Source: https://library.e.abb.com/public/ec3340484bbe4b33a09bfcd54a0b17a3/BBC_Revue_1941_f_12.pdf?x-sign=GeXs7 6M2N0URckluwl5yH0ZJtw4AQy6Qq7spyfE5JpI1Y6eB79ifb18XXTG6BWW