Ohm reading for relays/starters/contactors?

[JasonCo]

I don't have enough experience in the field, basically none when it comes to relays, and know a little bit about contactors. I just don't understand the basic principles.


1.

For above picture, I'll either read: 40 to 400, 0 to .2, 1.8 to 4k, OL.
2.

For above picture, I'll either read: 40 to 400, 0 to .2, 1.8 to 4k, OL.
3.

For above picture, I'll either read: 0 to .2, 10 to 400, OL.
4.

For above picture, I'll either read: 40 to 400, 0 to .2, 1.8 to 4k, OL.


What I don't understand, is when I put my meter probes up to the different terminals. I can't figure out what readings I'll get for ohms. I understand that if my meter leads are touching, it'll read 0. If its going through a coil it'll probably read like 40 to 400 like 1.9 to 4k. Will read OL if the leads are not touching in any way. So, I understand that part. I just don't understand these relays and what is what... Thanks for your help! :wallbash:

 

[JasonCo]

Okay been doing a couple hours of trying to figure this out. I understand it a bit better. Picture 3 I fully understand. The other 3 I am getting there.
In picture 2, G and H I'll read 0 on my meter if it is not energized?
Picture 1, if my leads are on 97 and 98. Are those 2 terminals connected to each other? Would it read 0 or OL?

 

[George Stolz]

We are not here to do your homework for you. What aspect of them is confusing you?

Edit: I'll give you a hint. You have to pay attention to both the "NC/NO" marks, the patterns of the numbers, and what the contacts are physically connected to (the contactor vs the overload block.)

Edit x 2: Sorry for leading with "not doing your homework." I just studied your post history and realized that is not your MO.

The main problem with these types of problems is it's hard to help you without doing it for you, and the questions are designed to make you think about how it behaves in different states (on, overloaded, off). I think it's probably best if you describe what you know about it and what you guess about it, and we can correct your errors.

 

[Strathead]

I am trying to understand anything about what you are asking. The entire post confuses me.

 

[ptonsparky]

I am trying to understand anything about what you are asking. The entire post confuses me.

Thank you!

 

[jim dungar]

Okay been doing a couple hours of trying to figure this out. I understand it a bit better. Picture 3 I fully understand. The other 3 I am getting there.
In picture 2, G and H I'll read 0 on my meter if it is not energized?
Picture 1, if my leads are on 97 and 98. Are those 2 terminals connected to each other? Would it read 0 or OL?

You must know how the contacts are related to each other, other wise you will always be lost.

This is a link to a wiring diagram book which does a fair job of covering basic circuits. Other manufacturers will have similar books.
http://www.schneider-electric.us/en/download/document/0140CT9201/

Look at page 4 and page 21.

 

[kwired]

Do you understand what a relay or contactor is and what they are used for?

Take one of them apart, and look at how they mechanically function.

When the coil is energized it magnetizes the core which pulls an armature up to the core. Connected movement of that armature then mechanically operates switch contacts, on a motor contactor there are usually some heavier rated contacts that are for make/break of the motor circuit as well as additional aux contacts that are used for additional control options. Some contacts are "normally closed" when the coil is not energized and others are "normally open", you may have a combination of normally open and normally closed on the same unit, or they may all be the same.

 

[Carultch]

Do you understand what a relay or contactor is and what they are used for?

Take one of them apart, and look at how they mechanically function.

When the coil is energized it magnetizes the core which pulls an armature up to the core. Connected movement of that armature then mechanically operates switch contacts, on a motor contactor there are usually some heavier rated contacts that are for make/break of the motor circuit as well as additional aux contacts that are used for additional control options. Some contacts are "normally closed" when the coil is not energized and others are "normally open", you may have a combination of normally open and normally closed on the same unit, or they may all be the same.

What is the essential distinction between a relay and a contactor? In concept to me, they seem like the same device purpose. A switch carrying the main current, not usually manually operable, which can be changed to a different position by a control circuit.

 

[iwire]

My own view is a relay is what you use to switch control circuits and contactors are used to switch power and lighting circuits at higher voltage and/or current levels.

 

[kwired]

What is the essential distinction between a relay and a contactor? In concept to me, they seem like the same device purpose. A switch carrying the main current, not usually manually operable, which can be changed to a different position by a control circuit.

I don't know, maybe it is a listing thing? Most things called a contactor seem to have optional components that can be installed, most things that are called a relay are fixed and have no add on options, maybe that is the distinction?

 

[jim dungar]

What is the essential distinction between a relay and a contactor? In concept to me, they seem like the same device purpose. A switch carrying the main current, not usually manually operable, which can be changed to a different position by a control circuit.

Contactors have historically been associated with switching power so they have a few 'big' contacts and are designed with relatively few operations. Their typical accessories include overload relays and 'status' contacts.
Relays have usually been associate as switching control circuits so they have lots of 'small' contacts and are designed for a relatively large number of operations. Their typical accessories include specialty contacts and modules.

Of course there are cross over devices, and industry terminology usages that pretty much prevent a single all inclusive definition.