Alpha Technologies BPT Series Bypass Transformer - Manual (Page 6)

2 Introduction
2.1 The Alpha Bypass Switch (BPS)
The Bypass Switch is a manually operated mechanical switch which is used to select an alter-
nate source of power for critical loads should the UPS require service or maintenance. Nor-
mally the output to the critical load is powered by the UPS and the Bypass Switch is in the UPS
position. If however, the UPS is taken off-line for service or maintenance, the Bypass Switch
can be switched to the Bypass position and the critical loads can still receive power directly
from the utility supply. There are two types of Bypass Switches available: Make Before Break
(MBB) and Break Before Make (BBM). These will be described later in this manual.
2.2 The Alpha Bypass Transformer (BPT)
The Bypass Transformer contains an Isolation transformer and is used in combination with the
Bypass Switch to provide utility isolation when the UPS is taken out of service. Using the BPT
the critical load is isolated from the utility power.
2.3 Bypass Switch Terminology
Number of Poles
The number of poles in a given switch refers to the number of sets of contacts available. A 2-
pole switch, for example, has two sets of contacts and can therefore be used to break or make
each side of a single voltage system. A single pole type switch is shown in Figure 2.1.
Each set of contacts (poles) in the bypass switch will pass 1 of 2 signals through to a common
line (COM). The contacts on each pole change positions together since they share a common
operating shaft connected to the switch knob (Indicated schematically by a dotted line through
the switch contacts. See figures in Section 6 of this manual.
Changeover Contacts
Each pole in the bypass switch comprises a set of changeover contacts. These contacts
selects one of two signals (Bypass or UPS) and passes it through to a common line (COM).
Refer to Figure 2.1 below, the mechanical arm connects the bypass line (contact A) to the
common side of the switch.
When the switch position is changed to select the UPS output, the mechanical arm switches
over to the UPS side of the switch. With contact B now connected to the common, the UPS
supply appears on the LOAD side of the switch.
Figure 2.1
Single Pole Switchover Diagram
UPS
Load side of switch
A
Bypass
Mechanical arm
COM
B
The Alpha BPS Series
Doc# 020-133-B0 Rev. 01 / 07
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