bigclive

Inside an NVR (No Volt Relay) (Patreon)

Published:

2023-03-20 02:24:09

Imported:

2023-03

Content

This is a very common component found on industrial equipment.

As well as acting as an on/off switch, it has the extra safety feature of latching magnetically, so that in the event of power failure equipment will default to an off-state so nothing starts unexpectedly when power is restored.

The construction is quite interesting, and also showcases the shading ring used on AC coils to increase magnetic force and reduce buzzing.

https://www.youtube.com/watch?v=vMCXb7AoPnU

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Inside an NVR (No Volt Relay)

An NVR (No Volt Relay) is a safety device commonly found on most workshop equipment, that acts as an on-off switch, but will default to off if the power fails. I thought it would be interesting to take one apart, and it was interesting to find that the off button also applies force to the contacts to make sure they part reliably even if they have welded together slightly due to the switching current. The shading ring on the magnet core is used to cause a phase shift so the AC powered magnet doesn't lose force as the sinewave passes through the zero crossing point. That also reduces the risk of buzzing from the coil. It's similar to the approach used in shaded pole motors to provide rotational direction. Here's the Wikipedia page for the shading ring:- https://en.wikipedia.org/wiki/Shading_coil This unit came from a UK seller. https://www.ebay.co.uk/itm/115501562742 If you enjoy these videos you can help support the channel with a dollar for coffee, cookies and random gadgets for disassembly at:- http://www.bigclive.com/coffee.htm This also keeps the channel independent of YouTube's algorithm quirks, allowing it to be a bit more dangerous and naughty. #ElectronicsCreators