WAGO SYSTEM 750 - Page 41

WAGO-I/O-SYSTEM 750 Function Description 41
750-493 3-Phase Power Measurement Module
Manual
Version 1.2.0
Measured value
50.1 Hz
59.9 Hz
cos phi
750-493
750-493/000-001
Process value
0xFFB2 (-78)
0x0059 (89)
Scaling factor PI
0.01 / LSB
0.01 / LSB
Equation
Measured value = Process value x Scaling factor PI
Measured value
-0.78
0.89
When calculating current-dependent values, the current transformer ratio
(CTR) must be taken into account when using a current transformer.
Current transformers
Current transformers are available on the market in different designs. On the
primary side, currents of 20 A, 25 A, 30 A, 35 A, 40 A, 45 A, 50 A, 75 A, 100 A
… 5000 A are supported, on the secondary side 1 A or 5 A.
For example, transformation ratios of 45:1 A (750-493) or 200:5 A (750-493/000-
001) are possible. Thus, the corresponding current transformer ratios (CTR) are
1:45 and 1:40.
The I/O module allows you to set user scaling using WAGO-I/O-CHECK or via
Register 32, bit 0. If the bit is set to 0, user scaling is disabled (off) and the
transformation ratio of the current is 1:1.
If the bit is set to 1, user scaling is enabled (on) and the transformation ratio is
already taken into account in the I/O module. The transformation ratio is set using
WAGO-I/O-CHECK or in Register 37. The divisor of the CTR (D-CTR) is set in
the register, i.e. according to the examples above:
• 1A variants:
CTR = 1:45,
D-CTR = 45
=> Register 37
• 5A variants:
CTR = 1:40,
D-CTR = 40
=> Register 37
In the I/O module, the RMS values of the currents are represented in the process
image according to the table "Measured values in the process image (PI)" above
as UInt16 with the following scaling:
• 1A variants:
0.001 A / LSB
• 5A variants:
0.005 A / LSB
Only the following maximum currents can be represented in the process image
and thus only the corresponding maximum CRT values can be supported:
1A variants:
0 ... 65535 at 1 mA/LSB => 0.000 ... 65.535 A
and thus: D-CTR max. = 50, transformation ratios max. = 50:1 A
5A variants:
0 ... 65535 at 5 mA/LSB => 0.000 ... 327.675 A
and thus: D-CTR max. = 50, transformation ratios max. = 250:5 A