Sine Systems ACM-1 Manual de usuario

Model ACM-1 AC Current Monitor

Version 2.00

Description

The Sine Systems model ACM-1 AC Current Monitor is designed to allow monitoring of AC

current by the RFC-1 remote control system. A common application is to verify the proper

operation of obstruction lighting on communications towers. More generally, it may be used

to telemeter the AC current consumption of any 115 or 230 volt device drawing from 1 to 70

amperes.

The ACM-1 AC Current Monitor can, as can any

individual monitoring system, fail suddenly and without warning. In

cases where a dangerous or life-threatening condition could exist if the

ACM-1 AC Current Monitor were to fail, the ACM-1 should not be used

as the sole monitoring means. One or more redundant monitoring

means should be used as necessary to achieve the reliability required by

the application.

The ACM-1 AC Current Monitor consists of a current transformer, a PC board containing the

electronics necessary to convert the output of the current transformer to the DC voltage

required by the RFC-1, and installation instructions/engineering documentation. The user

must supply any enclosures and/or junction boxes which may be required by national or

local electrical codes.

Installation

The ACM-1 AC Current Monitor should

be installed only by a person who is familiar with industrial electrical

wiring and the requirements of the national and local electrical codes.

Installation by other persons could result in a danger of fire or

electrocution.

The ACM-1 consists of a current transformer and a PC board which converts the output of

the current transformer to a DC voltage. The following diagram shows a typical installation:

2.00 Model ACM-1 AC Current Monitor page 1

The current transformer should be mounted at a location convenient to the AC wiring to be

monitored. The "hot" AC lead should be passed through the insulation tubing in the current

transformer. The two terminals on the current transformer should be connected to terminal

strip TB1 on the ACM-1 PC board with a length of two-conductor wire (not supplied). The

ACM-1 PC board can be mounted in any location. Applicable national and local electrical

codes should be followed in the installation and wiring of the current transformer. Under

normal conditions, the output of the current transformer is low voltage AC (less than 20 volts

rms). However, during lightning strikes or other transient voltage conditions, the voltage

may be very high and appropriate precautions should be taken.

Mounted on the output terminals of the

current transformer is a metal-oxide varistor. It is a black disc about

5/8" inch in diameter with two wires. DO NOT under any

circumstances operate the current transformer without the varistor

connected. This could present a significant danger that might not be

immediately apparent. If the varistor is disconnected, normal operation

will occur as long as the current transformer output leads are

connected to the load resistors on the ACM-1 PC board. If, however, the

load resistors become disconnected, the voltage at the output terminals

of the current transformer will instantly rise to several thousand volts

and will be quite dangerous. The function of the varistor is to provide a

back-up load to the current transformer and limit the output voltage to

a safe level in the event the ACM-1 PC board is disconnected.

The DC output terminals (TB2) on the ACM-1 PC board should connect to the telemetry

terminals on the RP-8 panel. If the ACM-1 is connected to monitor the lights on a

communications tower or other application susceptible to very high voltage transients, it is

highly recommended that an SP-8 Surge Protector be used with the RP-8 panel. Alternately,

two varistors should be installed at the telemetry terminals on the RP-8 panel to which the

ACM-1 is connected. One lead of one varistor should connect to the "+" telemetry terminal

2.00 Model ACM-1 AC Current Monitor page 2

and one lead of the other varistor should connect to the "-" telemetry terminal. The

remaining two leads should connect to the metal rack in which the RP-8 panel is mounted.

The varistor leads should be as short as possible. Two varistors are supplied with the ACM-1

for this purpose.

As factory wired, the ACM-1 PC board is set up to monitor a tower lighting circuit. The DC

conversion circuit will "smooth out" the voltage generated by the lighting current to a nearly

constant value, even if flashing beacons are used. Because of this, it is easy to monitor with a

voice-reporting telemetry system like the RFC-1. Also, because the monitored voltage is an

analog value, very small changes in lighting current can be observed. A 1% change in

current can easily be resolved. In most cases this is sufficient to detect the failure of a single

bulb in the lighting system.

