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What is the maximum earth fault loop impedance Zs for the Tesys U? What values are taken into consideration to calculate the Zs values?

The charts below detail the Earth Loop impedance (Zs) for the Tesys U range for any TN system based on the British Standard BS7671:2008+A3:2015

Two documents are also attached:
1) Sheet with Zs charts of Tesys motor circuit breakers:

  • Tesys GV2
  • Tesys GV3
  • Tesys GV4
  • Tesys GV7
  • Tesys U
2) Explaination of the calculation of the maximum Earth Loop Impedancee
This also includes additional information about:
  • Motor Rated devices
  • Ambient Temperature

Tesys U Range
Please refer to the charts below that detail the maximum earth loop impedance Zs for 0.4s disconnection time with Uo 230V

Tesys U
Reference Thermal Adjustment
Range In
Magnetic Tripping Current Im Tolerance
Im+20%
Maximum Loop
Impedance Zs
  (A) (A) (A) (Ω) 
LUC*X6** 0.15 .. 0.6 8.52 10.22 21.37
LUC*1X** 0.35 .. 1.4 19.88 23.86 9.16
LUC*05** 1.25 .. 5.0 71.00 85.20 2.56
LUC*12** 3 .. 12 170.4 204.48 1.07
LUC*18** 4.5 .. 18 255.6 306.7 0.71
LUC*32** 8 .. 32 454.4 545 0.40



Tesys U Integrated Morot starter

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