GB2103895A - Electronic controlling device for electrical equipment - Google Patents

Abstract

The inductive nature of transformers, motors and rotary converters is employed to detect the presence of an electrical load or short circuit at the secondary voltage terminals. A low voltage signal source is applied across the secondary voltage terminals of the transformer or windings. The frequency of the signal is chosen so as not to be significantly loaded by the impedance between the secondary terminals. A reduction in the amplitude of the signal source, occasioned by the application of an electrical load or short circuit to these terminals, causes connection of mains or primary electrical supply to the primary windings. The primary supply connection is maintained while secondary current flows, and is disconnected if secondary current ceases to flow for a prescribed interval. <IMAGE>

Description

SPECIFICATION Electronic controlling device for electrical equipment hereinafter referred to as the "device".

1)General The "device" consists of electronic circuitry and wiring constructed in the form of an electronic module or modules or forming part of a larger electrical system. The "device", when suitably connected to an appropriate item of electrical equipment, or forming part of such equipment, enables automatic switching on and off of mains electrical supply to the said equipment, without the need of additional or manual switches.

The "device" may be applied to a wide range of industrial electrical equipment for the purpose of achieving energy savings and reductions in operating costs, and offering increased standards of safety.

2) Applications The "device" enables the detection of the presence of an electrical load or short circuit at the secondary voltage terminals of electrical equipment, where the impedance at such terminals is inductive, and the resistance to direct current is in the order of, or less than, a few ohms.

The "device" is, therefore, suitable for use with transformers, motors and rotary converter, and is specifically intended for applications involving electric welding sets employing large single or multi-phase transformers. The primary windings of such transformers consume considerable amounts of power even when no load is attached to the transformer secondary. Since the act of attempting to strike an arc at the welding electrode imposes an electrical load or short circuit at the secondary voltage terminals of the welding set, the "device" thereby enables automatic switching of electrical power to the welding set as demanded by the welder operator.

The standby power losses resulting from continuous connection of the welding set to the mains supply are thereby eliminated.

Further, by detection of the flow of current in the secondary wiring, the "device" is able to ensure the maintenance of the mains supply for the duration of the welding process. When the flow of secondary circuit current ceases, indicating that welding has ceased, a timing circuit is initiated. If secondary circuit current is not detected again during the period of the timer, the mains supply is disconnected from the welding set. Detection of secondary circuit current resets the timer and mains supply is maintained to the welding set.

3) Principle of operation The "device" employs the inductive nature of transformers, motors and rotary converters to detect the presence of an electrical load or short circuit. A low voltage sinusoidal signal source is applied across the secondary voltage terminals of the welding set or electrical equipment. The frequency of the signal is chosen so as not to be significantly loaded by the impedance between the secondary voltage terminals. The application of an electrical load or short circuit to the said terminals, will cause a reduction in or loss of the high frequency signal. This is detected by appropriate circuitry causing mains supply to be connected to the welding set or equipment. Mains supply is maintained by timing circuitry initiated at this time. At the end of the predetermined time period, the mains supply is disconnected from the welding set.The timer is continuously reset by a control signal from circuitry monitoring the flow of current in the welding set secondary wiring, so that the mains supply is maintained while welding is in progress and thereafter for the period of the timer.

The "device" is equally suitable for use with AC welding sets and those incorporating rectifiers to provide a DC welding current.

4) Example application Refer to diagram figure 1 showing block schematic representation of a single phase AC welding transformer coupled to the "device" achieving automatic operation as described above.

Claims (Filed on 11 Aug 1982) The invention enables automatic connection and disconnection of the primary electrical supply to transformers, motors and rotary converters, to be controlled by the load imposed at the secondary voltage terminals, thereby eliminating the need for additional or manual switches.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (4)

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Electronic controlling device for electrical equipment hereinafter referred to as the "device".

1)General The "device" consists of electronic circuitry and wiring constructed in the form of an electronic module or modules or forming part of a larger electrical system. The "device", when suitably connected to an appropriate item of electrical equipment, or forming part of such equipment, enables automatic switching on and off of mains electrical supply to the said equipment, without the need of additional or manual switches.

The "device" may be applied to a wide range of industrial electrical equipment for the purpose of achieving energy savings and reductions in operating costs, and offering increased standards of safety.

2) Applications The "device" enables the detection of the presence of an electrical load or short circuit at the secondary voltage terminals of electrical equipment, where the impedance at such terminals is inductive, and the resistance to direct current is in the order of, or less than, a few ohms.

The "device" is, therefore, suitable for use with transformers, motors and rotary converter, and is specifically intended for applications involving electric welding sets employing large single or multi-phase transformers. The primary windings of such transformers consume considerable amounts of power even when no load is attached to the transformer secondary. Since the act of attempting to strike an arc at the welding electrode imposes an electrical load or short circuit at the secondary voltage terminals of the welding set, the "device" thereby enables automatic switching of electrical power to the welding set as demanded by the welder operator.

The standby power losses resulting from continuous connection of the welding set to the mains supply are thereby eliminated.

Further, by detection of the flow of current in the secondary wiring, the "device" is able to ensure the maintenance of the mains supply for the duration of the welding process. When the flow of secondary circuit current ceases, indicating that welding has ceased, a timing circuit is initiated. If secondary circuit current is not detected again during the period of the timer, the mains supply is disconnected from the welding set. Detection of secondary circuit current resets the timer and mains supply is maintained to the welding set.

3) Principle of operation The "device" employs the inductive nature of transformers, motors and rotary converters to detect the presence of an electrical load or short circuit. A low voltage sinusoidal signal source is applied across the secondary voltage terminals of the welding set or electrical equipment. The frequency of the signal is chosen so as not to be significantly loaded by the impedance between the secondary voltage terminals. The application of an electrical load or short circuit to the said terminals, will cause a reduction in or loss of the high frequency signal. This is detected by appropriate circuitry causing mains supply to be connected to the welding set or equipment. Mains supply is maintained by timing circuitry initiated at this time. At the end of the predetermined time period, the mains supply is disconnected from the welding set. The timer is continuously reset by a control signal from circuitry monitoring the flow of current in the welding set secondary wiring, so that the mains supply is maintained while welding is in progress and thereafter for the period of the timer.

The "device" is equally suitable for use with AC welding sets and those incorporating rectifiers to provide a DC welding current.

4) Example application Refer to diagram figure 1 showing block schematic representation of a single phase AC welding transformer coupled to the "device" achieving automatic operation as described above.

Claims (Filed on 11 Aug 1982) The invention enables automatic connection and disconnection of the primary electrical supply to transformers, motors and rotary converters, to be controlled by the load imposed at the secondary voltage terminals, thereby eliminating the need for additional or manual switches.