Owner`s manual

zero to +5V. The +2.495V is used as the reference for the LMC660 amplifiers, signal transformers, which are used
to measure the AC input and load voltages, and AC current transformers.
4.8.1.1 “Controller” Input Signals
The DC current sensor used to measure the battery current is “LEM” HTA types and require +15VDC, return, and
–15VDC. We do not have a negative 15VDC supply, thus the LEM was offset by 15V. The –48VDC battery line,
which is called AGND (“Analog Ground” after fusing) was connected to the “LEM’s” –15V terminal, the “return” was
connected to +14.97V, and the +15V terminal connected to +30V. This +30V is quasi regulated by a 16V zener
(anode connected to the +14.97V) and NPN transistor, TIP47. The HTA-X00 sensors are set up to produce an
output of +4.00 volts at rated DC current. The model number of the HTA-X00 changes depending on the number
of power module positions available in the “Receiver” cabinet. The field service setup software is needed to tell the
micro how many positions are available so that the proper scale factor can be programmed into the EEROM.
4.8.1.2 DC Current Measurement
Below is a table of “LEM” model numbers to be used in the various receiver configuration.
Power Module Model Current Output Max Current
Positions Number Rating voltage Measurement
1 HTA-100 100A 4.00 137.8A
2 HTA-200 200A 4.00 275.6A
3 HTA-300 300A 4.00 4133.9A
4 HTA-400 400A 4.00 551.2A
5 HTA-500 500A 4.00 689.0A
6 HTA-600 600A 4.00 826.8A
The actual maximum operating current is less than the rated current. For zero DC input current, the output of the
HTA-X00 sensor will be at zero with respect to its “return”, which is actually connected to +14.97V. At full rated
output current, the HTA- sensor will output 18.970V (14.97+4.00 =18.97). Sensors are intended to measure AC
current, thus have at lease a 141% DC measurement capability. The LMC660 amplifiers are set up to range
between +4.50V to +0.50V (HTA-100 measuring range of zero to +125A). The other HTA sensors produce the same
voltage swing for different current levels. The Micro scale factor is based on the number of power module positions
available, not power modules installed in the “Receiver” cabinet, and must be set up properly.
4.8.1.3 Analog Inputs
The table below identifies the eight analog inputs to the processor. The input will make a voltage that ranges from
+4.50V to +0.50V at the appropriate input port of the processor. Voltages to the analog input terminal of the
processor, which are between 0.10 and 0.25V are usable. Voltage above 4.75V may not be processed since the
minimum Vcc supply voltage to the processor is 4.75V via a linear regulator, LM7805CT or LM340T5.0.
Owner’s Manual
Theory of Operation page 4 — 11