METHOD FOR INDICATING A NEED FOR MAINTENANCE OF AN ELECTRIC DRIVE APPARATUS, AND AN ELECTRIC DRIVE APPARATUS

Abstract

The present invention relates to the field of testing and maintenance of electric automation devices, such as testing and maintenance of electric drive apparatuses and to the field of electric drives used for industrial applications, and more particularly to a method for indicating a need for maintenance of an electric drive apparatus and to an electric drive apparatus. An electric drive apparatus of an installation consisting of two or more electric drive apparatuses according to the present invention has a calculation unit for collecting maintenance data relevant to the maintenance of said electric drive apparatus, a maintenance need notification unit for determining a need for maintenance of said electric drive apparatus by analysing the collected maintenance data together with applicable values set for a maintenance scheme of said electric drive apparatus, a communication unit comprising a transmitter for sending information of the need for maintenance to other electric drive apparatuses of said installation, and a receiver for receiving information on the need for maintenance of said other electric drive apparatuses a maintenance alarm synchronization unit for generating a synchronized maintenance alarm of two or more electric drive apparatuses, and an alarm indication unit for indicating said synchronized maintenance alarm to the user.

Claims

1. A method for indicating a need for maintenance of an electric drive apparatus of an installation consisting of two or more electric drive apparatuses, the method comprising the steps of: collecting maintenance data relevant to the maintenance of said electric drive apparatus determining a need for maintenance of said electric drive apparatus by analysing the collected maintenance data together with applicable values set for a maintenance scheme of said electric drive apparatus sending information of the need for maintenance to other electric drive apparatuses of said installation, receiving information on the need for maintenance of said other electric drive apparatuses generating a synchronized maintenance alarm of two or more electric drive apparatuses, and indicating said synchronized maintenance alarm to the user.

2. A method according to claim 1, wherein after the step of generating a synchronized maintenance alarm, the information of the generated synchronized maintenance alarm is sent to other electric drive apparatuses of the installation.

3. A method according to claim 1, wherein said synchronized maintenance alarm comprises the information of the need of maintenance of only one electric drive apparatus of the one or more electric drive apparatuses in the installation.

4. A method according to claim 1, wherein in the step of indicating, said synchronized maintenance alarm is indicated to the user by showing said synchronized maintenance alarm on a display panel of at least one electric drive apparatus of said one or more electric drive apparatuses.

5. A method according to claim 1, wherein in the step of indicating, said synchronized maintenance alarm is indicated to the user with a light indication of a particular selected colour.

6. An electric drive apparatus of an installation consisting of two or more electric drive apparatuses said electric drive apparatus comprising: a calculation unit for collecting maintenance data relevant to the maintenance of said electric drive apparatus a maintenance need notification unit for determining a need for maintenance of said electric drive apparatus by analysing the collected maintenance data together with applicable values set for a maintenance scheme of said electric drive apparatus a communication unit comprising: a transmitter for sending information of the need for maintenance to other electric drive apparatuses of said installation, and a receiver for receiving information on the need for maintenance of said other electric drive apparatuses a maintenance alarm synchronization unit for generating a synchronized maintenance alarm of two or more electric drive apparatuses, and an alarm indication unit for indicating said synchronized maintenance alarm to the user.

7. An electric drive apparatus according to claim 6, wherein the maintenance alarm synchronization unit forwards the information of the generated synchronized maintenance alarm to the communication unit for communicating said generated synchronized maintenance alarm to other electric drive apparatuses of the installation.

8. An electric drive apparatus according to claim 6, wherein said synchronized maintenance alarm comprises the information of the need of maintenance of only one electric drive apparatus of the one or more electric drive apparatuses in the installation.

9. An electric drive apparatus according to claim 6, wherein said synchronized maintenance alarm is indicated to the user by showing said synchronized maintenance alarm on a display panel of at least one electric drive apparatus of said one or more electric drive apparatuses.

10. An electric drive apparatus according to claim 6, wherein said synchronized maintenance alarm is indicated to the user with a light indication of a particular selected colour.

11. An electric drive apparatus according to claim 6, wherein two or more or all of the units, i.e. data collection unit, a maintenance need notification unit, a communication unit, a maintenance alarm synchronization unit and an alarm indication unit, of the electric drive apparatus are combined as one unit.

12. An electric drive apparatus according to claim 6, wherein said transmitter and said receiver utilise a wireless communication protocol.

13. An electric drive apparatus according to claim 6, which further includes a synchronization algorithm utilized in said maintenance alarm synchronization unit.

