Overload Relays (Full Lecture)

In this lesson we'll take a brief look at overload relays, a sensory device that protects a motor from sustained excess current draw. An overload relay will allow a harmless temporary overload such as an inrush condition during motor starting, however, will trip if current is high enough to cause motor damage over time. The overload relay can be reset once conditions causing the overload event have been detected and resolved. (Full Lecture)
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[@eepower]

Thank you Jim for making these great videos. I (we) appreciate your time Sir.

[@danp8126]

Good job on making basic information easy to follow and understand.

[@madhushamal92]

Very informative. Thanks a lot for your effort taken

[@javierferrer4634]

Very nice video! I'm a dragline operator and a lot of this items are on it.

[@henrybartlett1986]

Informative as ever. Many thanks.

[@michaelcostello6991]

Great video. Thanks Michael

[@chrisampere]

Nice explanation sir jim. Thanks.

[@НиколаЂорђевић-ъ9с]

Thank you, sir.

[@Aadhvika_Vibes_04]

Hi Jim, Thermal overload is clearly explained. Please could you provide your inpur or make video like, With help of name plate information how can we can calculate the Trip class and Trip level (Sec) ? could you clarify this doubt

[@AaronB99999]

Before I started studying this stuff, I never would have guessed that switches made of massive hunks of metal and plastic (and Rube Goldberg type devices involving melting metals) were part of the modern industrial scene.

[@super-z8943]

MCB has bi-metal thermal tripping for continuous ( non- short circuit) over current, so how is it any different than overload relay? MCB can't protect the motor from undervoltage, but undervoltage would trip the thermal contacts even sooner by drawing a higher current. I am talking mostly about single phase motor application.

[@bigbadtech]

Sounds like it's functionally equivalent to an overload. Traditional overloads don't directly make or break primary connection but rather make or break connection to a pilot/control circuit. The contactor then makes or breaks primary connection at the behest of the overload. I like to think of traditional overloads as "sensory" devices only.

[@k50159]

Thanks so much

[@mariafreedom6069]

Interesting

[@nataala_]

Thank you for a great video. I have a challenge on hand I would appreciate your assistance. In resetting the the contactor from the overload state, must the machine be connected to mains power while the reset button is pressed and then the ON button pressed? I am terrified of making a mistake and destroying the machine. Many thanks in advance and once again for the training.

[@bigbadtech]

Ordinarily the overload reset is mechanical and can be reset with or without power.

[@nataala_]

@@bigbadtech Thank you Jim. It did not work - without or without power. The blue reset button did not stay pressed when I made the attempt without power. So, I turned it to the "Auto" position, connected to mains power and pressed the "On" button. The ironworker still did no start. But by pressing the black button in the middle of the DIL M32-10, the ironworker is energised - until I release he button. I am quite stumped - in spite of your quite clearly explained video. Does anyone have a clue what I am doing wrong please?

[@nataala_]

However, Jim, it says "Reset" between Hand and Auto without a notch. Does anyone know if rotating the blue button somewhere there might help? I am quite afraid to damage the machine; exchange rates are currently just murder.

[@natriumguy8537]

I love the starting music 😀😁

[@foxxmulder7524]

HI JIM, Great video ...Why is the overload relay in the neutral side of the coil?..Thanks.

[@bigbadtech]

This way it's got the last and final say about the operational state of the motor.

[@Dr-Shlomo-Cohen]

My Samsung inverter makes circuit breaker of the house go off as soon as the compressor starts. Lately the compressor has been making noise. No short between windings and the ground 11.7ohms between each winding. Do you have any suggestions?

[@bigbadtech]

I can only guess. Is the inverter tripping the CB or the comrpessor? I'm suspecting the massive surge of current known as "inrush" when the compressor motor is above the peak limitations of the inverter.

[@anonymousperson2578]

Hello Jim, thanks for all the informative videos! I'm working on a restaurant hood system's exhaust fans and wondering if you could offer some guidance for the overload settings. Recently, I found a group of overloads that were never set properly, and in fact, the operating range of the overloads were way too large for the application, so the customer lost all their motors when a phase loss occurred. As for the overload setting, let's say for example, the FLA on the motor label is 5.0 amps. Should I set the overload to the SFA rating of 1.15 times that amount? I'm thinking maybe a safety factor of 1.3 would strike a balance between motor protection and avoidance of nuisance tripping. Obviously, the motors are typically only started one time, in the morning, when they begin cooking and needing the hood, so inrush draw duration is limited. Thank you.

[@bigbadtech]

Good troubleshooting! I'm actually going to use this as an example for the class. As far as the setting for the overload I'd maybe put an ammeter in the circuit to determine the actual inrush that occurs. Another way of estimating inrush is with the locked rotor code. I detail the method in the "Motor Nameplate" lecture at: kzbin.info/www/bejne/n6vafouXYtSqqpI This way you can base your decision on good data.

[@rodstalwart8338]

Why is all motor overload relays made in 3 phase? Is there one made for single phase motors? Or common 3 phase OR can be used in 2 phase motors too?

[@bigbadtech]

Good question. I'm hoping to publish a bunch of motor lectures in the near future and one of the topics I hope to discuss is single phase AC motors and control. Ultimately you can use 3 phase AC equipment like contactors and overloads in single phase applications where instead of making and breaking connection or sensing current in 3 independent legs of a 3 phase AC system the 3 contacts or overload elements are wired in series such that they make or break connection and sense current in a single series path. Not only is there an element of redundancy in this method I'm presuming it saves manufacturers money by offering a limited range of products.

[@StoneysWorkshop]

If a pump motor claims to be thermally protected in single phase :automatic reset ,is it also necessary to have a motor starter setup on the power input?

[@bigbadtech]

This is more of a legal AHJ (authority having jurisdiction) question ... however ... the integrated overload would functionally serve as the overload element for the motor starter.

[@gadjettechover8423]

hi sir min 11.11 1)for class 10 3A, what is this 3A means? 2)for 4x3A=12A, where is this number 4 comes from? 3)for 18s, is it mean for continuous 12A current supply to motor in duration 12s, thermal overload contact will open & contactor will open? how about MCCB, will MCCB contact trip or stay close? . thanks

[@franciscopineda3859]

from the class 10 graph

[@franciscopineda3859]

it´s a point on the class 10 curve