ABB 10D1476, Инструкция по эксплуатации

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This may be expressed mathematically as:
(Equation #1)
E
s
= 1 BDV
α
where,
E
s
= induced electrode voltage
B = magnetic field strength
D = meter pipe diameter
V = liquid velocity
α
= dimensionless constant
Thus, the metered liquid constitutes a continuous series of conductive liquid discs moving through a
magnetic field. The more rapid the rate of liquid flow, the greater the instantaneous value of signal
voltage as monitored at the meter electrodes.
4.1.2 Magnet Coil Drive Circuits
In most conventional Magnetic Flowmeters the integral magnet coils are driven directly by the
customer’s 50/60 Hz power service. Notably, however, the design of the Series 10D1476 Magnetic
Flowmeter uses magnet drive circuits which are alternately energized bi-directionally at a low
frequency rate as commanded by the associated Converter/Driver assembly.
4.1.3 Volumetric Flow Rate Measurement
The Magnetic Flowmeter is a volumetric flow rate measuring instrument. This can be shown by
substituting the physical equivalent of liquid velocity into equation #1, preceding, as follows:
(Equation #2)
V = Q = 4Q
A
π
D
2
Substituting for V in equation #1
E
s
= 1 BD 4Q
α π
D
2
and solving for Q:
∴
Q =
πα D
2
.
Es
4 B
Since B =
β
E
r
and since
α
, D and
β
are constant:
10D1476 K-MAG MAGNETIC FLOWMETER INSTRUCTION MANUAL
4-2