Has anyone experienced generators being "blown", AC end field coils severly damaged because of power surges from emergency generator? Contracted service company claims this is the cause of 5 seperate incidents involving same 3 generators. Old Motion controls on old otis elevators with existing generators. No other problems reported in building due to power surges.

-- Jack Mueller (muellerjack@hotmail.com), February 23, 2000

Answers

if the frequency of the three phase is off even by a little it will cause extreme heat on those old gen's. if the 60 cycle is 58 or 62 as is usual on emerg. gen's you will lose alot of stator's as you already know

-- (rob625@aol.com), February 24, 2000.

Emergency power

When you remove power to an elevator with an overhauling load the generator will overspeed untill the brake sets and stops the machine. DC feedback can delay the brake from dropping and possably even delay the starter from dropping. If the power should come back on during this process damage will occur. Master emergency power control should have at least a 15 second delay to allow all activity to stop. before allowing power into the equipment

-- Fred Baltes (Elman101@aol.com), February 29, 2000.