HEIDENHAIN MANUALplus 620 Technical Manual page 191

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January 2012

The two 24 V output voltages of the PSL 13x are generated by two separate

power supplies. The + 24 V NC and + 24 V PLC voltages are separated from

each other by basic insulation and fulfill the requirements of EN 61800-5-1 for

low voltage electrical separation.

The 0 V line of the NC supply voltage must be connected separately to the

central grounding point of the machine (= central functional ground). The 0 V

NC voltage in the PSL 130 is therefore connected internally with the outward

conductor to signal ground (= central functional ground). An outward connec-

tor to protective ground will not be available for the 0 V PLC voltage until vari-

ant 03. With the variants up to and including variant 02, the 0 V PLC must be

tapped at terminal X90.4 and led to the central protective ground. In variant 03

and later variants, an outward connector at the PSL will be available for con-

necting the 0 V PLC voltage, too.

With the PSL 135, the connections to the central functional ground and pro-

tective ground must be realized over the 0 V connections. The respective out-

ward connections will not be available until the next hardware variants of the

The +24 V PLC voltage is also electrically separated by the power supply unit.

However, because of the connection to the PLC part of the HSCI system this

is a supply voltage with basic insulation. This voltage must not be linked with

other voltages.

The +5 V NC supply voltage for X74 of the PSL 135 is taken from the +24 V

NC supply voltage and is therefore galvanically connected with it.

For the entire HSCI system, the +24 V NC power supply voltage is

required to be safely separated voltage and must not be connected with

the +24 V PLC voltage of the system.

Protective Extra Low Voltage (PELV) according to EN 61800-5-1 must be

complied with for the +24 V NC power supply of the machine.

The 0 V signal of the PLC power supply must be connected by a 6 mm

conductor to the machine's central protective ground (PE).

Refer to your control's grounding diagram!

3.6 Supply Voltages in the HSCI System