Rockwell Automation 1901 SyncPro - Manual (Page 45)

Chapter
6
Monitoring
Power Factor Power in DC circuits is the product of voltage and amperes, thus:
W (watts) = E x I
However, in AC power circuits some period of time in each cycle
may have voltage and current of opposing sign (positive or
negative) and their product will be negative, denoting negative
power. This must be subtracted from the positive power for each
cycle to yield the net power. The correction factor applied to make
this is then a factor by which we multiply apparent power to
obtain actual power. This is known as Power Factor.
In a single phase AC circuit we find that:
W = E x I x PF = POWER
and that
VA (volt-amperes) = E x I = APPARENT POWER
For each cycle the power is positive when E and I are both either
positive or negative. The power is negative when one value is
positive with the other negative. The result is a power flow of
twice the line frequency, in and out of the load with the actual
power transmitted being the difference of the two.
Mathematically, it can be demonstrated that the Power Factor of a
circuit is equal to the cosine of the angle
θ
of lag or lead of the
current with respect to the voltage.
Faults Fault Detection and Diagnostics
The product incorporates numerous fault detections in addition to
the starting squirrel-cage protection and running pullout protection
previously mentioned.
Prior to starting the motor, diagnostics are performed that detect the:
a) Lack of 24V supply to the slip frequency generator.
b) Reversed Power Factor Leads between the SyncPro and isolator.
c) Lack of the EQUIPMENT SHUTDOWN (external fault) signal.
d) Loss of Setpoint Data.
1901-UM020C-EN-P – June 2013