POWER FACTOR AND WATTAGE UNIT TO BE USED WITH UNIVERSAL AVOMETER

This device operates on the principle of measuring the current flowing in the circuit under test and then neutralising its power component in the case of single phase or its reactive component in the case of a balanced 2 or 3 phase. A sinusoidal waveform of current and voltage as assumed.

PRELlMlNARY SETTINGS QF THE UNIT ARE:-
1. Remove the leads from the drawer and plug into the appropriate socket,
2. Set the volta e switch at a value to suit the supply. 
3. sat me Mov¡EMENr Reverse switch at its OFF position.
4. Sat the ADJUST knob at the position marked START.
5. Connect the short leads to the sockets marked P.F. at the top of the Avometer
6. Connect the long leads as below.

SINGLE PHASE. The voltage should be taken across the actual mains.
BALANCED 2 PHASE. The current as measured in one line the voltage being taken from across the other line to the neutral.
BALANCED 3 PHASE. The current as measured in one line and the voltage is taken across the other two Innes
UNBALANCED 3 PHASE. Regard each phase as a single phase test.

The Avometer on a suitable AC range should be connected in series with the load and the initial current measured.The object is to then obtain the minimum pointer pointer deflection by rotating the adjusting knob latter having set the 
reversing switch to the side which allows a reduction to take place. The minimum reading should be taken, the power factor being dependent on these two readings. Return adjusting knob and reversing switch to their initial positions.
	Never switch to a lower current range on the Avometer when adjusting for the minimum pointer indication. The Ö2 button can be used however to increase pointer deflection
	Circuits carrying current in excess of the maximum current range of the Avometer can be dealt with by using a suitable current transformer connected to the Avometer in the usual manner.

POWER FACTOR CALCULATOR
SINGLE PHASE The point on the switching arm corresponding to the initial (maximum) current should be superimposed
over the squared scale at a point corresponding to the minimum current single phase on the horizontal scale. The power factor is indicated on the scale at the exrtemity of the swinging arm. 
BALANCED 2 or 3 PHASE The initial current reading on the arm should be over the point corresponding to the minimum current on the vertical scale.
	If the main purpose of the test is to determine the power factor the relative value of the two readings only is required. The operation of the power factor calculator is simplified if the initial reading is brought to a whole number (100 if possible) by means of the ÒQÓ adjuster and the second reading take at this setting. Return the ÒQÓ adjuster to its normal position after use.

WATTAGE CALCULATOR,
SINGLE PHASE The voltage across the load should be first measured and the power factor then determined as described
above This power factor value on the circular calculator should be set to the point corresponding to the measured
voltage The power in watts or kilowatts may than be read opposite the point on the current scale which corresponds to
the maximum current reading.
BALANCED 2 PHASE The line/neutral voltage should be measured and the unity (1.O) power factor marked on the
calculator set against the voltage value. The wattage per phase is then read against the minimum current, it being unnecessary to measure the power factor. The total wattage as twice the phase wattage.
Alternatively the line/line voltage should be measured and the mar Vl2 on the calculator set against thus value. The
total wattage as then read a against the minimum current there being no necessity to determine the power factor. The voltage derived from line to line must not be applied to the Unit but merely used to facilitate computation on the wattage calculator.
BALANCED 3 PHASE. The line/line voltage should be measure and the mark Vl3 on the calculator set against this value.
The total wattage is then read against the minimum current  it being unnecessary to determine the power factor.
UNBALANCED 2 or 3 PHASE. The power in each phase must be determined as a single phase test the total power being
the sum of the individual phases.
For Òstar connectionÓ circuits the power in each phase is the product of the phase volts the line current and the power factor.
For delta connection circuits the power in each phase us the product of the line volts the phase current and power
factor. This latter case can only be determined if phase currents can be measured.
The current scale has only been marked from 10mA and the power factor from 0.1 upwards. If at any time values below
these are encountered the calculation can be based on say ten times the current or power factor and then the wattage indication be divided by ten.

AVO LTD AVOCET HOUSE 92/96 VAUXHALL BRIDGE ROAD
LONDON SW1
The word AVOMETER is our registered Trade Mark
Made ln England