User manual

2.2.4 Solid State Motor Overload
The MX
2
control has an advanced I
2
t electronic motor overload (OL) protection function. For optimal motor protection the MX
2
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
2
motor
overload function also implements a NEMA based current imbalance overload compensation, 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, section 7.1 on page 132 for more motor overload details and a larger graph.
Refer to http://www.benshaw.com/olcurves.html for an automated overload calculator.
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2 - TECHNICAL SPECIFICATIONS
11
1010
100100
10001000
1000010000
100 150 200 250 300 350 400 450 500 550 600 650 700 750 800100 150 200 250 300 350 400 450 500 550 600 650 700 750 800
Current % (FLA)Current % (FLA)
Seconds to TripSeconds to Trip
Class 5Class 5
Class 10Class 10
Class 15Class 15
Class 20Class 20
Class 25Class 25
Class 30Class 30
Class 35Class 35
Class 40Class 40
Figure 2: Commonly Used Overload Curves