5-210
M60 MOTOR PROTECTION SYSTEM – INSTRUCTION MANUAL
GROUPED ELEMENTS
CHAPTER 5: SETTINGS
5
Figure 5-108: Voltage dependent overload curves
This figure and the following procedure illustrate the construction of the voltage overload curves.
1.
Draw a curve for the running overload thermal limit. The curve is one that has been selected in the relay as a
THERMAL
MODEL CURVE
.
2.
Determine the point of intersection between the
THERMAL MODEL CURVE
and the vertical line corresponding to the per-
unit current value of
VD ACCEL. INTERESECT @ MIN V
(see point 2).
3.
Determine the locked rotor thermal limit point for the minimum voltage motor start. The coordinates of this point are
the per-unit current value of
VD STALL CURRENT @ MIN VOLTS
and the time value of
VD SAFE STALL TIME @ MIN V
(see point
1).
4.
The line connecting points 1 and 2 constructs the acceleration curve for the system voltage level defined by the
VOLTAGE DEPENDENT MIN MOTOR VOLTS
setting. The acceleration time-current curve for the minimum voltage starting
Summary of Contents for M60
Page 9: ...TABLE OF CONTENTS M60 MOTOR PROTECTION SYSTEM INSTRUCTION MANUAL ix INDEX ...
Page 10: ...x M60 MOTOR PROTECTION SYSTEM INSTRUCTION MANUAL TABLE OF CONTENTS ...
Page 552: ...5 344 M60 MOTOR PROTECTION SYSTEM INSTRUCTION MANUAL TESTING CHAPTER 5 SETTINGS 5 ...
Page 660: ...iv M60 MOTOR PROTECTION SYSTEM INSTRUCTION MANUAL ABBREVIATIONS ...