DE1029909B - Small electrical heat switch, in particular for protecting the windings of electrical machines - Google Patents

Description

GERMAN

In the case of small heat switches that are used in the winding of electrical machines, especially electric motors, be installed to protect the winding insulation from damage, premature aging and overheating to protect, the disadvantage occurs that if the winding temperature rises too rapidly, z. B. as a result Overload of the machine, an impermissibly high temperature difference between the winding and the Thermostat enters. The heat transfer from the • winding to the thermostat is namely through the insulation of the winding and the thermostat is severely hindered. A useful effect of the small heat switch can only be expected if the bimetal thermometer provided in the thermostat, the triggers the switching process, as quickly as possible and to the same extent as possible as the winding is heated itself and the thermostat is also embedded in the winding as insulated as possible, so that no undesirable heat losses occur at this point.

According to the invention, the small heat switch is designed so that to trigger the Switching process a bimetallic spring through which the winding current flows directly is used. The bimetal spring can be shaped in a manner known per se in such a way that there are abrupt switching movements for Performs momentary disconnection and connection of the control part. The bimetal cross-section is also advantageously dimensioned so that the specific losses and the heat capacity in the bimetal and in the winding wire are in the same ratio to one another

(Qbi '· Icu) = {Qu ■ ^c cu)' ■ (Qcu · ^c bi) ·

This ensures that the temperature rise with adiabatic heating in the winding and in the Thermostat is the same size. The thermostat is therefore almost at every load condition of the machine respond without delay and precisely at the moment in which the permissible for the winding Temperature is exceeded. Another advantage can also be achieved in that the bimetal spring is arranged isolated from the contact system controlled by it. It is then without further ado Series or parallel connection of the control circuits of several in different winding phases Thermostats possible. If it seems necessary in some cases, you can do without it further several contact systems are installed, the z. B. consist of a preliminary and main contact.

A further improvement can also be achieved according to the invention in that the bimetal thermostat a shunt is connected in parallel, thereby branching the motor current. To this It is possible to use one type of heat switch for all small electrical heat switches,

especially to protect the windings of electrical machines

Applicant:

Siemens-Schuckertwerke

Corporation,

Berlin and Erlangen,

Erlangen, Werner-von-Siemens-Str. 50

Dipl.-Ing, Fritz Gann

and Dipl.-Ing. Heinrich Haas, Bad Neustadt / Saale,
have been named as inventors

To use nominal currents. Finally, it is advantageous to put the bimetallic spring thermostat in a protective sleeve insert that the sleeve is inserted into the machine winding and the heat switch afterwards can be installed or replaced.

The drawing shows an embodiment of such a small heat switch designed according to the invention with bimetallic spring and isolated break contact shown in perspective view. 1 is an insulating plate, in the lower part of which a bimetallic spring is attached, which is used to trigger of the switch is used. The bimetallic spring2 consists in a manner known per se of an approximately hairpin-shaped shaped bimetallic sheet metal strip, both ends of which on the insulating plate or connecting pieces inserted there are rigidly attached. The bimetallic strip is deformed in a manner known per se so energized during installation that when it heats up when it exceeds a certain Temperature suddenly bends upwards. Over the bimetal strip are now on the insulating plate the contact spring 3 and the mating contact 4 are attached one above the other. From the front end of the Contact spring 3 also protrudes an insulating piece 5 down, onto which the possibly jumping up The end of the bimetallic spring strikes and so lifts the contact spring 3 from the mating contact. The small heat switch formed in this way is inserted into the protective sleeve 6 shown in dotted lines, which is inserted into the the winding to be monitored is inserted. A

809 510/372

Such a small heat switch can easily be retrofitted built into the winding and, if necessary, replaced.

Claims (6)

Patent claims:, 1. Small heat switch, especially to protect the windings of electrical machines with The switching process is triggered by a bimetal spring, characterized in that the bimetal spring is directly traversed by the winding current. 2. Switch according to claim 1, characterized in that the bimetal spring is known per se Way is shaped so that it has abrupt switching movement for momentary disconnection and connection of the control circuit. ■ 3. Switch according to Claim 1, characterized in that that the bimetal cross-section is dimensioned so that the specific losses and the heat capacity in the bimetal and the winding wire are in the same ratio to each other. 4. Switch according to claim 1, characterized in that the bimetal spring from that of her controlled switching contact system is arranged isolated. 5. Switch according to claim 1, characterized in that a shunt parallel to the bimetal spring is arranged. 6. Switch according to claim 1, characterized in that the bimetallic spring thermostat so in a contactor sleeve is inserted that the sleeve is inserted into the winding and the thermal switch can be retrofitted or replaced. Considered publications:
German Patent Nos. 867 861, 753 230;
French patent specification No. 984 671. 1 sheet of drawings © 809 510/372 5.58