THOMSON TS 880 - Normal Sequence of Operation - Closed Transition

TS 880 TRANSFER SWITCH
PM064 REV8 10/01/25 12 Thomson Technology
The generator will continue to supply the load until the utility supply has returned.
The retransfer sequence is completed as follows: when the utility supply voltage is
restored to above the preset values (adjustable from 70% to 99% of nominal) on all
phases, a utility return delay circuit will be initiated. Following expiry of the Utility
Return Timer (adjustable from 0 to 60 min.), the Transfer to Generator Supply signal
will be removed (contact opening), and then the Transfer to Utility Supply signal
(contact closure) will be given to the transfer switch mechanism. The load will then
retransfer the load from the generator supply back to the utility supply. Note: A
neutral delay timer circuit will delay the transfer sequence in the neutral position (i.e.
both power switching devices open) until the neutral delay time period expires
(adjustable from 0 to 60 seconds).
An engine cooldown timer circuit will be initiated once the load is transferred from
the generator supply. Following expiry of the cooldown delay period (adjustable
from 0 to 30 minutes), the engine start signal will be removed (contact opening) to
initiate stopping of the generator set.
5.1.2. NORMAL SEQUENCE OF OPERATION - CLOSED TRANSITION
TYPE TRANSFER SWITCH OPTION
For transfer switches equipped with the Closed Transition transfer option, the ATS is
configured to operate as follows:
Under normal closed transition operating conditions, the transfer switch operates
automatically during a failure and restoration of utility power and does not require
operator intervention.
When utility supply voltage drops below a preset nominal value (70 - 99% of rated
adjustable) on any phase, an engine start delay circuit will be initiated and the
transfer to utility supply signal will be removed (i.e. contact opening). Following
expiry of the engine start delay period (0 - 60 sec. adjustable) an engine start signal
(contact closure) will be given.
Once the engine starts, the transfer switch controller will monitor the generators
voltage and frequency levels. Once the generator voltage and frequency rises
above preset values (70 – 99% nominal adjustable) a warmup time delay will be
initiated. Once the warmup timer (0-60 Min adjustable) expires, the transfer to