ASCO 5010 Remote Display Unit
42
9.4
Phasor Display
The Phasor Display is a powerful tool for both ensuring correct installation and as a simple graphic device to act as an alarm for
failed power correction equipment.
As seen in Figure 26, the screen is divided in two. On the left side of the screen are the RMS values and their angles from the
origin of the sine cycle. On the right side of the screen is the graphic representation of the voltage and current vectors. The base
value from which all the others are compared is the Line-Neutral voltage input on V1. Neutral voltage is referenced to ground.
Figure 26: The Phasor Display
The phasor diagram is useful for diagnosing incorrect installation.
If the three voltages are not arranged at 0º, 120º, and -120º, the voltage polarity may not be correct.
If the phase angles of the currents are not as would be expected the following possibilities should be checked:
√
Current polarity
√
Miss match between voltage and current
9.5
Flicker Measurement
Flicker is a cyclic or quasi-cyclic RMS voltage fluctuation whereby the RMS voltage fluctuates 0.25-4% of nominal voltage at a
frequency in the range of 0.4-25 Hz. This type of disturbance has been historically defined as causing distress to workers due to
flickering lighting.
The EN50160 defines two types of calculations for arriving at values to be considered unacceptable to human perception of
flickering light due to voltage flickering. P
ST
(Perceptivity- short time) is a calculation over a period of 10 minutes, and P
LT
(Perceptivity- long time) is calculated from 12 consecutive values of P
ST
, for a 2 hour averaged value.
ASCO has developed algorithms that approximate the EN50160 values, but in a fraction of the time. The ASCO calculation
named Real-time PST is the same as the EN50160 P
ST
calculation, but is averaged over a period of 2, 10 and 60 seconds as
opposed to 10 minutes. Similarly, ASCO offers long time values of 1, 10 and 24 hours, as well as a 7 day long time value in
addition to the EN50160 two hour value for P
LT
.
The ASCO 5010 RDU displays the EN50160 values of P
ST
and
P
LT
as well as the ASCO Real-time P
ST
of 2 seconds and ASCO
P
LT
values of 10 hours and 10 days, as shown in the Flickering Measurement screen shown below.
