Month: September 2025

Features and Benefits

■ Inputs: 120/240 VAC or

125 VDC power feeds allowing

mixed AC and DC operation.

■ Outputs: Provides Harmony sys

tem power of 5. +15. and 24

VDC and field power of 24. 48 and 125 VDC.

■ Availability: Built-in power dis

tribution schemes support

single and dual (main and auxil

iary, AC and DC) power feeds

for 2N power configurations.

ControlIT

Modular Power System III

■ Reliability: Automatic load shar

ing of dual supplies reduces the

burden on an individual supply,

increasing the overall reliability and high MTBF.

■ Serviceability: Local status indi

cators, disconnects, and plug-in

cable assemblies facilitate on

line fault isolation and replacement.

■ Monitoring: Provides system DC

power outputs, field power out

puts, fan status, and cabinet

temperature monitoring.

■ Industrial Quality: Designed for

operating temperatures as high

as 70o C (inside cabinet) as well

as MIL-STD ratings for vibra

tions, IEC standards for EMI and

RFI, and UL ratings for flammability.

■ Price/Performance: Power factor

correction, electronic output

protection and lower costs are

inherent features.

■ Upward Compatibility: Compact

design allows for use in the new

standard ABB cabinets and as

replacement for older power

systems supplied with

Symphony™ and INFI 90® OPEN systems.

The Modular Power System III (MPS III) is specifically

designed for powering Harmony rack modules and associ

ated field mounted devices. The MPS III can provide 5. +15.

and 24 VDC system power as well as 24. 48. and 125 VDC for

field powered devices. Special features of the MPS III

include: power factor correction, on-line power supply

replacement, power and cooling status monitoring, and

adaptability to various power input sources. The MPS III

assembly includes all the hardware necessary for AC input

power distribution to the individual power supplies, DC out

put distribution, power and fan monitoring, interconnecting

cables, and cabinet mounting hardware.

A family of preconfigured power supplies has been engi

neered to provided various combinations of voltage options

and associated power ratings. The MPS III is designed to sup

port 2N power redundancy. Multiple preconfigured power

supply configurations are available to facilitate matching the

most cost-effective solution with project power requirements.

Detailed specifications relating to these supplies are listed in

the MPS III data sheet.

The positioner does not meet safety requirements under the

following conditions:

• during installation, configuration, repair and simulation

• during an inspection or proof-test

Before commissioning the positioner in a safety loop

application, the end user must check whether the installation

setup confirms to the system’s safety function.

The end user must verify also that the correct positioner has

been installed at the correct positioning point.

Whenever the positioners operating conditions are changed (for

instance, if the mounting position is changed or the setup is

modified), the safety function must be checked again.

The following constraints need to be considered when using the

positioner for SIL safety applications:

• Only the 4 to 20 mA setpoint signal is used for the safety

function, all other inputs or not part of the safety function.

• The proof-test specified within this safety manual (or an

equivalent test as specified for the final SIS safety

function) shall be performed before activating the safety

operation and in periodical cycles as demanded by the

final PFDAVG demands.

• The device is installed per manufacturer’s instructions

• The safety-related system (safety logic solver) must be

able to force the 0 mA signal direct or by using a safety

capable switch on the 4 to 20 mA signal.

• Materials are compatible with the final process conditions.

• The environmental, measurement and application limits

stated within the referenced documentations must be

considered accordingly for the SIL safety application.

The positioner safety function is declared as Type A element

with HFT=0 according to IEC 61508 capable to be used for SIL

Functional Safety Functions up to SIL 2.

According to IEC 61508-2. 7.4.7.4 a useful lifetime, based on

experience should be assumed.

The components of the positioner do not contain any specific

components with a reduced useful lifetime that are contributing

to the dangerous undetected failure rates.

Because the positioner is a moving masses system supplied by

instrumented air the final device usage and environmental

operating conditions (e.g., no/many open-close cycles,

good/bad supply air quality) will have an impact on the usefullifetime.

Therefore, the useful lifetime should be evaluated by the end

user according to the final plant experience data.

The Periodic Proof-Test methods within chapter Periodic Proof

Test and Maintenance on page 9 are suggested to validate the

correct safety function.

When final plant experience, proof testing and related field

monitoring data indicates a limiting useful lifetime by related

operating conditions, then the plant experience-based lifetime

must be used and considered on the failure rates, proof-test

intervals, and replacement intervals.

The safety function is activated if the electrical 4 to 20 mA

setpoint signal is set to 0 mA. This 0 mA signal might be forced

as direct logic solver/DCS output or by an additional electrical

open/close switch within the 4 to 20 mA setpoint line.

As reaction on the 0 mA signal the electronics, firmware &

position measurement is deactivated and bypassed, and the

mechanical pneumatic system of the positioner will be

depressurized into the fail-safe position.

The return spring of the attached pneumatic actuator will move

the valve to a safe end position (OPEN or CLOSED) subsequently.

The final safe state is achieved if the valve is located in the safe end position.

The time taken to reach the expected safe end position at the

process valve is only partly determined by the positioner; it is

also dependent on the attached actuator and valve assembly and

further external conditions, therefore the correct safety function

as expected within the final application must be checked during

installation & commissioning and the end user is responsible to

validate whether the safe state is achieved in the expected

direction and within the expected time frame.

Application area

The TZIDC is an electronically configurable 2-wire 4 to 20 mA valve positioner with HART® communication capabilities designed for

mounting on pneumatic linear or rotary actuators.

The TZIDC-200 is a variant designed with a flameproof enclosure as explosion protection concept.

The integrated I/P module with subsequent pneumatic amplifier is used to control the attached pneumatic actuator.

The SIL Safety Function is intended to open or close actuator/valves assemblies as emergency application.

By providing 0 mA as control/setpoint signal the positioner depressurizes the fail-safe actuator which return spring moves the valve

to a predefined, safe end position (either OPEN or CLOSED).

Figure 1 is demonstrating the safety instrumented function as example on a Tank Overfill Protection.

The TZIDC pneumatic system can be supplied in four versions: for single acting or double acting actuators and each with the ‘fail

safe’ or ‘fail-freeze’ safety behavior.

The SIL Safety Function is limited to the version: ‘single-acting, fail safe‘ in conjunction with pneumatic fail-safe actuators with

spring-return mechanism.