I have 3 ventilators that are rated for 120V/60 hz however my supply is 230/50 hz. I can use a step down transformer 230/120V however because of the frequency change i won't be able to have the same rpm. I was thinking to use a step down transformer and a vfd to overcome this but could not find...
The relay already installed has 59N protection. The VT's measure ground-phase voltage and calculate phase-phase voltage. So 59N can be set for a earth fault.
MV system with isolated neutral, the relay has 50N/51N protection set. It senses three phase currents and vectoral sums them, and it is set the %10 of the nominal load to trip. Would this be enough for ground fault protection ?
IEC 60364-5 Table A52-3 has a list of installation options for cable ampacities. It shows Items 70 through 73 as reference D ( underground in counduit, underground directly buried etc. )
Then I check PVC ( 70C )3 core cable ampacities, ( Table B52-4 Col7.)
It shows 122 Amps for 50 mm2 cable. (...