14. An electric drive apparatus according to claim 6 wherein said electric drive apparatus is a frequency converter.

15. A method according to claim 2, wherein in the step of indicating, said synchronized maintenance alarm is indicated to the user by showing said synchronized maintenance alarm on a display panel of at least one electric drive apparatus of said one or more electric drive apparatuses.

16. A method according to claim 2, wherein in the step of indicating, said synchronized maintenance alarm is indicated to the user with a light indication of a particular selected colour.

17. An electric drive apparatus according to claim 7, wherein said synchronized maintenance alarm is indicated to the user by showing said synchronized maintenance alarm on a display panel of at least one electric drive apparatus of said one or more electric drive apparatuses.

18. An electric drive apparatus according to claim 8, wherein said synchronized maintenance alarm is indicated to the user by showing said synchronized maintenance alarm on a display panel of at least one electric drive apparatus of said one or more electric drive apparatuses.

19. An electric drive apparatus according to claim 7, wherein said synchronized maintenance alarm is indicated to the user with a light indication of a particular selected colour.

20. An electric drive apparatus according to claim 8, wherein said synchronized maintenance alarm is indicated to the user with a light indication of a particular selected colour.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0049] FIG. 1 shows a block diagram of an electric drive according to prior art;

[0050] FIG. 2 shows a block diagram of an arrangement for indicating a need for maintenance of an electric drive apparatus according to prior art;

[0051] FIG. 3 shows a flow diagram of a method for indicating a need for maintenance of an electric drive apparatus according to prior art;

[0052] FIG. 4 shows a time schedule diagram of an arrangement for indicating a need for maintenance of an electric drive apparatus in an installation consisting of one or more electric drive apparatuses according to prior art;

[0053] FIG. 5 shows a block diagram of an arrangement for indicating a need for maintenance of an electric drive apparatus according to the present invention;

[0054] FIG. 6 shows a flow diagram of a method for indicating a need for maintenance of an electric drive apparatus according to the present invention;

[0055] FIG. 7 shows a time schedule diagram of an arrangement for indicating a need for maintenance of an electric drive apparatus in an installation consisting of one or more electric drive apparatuses according to the present invention.

[0056] Prior art drawings of FIGS. 1 to 4 have been presented earlier. In the following, the invention will be described in greater detail by means of preferred embodiments with reference to the accompanying drawings of FIGS. 5 to 7.

DETAILED DESCRIPTION OF THE INVENTION

[0057] FIG. 5 shows a shows a block diagram of an arrangement for indicating a need for maintenance of an electric drive apparatus according to the present invention. The electric drive apparatus according to the present embodiment is one electric drive apparatus of an installation consisting of one or more electric drive apparatuses. In regard to the need for maintenance indication arrangement, the electric drive apparatus according to the present invention has a calculation unit 7, a maintenance need notification unit 27, a communication unit 28, a maintenance alarm synchronization unit 29 and an alarm indication unit 9. The installation according to the present invention may consist of two or more electric drive apparatuses.

[0058] First, the calculation unit 7 of the electric drive apparatus collects and receives maintenance data, i.e. data relevant to the maintenance of the electric drive apparatus. The maintenance data may be collected and received from the various subsystems in the electric drive apparatus and in the application setting, these including electric drive subsystems, the input power feed and the load. The calculation unit 7 of the electric drive apparatus according to the present invention may also be used for collecting and receiving data for other purposes than for collecting the maintenance data.

[0059] Thereafter, the calculation unit 7 of the electric drive apparatus calculates maintenance algorithms of the electric drive apparatus according to present invention. The maintenance algorithms inform users about incoming maintenance actions. The calculation unit 7 then forwards the maintenance calculation data to the maintenance need notification unit 27. Alternatively, the calculation unit 7 stores the maintenance data to memory storage from which the maintenance need notification unit 27 can access the maintenance data. The calculation unit 7 may edit or further process the collected maintenance data before forwarding the maintenance data to the maintenance need notification unit 27 or storing the maintenance data to the memory storage.

[0060] The maintenance need notification unit 27 of the electric drive apparatus analyses the collected and calculated maintenance data together with the applicable values set for maintenance scheme of the electric drive apparatus and determines a notification of a need for maintenance of the electric drive apparatus. Because the changes in the electric drive apparatus and in its subsystems as well as the changes in the application setting may substantially contribute to the need for maintenance of the electric drive application, all relevant collected maintenance data is considered in the determination process. The electric drive apparatus according to the present invention may be provided with a possibility to update the previously set applicable values for maintenance scheme of the electric drive apparatus. The maintenance need notification unit 27 then notifies of a need for maintenance of the electric drive apparatus and forwards this notification to the communication unit 28.

