Silicon controlled rectifier power controller

ABSTRACT

A power controller generally includes a first switching device and a first bus bar mounted to the first switching device such that wiring may enter and exit the power controller. The first bus bar may have a face plate that extends at least partially above opposed side plates of the power controller and a mounting plate in electrical contact with the first switching device.

INFORMATION

DETAILED DESCRIPTION OF THE INVENTION

DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates aspects of one embodiment of a power controller according to the present invention.

FIGS. 2-4 illustrate aspects of one embodiment of a three-phase two-leg power controller according to the present invention.

FIGS. 5A and 5B illustrate aspects of one embodiment of a bus bar according to the present invention.

FIGS. 6A and 6B illustrate aspects of one embodiment of a bus bar according to the present invention.

FIG. 7 illustrates aspects of one embodiment of a power controller assembly according to the present invention.

FIGS. 8A-8C illustrate aspects of one embodiment of a cover according to aspects of the present invention.

FIGS. 9A and 9B illustrate aspects of one embodiment of a power controller assembly according to the present invention.

DETAILED DESCRIPTION

Referring to FIG. 1, one embodiment of a power controller is illustrated. In general, the power controller is designed to provide convenience in installation and wiring by eliminating the need for separate power distribution blocks and by reducing labor and the required amounts of power wiring and connections. The power controller also is designed to provide super operating performance through improved heat dissipation and an enhanced temperature warning and shutdown system.

In some implementations, the power controller may be utilized in industrial power applications in which high-voltage, high-amperage single or three-phase power is regulated and supplied (e.g., 120 to 575 VAC at 100 to 1200 A). For example, the power controller may provide an interface between a power generating facility and electrical equipment. The power generating facility may include a user-owned power generator or other power source for supplying power (e.g., poly-phase power) to the electrical equipment. The electrical equipment may include industrial machinery (e.g., power generation equipment, automotive finishing systems), manufacturing equipment (e.g., thin film manufacturing equipment, glass manufacturing equipment), and/or support systems such as heating systems (e.g., IR heating equipment, portable spot-heating equipment, ovens, kilns, environmental chambers, furnaces) and cooling systems (e.g., air conditioning systems, refrigeration systems).

To regulate power, for example, by muting each separate phase of poly-phase power, a power controller typically must include some type of switching mechanism. As shown in FIG. 1, the power controller includes one or more silicon controlled rectifier (SCR) switching devices for regulating power. While other solid-state devices may be utilized, SCR devices are preferable due to their fast cycle times and ability to modulate small amounts of power to a load allowing close temperature control.

The power controller may be configured to operate in single-phase and/or three-phase applications. For some single-phase applications, the power controller may include a SCR switching device having one pair of SCRs connected in inverse parallel to control the power output through a single current path or leg. For some three-phase applications, the power controller may include two SCR switching devices to control the power output through two legs of a three-wire load, i.e., a three-phase two-leg application. For other three-phase applications, the power controller may include three SCR switching devices to control the power output through all three legs of a three-wire load or three legs of a four-wire load, i.e., a three-phase three-leg application. Examples of three-wire load configurations include a delta load and an ungrounded WYE load. An example of a four-wire load configuration is a WYE load having a center point connected to ground.

The power controller may be implemented to control each SCR switching device in one or more modes. In most implementations, the power controller may utilize zero crossover control so that the SCRs gate only when the voltage across the SCR is zero. Examples of zero crossover control include On/Off firing, time proportional firing, and demand oriented transfer (DOT) firing. In On/Off firing, the SCR is triggered and power is supplied to the load whenever an input signal is present. In time proportional firing, the SCR is triggered when the voltage of the SCR goes positive. Proportioning the time that the SCRs are on verses the time they are off controls power to the load. DOT firing is similar to time proportional firing with the notable exception that the time base is not fixed. Reducing the time base to the minimum time base required to give the desired percentage output provides improved controllability. Accordingly, DOT firing is advantageous for applications where consistent heater and/or process control is critical.

