TS_604_01 PowerWave PW3000/TP User Manual UK 5/1/18 5
2: General Description
UPS Bypass input supply
A single phase bypass supply is connected directly to the Maintenance Bypass Switch and also to the bypass side of the
static switch, via the ‘Mains 2’ (M2) breaker and a fuse on the Input EMI Filter. In a standard installation the bypass input
terminals are usually linked to the mains input supply L1 terminal, so only one mains supply feed is required. This is often
referred to as a ‘Single Feed’ input configuration, as opposed to a ‘Dual Feed’ input where a separate bypass supply is
used. (See paragraph 3.7 for details concerning ‘Single Feed’ & ‘Dual Feed’ supply configurations.)
Battery charger
The battery charger can be powered from either the Mains Input or Bypass Input supply, and charges the internal (or
optional external) batteries when either of these supplies is present. It’s power source is selected by a relay which
automatically switches over to the Bypass Input supply when the Mains Input is not available. The charger is rated at 2A
but can be increased to 4A if required, depending on battery topology.
Rectifier / DC Converter
The Rectifier / DC Converter produces a controlled DC voltage for the Inverter input. This can be sourced either from the
UPS Mains input supply (AC) of from the battery (DC). An automatic changeover switch ensures that the two sources are
never connected to the Rectifier /DC Converter simultaneously, with the UPS Mains input always being accepted as the
preferred source provided it remains within specified limits.
Power Inverter
A single phase Inverter converts its DC input from the Rectifier / DC Converter into the required UPS output AC supply.
The output voltage is tightly regulated using advanced PWM techniques and the output frequency is similarly controlled.
Usually, the inverter operates at the same frequency as the UPS input/bypass supply; however, the UPS can be operated
in a frequency-changing mode whereby the input and output frequencies are different – e.g. 50Hz/60Hz input/output. Note
that when used as a frequency-changer, the UPS bypass circuit is automatically inhibited.
Static switch
The static switch block contains two static switches connected across a load transfer relay, one is connected to the bypass
supply and the other to the inverter output. When the load is transferred between the bypass and inverter the appropriate
static switch turns on for a brief period to maintain the load supply while the load transfer relay operates. The
microprocessor system automatically controls the load transfer between inverter/bypass sources as dictated by local
conditions (e.g. overload) and provides a means of performing a manual load transfer.
Output relay
The output relay is used to connect/disconnect the UPS output in a parallel module system, and enables the UPS to be
quickly isolated from the system in the event of a UPS fault.
Maintenance bypass switch
The Maintenance Bypass Switch connects the UPS AC Output terminals directly to the Bypass Input and provides a
means of temporarily supplying the load from the raw mains while the UPS is otherwise shut-down for maintenance repair.
It operates in a make-before-break fashion to ensure the load is supported during the transfer.
In order to protect the UPS inverter, the load must be transferred to the static bypass supply before the Maintenance
Bypass Switch is closed – this is performed automatically when the Maintenance Bypass Switch access cover is removed.
When the load is connected via the maintenance bypass the UPS can be shut down safely for repair, with the only
remaining live areas within the UPS being the input/output power connections and isolators.
UPS AC Output (load) supply
Figure 2.1 shows that the UPS output (Load Supply) can be provided through one of three power paths depending on the
UPS operating mode – the criteria for operating under each of these UPS modes is described in 2.3.2:
• From the inverter, via the inverter-side static switch and output relay
• From the static bypass line via the bypass-side static switch and output relay
• From the maintenance bypass line via the maintenance bypass switch