BENSHAW RediStart MX3 Series, User Manual

Page: 19 / 238

2.2.4 Solid State Motor Overload
The MX
3
control has an advanced I
2
t electronic motor overload (OL) protection function. For optimal motor protection the MX
3
control
has forty standard NEMA style overload curves available for use. Separate overloads can be programmed, one for acceleration and
another for normal running operation. The overloads can be individual, the same or completely disabled if necessary. The MX
3
motor
overload function also implements a NEMA based current imbalance overload compensation, RTD Biasing, user adjustable hot and cold
motor compensation and user adjustable exponential motor cooling.
The motor overload will NOT trip when the current is less than motor Full Load Amps (FLA) * Service Factor (SF).
The motor overload "pick up" point current is at motor Full Load Amps (FLA) * Service Factor (SF).
The motor overload trip time will be reduced when there is a current imbalance present.
z
NOTE: Refer to Theory of Operation, Chapter 7 in section 7.1 for more motor overload details and a larger graph.
Refer to http://www.benshaw.com/olcurves.html for an automated overload calculator.
11
2 - TECHNICAL SPECIFICATIONS
1
10
100
1000
10000
100 150 200 250 300 350 400 450 500 550 600 650 700 750 800
Current % (FLA)
S
e
c
o
n
d
s
to
T
ri
p
Class 5
Class 10
Class 15
Class 20
Class 25
Class 30
Class 35
Class 40
Figure 2: Commonly Used Overload Curves