In some implementations, the power controller may utilize a non-zero crossover control such as phase angle firing. In phase angle firing, the amount of power to the load is controlled by turning on the SCRs at different points in the AC cycle. The power controller may include current limiting features for maintaining a safe current level and soft starting features for slowly bringing the output voltage up to steady state upon power up.

In general, the power controller may include a firing package for controlling the SCR switching devices and/or other functions described herein. For example, the firing package (not shown) may include outputs connected to the respective gate input of each SCR switching device . Control or gate inputs for each SCR switching device may be supplied as inputs to the circuitry within the firing package, which, in turn, produces gating signals supplied as inputs to the SCR switching devices to gate the SCRs into conduction at the proper times.

In one embodiment, the firing package of the power controller may includes a “trigger” board (not shown) mounted on each of the SCR switching devices . The trigger board may contain the line voltage (e.g., 480 VAC, 575 VAC, etc.) used for firing the SCR device . Accordingly, the line voltage may be kept under the cover of a touch safe unit. The trigger board also may be provided with break-off tabs for allowing the trigger board to be sized for different sizes of SCR switching devices . In one implementation, the break-off tabs allow the trigger board to be sized and mounted to any one of four different sizes of SCR switching devices .

In one embodiment, the firing package may include a control board that allows selection of various control options. For example, the control board may allow the option of selecting an operating mode, such as proportional control and/or shorted SCR detection. In some implementations, a “plug and play” card incorporated with the power control board may be used to implement these features. Additionally, the control board may allow selection of single-cycle or three-cycle control. In some implementations, a jumper module may be used to implement this feature. For example, the jumper module may be used to convert a three-phase, three-leg shorted SCR detection board to either a three-phase, two-leg, or a single-phase shorted SCR detection board.

When conducting current, a voltage drop may be developed across the SCR device . This voltage drop generates heat (wattage equals amperage multiplied voltage drop) that must be dissipated to avoid damage to the components of the power controller. In the embodiment of FIG. 1, the power controller is structured and arranged to provide improved heat dissipation. As shown, the power controller includes a heat sink , upon which the SCR device is mounted. The heat sink includes a base and a plurality of spaceport fins , only one of which is shown here, for distributing heat. The heat sink may be constructed of stainless steel or any other suitable material.

The power controller also includes a fan installed at one end for drawing cooling air into the power controller . In some implementations, the power controller may include a step-down transformer (not shown) mounted on or above the heat sink and/or within the confines of a “touch safe” area. The step-down transformer may supply voltage to the fan (e.g., 120 or 240 VAC) and low voltage to the main board of a power supply, while drawing power from a voltage line.

The fan may be housed within a fan bracket . The mounting of the fan within the fan bracket , however, may limit the direction of the airflow provided by the fan . In order to direct the cooling air to where it is most needed, the power controller includes an air guide mounted to the base of the heat sink . The air guide completes a plenum chamber for forcing cooling air toward the heat sink . Namely, the sides of the fan bracket and the air guide may form a plenum chamber for the air from the fan . The percentage of cooling air directed from the fan to the fins of the heat sink can be increased or decreased by bending the portion of the air guide that forms the plenum chamber either up or down. As shown in the embodiment of FIG. 1, the air guide is bent at a 60° angle such that approximately 65% of the cooling air is forced through the heat sink fins and the remaining cooling air is directed on top of the heat sink .

As indicated by the direction arrows, the air guide divides the cooling air to force air over the base of the heat sink for cooling other components of the power controller . The use of the air guide in conjunction with the fan may cool critical parts on or above the heat sink , for example, the SCR switching device , the bus bars , and connectors mounted to the SCR switching device , and/or any other components mounted on or above the heat sink . While other functions of the bus bars , will be described in greater detail below, the bus bars , also function to dissipate heat within the power controller . In particular, the bus bar is mounted to the SCR switching device such that when cooled by the forced air, the bus bar dissipates heat from the SCR switching device .

The air guide also divides the cooling air to force air through the fins of the heat sink . Namely, the air from the lower portion of the fan is used to cool the heat sink fins . In general, the heat sink will offer greater resistance to the flow of air from the lower portion of the fan than to the relatively unobstructed flow of air from the upper portion of the fan. The air guide contains the air from the lower portion of the fan and thus forces cooling air through the heat sink cooling fins to ensure that sufficient cooling air passes.

