Page 1 Three-phase power is delivered in a variety of forms. The approach here is to utilize a non-Blondel solution (all non-neutral conductors measured independently) with a universal hookup. Any delta load can be viewed as an equivalent wye. Also, a wye without an accessible neutral can be treated the same way. A common service known as "high-leg delta" is handled a little differently in that it can be considered a 2-phase circuit (with two different voltages) requiring a PT suitable for each. Normally 3-phase measurement requires THREE PT's per processor connected through a Phase Selector Assembly. The general 3-phase hookup will look like this: A-phase PT \ B-phase PT ===Cat5=== Phase Selector Assembly ===Cat5=== mMII Processor C-phase PT / | Cat5 | Computer port
PT120's PT120's-to-PSA PT's and RS232-to-PSA PSA full All with Type 2 Processor *NOTE: The Terminal Board may have a second row of 16 terminals that is NOT USED at this time. Be very careful to route the blue pair in from the processor and back out to the computer without any crossing with other color pairs carrying 24 volts.
Cat5 Color Code Table 30c - Using Cat5 for Extended CT or PT Clusters Wire Color Extended CT Clusters Extended PT Clusters 1 orange (w white) A phase long A phase X2 2 white w orange A phase short A phase X1 (common) 3 brown (w white) B phase long B phase X2 4 white w brown B phase short B phase X1 (common) 5 green (w white) C phase long C phase X2 6 white w green C phase short C phase X1 (common) 7 blue (w white) spare spare 8 white w blue spare spare Page 3 * Extreme care must be used to avoid confusing the Cat 5 connections. The wires carrying 29 volts ac can make a nasty spark and damage the main board. Reversal of R1 and R2 will cause voltage reference for B-phase to be replaced with the voltage reference for A-phase. This could remain undiscovered and affect accuracy of readings (based on AAC rather than ABC). In a 3-phase wye (with accessible neutral), true power, mMI or mMII applications the PT primaries shall be wired as a wye with a connected neutral. (3/5/2008) The common point of this neutral is the PSA terminals 2, 4, and 6. Reversing a PT secondary is fine if needed to correct phase BE SURE TO VERIFY THAT SECONDARY VOLTAGES ARE BETWEEN 26 AND 32 VOLTS AC BEFORE CONNECTING TO PROCESSOR! Use appropriate PT for phase-to-phase voltage. 1/30/2008 - Verify PT terminal phasing in parts list (Readme2) or by the connections used in the desktop hookup. pic PT pri 1 A-phase H1 2 B-phase H1 3 C-phase H1 4 H2 for A,B, and C If polarity is not known, reversing PT secondaries on a trial-and-error basis is possible. Absolute phase identification is not essential. The leftmost can be A, etc. phase-to-phase voltage PT primary voltage 208 120 240 138.5* 416 240 480 277 *More than likely, this is a high-leg delta which only requires one PT120 and one PT208 The general 3-phase hookup will look like this: A-phase PT \ B-phase PT ===Cat5=== Phase Selector Assembly ===Cat5=== mMII Processor C-phase PT / | Cat5 | Computer port
A bank of three PT's may drive more than one processor extended according to Cat5 Color Code Table 30c - Using Cat5 for Extended CT or PT Clusters (above). Allow 2va (PT power rating) for each processor phase and be very careful not to cross wires between processors
Phase Selector Assembly. Table 31b - Phase Selection Channels: R1 R2 Processor toggles TP,AP (same as Powerstats Kit for mMI) 01 A ph TP,AP 0 0 02 B ph TP,AP 1 0 03 C ph TP,AP 1 1 04 A ph TP,AP 0 0 05 B ph TP,AP 1 0 06 C ph TP,AP 1 1 07 A ph TP,AP 0 0 08 B ph TP,AP 1 0 09 C ph TP,AP 1 1 10 A ph TP,AP 0 0 11 B ph TP,AP 1 0 12 C ph TP,AP 1 1 13 A ph TP,AP 0 0 14 B ph TP,AP 1 0 15 C ph TP,AP 1 1 16 A ph TP,AP 0 0 Phase sequence for a 120v wye can be determined this way. Identify the leading phase with the following tester: 60 watt bulb 60 watt bulb A ph ----0-------------|-------------0---- B ph | | | 15 watt fluorescent ballast coil (.75 henry) | | | neutral The leading phase will have the dim light and the lagging phase will have the bright one. *** 3-phase simulations 3-phase simulations Phase Selector Assembly tests w 120v wye High-Leg Delta test bed w 120/208/240 volts
Determine phase-to-phase voltage PPV. Enter voltage in SETUP as 1.7321 times PPV. e.g. 1.7321 * 208v = 360v. Enter in SETUP as actual CT size with voltage determined above. 1/25/2008 - This is to show 3x power usage for one phase and 1x ampere demand. >>> 3-Phase Unbalanced Delta or Wye Load Measured on Three Conductors With a Three-Phase Processor pic
Phase Selector Assembly. This would allow three 16-channel processors to meter 16 3-phase loads. The 16th channel is not wasted and less hardware is required (no Phase Selector Assembly). The downside is that information about any given 3-phase circuit resides on 3 separate processors and must be combined upon readout.
This is a most common service for a small one-customer commercial location. A single- phase 120/240 volt service is augmented with a 208 volt leg from an open delta (2 pot) or full delta (3 pot) utility drop. The 120/240 feeds standard fixtures and appliances and the 208v feeds lighting at a 90-degree phase shift. Proper phasing for an analytical installation is difficult to plan but easy to remedy. Phase rotation and identification is not necessary with this procedure. Install as for single-phase using a PT120 and reserving every 3rd channel (3,6,9,12, and 15) for 208v loads. The PT120 will feed A phase and B phase (reversed). Ensure that true power reads correctly on the single-phase channels (1,2, 4,5, etc.) reversing any incorrect CT connections. If more than half are wrong, reverse the PT120 X1,X2 connections first and check it again. Now connect the PT208 to C phase and check every 3rd channel. If more than half are wrong, reverse the PT208 X1,X2 connections. Reverse any remaining CT connections that are incorrect on the 208 volt circuits.
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