ITMI20011215A1 - CIRCUITUAL ARRANGEMENT TO SUPERVISE AN ELECTRIC LOAD - Google Patents

Description

Description of the industrial invention entitled: "Circuit arrangement for monitoring an electrical load"

Summary of the finding

The invention relates to a circuit arrangement for monitoring an electrical load (10) on a network (12) and for controlling the network switch (14, 20), where the load (10) is arranged galvanically separated from a switching device (50) overseer. This switching device (50) also has associated at least one sensor (30) of the characteristic operating values, at least one memory device for characteristic values of the load properties (10) and at least one further memory device. In the further memory device, with the initialisation of the switching device (50) and / or during monitoring, it is possible to store characteristic operating values of the load (10). The operating mechanism of the mains switch (14, 20) is designed in such a way that it opens when a predetermined operating characteristic value is reached or exceeded.

(Figure 1)

Description of the finding

The invention relates to a circuit arrangement for monitoring an electrical load on a direct current or alternating current electrical network and for controlling the network switch. The mains switch must be controllable via potential-free contacts and can preferably be implemented as a relay. A typical use for the invention is, for example, considered a circuit arrangement for controlling relay outputs in the case of a motor drive device for a power switch or for a motor protection switch. It is known to carry out circuit arrangements of this type as an amplifier module (DE 196 27 295 A1). The control of the amplifier module in this case takes place with an input signal of 24 VDC. The input signal can be produced directly by a switch, by a programmable controller with memory (SPS) or externally via a data bus. A relay with potential-free contacts is controlled with this signal.

This arrangement has drawbacks. When controlled via conventional relay outputs, the single-phase motor drive unit is exclusively switched on or off. However, the complicated mechanical structure of a motor drive device can lead to malfunctions over time, which can lead to overload. To detect the overload in accordance with the current state of the art, a semiconductor output with associated control and measuring section is used instead of a relay output. With this solution there is no longer any galvanic separation from the motor.

Also known is a module for a motor operator (US 5,657,193) which, when certain pre-assignable operating values, i.e. static, are exceeded, in the event of a short-circuit or in the event of an incorrect current, causes the motor to be switched off. The module cannot be used for dynamic monitoring of operating states.

The invention has the task of indicating a switching device for controlling the load with galvanic separation, with which it is possible to continuously monitor the load conditions and disconnect the load when an admissible operating value is exceeded.

The essential element of the invention is a switching device for monitoring an electrical load on a network and for controlling the network switch, where the load is disposed galvanically separated from the monitoring device. This switching device also has associated at least one operating characteristic value sensor, at least one (first) memory device for load property characteristic values and at least one (second) memory device. In the second memory device, with the initialisation of the switching device and / or during monitoring, it is possible to store characteristic operating values of the load. The control of the mains switch is designed in such a way that the mains switch opens when a predetermined operating characteristic is reached or exceeded.

Both static and dynamic operating parameters are considered as characteristic operating values of the load.

Further embodiments of the invention are formulated in the subordinate claims.

In particular, as an invention it is proposed to indicate a motor operator with galvanic separation and variable voltage supply, with which the load conditions of the drive device are continuously monitored and / or signaled (preferably via a field bus). motor, and with which, in the event of motor overload, the motor drive device is switched off via a relay.

The relay output is controlled by the switching device (microprocessor or discrete structure circuit). The microprocessor can be controlled via a 24 VDC input. The switching device preferably comprises a data interface (e.g. to a data bus), at least one information memory, a data entry element (e.g. a keyboard) and a data output device (e.g. a display). The control of the mains switch in the form of a relay output can take place via software instructions via a digital input or via a data interface (serial). The operating data of the load is monitored continuously via the switching device and saved after a preselectable monitoring status has been assigned. The operating data is preferably determined by means of a current sensor. The switching device is set to overload protection. The setting can be done as programming or fixed setting (as ASIC). In operation, the circulating current is compared with the maximum permissible limiting current respectively and, in the event of an overload, the mains switch is opened, i.e. the relay is activated and thus the relay contacts are opened.