The power controller also includes a ventilated back plate for exhausting the cooling air that passes over the top of the heat sink . The ventilated back plate also may be arranged as a structural member for pinning one or more heat sinks together. That is, in some implementations (e.g., two-leg configuration, three-leg configuration), the ventilated back plate may be secured to the bases of multiple heat sinks using pins inserted through drilled holes, for example. Each side plate (shown in cutaway view) of the power controller may mount to an adjacent side of the heat sink , the fan bracket , and the ventilated back plate to provide a rigid assembly.

This design minimizes inventory and cost as a single size heat sink may fund applicability in a variety of applications. Namely, one heat sink may be used for single-phase applications, two identical heat sinks may be used for three-phase two-leg applications, and three identical heat sinks may be used for three-phase three-leg applications. Accordingly, the need for large heat sinks or heat sinks of various sizes, which typically have been employed for two and three-leg power controllers, may be eliminated.

Referring to FIG. 2, a front view of one embodiment of a three-phase two-leg power controller is illustrated. As shown, the power controller includes three fans mounted within a fan bracket for supplying cooling air through the power controller . In some implementations, the fans may include wire fan guards for providing protection from the blades of the fans .

In this embodiment, the power controller includes two identical heat sinks shown behind the fans . Each of the heat sinks includes a plurality of fins extending from the base of the heat sink . The air from upper portions of the fans may be directed over the top of the heat sinks to cool components mounted on or above the heat sink . The air from lower portions of the fans may be directed through the heat sink fins .

The power controller also includes two identical bus bars and two identical bus bars . Adjacent sides of each of the two heat sinks may be secured together by pins, for example, to provide heat dissipation. In addition, the fan bracket may be used to secure the heat sinks together. The side plates of the power controller may mount to adjacent sides of the heat sinks and the fan bracket . In some implementations, a bar or other metal piece, extending from the fan bracket, for example, may be used to tic the heat sinks to each other.

Referring to FIG. 3, a rear view of one embodiment of a three-phase two-leg power controller is illustrated. As shown, the power controller includes two identical heat sinks . Each of the heat sinks includes a plurality of fins extending from the base of the heat sink . The power controller also includes two identical bus bars and two identical bus bars . Adjacent sides of each of the two heat sinks may be secured together by pins, for example, to provide heat dissipation. In addition, the ventilated back plate may be used to secure the heat sinks together. The side plates of the power controller may mount to adjacent sides of the heat sinks and the ventilated back plate .

As shown in FIG. 3, the ventilated back plate may include a plurality of exhaust holes for allowing forced air to exit the power controller . In this embodiment, for example, air from multiple fans (e.g., fans of FIG. 2) may be directed over the top of the heat sinks to cool components mounted on or above the heat sinks and may be directed through the fins of the heat sinks .

Referring to FIG. 4, a top view of one embodiment of a three-phase two-leg power controller is illustrated. As shown, the power controller includes two identical heat sinks , each with identical SCR switching devices and bus bars ,. Adjacent sides of each of the two heat sinks may be secured together by pins, for example, to provide heat dissipation for both of the SCR switching devices . In addition, the fan bracket and ventilated back plate may be used to secure the heat sinks together. The side plates of the power controller may mount to adjacent sides of the heat sinks , the fan bracket , and the ventilated back plate . In some implementations, a bar or other metal piece, extending from the fan bracket, for example, also may be used to tie the heat sinks to each other.

As shown in FIG. 4, the ventilated back plate may include a plurality of exhaust holes for allowing forced air to exit the power controller . In this embodiment, for example, air from multiple fans (e.g., fans of FIG. 2) may be directed over the top of the heat sinks by the air guide to cool the SCR switching devices . The openings in the top of the fan bracket are for wiring. The air also may cool other components mounted on or above the heat sink such as, for example, bus bars , bus bars , and power connectors (not shown). The connectors and connectors , respectively, may connect the bus bars and the bus bars to a spike protection element mounted on the heat sink .

