VAMP 150 - Page 43

VAMP Ltd
Motor protection relay
Technical Description
VAMP 150
VM150.EN005 Vamp 24h support phone : +358 (0)20 753 3264
15
If the motor manufacturer gives a t
6x
value instead of τ, the τ
can be calculated using equation 2.2.3.-2 assuming that the t
6x
is given for a motor in normal operating temperature. If the t
6x
is given for a cold motor then equation 2.2.3.-3 should be used.
Equation 2.2.3.-2
x
t
6
71⋅= τ
Equation 2.2.3.-3
x
t
6
5.35 ⋅= τ
The trip level is determined by the maximum allowed
continuous current I
MAX
. This current corresponds to the 100 %
temperature Θ
TRIP
i.e. the heat capacitance of the motor. I
MAX
depends of the setting k and setting Θ
AMB
, I
MAX40
and I
MAX70
.
MOTMAX
IkkI ⋅⋅=
Θ
The value of ambient temperature factor k
Θ
depends on the
setting Θ
AMB
, I
MAX40
and I
MAX70
. See Figure 2.2.3-1.
Figure 2.2.3-2. Behaviour of VAMP 150 T> protection stage