Category: Eaton

Introduction

Read these instructions carefully and inspect the equipment to

become familiar with it before trying to install, operate, service, or

maintain it .

Electrical equipment should be installed, operated, serviced, and

maintained only by qualified personnel .  Local safety regulations

should be followed .  No responsibility is assumed by Eaton for any

consequences arising out of the use of this material .

Eaton reserves right to changes without further notice .

Abbreviations

CB – Circuit breaker

CBFP – Circuit breaker failure protection

EMC – Electromagnetic compatibility

EPROM – Erasable programmable read only memory

HW – Hardware

LED  – Light emitting diode

LV  – Low voltage

ms – Millisecond

MV – Medium voltage

NC – Normally closed

NO – Normally open

PMSG – Permanent magnet synchronous generator

Rx – Receiver

SF –    System failure

SW – Software

Tx – Transceiver

uP2– Microprocessor

Assessment of Functional Safety

The design features and the techniques/measures used to prevent systematic faults are suitable for the use of

the MTLx546 and MTLx549 modules in safety functions up to SIL2 in a simplex architecture.

The hardware assessment shows that MTLx54x analogue output modules:

•  have a hardware fault tolerance of 0

•  are classified as Type A devices (“Non-complex” component with well-defined failure modes)

•  have no internal diagnostic elements

It should be recognised that the systematic capability of the products limits their application to SIL2 loops.

It is important that the effect of electromagnetic interference on the operation of any safety function is reduced

where possible. For this reason it is recommended that the cable connections from the logic solver to the isolator

modules be a maximum of 30 metres and are not exposed to possible induced surges, keeping them inside a

protected environment.

Similarly, operation of the equipment outside of its environmental ratings induces component stress and

temperature above the normal ambient of 60°C is to be avoided to ensure required performance.

Selection of product and implications

The analogue signal levels employed by the MTLx54x are within the operating range of 4-20mA under normal

conditions.

If the wiring between the isolator and field device are open circuit then the line-fault detect (LFD) operation of the

isolator forces the current taken into the input terminals to fall to a low value, which is less than the expected under

range value of 3.6mA. The MTLx546 and MTLx549 models also detect when the resistance in the field wiring is less

than fifty ohms indicating a short circuit condition, and this also is reflected into a low input current value.

This diagnostic aspect can be used by logic solvers that include a readback facility to monitor the output current from

their output cards or modules. Thus the ability to detect that the actual current being passed is not the desired value

can be used to determine the health of the instrument function. The same condition of the actual loop current falling

to a low level will also occur if the wiring between the logic solver and the isolator is open circuit.

Using a field device and logic controller, as defined in section 2. with an MTLx54x then a system-loop can be

implemented that applies functional safety together with intrinsic safety to meet the requirements of protection

against explosion hazards. Note that the transfer of HART communications through the isolator is not considered as

part of the safety function of the isolator.

It should be recognised that the systematic capability of the products limits their application to SIL2 loops.

It is important that the effect of electromagnetic interference on the operation of any safety function is reduced

where possible. For this reason it is recommended that the cable connections from the logic solver to the isolator

modules be a maximum of 30 metres and are not exposed to possible induced surges, keeping them inside a

protected environment.

Similarly, operation of the equipment outside of its environmental ratings induces component stress and

temperature above the normal ambient of 60°C is to be avoided to ensure required performance.

Associated System Components

There are many parallels between the loop components that must be assessed for intrinsic safety as well as

functional safety where in both situations the contribution of each part is considered in relation to the whole.

The MTLx54x module is a component in the signal path between safety-related actuators and safety-related

control systems.

The current to pressure converter, valve positioner, or other field device, must be suitable for the process and

have been assessed and verified for use in functional safety applications as well as its certification for hazardous

area mounting.

The safety system PLC shall have a current output with a normal operating range of 4-20mA but capable of

working over the extended range of 3 to 22mA for under- and over-range. Such controllers will normally also

include a readback facility to enable the detection of open or short circuits in the wiring.

The transmission of HART data is not considered as part of the safety function and is excluded from this analysis.

Variant Description

Functionally the MTL4500 and MTL5500 range of modules are the same but differ in the following way:

– the MTL4500 modules are designed for backplane mounted applications- the MTL5500 modules are

designed for DIN rail mounting.

In both models the hazardous area field-wiring connections (terminals 1-2. and 4-5) are made through the

removable blue connectors on the top of the modules, but the safe area and power connections for the MTL454x

modules are made through the connector on the base, while the MTL554x uses the removable grey connectors

on the top and side of the module.

