What size should the grounding wire for the 55KW motor enclosure be?
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For the ground wire of the 55KW motor’s wiring box, a 16-square millimeter wire is used. What are the specifications for the ground wire when grounding the motor housing? Should I choose 25 square millimeters or 16 based on the rated current?
The enclosure of the motor should be reliably grounded; the cross-sectional area of the grounding wire is usually chosen to be 1/3 of that of the power supply wire, with the cross-sectional area of the copper core wire being no less than 1.75 mm2.
Cables are generally chosen as VV-3*50+1*25; you might be using VV-3*35+1*16 cables. Which type to use is determined at the time of cable selection – once the cables have been installed, there is no choice left.
Is a 35 square millimeter cable within 100 meters sufficient for star-delta starting? Is that enough?
The cross-sectional area of the ground wire is usually chosen to be 1/3 of that of the power cable. Is it 1/3 of the motor cable’s cross-sectional area?
That’s enough; a regular motor requires 98.5A, an angle contactor needs 0.58 times that current, which is 57.13A, while a star contactor requires 0.33 times the current.
Star-delta starting requires 6 phase wires; for systems with a power rating of over 30 kW, soft starters are preferable, as autotransformers are also expensive. The star-delta connection is suitable for applications where starting occurs infrequently