Note that the current transformer has two holes that wires may be passed through. If the

tower lighting circuit is powered by both legs of a 240 volt circuit, the other hole may contain

the additional leg. Passing the wires through the holes from the same side of the current

transformer to the other will cause the output of the ACM-1 to be proportional to the sum of

the currents in each leg (assuming the legs are 180° out of phase). A piece of insulating

tubing should be added to the wire passing through the second hole.

For load circuits powered by two legs of a 208 volt 3 phase “Y” service, the same technique

may be used:

2.00 Model ACM-1 AC Current Monitor page 3

It should be noted, however, that the output of the ACM-1 will not be proportional to the

arithmetic sum of the currents in each leg. This is because the current in the sampled

conductors is 120° out of phase and not 180° as above. For many applications, this is not

important. As an example, assume that 10 amperes is flowing in both legs and the output of

the ACM-1 is calibrated to 100%. If the current in one leg drops to zero amperes, the ACM-1

output will drop to 57% instead of 50%. This is not good enough for precise measurements

but it is acceptable for approximate or “go/no go” measurements. If more precision is

required, it may be practical to measure a number of known failure conditions in advance. It

then becomes easy to correlate an unknown failure condition with previously observed ACM-1

output data.

Setting Current-Range Jumpers

The voltage at the output of the ACM-1 PC board is in the range of 0.75 to 2 volts DC. The

input current range which produces this output is determined by the jumpers installed at

locations JP1, JP2, JP3 and JP4 on the ACM-1 PC board. The following chart shows the

jumpers to be installed for various current ranges:

AC Current Install Jumpers Cut Jumpers

2-5 amperes JP1 JP2, JP3, JP4

5-9 amperes JP2 JP1, JP3, JP4

9-13 amperes JP1, JP2 JP3, JP4

13-17 amperes JP3 JP1, JP2, JP4

17-26 amperes JP2, JP3 JP1, JP4

26-37 amperes JP4 JP1, JP2, JP3

37-50 amperes JP3, JP4 JP1, JP2

50-70 amperes JP1, JP2, JP3, JP4 none

As an example, suppose that a lighting system has two 620 watt bulbs in a flashing beacon

and four 120 watt obstruction bulbs. This totals 1720 watts. We divide 1720 watts by 115

volts and get 14.9 amperes peak lighting current. Looking at the chart above we see that we

need to cut jumpers JP1, JP2 and JP4. JP3 should remain installed.

Linearity and Peak Current Weighting Jumpers

For special applications, JP5, JP6 and JP7 are provided. If linear operation over a wide range

of AC current is required, the load resistor for the current transformer should be placed at

the output of the bridge rectifier. This virtually eliminates the non-linearity at the low range

of the scale caused by the forward drop of the diodes. To do this, cut the jumpers at JP1, JP2,

JP3 and JP4. Install jumper JP5. A 1.8K resistor is already installed but this may need to be

changed depending on the AC current which is monitored. To determine the resistor value,

divide 6500 by the AC current to be monitored. For example, for a full scale reading of about

20 amperes, the load resistor (R5) should be about 325 (330) ohms. When monitoring tower

lighting circuits with a flashing beacon, JP5 should be left open and the load resistor(s) placed

at the input of the bridge rectifier. This permits the peak current to be monitored and

reduces changes in monitored current caused by slight variations in the beacon flasher duty-

cycle.

2.00 Model ACM-1 AC Current Monitor page 4

Output Averaging Jumpers

With jumpers JP6 and JP7 installed, the ACM-1 board has a long integration time-constant

which requires about two minutes to reach a final value. For the monitoring of lighting

systems with flashing beacons, this is a desirable characteristic. For other applications,

either JP6 or both JP6 and JP7 may be removed to reduce the integration time-constant.

