FORM 2
THE PATENTS ACT 1970
(39 OF 1970)
&
THE PATENTS RULES, 2003
(See section 10 and rule 13)
COMPLETE SPECIFICATION
TITLE: A MODULAR HIERARCHICAL RF INDUCTION HEATING SYSTEMS.
NAME: DIPANKAR NATIONALITY: INDIAN
ADDRESS:
EE Department, HT Bombay, Powai Mumbai 400076
The following specification describes the invention and the manner in which it is to be performed.

FIELD OF THE INVENTION:
The present invention relates to an energy efficient process of RF induction system for high rating/power operations. More particularly, the present invention relates to RF induction system consisting of modular hierarchical design of capacitor banks for high rating operations.
BACKGROUND OF THE INVENTION:
RF induction heating systems have resonant L-C-R (Inductor - Capacitor -Resistor) circuit either in series or in parallel as shown in Figure 1 and Figure 2 respectively. The resistor (1) is primarily designed to be the 'load5 of the system. The inductor coil (2) is wound around the load/crucible while capacitor bank (3) is connected either in series or parallel to complete the resonant circuit. The voltage source (4) and current source (5) is connected to the induction heater consisting of the RF coil.
In conventional RF induction heating systems the 'Tank' capacitors are fewer in number and of high current rating. Each capacitor may be rated at 100-200A. This requires huge bus bars to connect the capacitors and possible water cooling arrangement to take away the heat and keep the capacitors cool Also there are series or parallel inductances in the circuit topology of RF induction systems. It is observed that due to high currents even small parasitic inductances produce significant voltage drops.
The RF Induction system also requires cooling arrangement for capacitors having high current ratings. The heavy bus bars also mean larger couplings required to connect the bus bars to the load coil, which further leads to drop in reactive voltage, which adversely affects the efficiency of RF induction systems.
There is a need to reduce parasitic and leakage inductances and parasitic resistances to improve the efficiency of RF induction system. Furthermore high rated capacitors require cooling arrangements. There is also a need to reduce cost of production of RF induction system. The said drawbacks associated with the art

are overcome with an energy efficient process of RF Induction system for high power operations.
OBJECTS OF THE INVENTION:
One of the main objects of the present invention is to provide an energy efficient process of RF Induction system for high power operations.
It is another object of the present invention to improve the overall energy efficiency of RF induction system.
It is another object of the present invention to provide even distribution of current in all the capacitors in the bank leading to energy efficient RF Induction system.
It is another object of the present invention to provide an energy efficient RF Induction system that reduces parasitic and leakage inductances.
It is another object of the present invention to provide an energy efficient RF Induction system that reduces parasitic inductances and resistances.
It is another object of the present invention to provide easy assembly/disassembly of RF induction system.
It is another object of the present invention to reduce cost of production of RF induction system.
It is another object of the present invention to improve cooling arrangements of capacitors of RF induction system and reduce cost of the system.
SUMMARY OF THE INVENTION:
The present invention relates to an energy efficient process of RF induction system for high rating operations. The proposed RF induction system uses modular hierarchical design of capacitor banks, i.e. arrangement of many low current rated capacitors in sub-assemblies in 'star' network which reduces parasitic and leakage inductances and improves efficiency of the system. Any

parasitic inductance is consumed in the overall inductance of the series L-C-R circuit.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS:
The present invention will be described in more detail hereinafter with the aid of the description which relates to preferred embodiments of the invention explained with reference to the accompanying schematic drawings, in which:
Figure 1 is Series-resonant L-C-R Circuit
Figure 2 is parallel-resonant L-C-R Circuit
Figure 3a is capacitor sub-assemblies in 'Star' network - 'Capacitor Sub-bank'
Figure 3b is Capacitor Sub-banks in 'Star' Assembly
Figure 4 is capacitor bank with toroidal current transformer in series
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT:
The foregoing objects of the present invention are accomplished and the problems and shortcomings associated with the prior art, techniques and approaches are overcome by the present invention as described below in the preferred embodiments.
The full overview of the arrangement of the invention is shown in Figure 3a, Figure 3b and Figure 4.
One embodiment of the present invention is the capacitor sub-assemblies as shown in Figure 3a and Figure 3b. The identical capacitor sub-banks (71, 72,
71 7n) are created by connecting several low current rated capacitors (31, 32,
31 3n) (say for example O.OluF / 2000V polyester capacitors) in parallel with
each other on high current bus bars (6) (typically Brass, Copper or other high conductivity metal rods) to create large current capacity banks as shown in Figure 3a. Each capacitor sub-assemblies are identical to each other as shown in

