250V DC CONTACTOR

[zxfabb]

Hi, guys

I'm looking for a contactor to control a 250V DC motor-operated-valve.

DC-5, series-motor:
Full load current at 250V DC: 41 A
Locked rotor current at 250V DC: 362 A

Contactor:
Main-pole: 250V DC nominal, ranging from 180V to 280V
Coil voltage: 250V DC nominal, ranging from 180V to 280V
Operating current of auxiliary contact at 250V DC: 1A

Much appreciated if you recommend a proper type and manufacturer.

 

[templdl]

Hi, guys

I'm looking for a contactor to control a 250V DC motor-operated-valve.

DC-5, series-motor:
Full load current at 250V DC: 41 A
Locked rotor current at 250V DC: 362 A

Contactor:
Main-pole: 250V DC nominal, ranging from 180V to 280V
Coil voltage: 250V DC nominal, ranging from 180V to 280V
Operating current of auxiliary contact at 250V DC: 1A

Much appreciated if you recommend a proper type and manufacturer.

Check out Eaton Electrical, aka Cutler Hammer who still manufactures the old Westinghouse DC contactor's. Thee are two, the ME that goes from 5-150a and one that goes from 5-1800a. The design as to have been around since before electricity was even discovered.
http://www.eaton.com/Eaton/Products...ol/MillControlProducts/DCContactors/index.htm

 

[augie47]

Check out Eaton Electrical, aka Cutler Hammer who still manufactures the old Westinghouse DC contactor's. Thee are two, the ME that goes from 5-150a and one that goes from 5-1800a. The design has to have been around since before electricity was even discovered.
http://www.eaton.com/Eaton/Products...ol/MillControlProducts/DCContactors/index.htm

Wow! Had almost forgotten about those. Memory lane.,. I used to work at a mill that had a
slate wall full of them.. made one feel like they were in a Frankenstein movie.

 

[petersonra]

Hi, guys

I'm looking for a contactor to control a 250V DC motor-operated-valve.

DC-5, series-motor:
Full load current at 250V DC: 41 A
Locked rotor current at 250V DC: 362 A

Contactor:
Main-pole: 250V DC nominal, ranging from 180V to 280V
Coil voltage: 250V DC nominal, ranging from 180V to 280V
Operating current of auxiliary contact at 250V DC: 1A

Much appreciated if you recommend a proper type and manufacturer.

Have you looked at Siemens 3TC contactors? I think they are the old Furnas DC contactors. I have had good luck with them.

The Joslin-Clark stuff works Ok too. Now owned by Danaher.

A Siemens IEC contactor would probably work as well, although you might need two of them to do reversing.

You might be better off with some kind of DC drive. That is one monster valve actuator.

 

[Besoeker]

Wow! Had almost forgotten about those. Memory lane.,. I used to work at a mill that had a
slate wall full of them.. made one feel like they were in a Frankenstein movie.

Yes, we had those slate panels here. Completely open. Such kit would now get an instant prohibition notice. People who used or operated were expected to know what they were doing. Now it all has to be idiot proof.
I know it's pretty much the same both sides of the pond.

Anyway, the one's I had dealings with mostly for Ward Leonard systems feeding DC drive motors in steel mills and paper mills.
The slang term used for the DC contactors was clapper contactors - but more correctly bar and shaft as I recall.

 

[Besoeker]

Hi, guys

I'm looking for a contactor to control a 250V DC motor-operated-valve.

DC-5, series-motor:
Full load current at 250V DC: 41 A
Locked rotor current at 250V DC: 362 A

Contactor:
Main-pole: 250V DC nominal, ranging from 180V to 280V
Coil voltage: 250V DC nominal, ranging from 180V to 280V
Operating current of auxiliary contact at 250V DC: 1A

Much appreciated if you recommend a proper type and manufacturer.

Where does your DC come from?
Is it rectified AC
In which case you could possibly use an AC contactor. They cost less and are far easier to obtain.