[0061] The communication unit 28 receives the notification of a need for maintenance from the maintenance need notification unit 27. The information of the need for maintenance may for example inform about a need to change a cooling fan of the electric drive apparatus. The communication unit 28 of the electric drive apparatus according to the present embodiment comprises a transmitter for sending information to and a receiver for receiving information from other electric drive apparatuses 30, 31 of the installation consisting of one or more electric drive apparatuses.

[0062] In the present embodiment the communication unit 28 of the electric drive apparatus then communicates with, i.e. sends information to and receives information from other electric drive apparatuses 30, 31 of the installation. The communication unit 28 of the electric drive apparatus sends information of the need for maintenance, e.g. said notification of a need for maintenance, of the present electric drive apparatus to said other electric drive apparatuses 30, 31. The communication unit 28 of the electric drive apparatus also receives information on the need for maintenance of said other electric drive apparatuses 30, 31 in the near future. In the present embodiment the near future may be defined as a following period of 18 months, a following period of 12 months, a following period of 6 months or a following period of 3 months. The communication unit 28 and the other electric drive apparatuses 30, 31 may utilise any kind of communication protocol in communication, including a wireless communication protocol. The communication unit 28 then forwards the information of the need for maintenance received from the maintenance need notification unit 27 and the information of the need for maintenance received from the other electric drive apparatuses 30, 31 of the installation to the maintenance alarm synchronization unit 29.

[0063] The maintenance alarm synchronization unit 29 receives the information of the need for maintenance from the communication unit 28, analyses the received information of the need for maintenance and generates a synchronized maintenance alarm. The maintenance alarm synchronization unit 29 may use an algorithm for synchronisation of the maintenance and for optimization of the maintenance time of the one or more electric drive apparatuses in the installation. The maintenance algorithms inform users about incoming maintenance actions. The synchronized maintenance alarm comprises the information of the need of maintenance of the one or more electric drive apparatuses in the installation according to the present embodiment. The synchronized maintenance alarm may also comprise the information of the need of maintenance of only one electric drive apparatus of the one or more electric drive apparatuses in the installation according to the present embodiment. The maintenance alarm synchronization unit 29 then forwards the information of the generated synchronized maintenance alarm to the alarm indication unit 9.

[0064] The maintenance alarm synchronization unit 29 may also forward the information of the generated synchronized maintenance alarm to the communication unit 28 for communicating said generated synchronized maintenance alarm to other electric drive apparatuses 30, 31 of the installation. The communication unit 28 may then receive and send the information of the generated synchronized maintenance alarm received from the maintenance alarm synchronization unit 29 to other electric drive apparatuses 30, 31 of the installation.

[0065] The alarm indication unit 9 receives the information of the generated synchronized maintenance alarm from the maintenance alarm synchronization unit 29. The alarm indication unit 9 then indicates the synchronized maintenance alarm of the one or more electric drive apparatuses to the user by for example showing said synchronized maintenance alarm on a display panel of at least one electric drive apparatus of said one or more electric drive apparatuses. The alarm indication unit 9 of the electric drive apparatus according to the present invention may also comprise a light arrangement for indicating the generated synchronized maintenance alarm of the one or more electric drive apparatuses in the installation according to the present embodiment to the user with a light indication of a particular selected colour, e.g. red light indication. The alarm indication unit 9 may further have other communicating means based on any known technology, e.g. via a communication network, for properly communicating and indicating the synchronized maintenance alarm of the one or more electric drive apparatuses to the user.

[0066] In regard to the need for maintenance indication arrangement, two or more or even all of the units of the electric drive apparatus according to the present invention, i.e. the calculation unit 7, the maintenance need notification unit 27, the communication unit 28, the maintenance alarm synchronization unit 29 and the alarm indication unit 9 may be combined as one unit.

[0067] FIG. 6 shows a flow diagram of a method for indicating a need for maintenance of an electric drive apparatus according to the present invention. The electric drive apparatus according to the present embodiment is one electric drive apparatus of an installation consisting of one or more electric drive apparatuses. The installation according to the present invention may consist of two or more electric drive apparatuses.

