Brazil made pocket slide rule.

Data:

• Pocket slide rule, with scales initially for power factor correction and a table of wire diameters.
• Apparently, it is a type of Electro slide rule.
• Marked “Archimedes” with “inducon” logo.
• Made by the Brazilian factory of technical drawing materials Arquimedes.

Questions:

1. Is it really an Electro slide rule?
   Yes, it’s an AC Electro rule.
   It calculates the reactive capacitance Qc (in units of VAR or kVAR) required to reduce the phase angle between AC voltage and current from φ₁ to φ₂
     Qc = P ( tan( cos⁻¹(PF₁) ) – tan( cos⁻¹(PF₂) ) )
   Max current for given wire size can be read on A scale (1A to 100A) opposite wire gauge. Eamonn Gormley
2. Why are there 6 trigonometric scales?
   cos ɸ and tg ɸ scales used for power factor correction computation
     Can also be calculated with just one cos ɸ and one tg ɸ scale, but two of each is more convenient.
   tg ɸ scale is a linear scale.
   cotg ɸ = 1/tg ɸ is an inverse linear scale
     May be useful for some power factor computations.
     Can also be used to compute equivalent resistance of two resistors in parallel.
   sen ɸ (i.e., sin ɸ) scale can be used for some reactive power computation
   Note that none of the trig scales are logarithmic scales. Eamonn Gormley
3. What is the purpose of the "phi 0" scale?
   This is simply the phase angle ɸ in degrees (⁽⁰⁾ means degrees).
   All the trig scales can be read against this scale. Eamonn Gormley
4. How do you use the scales?
   Position PF₂ on cos ɸ₂ opposite PF₁ on cos ɸ₁
   On tg ɸ₁ at the tg ɸ₂ index, read tan( cos⁻¹(PF₁) ) − tan( cos⁻¹(PF₂) )
   Multiply this by real power P to get capacitive reactive power Qc. Eamonn Gormley