ABB REG670 - Page 515

• inverse curve A
• inverse curve B
• inverse curve C
• customer programmable inverse curve
The type A curve is described as:
n
n
k
t
U U
U
=
æ ö
- >
ç ÷
>
è ø
IECEQUATION2422 V1 EN (Equation 117)
where:
Un> Set value for step 1 and step 2
U Measured voltage
The type B curve is described as:
2.0
480
0.035
32 0.5
n
n
k
t
UU
U








IECEQUATION2423 V2 EN (Equation 118)
The type C curve is described as:
3.0
480
0.035
32 0.5
n
k
t
U U
U
×
= +
- >
æ ö
× -
ç ÷
>
è ø
IECEQUATION2421 V1 EN (Equation 119)
The customer programmable curve can be created as:
p
n
n
k A
t D
U U
B C
U
×
= +
æ ö
- >
× -
ç ÷
>
è ø
EQUATION1439 V2 EN
(Equation 120)
When the denominator in the expression is equal to zero the time delay will be infinity.
There will be an undesired discontinuity. Therefore a tuning parameter CrvSatn is set
to compensate for this phenomenon. In the voltage interval U
n
> up to U
n
> · (1.0 +
CrvSatn/100) the used voltage will be: U
n
> · (1.0 + CrvSatn/100). If the
programmable curve is used this parameter must be calculated so that:
1MRK502052-UEN B Section 9
Voltage protection
509
Technical manual