What Does The Kv Value Mean In Electric Motors?

The term 'KV' refers to the revolutions per minute (rpm) constant of any machine

. The KV number tells us how many revolutions the machine will turn when one volt is applied to the drive, with no load attached. Because the value refers to the operation of the machine at zero loading, the number will always be significantly higher than the corresponding real application rating. The KV rating is useful for evaluating the power capacity of an electric motor, as well as the torque level the drive is capable of producing.

The KV value is determined by the number of turns on the armature and the strength of the magnets used, as well as some other variables in the construction of the machine. Because the construction and organisation of an electric motor is usually so complex, the simple rating of a KV number allows the manufacturer and consumer to easily summarise the various parts and qualities of the drive in one rating. The KV number can also indicate the most suitable application for the machine in question. Low KV drives, for example, are best suited to heavy machinery.

Determining the KV rating of an electric motor isn't always as straightforward as looking up the manufacturer's specification sheets, unfortunately. Some manufacturers don't use KV as their primary measurement of speed and others privilege other categorical measurements in their advertising material. If you are choosing between different models of electric motors then you will probably need to understand a few different measurement systems in order to make the best judgement.

Firstly, you should understand that a higher KV number means that the drive has a higher rpm but lower torque and can run on higher voltages, whereas a lower KV value will mean that the machine has a lower rpm but higher torque and cannot run on high voltages. It is also important to remember at all times that the KV refers to torque with no loading, and that some manufacturers will use another rating system which takes typical loading into account.

The KV rating is considered to be most useful for evaluating brushless drives, however some manufacturers still use the brushed drive turn rating to measure this type of machine. This is done to clear up confusions between loaded and non-loaded measurements, but it does make it difficult for customers looking for a simple number to use in further calculations. Many experts advocate the use of KV measurements across the board for brushed and brushless electric motors, to clear up confusion and create an easy to comprehend standard.

by: Harrie Dadhwal

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