[0068] In the method for indicating a need for maintenance of an electric drive apparatus, e.g. a frequency converter, according to the present embodiment, a calculation unit 7 of the electric drive apparatus first collects and receives maintenance data, i.e. data relevant to the maintenance of the electric drive apparatus, and calculates 10 collected maintenance calculation data using maintenance algorithms of the electric drive apparatus according to the present invention. The maintenance algorithms inform users about incoming maintenance actions. The calculation unit 7 then forwards the calculated maintenance calculation data to a maintenance need notification unit 27. Alternatively, the calculation unit 7 may store the maintenance data to memory storage from which the maintenance need notification unit 27 can access the maintenance data. Furthermore, the collected maintenance data may be edited or further processed by the calculation unit 7 before forwarding the maintenance data to the maintenance need notification unit 27 or storing the maintenance data to the memory storage.

[0069] After the calculation 10 of the maintenance calculation data the collected and calculated maintenance data is analysed together with the applicable values set for maintenance scheme of the electric drive apparatus and a notification of a need for maintenance of the electric drive apparatus is determined 32 in the maintenance need notification unit 27 of the electric drive apparatus. As the changes in the electric drive apparatus and in its subsystems as well as the changes in the application setting may substantially contribute to the need for maintenance of the electric drive application, all relevant collected maintenance data is considered in the process of determination 32. In the method for indicating a need for maintenance of an electric drive apparatus according to the present invention the electric drive apparatus may be provided with a possibility to update the previously set applicable values for maintenance scheme of the electric drive apparatus. After the notification of a need for maintenance of the electric drive apparatus is determined 32 the maintenance need notification unit 27 then notifies of a need for maintenance of the electric drive apparatus and forwards this notification further to a communication unit 28 of the electric drive apparatus.

[0070] After the determination 32 of the notification of a need for maintenance of the electric drive apparatus the following step is the sending 33 of the information of the need for maintenance to other electric drive apparatuses 30, 31 of the installation. The communication unit 28 of the electric drive apparatus sends information of the need for maintenance, e.g. said notification of a need for maintenance, of the present electric drive apparatus to said other electric drive apparatuses 30, 31. The communication unit 28 of the electric drive apparatus according to the present embodiment has a transmitter for sending information to and a receiver for receiving information from other electric drive apparatuses 30, 31 of the installation consisting of one or more electric drive apparatuses.

[0071] After the sending 33 of the information of the need for maintenance to other electric drive apparatuses 30, 31 of the installation the following step is the receiving 34 of the information on the need for maintenance of said other electric drive apparatuses 30, 31 in the near future. In the present embodiment the near future may be defined as a following period of 18 months, a following period of 12 months, a following period of 6 months or a following period of 3 months. The communication unit 28 of the electric drive apparatus receives information on the need for maintenance of said other electric drive apparatuses 30, 31 in the near future. The communication unit 28 and the other electric drive apparatuses 30, 31 may utilise any kind of communication protocol in communication, including a wireless communication protocol. The communication unit 28 then forwards the information of the need for maintenance received from the maintenance need notification unit 27 and the information of the need for maintenance received from the other electric drive apparatuses 30, 31 of the installation to a maintenance alarm synchronization unit 29.

[0072] After the receiving 34 of the information on the need for maintenance of said other electric drive apparatuses 30, 31 the following step is the generating 35 of a synchronized maintenance alarm. The maintenance alarm synchronization unit 29 receives the information of the need for maintenance from the communication unit 28, analyses the received information of the need for maintenance and generates 35 a synchronized maintenance alarm of one or more electric drive apparatuses.

[0073] In the generating 35 of a synchronized maintenance alarm the maintenance alarm synchronization unit 29 may use a synchronization algorithm for synchronisation of the maintenance and for optimization of the maintenance time of the one or more electric drive apparatuses in the installation. The maintenance algorithms inform users about incoming maintenance actions. The synchronized maintenance alarm comprises the information of the need of maintenance of the one or more electric drive apparatuses in the installation according to the present embodiment. The synchronized maintenance alarm may also comprise the information of the need of maintenance of only one electric drive apparatus of the one or more electric drive apparatuses in the installation according to the present embodiment. The maintenance alarm synchronization unit 29 then forwards the information of the generated synchronized maintenance alarm to an alarm indication unit 9.

