Title of Invention

A WATERCOOLED HEATSINK MODULE FOR THYRISTOR DEVICES

Abstract

This invention relates to a water cooled heat sink module for thyristor devices comprising atleast 2 nos. of thyristors (1) sandwiched between devices atleast 3 nos of spacers of watercooled heatsink (2) with insulating spacers (3) on either side, the cooling water tubes (9) provided with coupling (10) for connecting the said heat sinks, a gate driver unit (11) mounted on the end plate (6) and connected to the thyristors, snubber resistors (14) mounted on the heatsink and reactors (15) mounted on busbars (16) in a modular form with stacking facility, characterized in that the clamping force for the thyristors (1) is provided through atleast 4 nos of special bolts (4) electrically isolated at one end with respect to end plate type 1 (5), and end plate type 2 (6) assembled with a indicator strip (21) and a load compensating arrangement (8) and disc spring washers (7) are provided between the end plates and the heat sink assembly to monitor and indicate the clamping force.

Full Text

"The invention relates to a watercooled heat sink module for thyristor devices. Thyristors are used in high power rated applications like converter/inventer. Their current ratings and hence performance is dependent on the heat dissipation capacity of the heatsink used in the assembly. Presently heatsinks are in the form of a simple metal plate or block with fins for better ocooling, Further improvement is possible with forced air circulation in the cubicle of the thyristor assemblies with ifinnedheatsinks. Though the present arrangement provides convenient stackings and removal of the heatsinks for maintenance or replacement, there are disadvantages with the air cooled heatsinks. The main disadvantage of the present system of air cooled heatsinks is the limitation of cooling with forced air. Water cooled heatsinks are also used for increasing the current rating of thyristor specially in thyristor for high power application. The disadvantage associated with the presents-water cooled , heatsink system is that it is used for specific application and is not a modular design. Therefore, the main object of the present invention is to propose a water cooled heatsink module for thyristor devices such that these conveniently modules are convieniently stacked depending upon the requirements. Another object of the present invention is to propose a water cooled heatsink with the added conveniences of air cooled heatsink such as easy maintainability, quick replacement and flexibility for different application. A further object of the present invention is to provide thyrigtor.5 with high efficiency water cooled heat sinks arranged such that the proper clamping force of the assembly is indicated and the assembly is complete with required resistors and capacitors provided as anubber circuit along the gate driver unit for providing firing pulse to the thyristor. A still further objective of the present invention is to propose a unique load compensating arrangement so that the convenience of removing the defective thyristor of the assembly without disturbing the other assembled thyristor. According to the present invention there is provided a water cooled heat sink module for thyristor devices comprising atleast 2 nos. of thyristors sandwiched between devices atleast 3 nos of spacers of watercooled heatsink with insulating spacers on either side, the cooling water tubes provided with coupling for connecting the said heat sinks, a gate driver unit mounted on the end plate and connected to the thyristors,, snubber resistors mounted on the heatsink and reactors mounted on busbars in a modular form with stacking facility, characterized in that the clamping force for the thyristors is provided through atleast 4 nos of special bolts electrically isolated at one end with respect to end plate type 1 and end plate type 2 assembled with a indicator strip and a load compensating arrangement and disc spring washers are provided between the end plates and the heat sink assembly to monitor and indicate the clamping force. The nature of the invention, its objective and further advertages residing in the same will be apparent from the following description made with reference to non limiting exemplary embodiments of the invention represented in the accompanying drawings : Brief Description of the accompanying drawings Figure : 1 shows the electrical scheme of the module. Figure : 2 shows the assembly detail of the complete module Figure : 3 shows the clamping force indicating mechanism. Figure : 4 load compensatory arrangement Figure : 5 High efficiency watercooled heatsink. In accordance with the present invention for a high current converter application it is necessary to configure a number of high current thyristors in parallel. The existing arrangement of stacking them in a vertical configuration has problems like providing electrical terminations with flexibility of connecting water terminations, and providing current sharing reactor in each path. This arrangement eliminates the problems by making compact size modular unit of 2 thyristors with all the required devices viz., snubber circuit, gate circuit, water cooled heatsink, reactors in such a way that the convenience of stacking these modules for the required rating can be easily achieved. This is shown in the electrical scheme of the module in figure 1 (a) shows the common cathode connection and Figure 1 (b) the common Anode & connection. In the Scheme xl & x2 are connectors, V is +24V, P the pulse, G is the ground and S is shield, VI and V2 are thyristors. R2 R3, R4 and R5 are snubber resistor, C1 and C2 are snubber capacitor, R1 and R6are discharge resistor, A is anode and K is cathode. G and L are gate and reactor respectively. Figure 2 shows the assembly details of the complete module in which 2 nos. of 77mm thyristors (1) are sandwiched between 3 nos. of water cooled he at sinks (2) with insulating spacers (3) on on either side. The clamping force for the thyristors is applied through 4 nos, of special bolts (4) electrically isolated at one end with respect to end plate type 1 (5), and end plate type 2 (6). An assembly of Disc spring washers (7) along with load compensating arrangement (8) is positioned between the end plates and the heat sink assembly to monitor and indicate the clamping force. The nut at one end of the four bolts are tightened uniformly. When the bolts are applied with slightly in excess of the preloaded clamping force, the indicating strip which is in preloaded condition will