 

[Sahib]

Where does your DC come from?
Is it rectified AC
In which case you could possibly use an AC contactor. They cost less and are far easier to obtain.

AC contactor for DC motor?!

 

[Besoeker]

AC contactor for DC motor?!

Although you could, most AC contactors have a DC rating, it is not at all what I'm suggesting.
If the DC is from rectified AC, you can switch on the AC side of the rectification system. It is commonly done.
Do you understand now?

 

[GoldDigger]

AC contactor for DC motor?!

If the current goes through zero periodically, an AC contractor would still be able to extinguish the arc.

OK as long as inductive effects did not keep the current flowing despite the pulsed voltage.

 

[Jraef]

Have you looked at Siemens 3TC contactors? I think they are the old Furnas DC contactors. I have had good luck with them.

The Joslin-Clark stuff works Ok too. Now owned by Danaher.

A Siemens IEC contactor would probably work as well, although you might need two of them to do reversing.

You might be better off with some kind of DC drive. That is one monster valve actuator.

In Siemens, the 3TC are the ones, it will take some effort to get a Siemens distributor to find them in the catalog, but they are there. The regular IEC contactors are not rated for switching DC. Well, technically they are, but the current rating is ridiculously low, ie a 160A AC contactor was rated something like 2A DC if I remember correctly. The same is true of most contactors designed for AC use, whether IEC or NEMA. The only ones still selling a NEMA contactor rated for DC motors and came in reversing config is AB. It's not the same Bulletin 500 evn though it looks like it, they change the catalog designation to 1370, but as far as i can tell it is not offered with a DC coil voltage ironically. It was an adaptation they used inside of Reliance DC drives when they took them over, and the drives had 115VAC controls, so that appears to be the only coil available for them.

ABB has a new DC contactor line called the GAF Series for the solar world that looks more like their IEC style contactors, it has a DC-5 rating, but unfortunately the smallest is rated 250A and I don't see any official motor HP ratings on them. Still, it might be smaller and less expensive than the old bar contactors. ABB also had or has an older line of DC motor contactors that were nice too, but they were based on the old ASEA EH line that I think has been discontinued now. Might be worth checking though, because they had reversing versions.

 

[petersonra]

Although you could, most AC contactors have a DC rating, it is not at all what I'm suggesting.
If the DC is from rectified AC, you can switch on the AC side of the rectification system. It is commonly done.
Do you understand now?

the only issue would be that for a valve actuator motor you would probably have to have some kind of reversing capability. So either two contactors or a dc drive of some sort.

 

[Besoeker]

the only issue would be that for a valve actuator motor you would probably have to have some kind of reversing capability. So either two contactors or a dc drive of some sort.

Good point and one that I'd missed. Apologies for that.

We have done a lot of DC drives with separately excited shunt fields. (Yes I know this is a series motor.)
The DC for the field comes from a rectifier.

For reverse operation, usually limited speed, we reverse the direction of the shunt field where full four-quadrant operation isn't required and would be overkill.
There are reversing contactors on the DC side of the of the rectifier. Because of the huge inductance of the shunt field, opening those contactors under load is a no-no.
There is also a contactor on the AC input to the rectifier.

The sequence for reverse operation is to drop the AC side contactor, allow the field to quench, change over those on the DC side under no load, and re-energise the AC contactor.
It isn't a dynamic reversal and for many applications it doesn't have to be.

Just in passing, reversing the direction of a series motor is just a bit more than reversing the polarity of the supply.

 

[GoldDigger]

Just in passing, reversing the direction of a series motor is just a bit more than reversing the polarity of the supply.

Yes, which is why a (universal) series motor can also be run off AC.

 

[GoldDigger]

Just in passing, reversing the direction of a series motor is just a bit more than reversing the polarity of the supply.

Yes, which is why a universal, series or otherwise, motor can also be run off AC.

