Abstract:
The subject matter of the invention is an inverter including a casing ( 1 ), said casing ( 1 ) including at least two casing chambers ( 2, 3 ) that are each closable through a separate cover ( 2   a,    3   a ).

Description:
FIELD OF THE INVENTION 
     The present invention relates to an inverter for a PV installation, including a casing. 
     In the utilization of alternative energy sources such as PV modules, inverters serve to convert direct current into alternating current. Such an inverter comprises a casing accommodating electronic power components. These electronic power components must be protected against environmental impacts, in particular against humidity. Such an inverter not only includes electronic power components but also at need a plurality of plugs or similar for connecting said inverter on the AC and on the DC side. Often enough, such an inverter also possesses a communication unit, for example in the form of a display that also has to be connected. 
     DESCRIPTION OF THE PRIOR ART 
     A converter is known from the document EP 0 994 559 A2, which is designed for indoor use only since the casing comprises, inter alia, openings through which water and dirt may penetrate. The converter possesses a casing with one chamber and a control head for placing thereon a connecting unit and a manual control unit. 
     An arrangement for concealing a fastening screw of the cover of a casing for electrical appliances is known from DE 24 55 689 A1. This flap, which serves to cover the screw, is retained by an additional screw so that the flap can only be removed if this additional screw is removed. 
     Inverters are installed by the electrician working on the site and mounting the PV installation. When known inverters are installed, the casing is opened for the electrician to accede the corresponding plug contacts. Since the mounting of such type inverters often occurs outdoors, the electronic power components are exposed to environmental impacts at least during mounting and installation. 
     It is known that the inverter casing accommodating the electronic power components must have a high IP-rating, namely the IP65 rating, in order to make certain that such an inverter is indeed protected against environmental impacts, in particular against humidity, when used outdoors. There is further the risk that the electrician damages intentionally or unintentionally parts of the power electronics when performing connecting operations on the inverter. When performing maintenance works on the PV installation, it is often enough the case that access must only be ensured to the discrete plug connections if e.g., PV modules need to be disconnected from the inverter or if a disconnection must occur on the AC side. This means that only the manufacturer or persons authorized by him are allowed to have access to the electronic power components for maintenance services. 
     BRIEF SUMMARY OF THE DESCRIPTION 
     This means that the object of the invention is to provide an inverter in which the electronic power components are not directly accessible for connecting operations only. 
     Accordingly, the solution proposed by the invention is that the casing includes at least two casing chambers, each one of them being closable by a separate cover, said cover having to be removed before the casing chamber can be opened. It appears therefrom that the electronic power components of the inverter may be housed in a separate casing chamber whilst the connecting plugs and the communication unit, in the form of a display for example, are housed in a second casing chamber that is disposed separately next to the first casing chamber in the inverter casing. Accordingly, it is not necessary to open the cover of the casing chamber accommodating the electronic power components for performing connecting operations. Advantageous features of the invention and particular embodiments thereof will become apparent from the dependent claims. 
     Referring to the arrangement of two chambers in the inverter casing, there is provided that the one first casing chamber accommodates the electronic power components, at least one electrical connection being provided to the first casing chamber from at least the second casing chamber, said electrical connection having an IP rating corresponding at least to that of the first casing chamber. 
     As already explained above, the electronic power components in the first casing chamber are connected on the AC side and on the DC side to the second casing chamber in which there are located the connecting elements. As also explained above, the chamber which accommodates the electronic power components must be protected against humidity in particular according to the IP65 rating. Accordingly, it must be ensured that the electrical connection between the first and the second casing chamber has at least the IP-rating of the first casing chamber, in the instant case for example at least the rating IP65. 
     Various variants may be envisaged to implement the AC side mains connection between the first and the second chamber through the wall that separates them. According to a variant, it is provided that the electrical connection includes a cable feedthrough. In this case, there is further provided that the first casing chamber, which comprises the electronic power components, possesses a terminal clamp for connecting the cable to the mains. 
     According to another variant of the invention, there is provided that the electrical connection includes a socket that is disposed in the wall to the first casing chamber, said socket serving to receive a plug with the power cord. 
     According to another variant, a lead-through terminal that is disposed in the wall to the first casing chamber is provided as the electrical connection. The implementation of such a lead-through terminal with the rating IP65 is also the subject matter of the invention. Accordingly, in order to ensure the tightness according to the rating IP65 referring to a lead-through terminal for example, there is provided that the lead-through terminal comprises a terminal body comprising a shield for abutting the wall of the first casing chamber, said terminal body comprising a clamping member through which the shield of the terminal body is pressed against the wall of the casing chamber. It is obvious therefrom that the shield of the terminal body is pulled against the wall by the clamping member during mounting so that the necessary tightness is ensured in the transition region between the one second chamber to the other first chamber. Advantageously, there is further provided that the shield comprises a peripheral seal by which the shield abuts the wall. 
     Referring to the clamping member, there is advantageously provided a clip that may be slidably received by the terminal body. Said clip is particularly configured like a U-shaped bar, the leg of said bar, when said bar is viewed from the side, flaring toward the bight segment of said bar. This means that the furthest the clip is pushed onto the terminal body, the more the terminal body is pulled against the wall together with the shield and the peripheral seal located thereon. 
