Eaton ATC-900 Automatic Transfer Switch Controller Glossary of terms and transition types

Glossary of terms and transition types

Available

A source is defined as available when it is within its undervoltage/

overvoltage/underfrequency/overfrequency/unbalance(if applicable)

setpoint ranges for the nominal voltage and frequency setting.

Unavailable

A source is defined as failed when it is outside of its undervoltage/

overvoltage/underfrequency/overfrequency/unbalance (if applicable)

setpoint ranges for the nominal voltage and frequency setting.

Normal source

The normal source is defined as the source that is preferred. The

preferred source setting allows the operator to select source 1.

source 2 or NONE as the preferred source. If NONE is chosen, the

preferred source or the normal source will be the source that is

presently attached to the load. The default is set as being source 1

as the preferred and normal source.

In-phase operation

The in-phase operation of an automatic transfer switch is an open

transition transfer. It will allow a transfer between two available

sources if the phase angle has a difference of five degrees or less.

See section 1.5.4 for more details.

As shown in the feature list of Appendix A, there are three scenarios

for in-phase:

32C= In-phase default to load voltage decay

32D= In-phase default to time delay neutral

32F= In-phase

The user setpoints for in-phase transition are as follows:

• Disabled (in-phase not used)

• Alarm on synchronization fail (will not switch and will show an alarm)

• Fallback to open on synchronization fail (To TDN or LVD)

For example, with the setpoint at fallback, using a two position

contactor, the switch will transfer to the other source if no synchroni

zation occurs, whereas a three position contactor will allow the use

of TDN or load voltage decay.