For initialisation by a user, the characteristic values of the load properties (eg the type of motor drive) menu driven can be entered via the user interface. The type of overload protection is automatically assumed by a presetting from the switching device (eg by a microprocessor). The user can also configure the overload protection by entering the operating voltage and the type of load operation (direct current, alternating current, inductive load, purely ohmic load, etc.). From the plurality of possible presettings of the switching device, the corresponding maximum current for controlling the mains switch is automatically associated. The current is monitored continuously or at pre-established intervals. The cadence can be set either as a fixed cadence (for example 800 μsec) or as a free cadence. Thus, for example, the starting current of a motor drive device can be stored as a characteristic. When the overload current is reached or exceeded in any instant or in one or more pre-assignable instants, the mains switch is opened. At least, an operational status signal is expected to occur when pre-assignable operating values are reached or exceeded during monitoring. The signaling can also be correlated with a storage of signaling data in a memory.

Short-circuit protection of the load is implemented in a conventional manner, for example with the aid of a safety device.

Further embodiments of the invention are indicated below:

the switching device is implemented as a microprocessor, as an integrated circuit or as a programmable command from memory. For example, the switching device can be implemented as an intelligent control in accordance with DE 19835 506 A1.

The switching device comprises control means for controlling the voltage supply of the load. With a control of the load voltage supply, the voltage supply can be varied according to pre-assigned characteristic values.

The operating characteristic sensor is designed as a digital or analog converter. There are a number of sensor types suitable for this purpose. In relation to the invention it is essential that the sensor is connected without galvanic intervention.

Preferably, the operating characteristic value sensor is a current transformer. There is at least one memory device for signals transmitted by the operating characteristic values sensor. The switching device can be controlled and / or monitored by remote data transmission. The mains switch is designed as a relay. The switching device is designed as a motor drive. The switching device is integrated in an amplifier module for controlling motor drive devices.

Each load (for example a motor drive device) in new state has a known current consumption. The characteristic values of the properties in the new state also belong to the possible default setting of the switching device. During operation, therefore, it is possible to detect an elevated current, so that in this way it is also possible to determine variations in the characteristic values due to mechanical wear of the load. The determined data can be used for signaling and / or for switching off or switching.

The advantages obtainable with the invention consist in the fact that the relay output, free of potential and galvanically separated, is operated protected against overloads by means of corresponding parameterization (relative to rated current, type of load).

The invention is shown in detail on the basis of the figures.

In particular:

Figure 1 shows a first embodiment of the circuit arrangement according to the invention,

Figure 2 shows a second embodiment of the circuit arrangement according to the invention,

Figure 3 shows a third embodiment of the circuit arrangement according to the invention.

In Figure 1, an electrical load 10, for example a motor drive device for a power switch, is connected to the mains voltage 12 and can be separated from the mains by means of a switch 14, made as a relay contact, and the relative switching device actuation of the switch. The switch is operated by means of a magnetic system 20. The connection line 18 will indicate the possibility of controlling the supply voltage by means of a switching device 50. The magnetic system 20 of the relay is controlled by means of a relay input 24 of the switching device 50 performed as a microprocessor. The switching device 50 can in particular form part of an electronic control relay. The switching device 50 can also be associated with a digital input 52 (24 VDC) and in addition a data interface 54, with which it is possible to control the switching device 50. The drawing does not show in detail that the device switch 50 can also comprise further transient or fixed memories of the information and a user interface. The user interface may contain a data entry device (e.g. a keyboard) and a data output device (e.g. a display). The relay output 24 can be controlled via software instructions, via the input 52 or via a data interface (serial) 54. The switching device 50 continuously monitors the operating data of the motor drive unit, where the The operating data are compared with data which are stored after pre-assignment of different preselectable monitoring states in the switching device 50. The operating data in this exemplary embodiment are determined in the form of the load current of the relay 14, 20 by means of a current sensor 30. In this case, the current is compared with the maximum permissible limit current respectively and in the event of an overload the relay output 24 is switched off (when the limit value is reached or exceeded). The current sensor 30 can be implemented as a current transformer or as a Hall sensor and is fed to an A / D converter in the switching device 50 which acts as a microprocessor.

The initialisation of the switching device 50 on protection against overload can be carried out as programming, or it takes place by transferring data via the serial interface (field bus) or by inserting it at the user interface.

