Specifications
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12
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’13 • SC-T-192
11. ACCOUNTING CALCULATION
(a) Selection of watt-hour meter
To calculate the account, it is necessary to procure a watt-hour meter at site. Select a meter according to the following items.
(b) Selecting the pulse unit
2) Selecting the pulse unit
①
Calculate the total of power supply capacity required for the air-conditioners to be connected.
②
Select provisionally an integrated wattmeter that fits to the requirement.
③
Maximum operating status of air-conditioner: Estimated overload condition expected in the summer season, for example:
If it is assumed to be the total power consumption × 1.2;
Example) Provided the total power consumption status = 100 kW and the power factor = 90%
If max. operating status = 100 × 1.2 = 120 kW, 3-phase, 200 V
I = 120 × 1,000/(1.732 × 200 × 0.9) = 385A
/
The watt-hour meter needs to have a capacity of 400 A.
If we select an oscillation device from Mitsubishi’s products of 400 A:
• K11 type – Select the pulse unit 100 kWh/P or 10 kWh/P
• K12 type – Select the pulse unit 100 kWh/P or 10 kWh/P or 1 kWh/P
* For a further small pulse unit, consult a watt-hour meter manufacturer.
④
Check for when the power consumption is 120 kWh (Example)
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If 0.1 kWh/P is selected when the pulse input is the largest: 1,200 P/h = 20 P/min, which means it is 20 pulses/min, and
so this is acceptable.
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If the duty cycle decreases to 1/10 (12 kWh), for example; If 10 kWh/P is selected, 1.2 P/h = 0.02 P/min, which means
that there is no pulse within 10 minutes. It becomes 28.8 pulses for a day. If 1 kWh/P is selected, it is 12 P/h = 0.2 P/
min, which means that there are 2 pulses/10 minutes.
Since it is sufficient for the calculation if there is 1 pulse a day, it is possible to use 10 kWh/P. However, since it is likely
to produce calculation errors depending on the duty cycle, it is better to use 1 kWh/P.
1) Restrictions on the pulse input receiving side
100 ms
or over
200 ms or over
Restriction on the device side
1 pulse or more/day (Desirable that it is 1 pulse/10-minute or more.)
Maximum count number of power pulse input