Explosion Proof Motors with Internal Temp Cutoff?

It is more common of late to contruct a motor with (a) temperature device(s) embedded in the windings, and to run a cable from it/them to the motor starter cubicle to carry out the control functions there.

The difficulties of changing-out heritage motors that are configured differently are appreciated.

Yes, this it the way we would build new plants.

Baldor has the internal high temp disconnect in the motor connection head but only up to 1 1/2 hp. I need 2 and 3 hp motors.

I remember seeing these in the mid 70's, these days motors have temp probes connected to relays that shut down the motor at the MCC.

As a suggestion which you have realised I guess, that new motors and that extra bit of control cabling is now required to have new motors with temp protection.

It is unusual to have Ex motors with moving internal contacts/relays these days.

I think it boils down to your going to have to run a new control cable to the motor for whatever type of temperature sensor you decide to use.

I've never come across FLP motors with internal disconnects, but the motors I worked on were a lot bigger

Dear Sir,

Such totally enclosed flameproof motors 550 volt, 120 KW were being used by

me in early 1973 to 1976. Motors were Russian make heavy duty,water cooled

with temperature sensor inside windings with tripping relay like relay contacts

in a FLOAT switch. Relay had gone defective sometime in 1974. It had to be

bypassed as there was no alternative. But motor was running very effectively.

At that time motor was dissambled and rotor & windings were looking like a NEW

Motor. If necessary motor can be used by convinient temperature sensors and

taking out control cable outside to starter panel.

Just for acedemic interest these heritage motors may be saved.

Yes, I can add a temp sensor to the motor case and high temp interlock, but will it be considered "safe", as safe as a new UL / FM approved motor?

I install temp sensors and interlocks all the time, but is there anything else which makes it meet code other than the "nameplate"?

you should be able to get an EX motor with the temp probe fitted in the stator, that would be more in line with the code rather than a DIY job of fitting the temp probe and trying to retro-fit the correct Ex junction box etc for the probe terminations.

The pre-fitted probe terminations would then be in the motor terminal junction box, all you need to do, as TonyS suggested, is install the correct type of cable plus EX glands for motor power and an additional Ex gland on your temp feedback cable to your MCC.

Yes, you have to run another cable, but as I see it there is no other option, not these days. Better safe than sorry!!

Any modification to the motor negates the FLP certificate!

I wasn't suggesting that he makes any mods, the probe should be fitted to the stator, the terminations should be in the terminal box, and the knock outs for the temp probe cable should be there. What I did say was DO NOT attempt to modify it...

you should be able to get an EX motor with the temp probe fitted in the stator, that would be more in line with the code rather than a DIY job of fitting the temp probe and trying to retro-fit the correct Ex junction box etc for the probe terminations.

The main thing is that the cable and glanding meet FLP requirements. If it doesn't the whole thing is invalid.

Agreed with comments of Mr. Tony S. FLP features,cable glands and terminal cover gaps should not be disturbed. Then it's ok.But why the temperature disconnect inside the motor required when it can be conviniently tripped from the starter.

If you read the original posting, its and OLD motor built to a design standard no longer with us, the OP want to replace these old motor and still wants to keep the thermal protection, which you already know. Thats how and why the thermal trip is inside the motor, not as todays modern motor's, with the trips located remotely.

Thank you Brich. Heritage motors must be kept intact till it is possible.