 

[hurk27]

At work we use allot of EC&M DC controls, we have some over 60 years old and still work.

But with a DC motor controlling a valve your going to need allot more then just a contactor unless your going to use a drive?? How are you going to reverse the motor? you will need to ramp or step up the speed as a DC motor of that size could do some damage if hit with full voltage/current right at the start, even our air compressors have a step up speed control that involves timers and resistor banks as well as field loss relays, and of course overloads both short term and long term.

The above link should have all you need to make this work.

 

[hurk27]

Although you could, most AC contactors have a DC rating, it is not at all what I'm suggesting.
If the DC is from rectified AC, you can switch on the AC side of the rectification system. It is commonly done.
Do you understand now?

Many times for low current applications like control work we use AC contactors to control a DC contactor (in this case the PLC controls a 120 volt AB 700 series contactor which controls a DC contactor that opens the brakes on a DC motor which is run by a drive), we do this by passing the DC current in series through two or more sets of contacts(to help extinguish the arc), but for higher current DC applications in most cases you will end up replacing tips very often using AC rated contactors.

I have yet to see an AC contactor used for any DC motor over 1hp.

Also almost all of our series DC motors we only swap the armature polarity, mostly because less chance of a field loss and a runaway motor which is also a good reason to use a field loss relay in the control circuit, also swapping the field can cause the interpol to offset the brush timing which can lead to commutator and brush damage so we use two double pole DC contactors to swap the armature polarity, I think the OP is going to need a way to soft start the motor, a AC to DC drive like the AB 1395 which we use a few of, or the power Flex 20p series would be a good choice as I'm thinking , but the sticker shock may be a problem if it is a small plant? but then a total reversing control system with resistor stepping is not going to be cheap either because DC control is not cheap.

Another possibility is a AC to DC stepper servo type control for a DC motor (if an encoder could be installed on the valve or motor) only if the valve will need to be stopped at variable positions and maybe controlled by 4-20 signal or other, But then a Fisher 4-20 over air controlled valve would have made more sense then.

I'm just not sure what the OP is trying to do or if he has the understanding of DC motor control? because I have not seen a DC motor being used for a valve unless it was a stepper motor with servo control but then again I'm still learning

 

[zxfabb]

Thanks for your help.

The DC supply is from a rectifier. Two 2-pole contactors are needed to directly change the polarity for reversing.

For the main poles of NEMA or IEC contactor, switching 250VDC is not a big deal, we can connect 3 or 4 poles in series to improve the ability. But it is really hard to find a coil rated 250VDC. Maybe nowadays it is not common in use, but only for some special applications like mining or railway.

 

[Besoeker]

Also almost all of our series DC motors we only swap the armature polarity, mostly because less chance of a field loss and a runaway motor which is also a good reason to use a field loss relay in the control circuit

A couple of points.
In a DC series motor, if the field goes open circuit the series citcuit is open and no current will flow.
An unloaded series motor will run away.

 

[Besoeker]

Thanks for your help.

The DC supply is from a rectifier. Two 2-pole contactors are needed to directly change the polarity for reversing.

If it is a DC series motor, reversing the supply polarity won't reverse the rotation.

For the main poles of NEMA or IEC contactor, switching 250VDC is not a big deal, we can connect 3 or 4 poles in series to improve the ability. But it is really hard to find a coil rated 250VDC. Maybe nowadays it is not common in use, but only for some special applications like mining or railway.

If the supply is from a rectifier, can't you operate the control circuit and contactor coils from the AC that feeds the rectifier?

 

[hurk27]

A couple of points.
In a DC series motor, if the field goes open circuit the series citcuit is open and no current will flow.
An unloaded series motor will run away.

Yea I think my brain has run away, I don't know why I said that as we have cranes with field loss relays on hoist lowering but the trolley or bridge doesn't, we have a over voltage relay on the series motors that will shut the motor down if the drive gear comes off or strips.