Why is length of power lead important

[Marnhullman]

I've seen warnings on certain power tools that the power lead must be kept as short as possible. Why is this?

Thanks

 

[bernardgreen]

Electrically a long lead will mean a higher voltage drop along the lead meaning the equipment will be supplied with a lower voltage when the quipment is taking current.

An un-necessarily long lead can create a trip hazard unless kept tidy when the equipment is being used.

That said an extension lead on a roll must be unrolled before use as otherwise the inside of the rolled up lead can get hot enough to melt the cable.

 

[sparkiemike]

A long lead will also increase the impedance (resistance), a high earth fault loop impedance will mean that under fault conditions a MCB or fuse might not trip. Which is why it always a good idea with socket outlets to have short lead and to have the circuit protected by a RCD or have one of those plug in RCDs plugged into the tool/extension lead when using hand tools or extension leads, as RCDs will still work with a much higher earth fault loop impedance.

 

[Marnhullman]

Thanks to SparkieMike and BernardGreen for very clear explanations.

 

[stillp]

The earlier answers might be correct, but the main reason to keep the lead on power tools as short as possible is to avoid mechanical damage such as drilling into/cutting through the cable. In the days when so-called 'professional' power tools were fitted with at least 10 feet of cable, they were usually repaired at several points along the length with insulation tape. A long lead is also susceptable to damage when tangled up and put back in the toolbox after a job.

 

[holmslaw]

..

 

[RossR]

Which would you rather replace: a damaged extension lead, or a powertool with a damaged flex?

 

[stillp]

Extension leads often, but not always, come on a reel, hence are less likely to be damaged and less likely to be tangled. In any case, the impedance of a short lead plugged into an extension lead is likely to be somewhat greater than the impedance of a long lead, so what's the point you are trying to make?