Operation

With the current transformer and ACM-1 PC board installed and connected to the RP-8 panel,

the AC circuit should be turned on. After waiting two minutes for the DC output voltage to

stabilize, the telemetry may be calibrated with the potentiometer on the appropriate channel

of the RP-8 panel. The reading may be calibrated to read directly in amperes if desired. For

example 14.9 amperes could be calibrated to "1490." For tower lighting circuits, however, it is

usually easier to calibrate the "normal" current, with all bulbs good, to something easy to

remember, like "1000." In other words, normal lighting current is "1000" or "100.0%." If the

reading drops to "0981" it means that the lighting current is 98.1% of normal.

When monitoring tower lighting current, the following points should be noted:

1) Remember that if the reading is calibrated to "1000," a change of 10 units is only a 1%

change in lighting current. Do not be alarmed at readings that "wander around" some as

long as the percentage variation is within appropriate limits.

2) The "normal" tower lighting current will rise and fall somewhat as the AC line voltage

rises and falls throughout its daily cycle. If absolute precision is required, monitor the AC

line voltage on a separate channel and compute the load resistance mathematically.

3) If a flashing beacon is used, variations in duty-cycle (ratio of off-to-on) will show up as

variations in lighting current. The ACM-1 is designed to minimize this effect but it still

can happen to some degree. In particular, an intermittently "sticky" mechanical flasher

might be responsible for erratic results. A flasher that fails in the "on" position will cause

a very high reading and a flasher that fails in the "off" position will cause a very low

reading.

4) Tower lighting current can change seasonally, particularly if the tower is tall or if the

AC run to the base of the tower is long. Due to the negative temperature coefficient of

copper wire, it may be normal to notice a slightly higher lighting current in the cold

winter months.

5) The current change by the failure of one bulb can be predicted mathematically. For

example, if a lighting system consists of two 620 watt and four 120 watt bulbs, a total of

1720 watts will be consumed if all bulbs are working. If one 120 watt bulb burns out, the

power consumption is reduced to 1600 watts. This is a change of about 7%. Therefore, if

the normal lighting current was calibrated to "1000," then the reading should drop to

about 0930 (down 7%) with the failure of one 120 watt bulb.

2.00 Model ACM-1 AC Current Monitor page 5

Parts List

R4 resistor, carbon film, 1/2 watt, 5%, 220 ohms

R3 resistor, carbon film, 1/2 watt, 5%, 430 ohms

R6, 7, 8, 9, 10, 11, 12, 13 resistor, carbon film, 1/2 watt, 5%, 510 ohms

R2 resistor, carbon film, 1/2 watt, 5%, 910 ohms

R1, 5 resistor, carbon film, 1/2 watt, 5%, 1.8K ohms

R14 resistor, carbon film, 1/2 watt, 5%, 3.3K ohms

D1, D2, D3, D4 diode, 1N4005

C1, C2, C3 capacitor, aluminum electrolytic, 4700 µF, 16 VDC

C4, C5 capacitor, monolythic ceramic, 0.1µF, 50 V

T1 current transformer, part number 3017

2.00 Model ACM-1 AC Current Monitor page 6

Tabla de contenidos

Manuales populares de Instrumento de medición de otras marcas

Suaoki

Suaoki D40 Manual de usuario

Elster

Elster BK-G1.6 Manual de usuario

Endress+Hauser

Endress+Hauser Deltabar FMD71 Manual

Duratool

Duratool D03128 Manual de usuario

Vega

Vega VEGAPULS 65 Manual de usuario

Tonghui

Tonghui TH2618B Manual de usuario

Tenmars

Tenmars TM-801 Manual de usuario

MSR

MSR 145 Manual de usuario

TPS

TPS WP-82 Manual de usuario

ELMETRON

ELMETRON CP-511 Manual de usuario

PCB Piezotronics

PCB Piezotronics 003C30 Manual de usuario

Tenma

Tenma 72-10465 Manual de usuario

Endress+Hauser

Endress+Hauser Proline Promag 50 Especificaciones técnicas

Siemens

Siemens SITRANS F Coriolis FCT030 Manual de lista de piezas

KLINGER

KLINGER CMF V Series Manual de usuario

EXFO

EXFO FTB-2 Manual de operación y mantenimiento

Keysight

Keysight M8290A Manual de usuario

ADTEK

ADTEK MW-5 Manual de usuario