Emerson unidrive m200 - Time for Motor Protection Accumulator to Reach 100%; Motor Protection Accumulator Reset

Time for Motor Protection Accumulator to reach 100%
The time for the MotorProtectionAccumulator (04.019) to change from its initial value to 100% is given by the following equation:
Time to reach 100.0% = -τ1 x ln[(1 - C1) / (C
0
- C
1
)]
C
0
represents the conditions that have persisted for long enough for the MotorProtectionAccumulator (04.019) to reach a steady state value. If the
motor current is I
0
then
C
0
= [(I
0
/ (K
1
x I
Rated
)]
2
C
1
represents the conditions that begin at the start of the time being calculated. If the motor current is I
1
then
C
1
= [(I
1
/ (K
1
x I
Rated
)]
2
Example 1: MotorThermalTimeConstant1 (04.015) = 179s, the initial current is zero, MotorRatedCurrent (05.007) ≤ MaximumHeavyDutyRating
(11.032) and the new level of current is 1.5 x MotorRatedCurrent (05.007).
C
0
= 0
C
1
= [1.5 / (1.05 x 1.0)]
2
= 2.041
Time to reach 100.0% = -179 x ln(1 - 1/C
1
) = -179 x ln(1 - (1 / 2.041)) = 120s
This is the default setting for Open loop and Closed Loop modes allowing an induction motor to run at 150% rated current for 120s from cold.
Motor Protection Accumulator Reset
The initial value in the MotorProtectionAccumulator (04.019) at power-up is defined by MotorProtectionAccumulatorPower-upValue (04.036) as
given in the table below.
Motor Protection Accumulator Power-
up Value (04.036)
Motor Protection Accumulator (04.019) at power-up
Power Down
The value is saved at power-down and is used as the initial value at
power-up
Zero The value is set to zero
Real Time
If a real-time clock is present and if Date/TimeSelector (06.019) is set
up to select the real-time clock then the value saved at power-down is
modified to include the effect of the motor thermal protection time
constants over the time between power-down and power-up. This
modified value is then used as the initial value at power-up.
If no real time clock is present and this option is selected then the
value saved at power-down is used as the initial value.
The MotorProtectionAccumulator (04.019) is reset under the following conditions:
1. SelectMotor2Parameters (11.045) is modified and MotorRatedCurrent (05.007) and M2MotorRatedCurrent (21.007) are different.
58
Unidrive M200 Parameter Reference Guide
Issue: 01.05.00.10