The embodiment, shown in Figure 2, of the circuit arrangement according to the invention can be used as an arrangement for protecting single-phase motor drive devices 10.1 and 10.2 (not shown in detail) (for example for power switches). In this case the magnetic relay systems 20.1 and 20.2 for the mains switches 14.1 and 14.2 are always and only controlled individually. Therefore it is possible to monitor the magnetic relay systems 20.1 and 20.2 with only a single current sensor 30.1. The arrangement according to Figure 2 can be implemented as an integrated amplifier module. In the circuit arrangement shown in Figure 3, the mains switch 14, 20 is designed as a four-pole relay or small contactor with the relay contacts 14 and the magnetic system 20 controlled by the switching device 50.1. By means of the mains switches 14, 20 also here a load, indicated with the identification mark 10, can be connected to a three-phase mains 12 with neutral conductor. The current flow through the load 10 is controlled by means of a sum current transformer 17. The sum current transformer 17 with its output via a ballast resistor 16 is carried on a single-pole relay contact 15 operated by a relative magnetic system of relay 21. The additional relay output 24.1 of the switching device 50.1 is permanently activated to keep the relay contact 15 closed. The sum current, detected by the current sensor 30, of the sum current transformer 17 is fed to the switching device 50.1 for evaluation.

The circuit arrangement according to Figure 3 therefore serves to monitor ground faults. The relay output 24.1, to be marked in the classical sense, of the switching device 50.1, designed for example as an electronic control relay, can be used as an analog input for further information thanks to its permanently closed state. The measured values recorded by the current sensor 17 by means of the switching device 50.1 can be compared with parameter values or with limit values, which are communicated via, for example, a keyboard or a serial interface 54. When the parameter values are exceeded (e.g. example amount and delay time) by the sum current detected, in the manner already described with reference to Figure 1, the load 10 is disconnected by means of the mains switch 14, 20 in the sense of an earth leakage disconnection.

Claims (13)

Claims 1. Circuit arrangement with a switching device (50; 50.1) to monitor an electrical load (10; 10.1; 10.2) on a network (12) to control a network switch (14, 20; 14.1, 20.1; 14.2, 20.2 ) of the load (10; 10.1; 10.2), where the load is galvanically separated from the monitoring device (50; 50.1) and the switching device (5) are also associated: at least one sensor (30; 30.1) relevant operating characteristic values of the load (10; 10.1; 10.2), at least one memory device for characteristic values of the load properties (10; 10.1; 10.2), at least one memory device, in which, upon initialization of the switching device (50) and / or during monitoring, it is possible to store characteristic operating values of the load (10; 10.1; 10.2), where the switching device (50; 50.1) opens the circuit breaker network (14, 20; 14.1, 20.1; 14.2, 20.2) upon reaching or exceeding a pre-assigned operating characteristic value. 2. Circuit arrangement according to claim 1, characterized in that the switching device (50, 50.1) is implemented as a microprocessor, as an integrated circuit or as a programmable command from memory. Circuit arrangement according to claim 1 or 2, characterized in that the switching device (50; 50.1) comprises control means for controlling (18) the voltage supply (12) of the load (10; 10.1; 10.2 ). Switching device according to one of the preceding claims, characterized in that the monitoring of the operating characteristics occurs at intervals of time. Switching device according to one of the preceding claims, characterized in that a signaling of the operating state takes place. Switching device according to one of the preceding claims, characterized in that the operating characteristic sensor (30) is designed as a digital converter or as an analog converter. Switching device according to the preceding claim, characterized in that the sensor (30; 30.1) of the operating characteristic values is a current transformer. Switching device according to one of the preceding claims, characterized in that there is at least one memory device for signals transmitted by the sensor (30; 30.1) of the operating characteristic values. Switching device according to one of the preceding claims, characterized in that the switching device (50; 50.1) can be controlled and / or monitored by remote data transmission (54). Switching device according to one of the preceding claims, characterized in that the mains switch (14, 20; 14.1, 20.1 ,; 14.2, 20.2) is designed as a relay. Switching device according to one of the preceding claims, characterized in that the switching device (50, 50.1) is designed as a motor drive. Switching device according to the preceding claim, characterized in that the switching device (50: 50.1) is integrated in an amplifier module for controlling motor drive devices. 13. Circuit arrangement according to one of the preceding claims, characterized in that a sum current transformer (17), connected to the load (10), on the output side together with the current sensor (30), relevant for the sum current, is carried on a contact system (21) of a further relay (15, 21) permanently maintained in the inserted state by means of the switching device (50.1).