Glossary

Absorbed Power

This is the load power that is required by the design. It has the units of Watts.

Apparent Load Power

This is simply a multiplication of the current by the voltage of the item. This has the units of VA. To fully describe this value, it is quoted with a power factor.

Current

This is the current that carries the power to the item. This has the units of Amps.

Electrical Load Power

The electrical load power of an item is the power supplied to the electrical item in order for it to supply the load power. Efficiency is given in terms of a percentage.

Electrical Load Power = Load Power / Item efficiency.

Line Voltage

This is the voltage value between the phases of a multi-phase supply.

Load Power

The load power of an item for the purposes of calculations in Engineer is the power that is actually delivered by the electrical item. For example, a 40kW motor delivers 40kW at the shaft.

Nameplate Power

This is the maximum load power an item can supply. It has the units of Watts or hp.

Phase Voltage

This is the voltage value between a phase and earth. This is the case even if the supply is multi-phase.

Phase voltage = Line voltage / √ 3

Power Factor

This is a factor that describes the relationship between the current and voltage waves that are being supplied.

If these waves are completely synchronised, then power factor is set to 1. This means the maximum power is being transferred.

If these waves are completely asynchronous, then power factor is set to 0. This means no power is being transferred.

There is a further factor, which is if the current wave is leading or lagging the voltage wave.

The normal convention is that current wave for practically all power-system loads i.e. induction circuits, lag the voltage wave. The consequence of this is:

• Positive Reactive Load Power is associated with Power Factor = lag e.g. Induction motor

• Negative Reactive Load Power is associated with Power Factor = lead e.g. Capacitors

Reactive Load Power

Since all induction circuits during the build-up of the magnetic fields absorb energy and then release it as the magnetic fields collapse the reactive load power reflects this power requirement. It is also known as “wattless”, as it is never lost. This has units of VAr.

It should be noted that although induction circuits require this power, capacitive circuits actually supply this energy.

Utilization Factor

This is the term used to indicate that the load power is higher that the estimation of realistic value. Other terms used for this factor are Usage or Diversity.

Note:
In this application there is a number and description. The number is called Diversity and is H in equations 5 and 6. The description is called Utilization.

Values vary between 0 and 1. This is expressed as a percentage.