7.3 Main contactor ON/OFF

The main contactor can be switched on and off via this menu. The fields above the buttons show whether the contactor may switch on and whether it really is on; a tick means “yes” in each case. What the contactor symbol in the upper menu bar shows is explained at the end of this section.

How the fields depend on each other is shown by the ladder diagram below. A rung conducts only if every contact in it is closed; a contact with a slash is a break contact, the circle at the end is a coil. The main contactor therefore pulls in only if all boards release, the operator switches it on and the external circuit is closed.

Figure 26: The release of the main contactor as a ladder diagram. The feedback measures the voltage ahead of the coil, not the position of the contactor contacts.

Enable ‹board›: One field per controller board. The tick is set when the board releases the main contactor. If it is missing, the board is holding the contactor off – because it has detected a fault itself, is still in update mode or is just starting up. The event log then shows WRN-99, “No release for main contactor” with the name of the board. The field reports what the board itself switches – whether the chain actually goes through is shown by “Boards OK”. On the causes, see FAQ-06, “Contactor does not pick up”. The ladder diagram shows how it fits together, Figure 26.

Control/Desired: The switching command last given by the operator – with the On and Off buttons below; after a restart the device restores the last state. The device also withdraws the tick by itself if the contactor does not report back or a board finds no phase. The event log then names the reason, see MSG-90, “Contactor off! Reason: Channel Board”, MSG-91, “Contactor off! Reason: External Safety Circuit” and MSG-92, “Contactor off! Reason: No phase despite command”. The ladder diagram shows how it fits together, Figure 26.

Feedback: Whether the coil of the main contactor is live – what is measured is the phase at the end of the safety circuit, not the position of the contactor contacts. If it does not arrive within four seconds of switching on, or drops out during operation, the device withdraws the command – that is the safety function, not a fault. If the feedback is present although the command is off, the relay on the display board is welded or the coil is fed externally: take the device out of service and notify customer service. A welded contactor itself is not detected by the device. The ladder diagram shows how it fits together, Figure 26.

The contactor symbol in the upper menu bar shows command and feedback in a single sign. It is red as soon as the contactor is commanded or its coil is live, and crossed out as long as the coil has no voltage. A red, crossed-out flash therefore means: commanded, but not switched on. If the state cannot be determined, a red exclamation mark appears, see FAQ-05, “Contactor symbols”.

Appearance	Command (target)	Feedback (actual)	Meaning
Flash crossed out, white	Off	Off	Normal state. The device is safely switched off.
Flash filled, red	On	On	Normal state. The device is active and the feedback confirms it.
Flash crossed out, red	On	Off	Discrepancy. The contactor does not pick up despite the command – usually the safety circuit is open. To investigate, see FAQ-06, “Contactor does not pick up”.
Flash outline, red	Off	On	Critical fault. The contactor coil is live although the software commands “off” – the relay on the display board is welded, or the coil is fed externally. Take the device out of service and notify customer service.

WARNING

When the main contactor is switched on, voltage can be applied to the tool connector at any time!

Before switching on, the device asks for confirmation: “Switch on main contactor?” Only the confirmation applies voltage. The prompt also appears when switching on is triggered from another operating path — at the end of the Wizard, for example.