For this video, we take a look at another three-phase electricity
meter. This one however, is operated with CTs.
Characteristics for GEC E43B R/M CT meter:
Three phase - four wire. 3x240v, 3x200A. 7.5 revs=kWh
CT Driven and mechanically ratioed. CT ratio=200/5.
Using CTs has the advantage of having a much higher loading
capacity as the current does not go through the meter itself, but
through Current Transformers (CTs) and is 'reduced-down' by a
certain ratio. This meter requires CTs with a ratio of 200/5.
Because the meter shown is not a "blank-5" meter, the meter has
been mechanically arranged inside to 'reverse' the downwards
current reduction of the CTs and so therefore, the meter has a
very low loadwheel speed. A "kWh reading multiplier" is not
needed with this electricity meter, as like it is on a "blank-5"
meter.
With a Blank-5 meter, they're not mechanically arranged inside
for a particular CT ratio, so can be used with any ratio CT,
provided that the maximum output of the CT does not exceed five
amps. Then, whatever the kWh reading is on the meter, a "kWh
multiplier" has to be used. As an example, if a Blank-5 meter has
CTs of 800/5, then the kWh multiplier would be 160. So, if a
Blank-5 meter was showing 163,289 kWh, that reading would
need to be multiplied by 160 to give the true amount of kWh
used.
A kWh multiplier can be found by discovering the CT ratio and
then dividing the larger number by the smaller number. Example:
A CT with a 800/5 ratio. Take the 800 and divide by 5. Answer is
160. That would be the kWh multiplier in that case.
Here are a few others:
CT ratio......................kWh multiplier
40/5..................................8
60/5.................................12
80/5.................................16
100/5...............................20
150/5...............................30
200/5...............................40
250/5...............................50
300/5...............................60
350/5...............................70
400/5...............................80
450/5...............................90
500/5...............................100
600/5...............................120
700/5...............................140
800/5...............................160
900/5...............................180
1000/5.............................100
1500/5.............................300
2000/5.............................400
2500/5.............................500
3000/5.............................600
3200/5*............................640
3500/5.............................700
4000/5.............................800
4500/5.............................900
5000/5.............................1000
*=this CT ratio was actually known to be used on an electricity
meter in a shopping centre in New Zealand!
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Suitable rate-changers for this meter: FULL HD!!
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Click here to see this meter's Accuracy Test:
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A bit later on this channel, we will be having a look at more
electricity meters in High Definition, so do stay tuned for those.
-Wayne's Electrical.
Video Thumbnail: YouTube Selected.
Video Number: VN-0006
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Tags used in this video:
Meter, Electric meter, Electricity meter, kWh meter,
Watthour meter, Three phase, CT meter,
Current Transformer, Dual tariff meter,
Dual rate meter, Off-peak meter, White meter,
Economy seven, Economy 7, Economy ten,
Economy 10, Quarterly meter, GEC Meters, GEC,
General Electric Company, E43B-R/M, E43BRM
Wayne's Electrical, Waynes Electrical, RPKWH7.5
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