RU2274838C1 - Device for testing quality of connection of electrodes in working soldered joint of thermo-electric transformer - Google Patents

Abstract

FIELD: electric engineering.

SUBSTANCE: device has constant voltage source, commutator, timer, launching device and device for registration of transition processes of alternation of electrical characteristics of thermo-electric transformer. Controlling coils of commutator power relay and signaling relay of commutator are connected to timer via launching device. Contacts of power relay of commutator are mounted with possible alternating connection of clamps for connecting electrodes of thermo-electric transformer either to direct current source, or to device for registration of transition processes. Clamps of signaling relay of commutator are mounted with possible disconnection of device for registration of transition processes from clamps for connecting electrodes of thermo-electric transformer.

EFFECT: improved productiveness of control and increased trustworthiness of diagnostics of quality of connection of electrodes in working soldered joint.

2 cl, 1 dwg

Description

The claimed invention relates to thermometry and can be used to assess the quality of manufacture of a thermoelectric converter.

It is known to use X-ray equipment for controlling the quality of electrode connections in the working junction of a thermoelectric converter. However, the use of an x-ray apparatus is associated with significant technological difficulties, in particular in ensuring the radiation safety of personnel. X-ray diffraction reveals the presence of microcracks and the penetration depth of the electrodes in the joint, however, in order to obtain a complete description of the weld and the heat-affected zone, x-ray patterns of the weld are needed in 3-4 directions at a magnification of 5-10. The use of x-ray for flaw detection of a large number of thermoelectric converters requires a lot of time, special equipment and specially prepared premises.

Closest to the claimed device is the technological equipment used in the method, involving the heating of the working junction at 360 ° C for 5 minutes and rapid cooling in water. At the same time, the transient process of changing the electrical resistance of the thermoelectric converter is recorded on sensitive equipment. With poor-quality junction manufacturing, emissions appear on the diagram tape, the reason for which is a sharp change in electrical resistance due to the appearance of microcracks / Temperature measurements. Directory. Publishing House "Naukova Dumka", 1984, p. 384 /. Thus, to implement this method, you need a tool for heating the working junction and its cooling, as well as a device for recording transient changes in electrical characteristics over time.

The disadvantage of the prototype device is its bulkiness, inconvenience in operation, low productivity. As a rule, at least 2-3 thermal shocks are carried out to confirm the presence of defects. The total time spent on heating, exposure and repetition of thermal shock reaches significant up to 30-40 minutes of time. In this case, the use of thermal shock can cause a change in the static characteristic of the thermoelectric converter. The magnitude of the change in electrical resistance depends on the cooling rate and the number of thermal shocks, which reduces the reliability of the measurements.

The authors were faced with the task of creating a device for checking the quality of electrode connections in the working junction of a thermoelectric converter, devoid of these disadvantages.

To solve this problem, a device is proposed for checking the quality of the connection of the electrodes in the working junction of a thermoelectric converter, including a device for recording transient changes in electrical characteristics over time. A distinctive feature of the proposed device is that it contains a constant voltage source connected to the input to the switch, which is equipped with terminals for connecting the electrodes of the thermoelectric converter, the control coils of the power relay and the signal relay of the switch are connected to the timer through the starting device, the input of the device for recording transient processes connected to the output of the switch, the contacts of the power relay of the switch are installed with the possibility of alternately connecting the terminals for the electrodes of the thermoelectric converter are connected either with a constant voltage source or with a device for recording transients, and the contacts of the signal relay of the switch are installed with the ability to disconnect the device for registering transients from the terminals for connecting the electrodes of the thermoelectric converter.

In addition, it is proposed to equip the device with a signal amplifier of a thermoelectric converter, the input of which is connected to the output of the switch, and the output is connected to the input of the device for recording transients.

The technical result consists in increasing the productivity and reliability of the diagnosis of the quality of the connection of the electrodes in the working junction.

The drawing shows a functional diagram of the inventive device, where 1 is a constant voltage source, 2 is a switch, 3 is a timer, 4 is a starting device, 5 is an amplifier, 6 is a thermoelectric converter, 7 is a device for recording transient processes, 8 are terminals for connecting electrodes of the thermoelectric converter, 9 - control coil of the power relay, 10 - control coil of the signal relay, 11 - contacts of the power relay, 12 - contacts of the signal relay.

The device operates as follows.

