Pilz PZE 9 safety relay

Configuration wiring method Maximum total cable resistance (Rmax) Applicable basic unit example

Single channel Y1 is connected to a safety contact of the basic unit, Y2 is directly connected to A2 (power supply negative/neutral) 24V DC: 50 Ω; 24V AC: 80 Ω PNOZ X (single channel output)

Dual channel (without short circuit detection) Y1 and Y2 are respectively connected to the two safety contacts of the basic unit, with no cross short circuit detection between them. 24V DC: 100 Ω; 24V AC: 160 Ω PNOZ X (dual channel)

Dual channel (with short circuit detection) Y1 and Y2 are connected to two safety semiconductor outputs of the base unit, which need to have cross short circuit monitoring DC: 5 Ω; AC: 10 Ω PNOZmulti or safety PLC

Important: Calculation basis for cable length

Lmax=Rmax/(Rl/km)

L max=R max/(R l/km)。 For example, using a 1.5mm ² copper cable (with a resistance of approximately 12.1 Ω/km), the maximum length under 24V AC dual channel short-circuit detection is approximately 160/12.1 ≈ 13.2 kilometers (which may be much smaller in actual engineering due to the influence of distributed capacitance). The manual provides resistance limits, but in practice, voltage drop should also be considered.

3.2.3 Feedback loop (Y3-Y4 terminals)

Feedback loop is the key to ensuring the integrity of safety functions. The basic unit determines whether the internal output relay of PZE 9 is working properly by monitoring the circuit between Y3-Y4. Standard connection method:

Connect the Y3 terminal of PZE 9 to the feedback input terminal of the base unit (such as Y1 or Y2 of PNOZ X), and connect Y4 to another feedback input of the base unit or the positive pole of the 24V DC power supply (depending on the base unit model). The schematic diagram in the manual indicates that Y1 and Y2 serve as feedback inputs for the base unit (such as PNOZ X) and are connected in series with the feedback loop of PZE. More specifically, the auxiliary contacts 91-92 of PZE 9 are used to display status, but the feedback loop itself is already connected internally? Reading manual: Y3 and Y4 are directly introduced, and users need to connect them to the feedback loop of the basic unit. In fact, PZE 9 has auxiliary contacts 91-92 inside, but the feedback loop wiring diagram shows that Y3/Y4 are connected in series in the feedback loop of the base unit. The operator should strictly follow the manual of the selected basic unit for wiring.

Attention: Auxiliary contacts 91-92 (N/C) are used for indication purposes (such as connecting indicator lights or PLC inputs) and must not be used for safety circuits. The feedback loop must use Y3-Y4 dedicated terminals.

3.2.4 Output Contact Wiring

Safety contacts: 8 pairs of normally open, terminal numbers 13-14, 23-24, 33-34, 43-44, 53-54, 63-64, 73-74, 83-84. These contacts can be used to cut off hazardous sources (such as motor contactors, valves).

Auxiliary contacts: 91-92 (normally closed), cannot be used for safety functions.

Fuse protection: To prevent contact welding, a suitable fuse or circuit breaker must be connected in series before the output contact. Recommended manual:

Safety contacts: fast fuse 10A, slow speed 6A, gG type 10A, circuit breaker (B/C characteristics) 6A.

Auxiliary contacts: fast fuse 4A, slow speed 2A, gG type 4A, circuit breaker 2A.

Wiring material: Copper wire is used, with a temperature resistance rating of 60/75 ° C. The torque of the screw terminal is 0.5Nm, and the stripping length is 6mm. The maximum size of single core flexible wire is 4mm ² (AWG 10), and the maximum size of double core flexible wire with the same cross-section is 2.5mm ² (AWG 14).

3.3 EMC and Wiring Rules

Control cables (input, feedback loops) should be routed separately from power cables (motors, frequency converters), with a minimum spacing of 200mm, or shielded cables should be used.

For capacitive and inductive loads, suppression circuits (such as RC absorbers, varistors, or freewheeling diodes) must be installed at both ends of the contacts to extend contact life and reduce interference.

Important warning: Do not switch small currents (such as a few milliamps) on contacts that have previously passed large currents, otherwise poor contact may occur due to surface oxidation of the contacts. If it is necessary to switch low-level signals, a gold-plated contact dedicated relay should be used.

Functional principle and safety working logic

4.1 Normal working sequence

Power on: POWER LED lights up.

Input circuit closure (basic unit safety contact closure):

Internal relay excitation, 8 safety contacts (13-84) closed, auxiliary contacts 91-92 disconnected.

CH.1 and CH.2 LEDs light up simultaneously (indicating that both channels are closed).

Input circuit disconnected (press emergency stop or open protective door):

The internal redundant contacts are immediately disconnected, the safety contacts are opened, and the auxiliary contacts are closed.

CH.1 and CH.2 LEDs turn off.

4.2 Safety features and fault detection

PZE 9 itself does not perform logical judgment, it relies on the feedback loop of the basic unit to detect its own faults:

Contact fusion welding detection: If a group of safety contacts cannot be opened due to overcurrent fusion welding after the input circuit is disconnected, the feedback circuit will remain conductive (because Y3-Y4 is still internally connected), and the basic unit will detect this abnormality during the next reset, preventing restart.