Bitronics QTWIE2, Руководство пользователя

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ML0030 August 2009 Copyright 2009 Bitronics, LLC
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2.0 PRINCIPLES OF OPERATION
Figure 1 - WATT/VAR Meter Exploded View (QTWIE1 Shown)
2.1 Modular Construction
The Bitronics WATT/VAR Meters are composed of two major modules, as shown in the
exploded view of the meter (Figure 1). The BASE MODULE consists of the case tube, the
back panel, the Current Transformer & Potential Transformer Board and the Power Supply
Board. The Base Module contains primarily passive components (transformers,
connectors, etc.) and cannot be serviced without removal from the panel. The
ELECTRONICS MODULE consists of the Analog Processing Board, Microcontroller Board
and the LED Display Board. Ninety percent of the active electronics (Integrated Circuits,
diodes, etc.) are contained within the three boards comprising the Electronics Module. This
module can easily be removed for maintenance without the need to remove the meter from
the panel, or to remove the meter from service (see section 4.4). Detailed descriptions of
each of the boards can be found in the following sections.
2.2 Input Signal Connections
The WATT/VAR Meters have six independent signal inputs; one current and one voltage for
each phase being measured. Current and voltage signals are connected directly to #10-32
brass studs on the rear panel of the instrument. WARNING - DO NOT overtighten the nuts
on the input connections, HAND tighten with a standard nutdriver, 12 inch-pounds is
recommended, MAXIMUM torque is 15 inch-pounds. The instrument can be connected
directly to current transformer (CT) or potential transformer (PT) circuits. The impedance
at the WATT/VAR terminals is nearly a short circuit (2 milliohms) for ammeters and high
impedance ( > 100 K-ohms) for voltmeters. These ideal impedances provide low burden
loads for the CT or PT circuits supplying the signals. The polarity of the applied signals is
important to the function of the instrument, and the signal terminals are labeled LO or HI to