Deni 5300 Specifications download pdf (Page 26)

Magtrol Model 5300 Three Phase Power AnalyzerChapter 8 - Operating Principles

Vrms= dt

Vo=

XYCosQ

Vrms=

V/F CONV.

Khz

VOLT

.0707

V/F CONV.

VOLT

.0707

Khz

.0707

V/F CONV.

Khz

VOLT

ISO

OPTO

VFo

ISO

OPTO

WFo

ISO

OPTO

AFo

I AMP

100

AMP

25A

100A

OUTPUTS

MPU

ISOLATED CIRCUIT

AMPS

INPUT

(FROM

SHUNTS)

VOLTS INPUT

(FROM

VOLTAGE

DIVIDER)

78B146-U7

78B146-U8

78B146-U9

78B146-U10

78B147-U1

78B147-U2

78B147-U7 78B147-U9 78B147-U10

78B147-U4

78B147-U5

78B147-U3

78B147-U11

78B147-U6

RANGE

(t)

Figure 15. 5300 Block Diagram

Also, the AMPS and VOLTS signals are input to a

precision four quadrant X-Y multiplier 78B147-U7,

averaged by an active two pole Butterworth filter

78B147-U8, converted to frequency in voltage to

frequency converter 78B147-U10 and isolated by optical

coupler 78B147-U11. The resulting frequency signal,

represents true power (V × I × Cos θ ), at a scale

factor of. 0.0707 volts per 1.0 kilohertz. There is 2500

volts isolation between the measured circuit and the AF

and WF

frequency signals.

DIGITAL PROCESSING

Frequency proportional signals of AMPS, VOLTS and

WATTS (AF

, VF

, and WF

) are integrated for a precise

period of 0.1 seconds for digital conversion and

processing via an eight bit microcomputer (MPU). The

MPU controls functions of range control, auto-zero, fine

calibration, BCD conversion and GPIB communications.

The MPU acquisition and conversion rate is 100 milliseconds

(10 readings per second) and the display updates at 500

milliseconds (2 updates per second). The MPU scans all

front panel push-button control inputs 25 times per second.

When a push-button is pressed, the appropriate program

loop is entered and the function is executed on the next

program cycle. No damage will result to the 5300 PA from

any combination of push-button selections.

In the AVG MODE (averaging), the 5300 PA integrates

the 10 data readings per second (AMPS, VOLTS and

WATTS) and then samples the averaged value for

display. As the sampled readings accumulate, the

changing display digits will steady down to provide a

stable measurement of true power (computed from

average VOLTS and AMPS). This technique works well

when the displayed digits are changing too fast to be

recognized as the power consumption changes.

DISPLAY “HELP”

If the AMPS or VOLTS displays show the word HELP,

the maximum peak range of the 5300 PA has been

exceeded. This can occur from a high rms input or the

peak of a high crest factor wave form. "HELP" can be

a transient condition resulting from high momentary

starting current and is of no danger if the "HELP"

message disappears after a few seconds. The Auto up-

ranging feature of the 5300 will automatically up range

the instrument as the current or voltage increases over

each ranges maximum, up to the 100 amps range. The

5300 can sustain an overload of up to 200 amps for 5

seconds, maximum. Circuit breaker(s) should be

installed for personal safety and protection of the 5300

PA. See "Current Overload." in Section 1 - Introduction.

POLYPHASE LINE BALANCE

Good polyphase line operating efficiency dictates that

line voltages and currents be closely balanced. Usually,

this requires putting some effort into balancing the loads.

Also, power factor (PF) measurements will be inaccurate

unless a good line balance is maintained.

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Deni 5300 Specifications Page 26

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