EDITORIAL NOTE APPLICATION NUMBER - 2007283338 This specification does not contain a page "1", therefore the description commences on page "2".
C:\NRPorbDCC\TRN\3942968 IDOC-lW19/2011 ELECTRIC CONTROL SYSTEM FOR CONTROL BOX FIELD The invention relates to an electronic control system, e.g., being suitable for various industrial motors and/or for a control box, which uses a computer control in an alumina refinery. BACKGROUND In the existing production process of the alumina refinery, the control for the production is generally implemented near machines and in a central control room respectively. It is required to operate manually by operator. But it is not convenience to implement the control, and automization is very low. Since a combination switch SA is positioned in the central control room and can not acquire field situation in time, when operator controls motors, accidents happen easily. Further, the cost of the existing control system is high. It is desired to address or ameliorate one or more disadvantages or limitations associated with the prior art, or to at least provide a useful alternative. SUMMARY In accordance with the present invention there is provided an electric control system for control box, which comprises a combination switch SA, a change over switch SE, a stop button SS, a start button SF, and an intermediate relay KS, characterized in that the combination switch SA has an end connecting to a common node between the change over switch SE and the stop button SS, and 2 CNRtbl\DCC\TRM3%8212_1 DOC-] 1/4/1011 another end connecting to an input end of PLC control system through an intermediate relay KA3, the combination switch SA is also connected to the start button SF and a contactor coil KM. Embodiments of the present invention provide an electric control system for control box to reduce cost of the control system, improve the automization, increase accuracy of the system and avoid the occurrence of accidents as possible. Embodiments of the present invention provide the following: an electric control system for control box, which comprises a combination switch SA, a change over switch SE, a stop button SS, a start button SF, and an intermediate relay KS, wherein the combination switch SA has an end connecting to the spot between the change over switch SE and the stop button SS, and another end connecting to an input end of PLC control system through the intermediate relay KA3, the combination switch SA is also connected to the start button SF and a contactor coil KM . Said combination switch SA is located in the control box. Said intermediate relay KS is connected to an output of the PLC control system. Simultaneously an auxiliary contact of the intermediate relay KS is connected to the contactor coil KM. The advantages and effect of embodiments of the present invention can be as follows: In embodiments of the present invention, the combination switch SA has an 3 C:\NRPotnhDCCTRNG942%8_J DOC-101/9/2011 end connecting to a common node between the change over switch SE and the stop button SS, and another end connecting to an input end of PLC in a central control room through the intermediate relay KA3. An onsite signal is outputted to the PLC control system in the center control room such that the PLC control system can acquire field situation in real time, achieving production linkage, PLC centralized control, and improvement of automization. The combination switch SA is located in the field control box, so when an onsite operator is testing run near machine or overhauling, an operator or a computer in the master control room cannot operate the motor, thus avoiding the occurrence of accident, and achieving the safety for production. It decreases the amount of the used cable, lowers cost, and improves accuracy. BRIEF DESCRIPTION OF THE DRAWINGS Preferred embodiments of the present invention are hereinafter further described, by way of non-limiting example only, with reference to the accompanying drawings, in which: Fig.1 is a circuit diagram of an embodiment of the present invention. DETAILED DESCRIPTION An electric control system for control box, which comprises a combination switch SA, a change over switch SE, a stop button SS, a start button SF, and an intermediate relay KS, wherein the combination switch SA has an end connecting to a common node between the change over switch SE and the stop button SS, and another end connecting to an input end of PLC control system through the 4 C\RPorbl\DCC\TR 394296SI DOC-M/191201[1 intermediate relay KA3, is described. The combination switch SA is located in the control box, and the intermediate relay KS is connected to an output end of the PLC control system. Now, the embodiments of the present invention will be described in detail with reference to the fig.1. However, the scope of the present invention is not limited to the embodiment. As shown in fig.1, the components of the described embodiments are connected as follows: the node 1 of the combination switch SA is connected to the node 23 of the start button SF, the node 27 of the start button SF is connected to the contactor coil KM, the node 2 of the combination switch SA is connected to the node 21 of the stop button SS, the node 3 of the combination switch SA is connected to the node 29 of the intermediate relay KS, the node 27 of the intermediate relay KS is connected to the contactor coil KM, the node 4 of the combination switch SA is connected to the common node 19 of the stop button SS and the change over switch SE, the node 17 of the change over switch SE is connected to the node 17 of a thermal relay KH, the node 7 of the combination switch SA is connected to the node 31 of the intermediate relay KA3, the node 8 of the combination switch SA is connected to the common node 19 of the stop button SS and the change over switch SE. The operational principle of the described embodiments is as follows: As shown in fig. 1, when the combination switch SA is switched to the left for 450, the nodes 1 and 2 of the combination switch SA are connected, at this point, 5 C :NRPorbl\DCC\TRM3942968_IDOC-IIV)9/20I 1 i.e. testing run near machine, overhauling mode, at the moment the start button SF is pressed and the contactor coil KM is turned on and powered on. The contact of the contactor KM in the main circuit is attracted and closed, and the motor is actuated due to powering on. When the motor must stop during it is operating, the stop button SS is pressed and the contactor coil KM is powered down, while the contacts of the contactor KM in the main circuit are open, and the motor stops due to powering down. If the motor or machine operation is abnormal during debugging or overhauling, the power supply should be cut off in time by the change over switch SE, the contactor coil KM is powered down and thus the motor stops. When the combination switch SA is switched to the right for 450, the nodes 3 and 4 of the combination switch are connected and the nodes 7 and 8 of the combination switch are connected. At this point, i.e. the production linkage or PLC centralized control, computer automatic control mode, at the moment the intermediate relay KA3 is powered on and the motor is allowed production linkage or PLC centralized control. In computer automatic control mode signals are inputted to the computer, at the moment the motor enters into the system and operates automatically according to program. When the PLC outputs, the intermediate relay coil KS is powered on and the auxiliary contact KS of it is attracted and closed, the contactor coil KM is turned on and powered on, the contact of the contactor KM in the main circuit is attracted and closed and the motor is actuated due to powering on. On the contrary, when the PLC does not 6 C:NRPortb\DCCTRN\3942%,8I DOC-10/19/2iII output, the motor stops due to powering down. Throughout this specification and the claims which follow, unless the context requires otherwise, the word "comprise", and variations such as "comprises" and "comprising", will be understood to imply the inclusion of a stated integer or step or group of integers or steps but not the exclusion of any other integer or step or group of integers or steps. The reference in this specification to any prior publication (or information derived from it), or to any matter which is known, is not, and should not be taken as an acknowledgment or admission or any form of suggestion that that prior publication (or information derived from it) or known matter forms part of the common general knowledge in the field of endeavour to which this specification relates. The reference numerals or symbols in the following claims do not in any way limit the scope of the respective claims. 7