thermal o/l and stalling relays...
thermal o/l and stalling relays...
(OP)
I have a bunch of data for various thermal o/l and stalling relays. can anyone tell me what it all means?
tap:(this is the current tap setting i'm assuming)
time setting: stall:45 (what does this mean? is this just the time setting on the relay like any other relay that goes along w/ the current tap setting above?)
ground: (is the the current tap setting (cts) for the ground ct?) should it have it's own time setting associated with it?
% overload: these are all listed as either 100, 110, 135. is this the % overload of the motor, ie: % of full load amps? does this represent the 50/51 relay (phase time delay and phase instantaneous?) should this have it's own time delay setting?
tap:(this is the current tap setting i'm assuming)
time setting: stall:45 (what does this mean? is this just the time setting on the relay like any other relay that goes along w/ the current tap setting above?)
ground: (is the the current tap setting (cts) for the ground ct?) should it have it's own time setting associated with it?
% overload: these are all listed as either 100, 110, 135. is this the % overload of the motor, ie: % of full load amps? does this represent the 50/51 relay (phase time delay and phase instantaneous?) should this have it's own time delay setting?






RE: thermal o/l and stalling relays...
I would imagine that a 'stall' setting of 45 would be a time setting to trip upon a stall condition, i.e. LRA for 45 seconds?
'Ground' should be for ground fault current, I'm assuming it's a current setting from your statement. It may have a fixed time delay if there is no setting for it.
'% overload' is interesting if it is on the same relay as 'tap'. It may be a setting based on the tap for overload pickup.
I'm also assuming that you don't have access to any manuals for these relays. Can you tell us manufacturer/model data?
RE: thermal o/l and stalling relays...
THERMAL O/L & STALLING RELAY
P&B GOULDS
Mn 5ALI-C53-5
-----------------------------
example:
tap - 74A (FLC of motor)
ct ratio - 100:5
time: curve 1 or 4
% overload - 1.05 * FLC
is the current tap setting = 1.05*(74A)*(5/100)?
RE: thermal o/l and stalling relays...
RE: thermal o/l and stalling relays...
RE: thermal o/l and stalling relays...
RE: thermal o/l and stalling relays...
RE: thermal o/l and stalling relays...
Phase imbalance is not the same as ground fault. Typically, motor protection would be concerned about a voltage imbalance, since a 1% imbalance of the voltage applied to a three-phase motor can cause a 10% current imbalance, and resulting overheating and damage.
As long as there are three CTs for the three-phase, three-wire system, typically in a wye configuration, you can sense current imbalance.
RE: thermal o/l and stalling relays...
phase imbalance and ground fault are totally independent where 5% imbalance voltage will lead to single phase scenario. Thus, phase imbalance relay is required.
I wonder why you dont have realy manuals?
Dandel,
1% imbalance voltage to 10% imbalance current is quite rough,
maybe 1%IV to 5-6%IC is a slim approximation.
GE motor management relay has 10% IC triggers the alarm while 15% IC triggers to trip.