VAMP Ltd
Motor protection relay
Technical Description
VAMP 150
VM150.EN005
Vamp 24h support phone : +358 (0)20 753 3264
11
2.2.2.
Stall protection I
st
> (48)
The stall protection unit I
st
> measures the fundamental
frequency component of the phase currents.
Stage I
st
> can be configured for definite time or inverse time
operation characteristic.
The stall protection stage protects the motor against prolonged
starts caused by e.g. a stalled rotor. While the current has been
less than I
Stop
= 10% x I
mot
and then within 200 milliseconds
exceeds I
StartMin
the stall protection stage starts to count the
operation time T according to equation 2.2.2. The equation is
also drawn in Figure 2.2.2-1. When current drops below 120 %
x I
MOT
the stall protection stage releases.
Equation 2.2.2.-1
START
MEAS
START
T
I
I
T
=
where,
T =
Operation time
I
START
= Start current of the motor. Default 6.00xI
MOT
I
MEAS
= Measured current during start
T
START
= Maximum allowed start time for the motor
TIME
CURRENT
I
START
T
START
IstartMin
Figure 2.2.2-1. Operation time delay of the stall protection stage I
st
>.
If the measured current is less than the specified start current
I
START
the operation time will be longer than the specified start
time T
START
and vice versa.