Note that the safe-area connection terminal numbers differ between the backplane and DIN-rail mounting models.

The analogue output models covered by this manual are:

MTL4546 and MTL5546    single channel, open and short cct LFD

MTL4546C, MTL4546Y, and MTL5546Y    single channel, open cct LFD

MTL4549. and MTL5549    dual channel, open and short cct LFD

MTL4549C, MTL4549Y, and MTL5549Y    dual channel, open cct LFD

INTRODUCTION

Application and function

The MTL454x and MTL554x are isolator modules which enable an analogue 4/20mA control signal to be

passed to a device located in a hazardous area from a safe area. The output current available to the hazardous

area is limited to comply with the requirements of the process explosion hazard. The modules are also

designed and assessed according to IEC 61508 for use in safety instrumented systems up to SIL2 when

the required function is to repeat the loop current within ±2%, and the safe state of the output is <3.6mA

(downscale). Higher integrity levels for a SIF can be achieved by using the modules in a voting architecture.

For ‘smart’ valve positioners using the HART protocol the units allow bi-directional communications

superimposed on the 4/20mA signal current.

There are no configuration switches or operator controls to be set on the modules – they perform a fixed

function related to the model selected. The MTLx546 models are single channel while the MTLx549 models

are dual channel, although both channels must not be used in the same safety instrumented function.

These modules are members of the MTL4500 and MTL5500 range of products.

Improving equipment s afety

Better termination

• Top/bottom dual chamber terminals provide a more secure

termination for wires of differing size, minimizing the chance that

a wire could become loose

• Applies to contactors up to 500A and manual motor protectors

(MMPs)/combination style controllers up to 65A

Removable electrical bridge

• Removing electrical bridge ensures starter is off-line

during servicing

• Applies to combination style starters up to 15A

Finger-safe and back-of-hand proof

• Requires no additional shield accessories

• Applies to contactors up to 150A and MMPs up to 65A

Improving equipment performance

Electronic DC coils

• Larger pick-up voltage tolerance and operation range

• Consistent switch-on and switch-off

• Voltage dip ride-through

• Surge suppression included 

Better motor performance and

protection

• Phase loss and phase imbalance protection conserve motor life

and ensure optimum motor performance

Excellent quality performance

• XT has best in class warranty PPM (parts per million) when

compared with similar electrical manufacturers

Improving equipment

usability

Slideable DIN rail adapter

• Allows for easy component replacement without removal

of adjacent components and terminations

• Allows for last minute changes and design flexibility

Visible coil power indication

• Enables easy troubleshooting and testing of contactor operation

• Applies to contactors and combination style starters up to 150A

Overload selectability

• 5:1 ratio current adjustment range, selectable trip class

(5. 10. 20. 30) and selectable reset style as standard, allowing

for greater flexibility using less part numbers

Lowering material costs Small contactors

• Smallest 10 hp contactor on the market

• All XT DC controlled contactors have the same depth as AC

controlled XT contactors

• Reduced panel space can help decrease enclosure size and

costs

Side-by-side mounting

• Low coil consumption allows for side-by-side mounting

• Reversing contactors require no additional width for the

mechanical interlock

• Reduced panel space can help decrease enclosure size and

costs

Combination style starters

• Replaces traditional breaker/fuse block with contactor and overload

• Reduced panel space can help decrease enclosure size and

costs

Electronic coils

• Efficient coil design—185A to 2000A

• XT contactors have low coil consumption, translating to

smaller, less expensive CPTs and power supplies

• Unique control scheme allows for direct control from a PLC or low

consumption command device 

• Can eliminate the need for a large CPT and interposing

relay leading to a reduction in component costs, and smaller

enclosure size and costs

Eaton’s comprehensive line of XT IEC power controls

The XT Line of IEC Power Control, consisting of contactors, overload relays,

mini controls, manual motor protectors and combination style starters,

is one of the world’s newest and most complete IEC Power Control product

lines on the market. The XT applies new technology and design to help

OEMs address five basic needs:

Improving production

Toolless assembly

• Requires no tools to assemble

• Applies to B-Frame (10 hp,15A) reversing and star-delta

contactors, combination stylestarters and surge suppressor

accessories

Combination style starters

• One unit replaces traditional breaker/fuse block with contactor

and overload, saving installation time and effort

Coil terminations

• Easily accessible coilterminations in the front of the

contactor make installation, testing, and replacement much

easier and safer