The electrodes of the tested thermoelectric converter 6 are connected to the terminals of the switch 8. In this case, in the initial state, the contacts of the power 11 and signal 12 of the relay of the switch 2 connect the electrodes of the converter 6 to the input of the device 7, which registers the initial thermoelectromotive force E ₁ . When the “START” button is pressed, timer 3 is turned on, the signal from the timer goes to the starting device 4, where commands are formed to turn on the power and signal relays of switch 2. Moreover, the command to turn on the signal relay and, accordingly, disconnect the device from the switch starts earlier and ends later, than the command to turn on the power relay. During the time set by the timer 3, a reverse polarity current is passed through the thermoelectric converter 6.

When the reverse polarity current is passed through the transducer 6 (“+” of the DC voltage source 1 is connected to the “-” of the thermoelectric transducer 6), three thermal processes appear simultaneously in the joint itself:

- heat absorption due to the Peltier effect;

- heat release due to ohmic heating of the junction;

- supply (removal) of heat to the junction from thermoelectrodes.

The amount of Peltier heat absorbed in the spa:

Q _p = I · Π · τ,

where Q _p - the amount of Peltier heat, J;

I is the magnitude of the current in the circuit, A;

Π - Peltier coefficient for a given pair of conductors, V;

τ - current flow time, s.

At the same time, the current passed through the converter causes ohmic heating of the working junction. The amount of heat released in the junction is determined by the formula

Q _d = I ² · τ · R _sp

where Q _d - the amount of Joule heat, J;

I is the magnitude of the current in the circuit, A;

τ is the current flow time, s;

R _sp - the resistance of the junction, Ohm.

The amount of heat input (removal) by thermoelectrodes depends on the magnitude and sign of the temperature gradient along the thermoelectrodes in the immediate vicinity of the junction:

Q _t = q · S = (λ / δ) · ΔT · S,

where Q _t is the amount of heat supplied (removed) to the junction due to thermal conductivity, J;

S - section of conductors, m ² ;

ΔT is the temperature difference in the zone near the transition, K;

λ is the thermal conductivity of the material of thermoelectrodes, (V / mK);

δ is the distance from the heat source to the transition, m

The integral amount of heat released in the junction zone is determined by the algebraic sum of 3 components (Q _p , Q _d , Q _t ) and can be either more or less than zero.

After the end of the direct current pulse, the switch 2 connects the thermoelectric converter 6 to the device 7 and the value of the thermoelectromotive force E _{2 is} recorded.

For a known good converter tested by all available methods, the nominal parameters are selected: the current value I _n and the duration of the current transmission time τ _and such that the total heat release Q in the junction at the time moment τ ₂ - the end of the current transmission is equal to zero.

For thermoelectric converters, the junction of which has no defects, the magnitude of the thermoelectromotive force recorded at the time of the passage of current does not change. As mentioned above, the presence of a technological defect in the working joint causes an increase in the electrical resistance of the joint. Consequently, when applied to the thermoelectric conversion element with the defective junction current pulse with nominal parameters I _n and τ _and increase the amount of generated heat of Joule Q _d. The total amount of heat Q _d and Q _t released in the junction zone will exceed the amount of absorbed Peltier heat Q _p . As a result of this, in thermoelectric converters, the junction of which has a defect, the value of the thermoelectromotive force E ₂ recorded at the time of the end of the current transmission becomes larger than the value of the thermoelectromotive force E ₁ registered before the current was transmitted. The excess of the value of E ₂ over E ₁ indicates the presence of a defect in the working junction.

Claims (2)

1. A device for checking the quality of the connection of the electrodes in the working junction of the thermoelectric converter, including a device for recording transients of changes in electrical characteristics over time, characterized in that it contains a constant voltage source connected to the input to the switch, which is equipped with terminals for connecting electrodes of the thermoelectric converter , the control coils of the power relay and the signal relay of the switch are connected to the timer through the starting device, the input of the device for I register transients connected to the output of the switch, the contacts of the power relay of the switch are installed with the possibility of alternately connecting the terminals for connecting the electrodes of the thermoelectric converter either with a constant voltage source or with a device for recording transients, and the contacts of the signal relay of the switch are installed with the ability to disconnect the device for registration transient processes from the terminals for connecting the electrodes of the thermoelectric converter. 2. The device according to claim 1, characterized in that it further comprises a signal amplifier of a thermoelectric converter, the input of which is connected to the output of the switch, and the input is connected to the input of the device for recording transients.