[Amps] Vacuum relay speed

[RFlabnotes at aol.com]

I have had the unfortunate of experience of breaking a few of them. The small 
ones, like the HC1 and RJ22, which are the fastest, get their speed from two 
main factors (my opinion, based upon a physical inspection). First, the only 
moving part is the blade itself, which is extremely light weight. Also, it 
moves very little, since the air gap between contacts is much smallet than normal. 
This is the main purpose of the vacuum.

Also, there is no additional armature to accelerate, like in a conventional 
relay. This is similar to reed relays (which are similarly fast), in which the 
magnetic field is induced directly into the contact blade by the coil. The 
base metal of the blade is made ferromagnetic to facilitate this. Actually, these 
relays are a lot like reed relays in operation.

These two factors (actually three, including the reduced air gap) all 
conspire to enhance the mechanical dynamics, resulting in the greatly increased speed.

73
Eric von Valtier K8LV