|Title of Invention||
"AN ELECTRICAL LOAD CONTROL DEVICE"
|Abstract||An Electrical Load Control Device An electrical load control device which comprises a timer, an overload detection circuit and a static switch. The timer is connected to an input means, said input means is a combination of a start push button, stop push button and a set-time potensiometer mounted on a dial.|
|Full Text||FIELD OF INVENTION
The present invention relates to a device used as a switch suitable to control electrical equipment/appliance (hereinafter called as "load"). A very preferred example is the control of water-pump for domestic or industrial use. The invention more specifically relates to a device essentially comprising a combination of timer control along with static switch and overload detection to achieve a comprehensive performance in small size, low cost, interrelated protection and low power-consumption.
The invention is an electronic pump-equipment control device to achieve desired performance characteristics and advantages.
BACKGROUND OF INVENTION
Timer control of electrical load is a very well-known concept. Various kinds of timers are also commercially available for such purpose. The standard technologies for timer are: (i) electronic (ii) electromechanical (using synchronous motor) and (iii) pneumatic. All the above technologies have their own advantages and disadvantages and they are in use for different kinds of applications depending on their suitability. However, these timers have been limited to industrial/professional applications or high-cost appliances because of their higher cost. Moreover, these
timers by themselves are component products and are not usable as a stand-alone functionally-complete product for domestic or other low-cost applications such as household pump control. Similarly the use of overload protection in low-cost/domestic applications also suffers from certain disadvantages. Technically, three methods are used for overload protection (i) thermal (or bimetallic): which is the slowest, cheapest and least accurate (ii) magnetic : which is of medium speed and cost and also lacks in accuracy (iii) electronic : which is more complex and costlier than the other two but fastest and accurate. The cheap thermal overload protection is not reliable for protection of electronic circuit for its low speed. Magnetic overload is also not fast enough. But both these have extensive application in switch cum overload units where ON/OFF switch function is integrated with overload, This integration requires a solenoid coil, contact mechanism along with ON and OFF button mechanism.
Such electromechanical complexity increases the size and cost of the ON-OFF-OVERLOAD switch (also sometimes known as STARTER switch).
The present invention incorporates the electronic pverload technology with associated high-speed operation and high accuracy at a low cost and size by predetermined sharing of circuit-resources with the other circuit blocs such as Electronic Timer and Static-Switch.
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Moreover, with advancement of technology it is now possible to have the constituent circuit building blocks with "off-line" technology. This means the circuits may operate directly from line voltage (230V AC) without need of step down power transformer, rectifier etc. This reduces size, weight and cost of the circuit, making it more attractive to the user.
The present invention thus incorporates a novel product concept namely a device with a combination of electronic circuit blocks so that a number of major advantages are actualised by such combination.
Thus, one object of the present invention is a complete and convenient timer control for the user in a single unit.
Other object of the invention is to combine circuit function of electronic timer, static-switch and overload-detection so as to combine their functions effectively and complementarily to each other.
Another object of the invention is to combine the load-switching device (i.e. the static-switch in this case) for both timer ON/OFF and overload protection trip (switch-off) so as to save cost, size and component material.
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A further object of the invention is to share some circuit components for both timer control and overload detection to save cost, size and component materials.
A still further object of the invention is to use fast electronic overload protection to protect the components of the invention itself from short circuit or overload at the output as well as to protect the load (such as a pump motor) from further damage without using any slow mechanical movements such as relays or contactors.
A further object of the invention is to provide a complete control for an electrical load (such as pump) in one unit so as to achieve the following results:
(a) Timer, overload-detection and static-switch combined in single-unit construction of small size.
(b) Comprehensive switch and control so that no other equipment such as starter, overload relay or ON/OFF switch may be required.
(c) Cheap and affordable for the common user.
(d) Over-current/Short-circuit protected so that the invention is not prone to failure.
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(e) Light, feather-touch START,STOP switches.
The invention includes the following controls to the user (a) "START" push button (b) "STOP" push-button (c) "SETTIME" potentiometer on a calibrated dial. These are used to (i) Start or switch on the load; (ii) Stop or switch-off the load manually, if required; (iii) Set the time interval over which the switch will remain "ON".
Thus, according to the invention there is provided an electrical load control device essentially comprising a timer, an overload detection circuit and a static-switch, said timer being connected to an input means, said input means being a combination of a start-push button, stop, push-button and a set-time potentiometer mounted on a dial.
The present invention provides an integrated load control device with combined timer, overload detection and static switch which essentially consists of an Electronic Timer, "START" push-button, "STOP" push button "SET TIME" potentiometer on a dial, a Static-Switch and an overload detection circuit along with a current-transformer (CT) wherein
said "SET-TIME" potentiometer and "START" push-button and "STOP" push-button are connected to the Electronic Timer as inputs.
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said Electronic Timer comprise of low-power IC-basd oscillator-counter of standard circuit configuration.
said Static Switch comprise of solid state AC-switch (such as triac or back-to-back thyristor) and a driver circuit which closes or opens the current path of an AC load on the basis on ON or OFF command by a voltage-signal at its input.
said overload-detection circuit comprise of low-power IC-based comparator and internal reference voltage source (such as a zener) of standard circuit configuration.