The power controller also may include a semiconductor temperature sensor mounted to the heat sink . In general, the temperature sensor provides improved accuracy (e.g., within ±3° F.) over a traditional thermostat. In one embodiment, the temperature sensor may include a crimp lug for potting the semiconductor sensor and providing a convenient way to monitor the temperature of the heat sink . The temperature sensor may be mounted to the heat sink in close proximity to the location where the SCR switching device is mounted.

In one implementation, the temperature sensor may sense the temperature of the heat sink and, in response, interact with circuitry to provide a warning signal (e.g., alarm). The warning signal indicates that the temperature is approaching a condition that will shut down the power controller . The warning signal may provide sufficient time for allowing the operator to take corrective actions to prevent an uncontrolled shutdown and/or for allowing the operator to perform an orderly shutdown.

In other applications, for example, in two-leg or three-leg applications having multiple identical heat sinks , a temperature sensor may be used on each heat sink . In such cases, each one of the temperature sensors detects the temperature of a corresponding heat sink and may trigger the warning signal and/or shutdown if necessary. While the temperature sensor may provide advanced warning of an approaching dangerous condition, there still may be times when an immediate shut down is warranted. Accordingly, the power controller also may be equipped with an emergency shut down contact for interrupting power output. In some cases, the emergency shut down may be initiated from a location remote from the power controller .

In addition to those described above, the power controller may employ further protective features. For example, a fuse may be connected between an associated SCR device and a bus bar . The fuse may be configured to protect the SCR device , for example, by interrupting the power flow if the equipment begins drawing excessive current. In some implementations, the fuse may include I2t fusing for providing over-current protection. In general, the SCR device may have a low transient thermal capacity and may be quickly damaged by high fault currents. A fuse configured with I2t fusing is ultra current limiting and well suited to protect against such faults. Because a fuse including I2t fusing typically may not be designed to protect the load, however, sub-circuit fusing specifically designed for load protection may be included. For example, sub-circuit fusing with a blown fuse indication may be included.

The power controller also may include shorted SCR detection designed to identify when a SCR switching device has failed in the shorted mode. In some implementations, a “plug and play” card may be incorporated into the firing package of the power controller to provide shorted SCR detection functionality. A light emitting diode (LED) and contact closure, for example, may be used to signal this condition.

Referring now to FIGS. 1-4, the power controller is designed to provide convenience in installation and wiring by eliminating the need for separate power distribution blocks and by reducing labor and the required amounts of power wiring and connections. The design of the power controller allows power wiring and load wiring to enter and exit from either end of power controller . This feature can greatly simplify the design of the panel layout in the enclosure and may result in a smaller enclosure being used.

As described above, the power controller may be used in industrial applications as an interface between a power generating facility and electrical equipment. In such implementations, the power controller receives power supplied from the power generating facility and regulates the distribution of power to load circuits of the electrical equipment. In general, power wiring may be used to make the necessary electrical connections between components of the power generating facility and components of the power controller as well as to make electrical connections among components of the power controller . Load wiring may be used to make the necessary electrical connection between components of the power controller and one or more load circuits in order to distribute power.

As shown in FIGS. 1-4, the bus bars , include face plates and mounting plates The face plates and mounting plates each include a plurality of holes for attaching wiring terminals or other components to the bus bars , and/or for mounting the bus bars , within the power controller . In some implementations, power wiring and/or load wiring may be threaded through the holes and attached to various components within the power controller .

In general, the bus bars , are mounted within the power controller such that wiring may enter and/or exit from either end of the power controller . For example, the face plates may be mounted parallel to and at least partially above the side plates of the power controller so that wiring attached to the bus bars , may enter and/or exit the power controller from either end. In some implementations, the bus bars , may be mounted at right angles (not shown) such that wiring may enter and/or exit either side of the power controller . Accordingly, power wiring and/or load wiring may enter and/or exit from either end and/or either side of the power controller . Furthermore multiple load circuits may be connected to the power controller from either end and/or either side of the power controller .

