hi

not nesessary

hi

usaully for engine protection we use bimetal so it is not nesessary use bimetal for inverter

hi

i offer to see this article

"choose the right electric motors for hazardous locations   "

The inverter can be made "self-protecting": It's got 'intellect' and it is able to shut-off the output. Thus no sort of external protection is necessary.

Classic motors are different: as they do not have any 'brains', there is a need to protect them in case of overload, shurt circuit etc.

In my ambient this is called a "motor protection switch" - consisting of a fast-acting 'fuse' (actually a magnetically engaged switch) in combination with a slow acting device that is normally not a bimetal element, but acting very much like a such.

Hi

It is not necessary but we could

It"s nonsense to use bimetal protection in such an  intelectual devise like invertor, in which protection of switches should be used.

Folks, 

In my opinion, U. Dreher has the right idea,

a good electrical engineer's method. 

"Fast Acting" device in combination with a "Slow Acting" device. 

Each doing a different protective function. 

=================================

To which I wish to add my experienced input : 

Since this discussion seems so restricted,

addressing only bi-metallic controls,

I am summarizing the information

in order to provide a broader perspective in this interesting subject.

Information here is summarized

from the U.S. National Electricl Code "HandBook"

and personal engineering in-the-field experience.

Please note that

I am not interested in personally pursuing

a discussion about these issues,

as the safety rules of various countries

and the technical language barriers

will make impossible any exact advice.

I am presenting

three Broad Categories of Electrical Over-Current functions

for your consideration and/or discussion .

There are devices in use

which include several of these functions in a single unit,

which only adds to the complexity of any discussion.

(1) Short Circuit and Ground Fault protection :

Fuseable Links .

Quick acting. ( Time Delay models are available ).

Least Expensive.

(2) Overload protection  :  

Circuit Breakers , medium speed acting,

(a) 

Magnetic are quick acting for severe overload protection

( like Fuseable Links ).

(b)

Bi-Metallic are Inverse-Time mechanism, tolerating Start-up Currents.

Bi-Metallic Protect an operating current that's too high,

    over a 5 sec to 30 sec time period in general.

Bi-Metallic Protect at 115% to 125% of motor nameplate current rating.

Bi-Metallic are Very often the only method used.

Medium expense.

(3) Over-Load Controller  :

Precise adjustments and long term response. 

These are called "Over-Load Contactor Relays" by Schneider Square-D

for their LR2Kk0312 device,   which I have here in my shop.  

"Overload Contactor Relay 3 phase

with 3.8 to 5.5A Relay Setting Range"

and long time sensing.  

Single-phase and three-phase models. 

Used in connection with motor starters / controllers. 

* Can be set closely to the optimal running current,

and can sense over a long period before tripping.

* Can give warning of small over-currents lasting for many hours,

which can indicate minor current increases,

which indicate RPM reduction and motor heating.

* Most Expensive.

=================

I hope this helps.

If you need more information or discussion

I suggest you contact an electrical engineer/contractor

in your area/country. 

Glen Ellis

Thank you for your answer

Hi

I think the  inverter must be used in engine.

hi

eny electrical equipments needs protection.

i think that bimetal is overcurrent protection and is necessary for motors. thus inverter needs bimetal protection too.

it is not nesessary

hi

not nesessary

hi

relay bimetal not nesesary.

it is not nesessary