Wikipedia:Reference desk/Archives/Mathematics/2013 September 3
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September 3
editgeneralized eigenvalue maximization using convex feasibility
editFind a family of convex functions such that .
AnalysisAlgebra (talk) 04:27, 3 September 2013 (UTC)
capacitive vars
editif a 1 kw motor operates at 80% power factor ,how many cap vars are required to increase the power factor to 90% ??cant seem to find the formoula?? — Preceding unsigned comment added by 204.152.90.10 (talk) 19:40, 3 September 2013 (UTC)
- If this is a homework question, then it's probably intended that you work it out rather than look up a formula. I suggest you assume that either the current or the voltage is known: so (for example) assume that the voltage is V. Then work out:
- What is the in-phase (with V) component of the current (we have the power remember)?
- What is the magnitude of the current for 80% power factor?
- What is the quadrature (to V) component of the current (Pythagoras may help you here)?
- What would the quadrature current be if the power factor was actually 90%?
- How much must you reduce the quadrature current to change the power factor from 80% to 90%
- Remembering that the voltage was assumed to be V, how many volt-amps is that?