In some implementations, for example, NEMA standard two hole copper crimp lugs may be used in securing lugs to the bus bars , and in securing wire in a crimp lugs. While other materials may be used, NEMA standard two hole copper crimp lugs provide superior connections while providing space not possible with compression type lugs that accept various size wires. Additionally, in some implementations an insulator may be provided between bus bars , that is held in place by the bus bars , and SCR switching devices requiring no screws or other hardware.

The design of the power controller also allows power distribution to be provided directly from the bus bars ,. For example, a power connection lug may be mounted to the bus bar and/or the bus bar for distributing power. This feature eliminates the need for separate power distribution blocks and associated wiring and connections and may save two or three times the space of the power controller itself. Furthermore, by minimizing the number of components and connections, the cost is reduced and reliability is increased for the power controller .

FIGS. 5A and 5B illustrate one embodiment of bus bar and FIGS. 6A and 6B illustrated one embodiment of bus bar . In most implementations, the bus bars , may be constructed of plated copper, for example, tin-plated copper. While other materials may be used, tin-plated copper exhibits less corrosion and heat build-up than materials such as plain copper or aluminum.

As shown, each of the bus bars , respectively includes a face plate a mounting plate ,, and a plurality of holes for mounting, connecting, and/or routing purposes. In one implementation, the bus bars , are structured to be used with multiple connectors of various sizes, for example, ranging from #8 AWG to 500 MCM. The bus bars , may allow entry or exit of such connectors from either end when mounted within a power controller. In addition, the bus bars , may be designed to provide direct power distribution, thus eliminating the need for separate power distribution blocks and associated wiring and connections.

Referring to FIG. 7, a power controller assembly may be constructed by attaching a removable cover to the power controller . The power controller assembly is designed to be “touch safe”—that is, the cover provides protection from components of the power controller that become electrically hot during use.

In general, the cover has a top surface , opposed side surfaces , and opposed end surfaces . As shown, the side surfaces each include partial sides for accommodating and engaging the fan bracket , the back plate , and the side plate of the power controller when the cover is attached. The side surfaces also may include locking members for engaging the power controller . When the cover is removed from the power controller , unobstructed access is provided to the bus bars , such that wires can enter and exit either direction of the power controller and power distribution may be provided directly from the bus bars ,.

FIGS. 8A-8C illustrate elements of one embodiment of an end surface of the cover . As shown, the end surface may be constructed from an end plate , an outer shell , and an insulator . In this embodiment, the end plate is secured to the outer shell by inserting pins into corresponding mounting holes In some implementations, corresponding surfaces of the outer shell may be integral with the top surface and side surfaces of the cover . As shown in FIG. 8B, for example, the side surfaces of the outer shell may include the locking members .

The end plate may include one or more windows for allowing wires to pass through the ends of the cover and attach to components of a power controller (e.g., bus bars ,). For example, power line wiring and/or load wiring may align with the windows and enter or exit either end of the power controller . In some implementations, the number of windows may be twice that which is normally used in a particular application, owing to the option of running wires in either direction.

Referring to FIG. 8C, an insulator may be used for covering the windows of the end plate . In some implementations, the insulator may include a gasket material such as, for example, styrene butadiene rubber (SBR) to seal the windows . The insulator includes slits cut to allow wires to pass. The slits may be held together with tape (not shown) on the back of the insulator . When the tape is removed, wiring may pass into the windows through the slits in the insulator . Unused windows remain taped to maintain the “touch safe” feature. The insulator also may include an adhesive for adhering to the back of the end plate .

FIGS. 9A and 9B illustrate a power controller assembly constructed by attaching the removable cover to the power controller . As shown, when the cover is removed from the power controller , unobstructed access is provided to the bus bars , such that wires can enter and exit either direction of the power controller and power distribution may be provided directly from the bus bars ,. It can also be seen that the location of the fuses are such that they can be readily removed without disturbing the wiring.

