Common mode noise
Electrical noise generated between the power conductors and ground, i.e., between the line feed and ground or between the neutral line and ground.

Critical load
Devices and equipment whose failure to operate satisfactorily jeopardizes the healthy and/or safety of personnel, and/or results in loss of function, financial loss or damage to property deemed critical by the customer.

Ground
A connection from an electrical circuit to the earth for the purpose of safety.

Harmonic distortion
A steady-state distortion of the normal sine wave caused by a non-linear load.

Inverter
A device that converts direct current to alternating current.

Isolated ground
An insulated grounding conductor run in the same conduit as the supply conductors. This conductor is insulated from the metallic raceway and all ground points throughout its length.

Isolation transformer
A device that electrically separates electronic equipment from the incoming power system, reducing unwanted electrical noise.

Kilo-volt ampere
An electrical unit related to the power rating of a piece of equipment. Abbreviated kVA.

Line conditioner
A device connected into the electrical power supply that provides voltage regulation for sags and swells. Can also reduce electrical noise. Also known as power conditioner.

Neutral
A designation of one of the power-carrying conductors for power distribution, normally at or near ground potential.

Noise
A distortion of the normal sine waveform.

Normal mode noise
Electrical noise between or among all active power conductors, including the neutral conductor.

Overvoltage
An increase in voltage outside the normal tolerance lasting greater than one minute. Also known as swell.

Per unit
1.0 per unit equals 100 percent, or nominal. Abbreviated p.u.

Power factor
The ratio of total power input (in watts) to total volt-ampere input.

Rectifier
A device that converts alternating current power to direct current power.

Sag
A period of lower-than-normal voltage lasting up to one minute, with magnitude of 0.1 to 0.9 per unit.

Separately derived source
A source that allows the bonding of the neutral to ground, such as a generator or isolation transformer.

Single point grounding
The act of grounding all equipment together so that it maintains the same ground reference, eliminating ground currents.

Static
Electrical charge that builds up due to friction between two materials.

Transient
A high voltage electrical pulse of very short duration. Also known as impulse, spike or surge.

Transient voltage surge suppressor
A device that provides protection against short duration (microsecond to millisecond) voltage increases.

Uninterruptible Power Supply
A system designed to automatically provide power without delay or transient, during any period when the normal power supply is interrupted.

Undervoltage
A reduction of voltage supplied to electrical equipment of duration longer than one minute, with magnitude 0.8 to 0.9 per unit.

^ Return to top of page ^