[0074] After the generating 35 of the synchronized maintenance alarm the maintenance alarm synchronization unit 29 may also forward the information of the generated synchronized maintenance alarm to the communication unit 28 for communicating said generated synchronized maintenance alarm to other electric drive apparatuses 30, 31 of the installation. The communication unit 28 may then receive and send the information of the generated synchronized maintenance alarm received from the maintenance alarm synchronization unit 29 to other electric drive apparatuses 30, 31 of the installation.

[0075] After the generating 35 of the synchronized maintenance alarm the following step is the indicating 36 of the synchronized maintenance alarm of the one or more electric drive apparatuses to the user. In the method for indicating a need for maintenance of an electric drive apparatus according to present embodiment, the alarm indication unit 9 receives the information of the generated synchronized maintenance alarm from the maintenance alarm synchronization unit 29. The alarm indication unit 9 then indicates 36 the synchronized maintenance alarm of the one or more electric drive apparatuses to the user by for example showing said synchronized maintenance alarm on a display panel of at least one electric drive apparatus of said one or more electric drive apparatuses.

[0076] The alarm indication unit 9 of the electric drive apparatus according to the present invention may also comprise a light arrangement for indicating 36 the generated synchronized maintenance alarm of the one or more electric drive apparatuses in the installation according to the present embodiment to the user with a light indication of a particular selected colour, e.g. red light indication. The alarm indication unit 9 may further have other communicating means based on any known technology, e.g. via a communication network, for properly communicating and indicating 36 the synchronized maintenance alarm of the one or more electric drive apparatuses to the user.

[0077] In the method for indicating a need for maintenance of an electric drive apparatus according to the present invention, the process of calculating 10 maintenance calculation data, determining 32 the notification of a need for maintenance, sending 33 of the information of the need for maintenance to other electric drive apparatuses 30, 31 of the installation, receiving 34 of the information on the need for maintenance of said other electric drive apparatuses 30, 31 of the installation, generating 35 of the synchronized maintenance alarm, and indicating 36 of the synchronized maintenance alarm of the one or more electric drive apparatuses to the user is repeated continuously and continued 37 until the electric drive apparatus is turned off or until the maintenance alarm indication feature is turned off.

[0078] FIG. 7 shows a time schedule diagram of an arrangement for indicating a need for maintenance of an electric drive apparatus in an installation consisting of one or more electric drive apparatuses according to the present invention. A timeline shown in the time schedule diagram of FIG. 7 is marked with a reference number 38. The installation according to present embodiment comprises several electric drive apparatuses 39, 40, 41, 43, 45, 46. Here, in each one of said several electric drive apparatuses 39, 40, 41, 43, 45, 46 maintenance data, e.g. time, usage and conditions, is collected and calculated. Furthermore, in each one of said several electric drive apparatuses 39, 40, 41, 43, 45, 46 the collected and calculated maintenance data is analysed together with the applicable values set for maintenance scheme of said electric drive apparatus and a notification of a need for maintenance of said electric drive apparatus is determined independently based on the analysis.

[0079] In the present embodiment, each one of said several electric drive apparatuses 39, 40, 41, 43, 45, 46 has a transmitter for sending information to and a receiver for receiving information from other electric drive apparatuses 39, 40, 41, 43, 45, 46 of the installation consisting of one or more electric drive apparatuses. The transmitter of the electric drive apparatus sends information of the need for maintenance, e.g. said notification of a need for maintenance, of the present electric drive apparatus to said other electric drive apparatuses 39, 40, 41, 43, 45, 46. Respectively, said receiver of the electric drive apparatus receives information on the need for maintenance of said other electric drive apparatuses 39, 40, 41, 43, 45, 46 in the near future. The transmitter and said receiver of the electric drive apparatuses 39, 40, 41, 43, 45, 46 may utilise any kind of communication protocol, including a wireless communication protocol.

[0080] In the present embodiment, at least one of said several electric drive apparatuses 39, 40, 41, 43, 45, 46 has determined the information of the need for maintenance of the electric drive apparatus 39, 40, 41, 43, 45, 46 itself and has received and the information of the need for maintenance received from the other electric drive apparatuses 39, 40, 41, 43, 45, 46 of the installation, analyses the determined the information of the need for maintenance of the electric drive apparatus 39, 40, 41, 43, 45, 46 itself together with the received information of the need for maintenance received from the other electric drive apparatuses 39, 40, 41, 43, 45, 46 and generates a synchronized maintenance alarm 42, 44, 47 for maintenance of the electric drive apparatuses 39, 40, 41, 43, 45, 46.