The windows may be designed to align exactly with the largest wires accommodated (e.g., 500 MCM). Smaller wires may be slightly offset in the window or may be bent slightly to align exactly in the center. In this embodiment, the cover includes eight windows for providing the option of running power wiring and/or load wiring from either end. In some cases, only half of the windows are used while the others remain sealed by tape on the back of the gasket material

In general, the design of the power controller is compact and readily assembled and results in a smaller footprint per amp, especially on touch safe designs. Accordingly, the size of the power controller may be substantially reduced, while still offering the highest level of performance and functionality.

A number of implementations have been described. Nevertheless, it will be understood that various modifications may be made and that other implementations are within the scope of the following claims.

CLAIMS

1. A power controller comprising: a first switching device; and a first bus bar mounted to the first switching device such that wiring may enter and exit the power controller, the first bus bar having a face plate extending at least partially above opposed side plates of the power controller and a mounting plate in electrical contact with the first switching device.

2. The power controller of claim 1, wherein the wiring may enter and exit ends of the power controller in a direction substantially parallel to the opposed side plates.

3. The power controller of claim 1, wherein the wiring may enter and exit sides of the power controller in a direction substantially perpendicular to the opposes side plates.

4. The power controller of claim 1, wherein the wiring comprises at least one of power wiring and load wiring.

5. The power controller of claim 1, wherein the power controller is configured to provide power distribution directly from the first bus bar.

6. The power controller of claim 1, wherein the first bus bar comprises a plated copper material.

7. The power controller of claim 6, wherein the plated copper material comprises tin-plated copper.

8. The power controller of claim 1, wherein the face plate of the first bus bar comprises a plurality of holes.

9. The power controller of claim 8, wherein the plurality of holes comprises holes of different sizes for accommodating connectors of different sizes.

10. The power controller of claim 10, further comprising one or more lugs mounted to the first bus bar.

11. The power controller of claim 10, wherein at least one lug comprises a two hole copper crimp lug.

12. The power controller of claim 10, wherein at least one lug comprises a power distribution lug.

13. The power controller of claim 1, wherein the first bus bar is electrically connected to one or more load circuits.

14. The power controller of claim 1, wherein the power controller is configured to supply at least one of single-phase power or three-phase power to using equipment.

15. The power controller of claim 1, further comprising a firing package for controlling the first switching device.

16. The power controller of claim 15, wherein the firing package comprises one or more plug and play cards.

17. The power controller of claim 16, further comprising a plug and play card for providing proportional control.

18. The power controller of claim 16, further comprising a plug and play card for shorted SCR detection.

19. The power controller of claim 15, wherein the firing package comprises a jumper module for selecting between single-cycle control and three-cycle control.

20. The power controller of claim 15, wherein the firing package comprises a trigger board mounted on the switching device.

21. The power controller of claim 20, wherein the trigger board contains a line voltage for triggering the first switching device.

22. The power controller of claim 20, wherein the trigger board is configured for use with different sizes of switching devices.

23. The power controller of claim 20, wherein the trigger board comprises one or more break-off tabs.

24. The power controller of claim 1, wherein the power controller is structured and arranged in at least one of single-phase configuration, a three-phase two-leg configuration, and a three-phase three-leg configuration.

25. The power controller of claim 1, further comprising a second bus bar mounted such that wiring may enter and exit the power controller, the second bus bar having a face plate extending at least partially above the opposed side plates of the power controller.

26. The power controller of claim 25, wherein the power controller is configured to provide power distribution directly from at least one the first bus bar and the second bus bar.

27. The power controller of claim 25, further comprising an insulator between the first and second bus bars that is held in place by the bus bars and the switching device.

28. The power controller of claim 25, further comprising: a second switching device; a third bus bar mounted to the second switching device such that wiring may enter and exit the power controller, the third bus bar having a face plate extending at least partially above opposed side plates of the power controller and a mounting plate in electrical contact with the second switching device.

29. The power controller of claim 28, wherein the power controller is configured to provide power distribution directly from at least one the first bus bar, the second bus bar, and the third bus bar.

30. The power controller of claim 28, further comprising a fourth bus bar mounted such that wiring may enter and exit the power controller, the fourth bus bar having a face plate extending at least partially above the opposed side plates of the power controller.

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