Metal oxide varistor formulation

Patent metadata

Field	Value
Publication number	US-11315709-B2
Application number	US-202017123943-A
Country	US
Kind code	B2
Filing date	Dec 16, 2020
Priority date	Dec 20, 2019
Publication date	Apr 26, 2022
Grant date	Apr 26, 2022

Abstract

Provided are metal oxide varistors comprising a sintered ceramic, in which the ceramic comprises, by weight, about 91.0% to about 97.0% ZnO, at least 0.3% Mn, at least 0.4% Bi, at least 1.0% Sb, and 0.50% or less Co. The metal oxide varistors as disclosed herein may exhibit reduced power dissipation, improved thermal stability, and may be produced at a lower cost relative to conventional MOV devices.

First claim

What is claimed is:

1. A metal oxide varistor comprising:
a sintered ceramic comprising, by weight:
about 91.0% to about 97.0% ZnO;
at least 0.3% Mn;
at least 0.4% Bi;
at least 1.0% Sb; and
0.5% or less Co.

2. The metal oxide varistor of claim 1 , wherein the ceramic comprises 0.3% or less Co by weight of the formulation.

3. The metal oxide varistor of claim 1 , wherein the ceramic comprises 0.2% or less Co by weight of the formulation.

4. The metal oxide varistor of claim 1 , wherein the ceramic comprises 0.1% or less Co by weight of the formulation.

5. The metal oxide varistor of claim 1 , wherein the ceramic is free of Co.

6. The metal oxide varistor of claim 1 , wherein the ceramic comprises, by weight:
at least 0.3% to about 1.0% Mn;
at least 0.4% to about 2.0% Bi; and
at least 1.0% to about 3.0% Sb.

7. The metal oxide varistor of claim 6 , wherein ceramic comprises, by weight:
about 0.4 to about 0.8% Mn;
about 0.5% to about 1.0% Bi; and
about 1.5% to about 2.5% Sb.

8. The metal oxide varistor of claim 6 , wherein the combined amount of MnO and CO 3 O 4 is about 0.75% to about 1.25% by weight.

9. The metal oxide varistor of claim 6 , wherein a molar ratio of Sb to Bi is 2:1 or greater.

10. The metal oxide varistor of claim 6 , wherein a molar ratio of Sb to Bi is 4:1 or greater.

11. The metal oxide varistor of claim 1 , wherein the ceramic further comprises an additive comprising Ag, Al, B, Cr, K, Ni, Si, Sn, or a combination thereof.

12. The metal oxide varistor claim 1 , further comprising a first electrode having a first electrode surface and a second electrode having a second electrode surface, wherein each of the first electrode surface and the second electrode surface has an area of at least 4 cm 2 , and wherein a distance between the first and the second electrode surfaces is at least 15 mm.

13. The metal oxide varistor of claim 1 , wherein the metal oxide varistor has a maximum continuous operating voltage (MCOV) of at least 3.0 kV RMS.

14. The metal oxide varistor of claim 13 , wherein the maximum continuous operating voltage (MCOV) is at least 4.5 kV RMS.

15. The metal oxide varistor of claim 1 , wherein the metal oxide varistor has a 60 Hz power dissipation of less than 0.1 W/kV of maximum continuous operating voltage (MCOV) at 100° C. or less than 0.2 W/kV of maximum continuous operating voltage (MCOV) at 150° C.

16. The metal oxide varistor of claim 1 , wherein the ratio of the 150° C. power dissipation to the 20° C. power dissipation, both measured at 60 Hz at MCOV, is less than 20.

17. A surge arrester for protecting one or more conductors against a power surge, the surge arrester comprising the metal oxide varistor of claim 1 , wherein a surge current travels from a conductor to ground through the metal oxide varistor.

18. The surge arrester of claim 17 designed for high voltage applications covered by IEEE C62.11 or IEC 60099-4, and which is rated for a 4×10 μs surge current of about 65 kA or higher.

Assignees

• Hubbell Inc

Inventors

• Poterala Stephen Franklin

Classifications

• H01C7/102

  Varistor boundary, e.g. surface layers (H01C7/12 takes precedence) · CPC title

• H01C7/12

  Overvoltage protection resistors; Arresters · CPC title

• H01C7/112 Primary

  ZnO type · CPC title

• H01C7/108 Primary

  Metal oxide · CPC title

• C04B35/453

  based on zinc, tin, or bismuth oxides or solid solutions thereof with other oxides, e.g. zincates, stannates or bismuthates · CPC title