Hubbell LX-440 - Manual (Page 6)

Transfer Switch
Page 6 of 16 Pages
The Hubbell Transfer Control Module, LX-301, controls transfer to the emergency source and retransfer
to the normal source. The LX-440 non-automatic transfer switch does not come with a Control Module.
A selector switch initiates transfer and retransfer.
Automatic Operation
Transfer to Emergency Source
The Control Module monitors the normal source phase voltage for acceptable limits of drop-out and
pick-up. A NORMAL OVERRIDE ON MOMENTARY OUTAGE time delay is provided to override voltage
dips causing nuisance starting of the engine generator set. If the normal source voltage is restored above
the pick-up setting within the time delay period, the delay timer is reset.
If the NORMAL OVERRIDE ON MOMENTARY OUTAGE time delay expires before the normal source
voltage is restored, the normal source electronic control initiates engine starting of the generator set
and/or activates the emergency source electronic control. The engine control relay is a 12 VDC latching
relay on the Control Module. The customer connections for the engine start contacts are on PTB1
located on the left side of the transfer switch mounting panel. Refer to the Field Connections Wiring
Diagram posted on the inside of the cabinet door and in the drawing packet for customer connections.
The emergency source electronic control monitors the emergency source for the acceptable voltage and
frequency pick-up levels. When both the voltage and frequency of the emergency source are verified,
24 VDC from the Control Module energizes the TCR (Transfer Control Relay). The normally open
contacts of the TCR close to power the transfer switch switching mechanism via emergency transformer
XFMR2. After the emergency source contacts close, auxiliary contacts TSEb1 open to disconnect
power to the switching mechanism.
Transfer switches with the NEUTRAL POSITION TIME DELAY , stop in the neutral position. After the
adjustable time delay expires, Q1 on the TCR board turns on to energize the TR relay. The TR relay
contacts close to re-connect power to the switching mechanism to complete the transfer.
An EMERGENCY OVERRIDE ON MOMENTARY OUTAGE time delay is provided to override momentary
voltage dips preventing the transfer switch from retransferring to the normal source. If the emergency
source voltage is restored above the pick-up setting within the delay period, the delay timer is reset.
Retransfer to Normal Source
When the Control Module detects that the normal source voltage rises above the pick-up settings, the
timing sequence starts for retransfer to the normal source. The RETRANSFER TO THE NORMAL time
delay starts to allow the normal source to stabilize before retransfer. If the normal source does not meet
pick-up requirements, the delay timer is reset.
At the end of this delay, the TCR is de-energized. The normally closed contacts of the TCR close. The
switching mechanism is then powered by 120 V from the normal transformer, XFMR1, through the
TCR relay contacts. After the normal source contacts close , auxiliary contact TSNb1 opens to
disconnect power to the switching mechanism.
Transfer switches with the NEUTRAL POSITION TIME DELAY, stop in the neutral position. After the
adjustable time delay expires, the TR contacts close to complete transfer.