DE1009702B - Miniature heat switch, in particular for temperature monitoring of the windings of electrical machines and devices - Google Patents

Description

GERMAN

The invention relates to the improvement of a miniature heat switch, which is used in particular for temperature monitoring is used for the windings of electrical machines and devices and usually with a Bimetal member is provided, which works as a triggering temperature measuring element. Such miniature heat switches have in the known designs in particular the disadvantage that the temperature of the to monitoring winding, especially with a steep rise in temperature, is not detected correctly. the The invention is based on the following consideration:

The measurement error U of a thermometer for temperature changes is determined by the relationship U = T -tgd [° C], where T is the time constant of the thermal coupling (coupling value) between the measuring body and the thermometer and δ is the temperature rise angle of the thermometer. If the coupling value T is small, then δ can be set equal to the temperature rise angle α of the measuring body. It is also T = c / Γ, ie equal to the quotient of the thermal capacity c of the thermometer and the thermal conductivity Γ of the heat path from the measuring body to the thermometer. In order to make the measurement error disappear, the heat capacity of the thermometer would have to be made equal to zero, or the thermal conductivity of the heat path would have to be infinitely large. However, neither can be achieved. However, the present invention shows a possibility of keeping the temperature measurement error so small that it is practically irrelevant.

According to the invention, the miniature heat switch is designed for this purpose in such a way that the bimetallic element consists of a bimetallic strip that is connected to the electrical conductor to be monitored without insulating intermediate layer directly, e.g. B. is connected by spot welding. The bimetal strip is designed according to the invention only so large that there is only one local heat capacity of the electrical conductor does not increase in size significantly. The miniature heat switch is also advantageous carried out in a simple manner so that the free end of the bimetallic strip when it is bent establishes the connection with an isolated mating contact through which a signal resp. Control circuit for switching off the machine can be closed or opened. To increase the switching capacity can also be provided for instantaneous switching.

The drawing shows an embodiment of such a miniature heat switch designed according to the invention shown in longitudinal section on an enlarged scale. 1 is a tube attached to the one end open and closed at the other end

Miniature heat switches, in particular

for temperature monitoring of the

Windings of electrical machines

and devices

Applicant:

Siemens-Schuckertwerke

Corporation,

Berlin and Erlangen,

Erlangen, Werner-von-Siemens-Str. 50

Dipl.-Ing. Heinrich Haas, Bad Neustadt / Saale,
has been named as the inventor

and forms the housing of the miniature heat switch.

It can be made of metal or a plastic. There is one in the open end of the tube Insulating washer 2 used, which has a hole 3 in the middle, through which the bifilar wound loop of the electrical conductor 4 to be monitored is introduced. The free end of this loop is through the insulating washer 5 held. Wrapped on the bifilar Loop is now not far from the hole 3, a bimetallic strip 6 by spot welding attached. The free end of this bimetallic strip has a contact 7 that faces a contact 8, which is attached to the mating contact spring 9. The mating contact spring 9 is on an annular Mounted bearing body 10, which sits on an insulating sleeve 11, which is wound on the bifilar-wound conductor loop 4 is appropriate. On the bearing body, a rotatable cam 12 is also attached, through which Rotation of the distance of the contact 8 from the contact 7 is adjustable. On the bearing body 10 is a Line 13 connected, which through a hole in the insulating disk 2 to the outside to a display or Warning device is performed. A miniature heat switch designed in this way only has one very small measurement error. Thus, in tests with a switch designed in this way, the Measurement error with a temperature rise of 50 ° C / s approx. 50 ° C. This corresponds to a coupling value of around 1 second, while the coupling factor is much higher with the switches known so far, z. B. is more than 8 times.

709 547/322

In some cases, several isolated contacts can be provided, one of which is to be switched off the machine first a z. B. triggers a visual or acoustic warning sign. Is beneficial Furthermore, the miniature heat switch od in such a small tube. Like. To be arranged that it is in the winding head an electrical machine can be used. The switch itself can then optionally readjust or replace at any time.

Claims (7)

Claims: 10 1. Miniature heat switch, especially for monitoring the temperature of electrical windings Machines and devices with a bimetallic element serving as a triggering Teniperaturmeßelement, characterized in that the bimetallic member consists of a bimetallic strip that is connected to the monitoring electrical conductor without an insulating intermediate layer directly, z. B. by spot welding, connected is. 2. Miniature heat switch according to claim 1, characterized in that the bimetallic strip only has a size that does not significantly increase the local heat capacity of the conductor. 3. Miniature heat switch according to claim 1, characterized in that the free end of the Bimetallic strip when it is bent, the connection with an isolated mating contact produces, through which in a known manner a signal or control circuit for switching off the machine can be closed or opened. 4. miniature heat switch according to claim 1, characterized in that a plurality of isolated contacts are provided, one of which before switching off the machine a z. B. optical or acoustic warning signal triggers. 5. miniature heat switch according to claim 1, characterized in that the distance of the mating contact from the bimetallic strip z. B. is adjustable by means of a rotatable cam. 6. miniature heat switch according to claim 1, characterized in that it is in a tube Od. The like. Is arranged, which is inserted interchangeably in the end winding of an electrical machine. 7. miniature heat switch according to claim 6, characterized in that in the advantageous Insulating material existing tube (2) for holding the introduced, appropriately twisted bifüar Conductor piece serving insulating disks are used and that at one end of the The bimetallic strip is attached to the conductor, while an insulating sleeve sits on the other end, on which the adjustable mating contact is attached, through which the end of the tube closes Insulating washer through with a warning or Switch-off device is connected. Considered publications:
H. Titze: »Errors u, error protection in electr. Three-phase systems ", Volume 2, p. 151, Springer-Verlag 1953. 1 sheet of drawings © 709 54-7S22 5.57