This automatic transfer switch uses a ComAp ATS Controller combined with motor contactor switching to provide a fully-featured ATS with full metering & history logging, and can also be remotely monitored.

• InteliATS 50
• InteliATS 70 includes PLC logic blocks

• An Auto Mains Fail Transfer Switch using relay logic is also documented here.

(DSN) files can be edited with TinyCAD.

Contactors K-U [3] and K-G [5] are mechanically and electrically interlocked to ensure that only one can be closed at a time.

• Utility Connected: Two Green indicators (L-U, L-KU)
• Generator Connected: Two Blue Indicators (L-G, L-KG)
• Load Connected: White Indicator(s) (one per phase, if desired)
• K-G [3], K-U [4]: Utility & Generator Power Contactors, 400 Amp 3-pole

1. Starting with Utility Power being supplied to the load: Contactor K-U [3] is closed, and all timers have expired.
2. Power is removed from the coil for K-U [3] if:
   1. Utility power fails
   2. Voltage on any phase exceeds minimum or maximum voltage setpoint.
   3. Frequency exceeds minimum or maximum setpoint
   4. Phase rotation is reversed
3. When K-U [3] opens:
   1. Load is disconnected (Preventing damage to equipment caused by low voltage.)
4. If utility power fails to return within 5 seconds:
   1. InteliATS closes KGS [6] to start the genset
5. Once the generator is running, the InteliATS:
   1. Qualifies input for minimum, maximum voltage on all phases, correct phase rotation, minimum, maximum frequency
   2. Illuminates L-G (Blue) indicating generator power is OK.
   3. Begins countdown (5 seconds).
6. K-G [5] then closes:
   1. Supplies generator power to the load
   2. Opens the neutral connection for the coil on K-U [3], preventing K-U [3] from closing by accident.
   3. Illuminates L-KG (Blue) indicating that generator is supplying the load.

1. When Utility Power returns, InteliATS:
   1. Qualifies input for minimum, maximum voltage on all phases, correct phase rotation, minimum, maximum frequency
   2. Indicator L-U (Green) illuminates to confirm utility grid voltage is acceptable
2. Begins time delay (15 minutes), which ensures:
   1. The utility grid has time to stabilize
   2. Delays adding loads to the grid after an outage
   3. Eliminates short-cycling if the grid drops again shortly after returning
   4. Provides a minimum run-time for the generator to ensure it gets up to operating temperature
3. Opens the coil for K-G [5]:
   1. Disconnects load from Generator
   2. Connects neutral of K-U [3] coil
4. K-U [3] closes after setpoint time-delay (as short as 1mS)
   1. Connects load to Utility Grid
   2. Disables K-G [5] by disconnecting neutral of coil
   3. Illuminates L-KU (Green), indicating Utility/Grid is supplying load
5. Begins time delay (2 minutes) for Generator cool-down (running with no load)
   1. Opens KGS [6] to disconnect the generator auto-start signal
   2. Genset stops

• Operating S2, Manual Bypass, forces selection of Utility or Generator power and bypasses InteliATS controls
  • S2 is mounted inside protective shroud to prevent casual operation
• Operating S1, Auto/Gen, forces selection of Generator by InteliATS
  • InteliATS will start generator, qualify power, then turn off K-U [3] and turn on K-G [5] after setpoint delay (as short as 1mS).
• Switching S1 back to Auto will switch back to Utility power if it is qualified based on normal setpoint limits.

• Operating the Emergency Stop (E-Stop) mushroom switch immediately disconnects all power sources and shuts down genset, if it is operating.
• The E-Stop must be turned clockwise to release the latched condition, and the alarm reset on the InteliATS in order to return to normal operation.

• BOM 117 -- Google Sheets
• BOM 117 -- Web Page