Electricity: motive power systems – Induction motor systems – Primary circuit control
Patent
1983-01-07
1984-10-02
Truhe, J. V.
Electricity: motive power systems
Induction motor systems
Primary circuit control
318809, H02P 536
Patent
active
044750749
ABSTRACT:
An apparatus for determining the common frequency w of two independently variable a-c quantities is described. In a rotating-field machine, the flux, for instance, is described by two electrical a-c quantities which together determine the magnitude and direction of the field. The two a-c quantities are variable independently of each other and the instantaneous direction of the field is given by an angle.alpha. according to the relation a.sub.1 /a.sub.2 =cotan.alpha., where a.sub.1 and a.sub.2 are the two a-c quantities. In order to determine the frequency of rotation w=d.alpha./dt of the field from these quantities, the quantities a.sub.1 and a.sub.2 are each fed to smoothing stages and thence to a computing circuit, wherein the quotient (d.sub.1 .multidot.a.sub.2 -d.sub.2 .multidot.a.sub.1)/(d.sub.1 .multidot.a.sub.1 +d.sub.2 .multidot.a.sub.2) proportional to the frequency is formed from a.sub.1 and a.sub.2 and the smoothed quantities d.sub.1 and d.sub.2. The use of differentiators is thereby avoided, which would cause a phase error as well as difficulties when harmonics of the quantities a.sub.1 and a.sub.2 are present.
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Evans A.
Siemens Aktiengesellschaft
Truhe J. V.
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