MYERS MP Series, Installation, Operation & Maintenance Manual

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2.1.3 Theory of Operation
The Myers Emergency Power Systems (MPP) battery backup system (BBS) consisting of
three main components.
MP2000E BBS module- The BBS component has two main operating modes: On Line and
On Battery. When On Line the BBS functions as a line interactive back up system. Line
interactive BBS units are designed so that the inverter is always connected to the output
of the BBS. When line power is present, the inverter operates in reverse to charge the
battery. When utility power fails, the BBS reverses the power flow from the inverter and
provides power to the load. This design provides better filtering than a standby unit
because the inverter is always connected to the load.
Line interactive MP2000E also incorporates Buck and Boost, an automatic voltage
regulator. Buck and Boost allows the BBS to effectively step-up or step-down the
incoming line voltage without switching to battery power. This allows the BBS to correct
most long term over-voltages or under-voltages without draining the batteries. Another
advantage is that it reduces the number of transfers to battery which extends the lifetime
of the batteries.
On Battery Mode: The batteries supply direct current to the MP2000E inverter. The BBS
filters the DC input through input capacitors and metal oxide silicon field effect transistors
(MOSFET) that feeds a transformer that steps the voltage up to 120 VAC. The 120VAC,
60Hz waveform generated by the MP2000E inverter is a pure sine wave.
Full Intersection Operation: The MP2000E is designed to supply full backup power within
the BBS rating.
Red Flash Intersection Operation: By wiring and programming any one of the six dry
contacts on the MP2000E to the traffic signal controller red flash circuit , see Figure 15.
The terminal block is opto-isolated and shares a common ground with the serial interface.
Each of the six programmable contacts can be programmed for one or more functions
such as: The Timer, Low Battery and On Batt. The relay contacts are Form C type, i.e.
Each of the six programmable contacts has Common (C); Normally Closed (NC) and
Normally Open (NO) contact position.
On Batt: This relay energizes when Utility Input line power is unqualified.
Low Battery: These relays energize when the battery drops below the programmed
battery capacity. The default value is 47.5VDC or 40% battery capacity.
Timer: These relays energize after the unit has been in Battery mode for the programmed
time period. The factory default value is 2 hours.