (x(t), y(t)) into a forward part and a backward part and- on the basis of the forward part and the backward part decide if: a) the rotation direction is clockwise, b) the rotation direction is counterclockwise or c) there is no rotation.

2. System (2) according to claim 1, wherein the system (2) is configured to:- carry out a Fourier transformation and hereby determining the rotational speed (RPM) of the motor (8);- for the rotational speed (RPM) of the motor (8) determining and comparing the length of the forward part (T M) and the length of the backward part (rbRPM) and- conclude that the rotational direction is clockwise if the length of the forward part (rfRPM) is longer than the length of the backward part (rfRPM) and- conclude that the rotational direction is counterclockwise if thelength of the backward part (rbRPM) is longer than the length of the forward part (rfRPM) .

3. System (2) according to claim 1 or 2, wherein the signals (28) are vibration signals.

4. System (2) according to claim 1 or 3, wherein the signals (28) are magnetic field signals (28) from the rotating magnetic field of the motor (8).

5. System (2) according to one of the preceding claims 2-4, wherein the system (2) is configured to carry out a peak search and hereby identifying the rotational speed (R.PM) of the motor (8).

6. System (2) according to one of the preceding claims, wherein the detection unit (24) comprises a communication module (36) configured to wirelessly transmit detected data (28).

7. System (2) according to one of the preceding claims, wherein the detection unit (24) comprises a coil assembly (60).

8. System (2) according to one of the preceding claims, wherein the detection unit (24) comprises an accelerometer (38).

9. System (2) according to one of the preceding claims, wherein the detection unit (24) is configured to provide real time measurements of the signals (x(t), y(t)).

10. System (2) according to one of the preceding claims, wherein the detection unit (24) is attached to the motor (8) or to a structure attached to the motor (8).

11. System (2) according to one of the preceding claims, wherein the detection unit (24) is integrated in the motor (8).

12. A method for detecting the rotational direction (p) of an electric motor (8), wherein the method comprises the step of detecting signals (x(t)) in a first dimension along a first axis (X) and signals (y(t)) in a second dimension along a second axis (Y) extending perpendicular to the first axis (X), wherein said signals (x(t), y(t)) are generated by the motor (8), wherein said signals (x(t), y(t)) are indicative of the rotational direction (p) of the motor (8), characterised in that the method comprises the following steps:- processing the signals (x(t), y(t)) and hereby generating a complex vector defined as: (1) x(t) + j-y(t),- carrying out a Fourier transformation of the complex vector x(t) + j y(t) and hereby splitting the signals (x(t), y(t)) into a forward part and a backward part and- on the basis of the forward part and the backward part deciding if: a) the rotation direction is clockwise, b) the rotation direction is counterclockwise or c) there is no rotation.

13. Method according to claim 12, wherein the method comprises the following steps:- carrying out a Fourier transformation and hereby determining the rotational speed (RPM) of the motor (8);- for the rotational speed (RPM) of the motor (8) determining and comparing the length of the forward part (rfRpM) and the length of the backward part (rbRPM) and- concluding that the rotational direction is clockwise if the length of the forward part (rfRPM) is longer than the length of the backward part (rbRPM) andconcluding that the rotational direction is counterclockwise if the length of the backward part (rbRPM) is longer than the length of the forward part (rfRPM) .

14. Method according to one of the preceding claims 12-13, wherein the signals (28) are vibration signals.

15. Method according one of the claims 12-14, wherein the signals (28) are magnetic field signals (28) from the rotating magnetic field of the motor (8).

16. Method according to one of the preceding claims 12-15, wherein the method comprises the step of carrying out a peak search and hereby identifying the rotational speed (R.PM) of the motor (8).

17. Method (2) according to one of the preceding claims 12-16, wherein the method comprises the step of wirelessly transmitting detected data (28).

18. Method according to one of the preceding claims 15-17, wherein the magnetic field signals (28) are detected by a detection unit (24) comprising a coil assembly (60).

19. Method according to one of the preceding claims 14-18, wherein the method comprises the step of applying an accelerometer (38) to provide the vibration signals.

20. Method according to one of the preceding claims, wherein the method provides real time measurements of the signals (x(t), y(t)).

21. Method according to one of the preceding claims, wherein the signals (x(t), y(t)) are detected by a detection unit (24) that is attached tothe motor (8) or to a structure attached to the motor (8).

22. Method according to one of the preceding claims 12-21, wherein the signals (x(t), y(t)) are detected by a detection unit (24) that is inte- grated in the motor (8).

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