Question about Solenoids (Relay/Starter/Contactor) - Electrician Talk - Professional Electrical Contractors Forum
CLICK HERE AND JOIN OUR COMMUNITY TODAY, IT'S FREE!
Go Back   Electrician Talk - Professional Electrical Contractors Forum > Electrical Forum > General Electrical Discussion


Like Tree7Likes
  • 1 Post By Jhellwig
  • 1 Post By TRurak
  • 2 Post By B-Nabs
  • 3 Post By just the cowboy
Reply
 
Thread Tools Display Modes
Old 10-02-2016, 07:43 PM   #1
Senior Member
 
Join Date: Mar 2015
Location: Houston Texas
Posts: 567
Rewards Points: 1,130
Default Question about Solenoids (Relay/Starter/Contactor)

The current required to cause a solenoid (or relay or starter or contactor) to close is ___ the current required to keep it closed.

Less, more, or the same?

I'm just starting to learn about relays and contactors. I understand the practicality and uses of them but don't really understand enough I guess to answer this question..

So a relay gets power and the NORMALLY OPEN contacts now close and the NORMALLY CLOSED contacts now open. So... I just don't understand the question.. Is this some sort of trick question or something, I just don't understand it haha.
JasonCo is offline   Reply With Quote
Join Contractor Talk

Join the #1 Electrician Forum Today - It's Totally Free!

ElectricianTalk.com - Are you a Professional Electrical Contractor? If so we invite you to join our community and see what it has to offer. Our site is specifically designed for you and it's the leading place for electricians to meet online. No homeowners asking DIY questions. Just fellow tradesmen who enjoy talking about their business, their trade, and anything else that comes up. No matter what your specialty is you'll find that ElectricianTalk.com is a great community to join. Best of all it's totally free!

Join ElectricianTalk.com - Click Here JOIN FOR FREE


Warning: The topics covered on this site include activities in which there exists the potential for serious injury or death. ElectricianTalk.com DOES NOT guarantee the accuracy or completeness of any information contained on this site. Always use proper safety precaution and reference reliable outside sources before attempting any construction or remodeling task!

Sponsored Links
Advertisement
 
Old 10-02-2016, 07:50 PM   #2
Senior Member
 
Join Date: Jun 2010
Location: Brisbane, Australia.
Posts: 2,950
Rewards Points: 1,536
Default

I would guess that the kick in would be slightly higher than the hold.
how ever how significant it is I am not sure !

dmxtothemax is offline   Reply With Quote
Old 10-02-2016, 07:55 PM   #3
Senior Member
 
Join Date: Mar 2015
Location: Houston Texas
Posts: 567
Rewards Points: 1,130
Default

Found this little bit of information in my book.

"Solenoids are constructed of many turns of wire wrapped around a magnetic laminate assembly. Passing electric current through the coil causes the armature to be pulled toward the coil. Devices may be attached to the solenoid to accomplish tasks like opening and closing contacts."

So... Still I can't figure out the answer lol
JasonCo is offline   Reply With Quote
Sponsored Links
Advertisement
 
Old 10-02-2016, 08:01 PM   #4
Senior Member
 
Join Date: Mar 2015
Location: Houston Texas
Posts: 567
Rewards Points: 1,130
Default

Oh I misread the question and also found the answer in the mean time.

"Solenoid coils draw more current when first energized than the amount that is required to keep them running. In a solenoid coil, the inrush current is approximately 6 to 10 times the sealed current. After the solenoid has been energized for some time, the coil becomes hot, causing the coil current to fall and stabilize at approximately 80% of tits value when cold. Etc..."

So, the answer is MORE!

Thanks for your help! Got it now
JasonCo is offline   Reply With Quote
Old 10-02-2016, 08:09 PM   #5
Sparks fly from my finger
 
Jhellwig's Avatar
 
Join Date: Jun 2014
Location: Ottumwa, Ia
Posts: 2,471
Rewards Points: 4,559
Default

The answer are always in the material. Good job finding it. If you can't figure it out don't ask just for the answer. Ask for the why also.
Miller6386 likes this.
__________________
Murphy's law is a pain in my butt.
Jhellwig is offline   Reply With Quote
The Following User Says Thank You to Jhellwig For This Useful Post:
JasonCo (10-02-2016)
Old 10-02-2016, 08:22 PM   #6
Senior Member
 
Join Date: Apr 2016
Posts: 683
Rewards Points: 52
Default

80% of tits....... Lol
B-Nabs likes this.
TRurak is offline   Reply With Quote
Old 10-02-2016, 08:40 PM   #7
Senior Member
 
Join Date: Mar 2015
Location: Houston Texas
Posts: 567
Rewards Points: 1,130
Default

Quote:
Originally Posted by TRurak View Post
80% of tits....... Lol
Whoops! I guess I value tits at 80% when they are cold
JasonCo is offline   Reply With Quote
Old 10-02-2016, 08:46 PM   #8
Bilge Rat
 
Join Date: Aug 2007
Location: Fernley, Nevada (near Reno)
Posts: 6,825
Rewards Points: 3,258
Default

Here are some specs from the Allen Bradley book.....

Size 2 starter, (Max 25HP @ 460 volts), the coil inrush is 240 VA and the holding is 29 VA.

Size 6 (400 HP @ 460 volts) inrush is 4860 VA and holding is 254 VA.