become free to move side ways. This measure would ensure the required clamping force on the devices. The cooling water tubes connecting the heat sinks (9) are terminated on quick disconnect couplings (10) fixed on end plate. The gate driver unit (11) is also mounted on the end plate and is wired to the thyristors. The anubber capacitors (12) are fixed on the protective polycarbonate cover (13) and the snubber resistors (14) are mounted on heat sinks which are fixed to the middle water cooled heat sinks for effective cooling. The reactors (15) are fitted on to the 2 other busbars (16). Hie unique features of this assembly are : a) incorporation of clamping force indicating mechanism with which the indicator becomes free to move at the predetermined clamping load ensuring the verification of correctness of clamping force without disturbing the assembly. The details of this are shown in figure 3. The functioning of this is an follows : Hie end plate is assembled with 2 disc springs (7) along with spacers (17), (18) and clamped with a bolt (19) & nut (20) with the indicator strip (21) at the outside end of end plate. The disc spring unit is pre-compressed to the required clamping force using any loading arrangement and the nut (20) is tightened in this condition & locked to the screw using Loctite adhesive. Hie indicator strip will be clamped & will not move till die disc spring unit is compressed to the pre loaded condition. When the clamping force is slightly in excess of the force, the indicating strip will become free to move sideways. This would indicate correct clamping force. b) Load compensatory arrangement assembly, (fig.4) does the function of keeping the thyristor, heat sink interface contact pressure to a value of 20 kgs during the process of replacement of a defective myristor from the assembly. For removing me defective myristor of me assembly, the main clamping pressure is to be eased out by unscrewing the nuts (22) on the special bolts (4). When the clamping force is reduced to zero, it is likely mat the established interface between myristor & heat sinks can get disturbed and it likely mat me dust surrounding the device contact area can get included in the contact areas of the device & heat sinks. This can affect adversely the thermal resistance of the device. In order to prevent this, a load compensating arrangement has been introduced which will also provide indication about the extent the clamping nuts to be loosened for the device removal at the same tune provide a nominal spring clamping force of about 20 kgs. This force prevents disturbance of die contact areas of die healthy diyristor and die 2 heat sinks in contact with it. The load compensating arrangement (8) which maintain a minimum interface contact pressure between (he myristor and heat sink is positioned between the end plates type 1 and 2. This helps in maintaining die interface between the thyristor and heat sink which can likely to get disturbed when the clamping force is reduced to zero dining removal of defective rayristor. The mechanism consists of compression spring (23) assembled with a plunger (24) inside the housing (25). The plunger has a circular groove on its periphery at a distance of 6mm from the bottom seating of the plunger. This groove (26) is marked with coloured paint so mat die movement of me plunger by 6mm can be seen while unloading the clamping force. c) The high efficiency water cooled heat sink (fig.5) The heatsink (2) made of drawn copper flat has 2 water connection terminations (27) and (28) threaded with 3/8 "BSP (British standard pipe)". A flat seating at the end threading provides seating for the water sealing gasket. These ports connect to 2 water plenums on either side of heatsmk and these water chambers (29) (30) are connected by a no. of small holes made in a row along the flat surfaces of he at sink so that the heat conducted to the surfaces of heatsink can be effectively taken out by the water in Among circulation through (31) Among these small holes 2 holes with guide bushes (32) provide alignment between heatsinks of the assembly. The heatsmk surface, is covered by electro less nickel coating for providing proper interface between thyristor surface and heatsink. The invention described hereinabove is in relation to a non-limiting embodiments and as defined by the accompanying claims. CLAIM 1. A water cooled heat sink module for thyristor devices comprising atleast 2 nos. of thyristors (1) sandwiched between devices at least 3 nos of spacers of watercooled heatsink (2) with insulating spacers (3) on either side, the cooling water tubes (9) provided with coupling (10) for connecting the said heat sinks, a gate driver unit (11) mounted on the end plate (6) and connected to the thyristors, snubber resistors (14) mounted on the heatsink and reactors (15) mounted on busbars (16) in a modular form with stacking facility, characterized in that the clamping force for the thyristors (1) is provided through at least 4 nos of special bolts (4) electrically isolated at one end with respect to end plate type 1 (5), and end plate type 2 (6) assembled with a indicator strip (21) and a load compensating arrangement (8) and disc spring washers (7) are provided between the end plates and the heat sink assembly to monitor and indicate the clamping force. 2. A watercooled heat sink module as claimed in claim 1, wherein the said clamping force indicating mechanism comprises atleast 2 disc spring washers (7) with spacers (17,18) and clamped with a bolt (19) and nut (20) with indicator strip (21) at the outside end of said end plate (5,6). 3. A watercooled heat sink module as claimed hi claim 1 or 2, wherein the said indicator strip (21) is free to move sideways and indicates correct clamping force with the disc spring (7) compressed to the pre loaded condition. 4. A watercooled heat sink module as claimed in claim 1 wherein the said load compensating arrangement (8) comprises of compression spring (23) and a plunger (24) mounted inside the housing (25), the said plunger (24) being provided with a circular groove (26). 5. A watercooled heat sink module as claimed in claim 1 wherein the heat sink (2) is made of drawn copper and coated with Nickel and provided

Documents:

1634-DEL-1997-Abstract.pdf

1634-del-1997-claims.pdf

1634-del-1997-correspondence-others.pdf

1634-del-1997-correspondence-po.pdf

1634-del-1997-description (complete).pdf

1634-del-1997-drawings.pdf

1634-del-1997-form-1.pdf

1634-del-1997-form-19.pdf

1634-del-1997-form-2.pdf

1634-del-1997-form-3.pdf

1634-del-1997-gpa.pdf