The invention will now be described in detail with reference to drawing accompanying the (Provisional Specification.) It is original specification- socity it.
Fig. 1 shows the functional circuit blocks and associated components along with the interconnections.
With reference to the above drawing, the operation of the load control may be described as follows.
The user sets the time interval (to be powered "ON") by setting the knob of the potentiometer (1) on the appropriate position on the calibrated dial. The setting
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Electrical processor changes the internal resistance of the potentiometer such that the oscillator-counter circuit of the Electronic-Timer (4) produces the appropriate time-interval at its output. It may also be mentioned here that the time-interval setting may also be achieved digitally by digital thumb-wheel-switches.
The output of the Electronic Timer are two voltage levels for ON and OFF which are shown as two separate lines for clarity of representation. This output normally remains in the "OFF" condition. As soon as the user pushes the START push-button, the output of the Electronic Timer becomes "ON" This output remains in this state of "ON" during the period of the time-interval which is set by the SET-TIME potentiometer. If the user pushes the "OFF" push button within this interval, the output of the Electronic Timer goes back to the OFF state instantaneously. Otherwise, after elapse of the time interval, as set by the SET-TIME potentiometer the output of the Electronic Timer reverts back to the "OFF" state.
The output of the Electronic Timer is connected to the input of the Static-Switch (5). This input is to enable or control input of the driver which triggers the solid-state AC switch such as a triac or back-to-back thyristors. So,
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when the output of the Electronic Timer is ON, the drive triggers the AC-switch, the current path for the external load is closed and the load, properly connected to mains as shown in Fig.l, becomes energised. When the output of the timer reverts to "OFF" state, the driver ceases to trigger the AC-switch which becomes "OFF" or open clarical error The load gets disconnected from the mains. A variation of this invention may be made by using a relay/contactor instead of a Static-Switch which would be inferior in performance such as speed, life-expectancy or safety against short circuit at the load. However, certain advantages of combined performance (of timer, over-load detection and load-switch) will still remain available.
There is a current transformer CT (9) on the current clarical error path which senses the amount of current passing through the static-switch to the load. This sensed value is an input to the overload detection circuit (8). This input is compared to an internal reference generated in the detection circuit. This reference corresponds to the maximum value of the current which may safely pass through the static switch and which is also the rating of the particular unit of this present invention as printed-on information to the user. Consequently, this maximum value of the current is also the maximum set value for the load (such as a pump motor) as per the proper
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choice of the user. If this maximum value is exceeded, the comparator of the overload detection circuit produces an output voltage level which is interpreted as TRIP (or shut-off) for the load. This voltage-level is applied to the input of the Static-Switch as OFF as shown in FIG.l. Consequently the driver-circuit of the Static-Switch cease to trigger the AC-Switch and the switch opens and the load current is shut-off.
The invention described hereinabove is only by way of an example. The obvious modification and/or alteration of the component parts or assembly will be well within the knowledge of a skilled person and will thus fall within the purview of this invention.
1. A stand-alone bad control device adaptable to electronic appliances, in
particular electronic appliances, in particular electronic pumps, the device
- as electronic timer comprising an oscillator-counter;
• atleast two push buttons and a potentiometer connected to the electronic timer as inputs;
- an overload detection circuit comprising a comparator and having
an internal voltage source;
a current transformer disposed on the current-path for sensing the value of the passing current, characterized in that
- a static switch having a driver circuit is disposed in the device
circuit configuration which closes or opens the current path of the
toad of the pump in correspondence with the voltage signals beings
being transmitted by the electronic timer.
2. The device as claimed in claim 1 wherein said electronic timer comprises a low-power IC-based oscillator connector of standard circuit configuration.
3. The device as claimed in claim 1 where in said static switch comprises a sold state AC-switch and the driver which closes or opens the current path of an AC load on the basis on ON or OFF command by a voltage signal at its input
4. The device as claimed in claim 1 wherein said atleast two push buttons comprises a start push-button, and a stop push-button.
5. The device as claimed in claim 1, wherein said potentiometer comprises a set-time potentiometer set on a dial.
6. The device as claimed in claim 1, wherein said over-load detection circuit comprises of a tow-power IC-based comparator and initial reference voltage source of standard circuit configuration.
7. The device as claimed in claim 3, wherein said solid state AC-switch comprises triac or back-to-back thyrlstors.
8. The device as claimed in claim 5 wherein said internal reference voltage source means a zener or equivalent.
9. A stand-lone load control device adaptable to electronic appliances, in particular electronic appliances, in particular electronic pumps device substantially as herein described with reference to the drawing accompanying the provisional specification.
An Electrical Load Control Device
An electrical load control device which comprises a timer, an overload detection circuit and a static switch. The timer is connected to an input means, said input means is a combination of a start push button, stop push button and a set-time potensiometer mounted on a dial.
|Indian Patent Application Number||1445/CAL/1998|
|PG Journal Number||13/2007|
|Date of Filing||12-Aug-1998|
|Name of Patentee||SIGNOTRON (INDIA) PVT LTD.|
|Applicant Address||NO J-6 BLOCK-EP ,SECTOR V,SALT LAKE ELECTRONICS COMPLEX CALCUTTA 700091|
|PCT International Classification Number||H 02 H 9/00|
|PCT International Application Number||N/A|
|PCT International Filing date|