[0081] In the present embodiment, said at least one of said several electric drive apparatuses 39, 40, 41, 43, 45, 46 may also send the information of the generated synchronized maintenance alarm to the other electric drive apparatuses 39, 40, 41, 43, 45, 46 of the installation. In the presented installation according to present embodiment said several electric drive apparatuses 39, 40, 41, 43, 45, 46 give a synchronized maintenance alarm 42, 44, 47 in synchronisation with each other. In said maintenance alarm synchronization unit 29 there is a synchronization algorithm utilized. The electric drive apparatuses 39, 40, 41, 43, 45, 46 of the installation are communicating with each other and a synchronization algorithm adjusts a simultaneous synchronized maintenance alarm on group of electric drive apparatuses which maintenance is due at approximately same calendar time.

[0082] In the presented installation according to present embodiment the electric drive apparatuses 39, 40, 41 give a synchronized maintenance alarm 42 in March; electric drive apparatus 43 gives a synchronized maintenance alarm 44 in July; and electric drive apparatuses 45, 46 give a synchronized maintenance alarm 47 in November. The synchronized maintenance alarm 42, 44, 47 comprises the information of the need of maintenance of the one or more electric drive apparatuses 39, 40, 41, 43, 45, 46 in the installation according to the present embodiment. The synchronized maintenance alarm 44 may also comprise the information of the need of maintenance of only one electric drive apparatus 43 of the one or more electric drive apparatuses 39, 40, 41, 43, 45, 46 in the installation according to the present embodiment.

[0083] In the presented installation according to present invention said several electric drive apparatuses 39, 40, 41, 43, 45, 46 give synchronized maintenance alarms 42, 44, 47 in synchronisation with each other and indicate the information of the synchronized maintenance alarms 42, 44, 47 to the user by for example showing each of the alarms 42, 44, 47 on a display panel of at least one electric drive apparatus of the one or more electric drive apparatuses 39, 40, 41, 43, 45, 46.

[0084] The electric drive apparatuses 39, 40, 41, 43, 45, 46 according to the present invention may also comprise a light arrangement for indicating the generated synchronized maintenance alarms 42, 44, 47 of the one or more electric drive apparatuses 39, 40, 41, 43, 45, 46 in the installation according to the present embodiment to the user with a light indication of a particular selected colour, e.g. red light indication. The electric drive apparatuses 39, 40, 41, 43, 45, 46 may further have other communicating means based on any known technology, e.g. via a communication network, for properly communicating and indicating 36 the synchronized maintenance alarms 42, 44, 47 of the one or more electric drive apparatuses 39, 40, 41, 43, 45, 46 to the user.

[0085] The electric drive apparatuses 39, 40, 41, 43, 45, 46 of the installation according to the present invention are maintained in synchronization and several electric drive apparatuses 39, 40, 41, 43, 45, 46 can be maintained in one maintenance visits instead of each one of the electric drive apparatuses 39, 40, 41, 43, 45, 46 being maintained separately in separate maintenance visits.

[0086] The present invention enables a wireless communication and synchronization of alarms and also improves user experience while several electric drive apparatuses 39, 40, 41, 43, 45, 46 can be maintained at once instead of receiving several single service calls. The synchronized maintenance alarms 42, 44, 47 according to the present invention save maintenance costs by grouping maintenance actions and thus causing less maintenance visits to the installation site. A proper, timely and efficient synchronized maintenance of the electric drive apparatuses 39, 40, 41, 43, 45, 46 contributes to reliable and efficient operation and to the overall operational efficiency of the electric drive apparatuses 39, 40, 41, 43, 45, 46 and the installation as whole.

[0087] In particular, when the installation has several electric drive apparatuses, the maintenance solution according to the present invention brings about substantial efficiency in maintenance.

[0088] With the help of the solution according to the present invention the electric drive apparatuses 39, 40, 41, 43, 45, 46 of the installation can be maintained more efficiently. The synchronized maintenance alarms 42, 44, 47 according to the present invention make it possible to maintain several electric drive apparatuses 39, 40, 41, 43, 45, 46 in one maintenance visit. The solution for indicating a need for maintenance of an electric drive apparatus according to the present invention leads to less maintenance visits and causes inefficiency in the installation brings substantial efficiency in the installation and in the maintenance. The solution according to the present invention may be utilised in e.g. frequency converters or in any electric drive apparatuses.

[0089] It will be obvious to a person skilled in the art that, as the technology advances, the inventive concept can be implemented in various ways. The invention and its embodiments are not limited to the examples described above but may vary within the scope of the claims.