Method and device for obtaining power intended to supply a consuming appliance from a conductor traversed by an alternating electrical current
A method and a device are described for obtaining power intended to supply a consuming appliance from a conductor traversed by a primary electrical current, in which a core of magnetic material and a conductive solenoid wound about the core are positioned in a position remote from the conductor to obtain a secondary current in the solenoid from a magnetic field flux generated in the solenoid by the conductor, core and solenoid. The conductive solenoid is connected to the consuming appliance by a circuit adapted to convert the secondary current into a power intended to supply the consuming appliance through a related voltage and output current.
1. Method for obtaining power intended to supply a consuming appliance from a conductor traversed by a primary electrical current (I P ), said method being characterized in that it comprises the following steps:
placing, in a position remote from said conductor, a core of magnetic material and a conductive solenoid wound about said core to obtain a secondary current (I S ) in the solenoid from a magnetic field flux generated in said solenoid by said conductor, core and solenoid,
said conductive solenoid being connected to the consuming appliance ( 26 ) by conversion means adapted to convert said secondary current (I s ) into a power (P g ) intended to supply the consuming appliance through a related voltage (V dc , V ac ) and output current (I dc1 , I ac ), wherein the power (P g ) is produced to supply the consuming appliance through the related voltage (V dc , V ac ) and output current (I dc1 , I ac ) using the following steps:
transforming the secondary current (I S ) into an intermediate current (I dc ) using a transducer;
converting the intermediate current (I dc ) into a comparison voltage (V Idc ); and
comparing the comparison voltage (V Idc ) with a reference voltage (V ref ) to obtain the output current (I dc1 , I ac ) supplied to the consuming appliance;
when the power (P g ) supplied to the consuming appliance increases following the uncontrollable increase in the primary current (I P ) stopping the output current (I dc1 , I ac ) at a threshold value associated with an imposed current value (I SS1 ) that is lower, by a predetermined quantity, than a secondary saturation current value (I SS ) of the magnetic material of the core; and
when the power (P g ) applied to the consuming appliance increases following a further uncontrollable increase in the primary current (I P ), detecting the value of the voltage (V dc , V ac ) applied to the consuming appliance ( 26 ) and when said value reaches a predetermined limit value (V MAX ) letting an output current (I dc1 , I ac ) greater than said threshold value flow, causing saturation of the core and consequently a reduction in the power (P g ) applied to the consuming appliance.
2. Method according to claim 1 , wherein the step of checking when the output current (Idc 1 , Iac) reaches the first threshold value includes the step of determining when the voltage (Vdc, Vac) applied to the consuming appliance reaches a value close to a predetermined value (Vswitch).
3. A device for obtaining a power intended to supply a consuming appliance from a conductor traversed by a primary electrical current (I P ),
said device being characterized in that it includes:
a core of magnetic material and a conductive solenoid wound about said core and connected to the consuming appliance, said core and solenoid being positioned in a position remote from said conductor;
a conversion unit connected to the solenoid and intended to be connected to the consuming appliance;
said conversion unit being adapted to transform at least a portion of the magnetic field flux generated in said solenoid by said conductor, magnetic core and solenoid into power (P g ) intended to supply the consuming appliance without there being any electrical contact with said conductor;
said conversion unit including:
a converter adapted to receive a secondary current (I S ) associated with the power (P g ) generated from said magnetic field flux and to transform same into an output current (I dc1 , I ac ) supplied to the consuming appliance;
a current transducer arranged for receiving the intermediate current (I dc ) and converting same into a comparison voltage (V Idc );
an error amplifier connected to the current transducer that is adapted to compare said comparison voltage (V Idc ) with a reference voltage (V ref ) and to produce a comparison current (I ref ); and
a PWM module in a feedback loop with the error amplifier that is adapted to receive the comparison current (I ref ) and to produce the output current (I dc1 , I ac ),
and in that said conversion unit is arranged for:
when the power (P g ) supplied to the consuming appliance increases following the uncontrollable increase in the primary current (I P ), stopping the output current (I dc1 , I ac ) at a threshold value associated with an imposed current value (I SS1 ) that is lower, by a predetermined quantity, than a secondary saturation current value (I SS ) of the magnetic material of the core; and
when the power (P g ) applied to the consuming appliance increases following a further uncontrollable increase in the primary current (I P ), detecting the value of the voltage (V dc , V ac ) applied to the consuming appliance and when said value reaches a predetermined limit value (V MAX ) letting an output current (I dc1 , I ac ) greater than said threshold value flow, causing saturation of the core and consequently a reduction in the power (P g ) applied to the consuming appliance.
4. Device according to claim 3 , wherein the converter further includes:
a first division resistance (R 1 ) arranged in series with a second division resistance (R 2 ), said first and second division resistances (R 1 , R 2 ) being positioned on the non-inverting leg of the amplifier;
a first Zener diode arranged in parallel with the second division resistance (R 2 ),
said first and second division resistances (R 1 , R 2 ) and said first Zener diode being adapted to control the output current (I dc1 , I ac ).
5. Device according to claim 4 , wherein the converter further includes:
a third division resistance (R 3 ) positioned on the non-inverting leg of the amplifier;
a fourth division resistance (R 4 ) and a second Zener diode arranged in series with said fourth resistance (R 4 ), said fourth division resistance (R 4 ) and second Zener diode being linked between a connection point placed on the non-inverting leg of the amplifier between the first division resistance (R 1 ) and the current transducer and the non-inverting terminal of the amplifier;
said third and fourth division resistances (R 3 , R 4 ) and said second Zener diode being adapted to cause the output current (I dc1 , I ac ) to exceed a first threshold value associated with a secondary saturation current (I SS ) such as to saturate the magnetic material of the core.