700-HB relay (basic 3 pole ice cube type) inrush is 2.85 VA and holding is 1.9 VA.

An actual control power transformer is larger and heavier that a basic power transformer of the same rating because it is designed to handle the high inrush or a starter coil.

BTW, you've likely seen relay contacts listed as form A, B or most common, C. Form A is normally open, B is normally closed and C is double throw.

Further, you may have seen contact ratings expressed as A300, B600 or C150. The number here is the maximum voltage and the letter is A = 7200 VA make (closing of the contact) and 720 VA break (opening of the contact). B = 3600 VA make and 360 VA break, C = 1800 VA make and 180 VA break.

What will happen if a size 6 starter with a 120 volt coil is controlled by a relay with a C300 rating?

How about a size 2 with the same relay?
micromind is offline   Reply With Quote
Old 10-02-2016, 10:33 PM   #9
Senior Member
 
Join Date: Mar 2015
Location: Houston Texas
Posts: 567
Rewards Points: 1,130
Default

Ill answer this but its too late right now, got to head off to sleep. I'll give it a go tomorrow!
JasonCo is offline   Reply With Quote
The Following User Says Thank You to JasonCo For This Useful Post:
micromind (10-02-2016)
Old 10-03-2016, 09:13 AM   #10
Senior Member
 
Join Date: Jul 2013
Location: Indiana
Posts: 661
Rewards Points: 114
Default

Perry much anything with coils is going to be 6 to 8 times full load. You can read up on transformers to find out why. Gl

Sent from my C6725 using Tapatalk
Flyingsod is offline   Reply With Quote
Old 10-03-2016, 09:41 AM   #11
Senior Member
 
Join Date: Jan 2011
Location: canada
Posts: 1,490
Rewards Points: 2,094
Default

ac = more pickup. DC = same
oliquir is offline   Reply With Quote
Old 10-03-2016, 09:51 AM   #12
Watt Pusher
 
B-Nabs's Avatar
 
Join Date: Jun 2014
Location: Port Coquitlam, Canada
Posts: 2,414
Rewards Points: 480
Default

Also the holding current is lower than the pull-in current mostly because of the establishment of inductive reactance, not so much because of heat. Heat plays a role, I'm sure, but it's the inductive reactance that makes up the majority of the impedance in any inductive device (also eg. transformer, motor).
Big John and telsa like this.
__________________
Is that a real poncho or is that a Sears poncho?
B-Nabs is offline   Reply With Quote
Old 10-03-2016, 10:42 AM   #13
Senior Member
 
FaultCurrent's Avatar
 
Join Date: May 2014
Location: California
Posts: 496
Rewards Points: 931
Default

Depends on whether the solenoid has a DC or AC coil. They have much different characteristics. The AC coil has resistance and reactance. DC no XL just pure resistance of the windings.

So the AC coil has an inrush of current until the magnetic field builds up.
__________________
At it since 1971 and still going....kind of.
To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.

Grandpa was old, and he was slow. But he got there.
FaultCurrent is offline   Reply With Quote
Old 10-03-2016, 10:53 AM   #14
Senior Member
 
MikeFL's Avatar
 
Join Date: Apr 2016
Location: The Sunshine State
Posts: 5,953
Rewards Points: 800
Default

Pull a spec sheet and look at the waveform.
It's going to be "greater than" but I want you to see that on the spec sheet so you see the magnitude and duration which helps you understand why.

Good luck with your studies.
__________________
Michael Gookin, President
GPS Timers

To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.

(833) GPS-TIME
MikeFL is online now   Reply With Quote
Old 10-03-2016, 12:04 PM   #15
Senior Member
 
just the cowboy's Avatar
 
Join Date: Sep 2013
Location: Colorado Springs Colorado
Posts: 1,815
Rewards Points: 326
Default Real world advice

Now that you may understand how it works, let me tell you something that may cause you to not look like a . Never remove the armature of a contactor or solonoid, then enegerize it. With out the iron center the current will never stabilize and burn it up, sometime pretty quick. So this way you won't let out the magic smoke.
Cowboy
__________________
The cost of our answers are not free, we charge you a answer back.
"DID THIS FIX IT??"
just the cowboy is online now   Reply With Quote
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Hot Tub Install Question About Wiring Canaduh Canadian Electrical Forum 38 02-16-2017 10:41 PM
Help with 400A 3PH 120/208 service question MacCallum Electric Canadian Electrical Forum 7 09-27-2016 07:05 AM
Need some help Might be a dumb question sub2001zero General Electrical Discussion 5 09-26-2016 05:15 PM
Knob & Tube question - ethics AmishCountrySparky General Electrical Discussion 43 04-02-2016 04:28 PM
Quick Freebie Question simpledoug UK Electrical Forum 8 01-22-2016 10:34 AM


All times are GMT -4. The time now is 03:58 PM.


Powered by vBulletin® Version 3.8.8
Copyright ©2000 - 2020, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.1
vBulletin Security provided by vBSecurity v2.2.2 (Pro) - vBulletin Mods & Addons Copyright © 2020 DragonByte Technologies Ltd.
User Alert System provided by Advanced User Tagging (Pro) - vBulletin Mods & Addons Copyright © 2020 DragonByte Technologies Ltd.
Our Pro Sites Network
ContractorTalk.com | DrywallTalk.com | HVACSite.com | PaintTalk.com | PlumbingZone.com | RoofingTalk.com