To conform with EN60204-1, machines with a rated power of less than 3kW and a maximum of two external control devices (e.g. limit switches, Emergency Stop devices, etc.) are allowed to be operated without a control transformer. With three control devices and more there has to be a control transformer with overcurrent protection (see circuit diagram K3000 with isolating transformer).
All switches with limit switch function and Emergency Stop function are of release-free design. This means that switching on is impossible when the control device has responded.
All control devices are connected to the supply line of the undervoltage trigger. When a control device (limit switch, Emergency Stop controller) is actuated, the undervoltage trigger responds and the machine is stopped immediately. Switching on is impossible when a control device is actuated.