HVAC: Potential Relay VS Current Relay (Potential Relay Explained / Current Relay Explained)
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- Опубліковано 1 лип 2024
- HVAC Potential Relay VS Current Relay (Potential Relay Explained / Current Relay Explained) HVACR (Heating, Ventilation, Air Conditioning / Refrigeration) Potential Relay Explained (Potential Relay Wiring Diagram) 521 Relay Sequence Of Operation / Potential Relay Wiring / Potential Relay VS Current Relay / Potential Relay Troubleshooting / Potential Relay Refrigeration / Potential Relay Connection / Potential Relay Start Capacitor Wiring Diagram / (Current Relay Wiring Diagram) Sequence Of Operation & Troubleshooting / Current Relay Wiring / Current Relay troubleshooting / Current Relay Start Capacitor Wiring Diagram / What Is A Current Relay / How Does a Current Relay Work / Current Relay Working Animation
HVAC: Current Relay Explained
• HVAC: Current Relay Ex...
HVAC: Potential Relay Explained
• HVAC: Potential Relay ...
CURRENT RELAY:
When power is applied through the cycling control, both the run (main) winding and the relay coil see locked rotor current because they are in series with one another. The start winding cannot experience any current flow because of the normally opened contacts of the relay being wired in series with it.
Because both run winding and relay coil experience locked rotor current, the relay coil will form a strong electromagnetic field around it from the high locked rotor current draw of the run winding. Because the relay coil has a very low resistance (usually under 1 ohm), it will not be a large power consumer to interfere with the run winding's power consumption needs. The strong electromagnetic field formed around the relay's coil will make it an electromagnet. This is caused from the iron core that the relay coil is wrapped around. This magnetism is the force that will close the normally open contacts in series with the start winding and start capacitor. The motor's rotor now starts to turn.
Once the start winding is closed, the motor will quickly accelerate in speed. Once the motor has reached about three-fourths of its rated speed, the current draw of the run winding will decrease from a counter electromagnetic force (CEMF) on it. It is this reduced flow that will decrease the electromagnetic force in the iron core the relay coil is wrapped around. Now, spring pressure or gravity forces the contacts between (L and 2) or (L and S) back to their normally opened position.
On capacitor start motors, this action takes both the start capacitor and start winding out of the circuit. On capacitor start-capacitor run motors, the action only takes the start capacitor out of the circuit. The start winding will be left in the circuit by the run capacitor's wiring. But line power will not be directly applied to the start winding.
POTENTIAL RELAY:
When power is applied through the cycling control, both the run and start windings are energized. The run and start capacitors provide the phase shift for starting torque because their capacitances add up when wired in parallel. In fact, both capacitors are wired in series with the start winding and in parallel with the run winding.
The run capacitor limits the current that will pass through the start winding when the motor is running, because they are wired in series. The run capacitor also provides running torque when the motor is up and running.
The operation of the potential relay is based on the increase in back-EMF or a bucking voltage that is generated across the start winding as the motor increases in speed. The large metal mass of the motor’s rotor turning at high speeds with motor windings in close proximity has a voltage-generating effect.
The generated back-EMF opposes line voltage and can be measured across the start winding or across the coil of the potential relay at terminals 2 and 5. The back-EMF is usually a higher voltage than the line voltage and can be in the 400-V area.
The back-EMF voltage generated across the start winding causes a small current to flow in the start winding and potential relay coil, because they are in the same circuit. When the back-EMF has built up to a high enough value (referred to as pick-up voltage), the contacts between terminals 1 and 2 will be picked up (“opened”). This will take the start capacitor out of the circuit.
Pick-up voltage usually occurs when the motor has reached about three-fourths of its speed. The start winding is still in the back-EMF circuit, keeping the relay’s coil energized while the motor is running at full speed.
The contacts open because of the electromagnetic force (magnetism) generated in an iron core around which the relay’s coil is wrapped.
When the cycling control opens, line voltage is taken away from the motor. The motor’s rotor decreases in speed. Thus, the back-EMF generated across the start winding decreases in magnitude. The relay’s coil now sees a lower back-EMF and no longer can generate enough magnetism in its iron core to keep contacts 1 and 2 open.
Thanks for watching!
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You're the best technician, I like how you explain everything step by step
You and HVACR are my go to channels for hvac info. You make it easy to understand, thank you
Li srelay contecting coil eizing main poin ruing point wind restanc high starting poin capcter eigzing sc. Cap rely colsed fushion donw l2 olp ans ciuit l1 l2 ruing systom .mena comprssar ruing poin systom
Current relays are good in systems with smaller start up amps. Systems with fixed orfice often have less amps due to lack of a pressure difference. Great lesson your a true tech man
Thanks 👍🏼 love it. Could you do a troubleshooting vid on these.
Thank you so much I learned a lot. I am visual learner, your videos helped me so much to understand how stuff works. Your explanations are so easy to understand.
You make it life easy to undestand l really apreciate for your time to make this video
I really can’t say thank you enough I appreciate the video!!!
Easy to understand great explanations appreciate it keep up the great work. I look forward to your video bro!!! #hvac/r#kingoftrades#
Thank you! for explaing the function of both relays
I didn’t get it in trade school. I finally understand it.
Well explained, appreciate it!
Would you need a 208v cap or a 165v cap for this cct
Amazing video❤
you are the best
Interesting subject. Well presented and explained. Great job JMT.
Vy ery nice baccal usin ac systom usin oasiin ry usin engerizing emf eray curent ely usl ing v ..rey nily using full starting the cmpessar a csr cmressar can be started diecting with out rely as follows contect one the suly l1 to comerssar termmials suppey wis l1 to compressar termials Rnd the other L2 the comprssrterminals c contact starting and runingcapaciterin serires ith the sattingwin as shown isconeactthe starting capactieror the connectio ro starting to terminanl s after ther o motorfushion ater split ac sihle phase ac into phase the starting capaciter is dis connecting the relay after satring but ruing capciyer remains in the circuitwhil compers is working which increase the efficiency of the moterthis type of moter is used ac water cooler and other commercial refrigeration compressors for starting psc cmprssor moter starting in not required .. voltage rely potshion using realy 5and 2 .1 conshing 4.and 6 mt dumey point any other adshion usi usin liene or loop connetctin usi need coneated no ok not using mt ok
Vltge realy box type using same fushion potshion realy engzing using cacer cnneshion us ruing and engzing usin power give sating power systom startin oint coil and engrzing ruin poin capciter sysytom ruin c come on pointed us old and connecting ok jonnery gues ..
NICE
Your good
I like the video
Nice music, but I would like to see exactly and precisely how the physical contacts are made to close and open in both the current relay and the potential relay. Ty.
👍🏼
At 6:18 you say the potential relay opens and the compressor continues to run on the "start" windings... I think you meant to say run... Otherwise great videos👍
I was looking for clarification on that same point. Thank you
Is a compressor using a ptc relay use the current relay
No! the ptc replace the current relay
💪👍🇺🇸❄
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Why do you use capacitor symbol to represent a normally open contact?
I asked the same question, Its very confusing if you have any electrical knowledge.
That's the points symbol... Which is appropriate in this context
@@MrRUKidddingMeagree it makes sense