DE2400328B2 - PROCESS FOR MANUFACTURING HEAVY-DUTY GROUND RESISTORS - Google Patents

Description

The invention relates to a method for producing heavy-duty ground resistors, in which electrically conductive carbon is mixed in finely divided or dispersed form with Portland cement and compression molded the mixture and then for several hours at room temperature to set of Portland cement is stored before being treated with superheated steam at temperatures above 120 ° C and is dried.

A method of this kind is in DT-PS 9 32 917 described. Furthermore, from the SU inventor's certificate 71 467 there is a method for producing composite resistors known to have electrically conductive carbon with portland cement in a ratio mixed from 30:70 to 70:30 percent by volume and the mixture obtained in this way a vibration compression subjected, stored, steamed and finally until a constant weight is reached is dried. This changes the size of the specific electrical resistance of · 10 «Ω · cm to 20 Ω · cm.

The main disadvantages of the known processes are:

1. Significant consumption of conductive carbon such as pitch electrode coke, soot and the like for the production of resistors with a required electrical conductivity.

2. Difficulties in the manufacture of resistors with different, especially low ones Resistivity values.

3. A small range for the change in volume concentration of carbon in proportion to portland cement.

4. A still relatively low specific load capacity of the ground resistances obtained.

The invention is based on the object of providing a simpler method for producing mass resistance

Stand tu develop that while avoiding the disadvantages mentioned above leads to ground resistances, which show good constructive and electrotechnical properties, an extremely low inductance, a higher permissible load capacity, a higher permissible current density and a higher dielectric strength when only small amounts of conductive material are used.

This object is achieved in that, according to the invention, the mixture of 5 to 85% by volume of carbon and 15 to 95% by volume of Portland cement, to which 12 to 18% by volume of water, based on the solid mixture components, is added during 1 pressed to 5 minutes with a pressure of 245-9810 N / cm ^2, then maintained at a temperature of 15 to 25 ^0C and at a relative humidity of 98% for 16 to 24 hours, then at a temperature of 80 to 200 ° C exposed to a steam atmosphere and finally dried at a temperature of 150 to 200 ° C until a constant weight is reached.

The method according to the invention makes it possible. Manufacture ground resistors for heavy current engineering, which have sufficient reproducibility of their electrical properties, an extremely low inductance (30 microhenry), a small non-linearity and a small temperature coefficient of resistance and with a flashover voltage of up to 600-800 V / cm and a current density of up to 30 A. / cm- 'are able to absorb and dissipate energies of up to 250-500 J / cm ^{3 once in brief switching operation.}

The invention is explained in more detail below on the basis of a detailed description.

The process for the production of masue resistors consists in that the components mixed in a volume ratio of 5:95 to 85:15 - finely ground or dispersed electrically conductive carbon and Portland cement - are mixed with 12-18% water (based on the volume of the solid phase) is added, placed in a mold and pressed therein for 1 to 5 minutes at a pressure of 245 to 9810 N / cm ² , after which the respective resistor is driven out of the mold and for 16 to 24 hours in a chamber at a temperature of 15 up to 25 ° C and a relative humidity of approx. 98%. Then, the resistance to a treatment with saturated or superheated steam at a temperature of 80 to 200 ⁰ C and a subsequent drying at a temperature of 150 to 200 ° C until a constant weight is subjected. This produces ground resistances with different nominal values of the specific electrical resistance.

The table below gives data for ground resistors manufactured using the method described compiled:

Serial Volume ratio Press pressure More specific No. Carbon/ electrical Portland cement resistance (in %) (in kp / cm ² ) (in Ω cm) 1 43:57 25th 5700 2 the same 50 2000 3 the same 100 1100 4th the same 300 500 5 the same 500 100

continuation

Serial Volume ratio Press pressure More specific No. Carbon/ electrical Pürilund / cmcm resistance (in ¹ Vu) (in kp / cm- ') (m Ll cm)

6th the same 700 60 7th the same 1000 34 8th 5:95 500 1.10 " 9 10:90 500 1.104 10 20:80 500 1.103 11th 85:15 500 1 IQ

The inventive method makes it possible to formulate high performance mass resistance to electrical resistance values from 0.2 to 2.15 ⁵ ohms, which are suitable in momentary switching operation as fo> high power installations characteristic is energy on the order of millions | oule take and to dissipate.

The resistors mentioned can be used as highly resilient active current-limiting damping, shunt- and braking resistors and the like can be used in electrical power systems.

For example, the resistors can be used to build a plant to reduce the speed can be used for voltage recovery in substation busbars, which system is replaced by a suitable interconnection of the resistors can obtain practically unlimited power.

Claims (1)

Claim: The method is mixed for producing high-strength mass resistors, wherein the electrically conductive carbon in finely divided or particulate form with Portland cement and press-molded, the mixture and then stored until setting of the Portland cement several hours at room temperature before at temperatures of about 12O ⁰ C with superheated steam is treated and dried, characterized in that the mixture of 5 to 85% by volume of carbon and 15 to 95% by volume of Portland cement, to which 12 to 18% by volume of water, based on the solid mixture components, is added, during 1 pressed for up to 5 minutes at a pressure of 245 to 9810 N / cm ² , then kept for 16 to 24 hours at a temperature of 15 to 25 ^° C. and at a relative humidity of 98%, then at a temperature of 80 to 200 ^° C exposed to a steam atmosphere and finally ^{dried at a temperature of 150 to 200 0} C until a constant weight is reached d.