Figure 3b. 'Star' network topology is used for connecting capacitor several sub-
banks (71, 72, 71 7n), which reduces unevenness of current distribution across
the full capacitor bank. Each sub-bank acts as a 'super capacitor' arranged in a higher order of star network. Further the topology of connecting many identical
capacitors (31, 32, 31 3n) to form identical sub-banks results in low effective
series impedance (resistance and inductance) of each such identical sub-banks.
The arrangement of the identical capacitor sub-assemblies (71, 72, 71 7n),
made from many smaller identical capacitors provides large surface area to the capacitor sub-banks. This large area is quite good for natural or forced air-draught cooling to keep them cooler. Further the sub-banks use non-water cooled capacitors (3), which are inexpensive as compared to the costly standard water cooled capacitors. Also the use of non-water cooled capacitor reduces the cost of cooling systems employed for cooling the standard water cooled capacitors practiced in the art.
The identical capacitor sub-assemblies (71, 72, 71 7n), are added to or removed
from the capacitor bank by fasteners. This modularity allows faster assembling/disassembling of capacitor assemblies during servicing. The modularity further eases the fault-finding of defective/shorted sub-assemblies.
In another embodiment of the present invention as shown in Figure 4, the
capacitor sub-assemblies are connected in series with transformers which in turn
are connected to corresponding amplifiers. All amplifiers and transformers (10)
are driven in 'phase-sync' with one another. Each transformer adds series voltage
to the resonant circuit and shares total power output. The identical capacitor sub-
assemblies (71,72, 71 7n) are excited using series voltage sources from one or
more toroidal current transformers (9). The coil / inductor (2) is made of a water cooled copper tube having several turns as the secondary winding. The coils of different designs (varying inductance) are connected with ease in the LC circuit using 'Swagelok' like water sealed couplings. The toroidal transformers (9) are slipped on the coil by opening the same 'Swagelok' couplings.

The inductor coil (2) gets heated due to large resonant current, hence the inductor
coil (2) is cooled using water or any other coolant fluid flowing through the
closed-looped coil having inlet (13) and outlet (14) as shown in Figure 4. The
coil is made of hollow copper tubes wound in close-circuit configuration, having
radiators, heat exchangers etc. present on it for effective cooling. The coolant is
being circulated through the coil with the help of a circulation pump. Coolant
also cools the high current bus-bars (8) to which the capacitors sub-assemblies
(71, 72, 71 7n) are attached.
Toroidal transformers (9) are made by winding a single primary layer on ferrite toroidal core, this helps reduce parasitic losses and leakage flux. Other core geometry such as UI or UU, may be used with less effectiveness.
Thus compact RF induction systems are created using integration of multiple
toroidal transformers (9), induction coil (2) and capacitor bank assembly (71, 72,
71 7n), Due to simplicity and modular nature of the design, use of non-water-
cooled capacitors and the standardization of the components the proposed
invention also reduces the total bill of material and hence the overall cost of
manufacture.
The foregoing descriptions of specific embodiments of the present invention have been presented for purposes of illustration and description only. They are not intended to be exhaustive or to limit the present invention to the precise forms disclosed, and obvious modifications remain possible, in particular from the point of view of the design of the various elements or by substitution of equivalent methods, without thus departing from the scope of protection of the invention.

I/We claim:
1. An energy efficient process of RF induction system comprising:
(a) identical capacitor sub-assemblies (71, 72,71......7n) are created by
connecting several low current rated capacitors (31, 32, 3, 3n) (such as
O.OluF / 2000V polyester capacitors) in parallel with each other on high current bus bars (6) (typically Brass, Copper or other high conductivity metal rods) to create large current capacity banks;
(b) identical capacitor sub-assemblies (71, 72,71 7n) are connected in 'star'
network topology on the main bus-bar (8) and are excited by using series voltage sources (such as by using one or more toroidal current transformers (9));
(c) The inductor coils of different designs (varying inductor 'L') are made of close-loop hollow copper tubes having several turns and are connected with ease in the LC circuit using quick release 'Swagelok' like water sealed couplings;
(d) toroidal transformers (9) are slipped on the coil / inductor (2) of the LC circuit using quick release 'Swagelok' like water sealed;
(e) coolant is circulated by using a circulation pump through inductor coil (2) made of hollow copper tube and the main bus-bar (8) through inlet (13) and outlet (14) to cool the same;
whereby each identical sub-assembly produces low series impedance (resistance and inductance), thus reducing parasitic losses and leakage flux thereby current is evenly distributed across full capacitor bank, increasing the efficiency of the system for high rating operations without hot spots.
2. The identical capacitor sub-assemblies (71, 72,71......7n) of RF induction
system as claimed in Claim 1 wherein identical capacitor sub-assemblies (71, 72,71......7n) gives large surface area for cooling.

3. The identical capacitor sub-assemblies (71, 72,71......7n) of RF induction
system as claimed in Claim 1 wherein capacitor sub-assemblies are added or removed to the capacitor bank using quick release mechanisms such as fasteners for high rating operations.
4. The torodial transformer of RF induction system as claimed in Claim 1 comprises of multiple transformers and amplifiers.
5. The torodial transformer of RF induction system as claimed in Claim 1 and Claim 4 wherein each transformer gets power from the corresponding amplifier connected to it.
6. The torodial transformer of RF induction system as claimed in Claiml and Claim 4 wherein each transformer adds series voltage to the resonant circuit and shares total power output.
7. The identical capacitor sub-assemblies (71, 72,71......7n) of RF induction
system as claimed in Claim 1 wherein identical capacitor sub-assemblies (71,
72,71......7n) are excited using series voltage sources by one or more toroidal
current transformers (9).
8. The coil / inductor (2) of the LC circuit of RF induction system as claimed in Claim 1 wherein the coil / inductor (2) is made of water cooled copper tube having several turns as the secondary winding.
9. The water cooled closed-loop coil having inlet (13) and outlet (14) of RF induction system as claimed in Claim 1 wherein coolant fluid is circulated using a pump through the close-loop hollow copper tubes having radiators, heat exchangers etc. to cool inductor coil (2) and high current bus-bars (8) to which the capacitors sub-assemblies (71, 72,71......7n) are attached.