GE MM3, Instruction Manual, Page: 207 / 230

MM3 MOTOR MANAGER 3 – INSTRUCTION MANUAL 10–1
MM3 Motor Manager 3
Chapter 10: Miscellaneous
GE Consumer & Industrial
Multilin
STOP
RUNNING
RELAY A RELAY A
STOPPED RELAY B RELAY B
TRIPPED AUX RELAY 1 AUX RELAY 1
ALARM AUX RELAY 2 AUX RELAY 2
VALUE
MESSAGE
AUTO MANUAL
STORE
RESET
ACTUAL
SETPOINT
START
A
START
A
START
B
START
B
Miscellaneous
10.1 Asymmetrical Starting Current
10.1.1 Overview
It is commonly known that current lags voltage by 90° when a voltage is applied to a purely
inductive load. As can be seen below, if the AC voltage is applied at a peak, the current will
rise from 0 A to its peak, 90° later in time. It may also be seen that during the time voltage
completes a positive or negative half-cycle, current has made the transition from one peak
to another.
Figure 10-1: Current-voltage Phase Difference
Thus, as shown in the second figure below, if voltage is applied at a zero crossing, current
will make the transition from minimum peak to maximum peak. Current of course, cannot
instantaneously be at its minimum value, it must begin at zero.
Thus it rises from zero to a value that is equal to 2 times the peak value (2 × I
max
).
current
I
max
voltage
2
1
0
–1
–2