     More specifically, for the bar to be slidably received by the terminal body, there is provided that the terminal body comprises rail-shaped seats for the legs of the bar, an abutment edge for the bar being respectively provided on the portion turned away from the shield on the rail-shaped seat, said abutment edge being configured to taper according to the configuration of the bar legs. Through this abutment edge, it is achieved that the bar, and also the clip, are pulled continuously against the wall located on the one side of the bar while they are moved to be placed onto the terminal body so that, as already explained, the shield is pressed against the wall. To secure the clip onto the terminal body, appropriate detent means are provided. 
     The invention will be described in closer detail herein after by way of example with reference to the drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  schematically shows the inverter casing with the two removed covers for the two casing chambers; 
         FIG. 2  shows a portion of the wall between the first and the second casing chamber, a socket for receiving a mains connecting plug being provided on the wall; 
         FIG. 3  shows an illustration like in  FIG. 1 , a lead-through terminal being provided in the wall and a mains connecting terminal being provided in the first casing chamber; 
         FIG. 4  shows the lead-through terminal shown in  FIG. 3  in a side view; 
         FIG. 5  shows a sectional view taken along the line V-V in  FIG. 4  over the entire width of the lead-through terminal at a larger scale; 
         FIG. 6  shows a side view of the bar  40 ; 
         FIG. 7  shows the sectional view taken along the line VII-VII in  FIG. 4  at a correspondingly enlarged scale like in  FIG. 4 . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The casing  1  of the inverter has the two chambers  2  and  3 , the first chamber  2  showing the electronic power components  4  that are merely outlined in the first casing chamber  2 . The two casing chambers  2  and  3  are separated by the wall  5 . The wall  5  however comprises additional plug elements  6  for establishing on the DC side the connection with the PV modules to the electronic power components (not shown) in the chamber  2 . On the AC side, there is provided a power cord  7  that is led through the wall  5  from the second casing chamber  3  into the first casing chamber  2 . In said first casing chamber  2 , there is located the mains connecting terminal  8  that receives the discrete strands of the cable  7 . The cable feedthrough  10  through the wall  5  has the rating IP65 since the first casing chamber  2  is also protected against environmental impact, more specifically against humidity, according to this rating. This means that the cover  2   a  that covers the first casing chamber  2  comprises a seal so that the first casing chamber is to be assigned to the rating IP65 with respect to the protection against environmental impact. The second cover  3   a  covers the casing chamber  3 , a peculiarity to be noted being that the cover  2   a  exhibits flaps  2   b , one of them serving to receive a screw  2   c  that is screwed from the top into the front side of the wall  5 , thus serving to fix the cover  2   a  to the first casing chamber  2 . The important point is that the cover  3   a  covers the flaps  2   b  with the screw  2   c  so that the cover  3   a  must first be removed before the casing chamber  2  may be opened. This serves as an additional safety measure in order to prevent the electrician from also opening the first casing chamber out of mere thoughtlessness, even if it is not necessary. 
     As already explained above, the cable feedthrough  10  in  FIG. 1  is to be rated IP65. 
     According to  FIG. 2 , a socket  20  is provided in the wall  5  as a variant of a connection of the power cord to the power electronics, said socket  20  also being rated IP65. The plug labelled at  21  of the power cord  7  is received by the socket  20 . 
     Referring to  FIG. 3 , a lead-through terminal  30  is disposed in the wall  5  as another variant of a connection of the power cord to the power electronics, said lead-through terminal comprising on the one side, i.e., assigned to the casing chamber  3 , connections for the power cord  7 . In the casing chamber  2 , there is located a mains connecting terminal  8  that is received by the discrete cable strands. 
     The  FIGS. 4 through 7  are directed to the configuration of the lead-through terminal  30 . The lead-through terminal labelled at  30  has the terminal body  31  as well as the shield  32  with the peripheral seal  33 . The lead-through terminal  30  abuts with its shield the wall  5  between the two casing chambers  2  and  3 . On either side, the terminal body  31  has rail-like seats  34  ( FIG. 5 ) in the form of dovetail guides, an abutment edge  35  being provided in the region of the rail-like seat  34 . The U-shaped bar labelled at  40  ( FIG. 6 ), which consists of the two legs  41  and of the bight portion  43  connecting the legs, comprises on its leg  41  a T-shape configuration  45  with one guiding leg  46  and one guiding bight portion  47  extending transverse thereto and corresponding to the rail-like seat in the form of a dovetail guide  34  for the leg  41  of the bar  40  to be slidably received by the rail-like seat  34 . Whilst the bar  40  is inserted by pushing it pursuant to the arrow  50  shown in  FIG. 4 , the bar  40  gets nearer to the shield  32  by virtue of the conical shape of the legs  41  ( FIG. 4 ) and the abutment of the legs  41  on the abutment edge  35 . It appears therefrom that, the more the bar  40  is pushed onto the terminal body, the more the shield  32  with the seal  33  is pressed against the wall  5 , which has not been illustrated in  FIG. 4 . Detent elements  49 ,  49   a  in the form of detent noses that engage into each other in a snap-fit connection are provided between the leg  41  of the bar  40  and the terminal body to fix the bar  40  onto the terminal body  31 .