Forums » Electrical Engineering

3ph, motor

    • 27 posts
    January 30, 2019 10:44 AM PST

    230 V,  3ph, motor. But 3 conductor why not 5 conductors? Is this 3 phase, 2 phase or 1 phase motor?

    • 141 posts
    January 30, 2019 11:27 AM PST

    This is a 2 HP single phase 230v motor..  No neutral is needed as you get 230 V across 2 hot legs in either a single phase system or a 3 phase delta system

    • 27 posts
    January 30, 2019 11:46 AM PST

    Based on NEC Articles, 110V is a single phase and 230V is a 3 phase? But this figure does not match NEC standard. 3 phase delta needs 3 conductor except neutral or ground and 3 phase Wye system needs 5 conductors or 4 conductors?

    • 141 posts
    January 30, 2019 1:16 PM PST

    110v is single phase but it is no longer called 110V.  It is called 120v because the power company's usually bring higher voltages than they used to.  

     

    110v is single phase

    240v is single phase

    208v is 3 phase

    240 is also 3 phase with a high leg.

     

    If the power company delivers 3 wires to a building they are delivering 2 hot wires (single phase) that are out of phase with each, and a neutral.  From neutral to either hot conductor is 120v and across the 2 hot conductors is 240v.

    If the power company delivers 4 wires it is usually 3 hot conductors (3 phase) and a neutral.  You will measure 120v from neutral to any of the 3 hot legs.  You will measure 208v across any combination of hot wires if the system is a 3 phase "Y" configuration.

    A 3 phase delta system has 120V from neutral to 2 of the hot wires and the to the third hot wire it may measure 200v or there about.  Across any combination of the hot conductors it will measure 240v

     

    There are other systems also with different voltages, etc.

     

    In the diagram above it could be 2 legs from a 3 phase delta or it could be the 2 hot conductors from a single phase system.  Either way the motor would be called a single phase motor.

     

    • 200 posts
    February 1, 2019 8:59 AM PST

    Thanks for the suggestion for this topic, Terry.

    Gentlemen, if I may, discussing the Terry's question about the motor in diagram ONLY, not other issues raised by Dennis about provider voltages, type of winding.

    The motor in the diagram is a 2-PHASE motor for sure. What gives the hint? Mainly the circuit breaker installation:
    {insert Image: CB install-2ph-motor=imgsnap094.png}


    The reasons are:
    1. The CB is breaking both conductors RED and BLACK, so both conductors MUST be different phases. For safety reasons, no Neutral or Ground can be broken under any circumstance, as far as I know;

    2. Motor voltage: 230V, meaning 2 phases: 110V(red) + 110V(blk) = 220V (up to 240V, depending on the location or power company);

    3. Cable colors, it is an usual procedure, not necessarily mandatory:

    3.1 Phases: RED, BLACK, WHITE..., (not sure about: yellow, dark-blue,...), in this case of 2-phase 230V motor, both phases are connected to the motor winding - in truly this is a 2-conductor motor to make the motor run;

    3.2 Neutral: LIGHT-BLUE (usually), NOT in use in this case of 2-phase 230V motor. Neutral is mandatory when in use on 1-phase 110V motor, also connected to the motor winding, otherwise it can't run. NO breaker on Neutral line;

    3.3 Ground: GREEN, GREEN/YELLOW - in this case (Equipment) Ground is connected to the motor case for safety reasons, NOT to the motor winding, it's NOT intending to make the motor run;

    Regards


    This post was edited by Alex de Moura at February 1, 2019 9:05 AM PST
    • 141 posts
    February 1, 2019 9:25 AM PST

    Alex, I understand what you are saying but 2 hots and a ground is not 2 phases it is single phase. It is sometimes called split phase because the 2 lines are 180° out of phase with each other.

     

    The two 120 V AC lines are supplied to the premises from a transformer with a 240 V AC secondary winding which has a center tap connected to ground. The system neutral conductor is connected to ground at the transformer center tap. This results in two 120 V AC line voltages which are out of phase by 180 degrees with each other. When required, 240 V AC can be obtained by connecting the load between the two 120 V AC lines.

     

    2 phase does exists but is very rare and I think the lines are 90° out of phase with each other.

     

    https://en.wikipedia.org/wiki/Two-phase_electric_power

    • 62 posts
    February 1, 2019 9:45 AM PST
    Dennis Alwon said:

    Alex, I understand what you are saying but 2 hots and a ground is not 2 phases it is single phase. It is sometimes called split phase because the 2 lines are 180° out of phase with each other.

     

    The two 120 V AC lines are supplied to the premises from a transformer with a 240 V AC secondary winding which has a center tap connected to ground. The system neutral conductor is connected to ground at the transformer center tap. This results in two 120 V AC line voltages which are out of phase by 180 degrees with each other. When required, 240 V AC can be obtained by connecting the load between the two 120 V AC lines.

     

    2 phase does exists but is very rare and I think the lines are 90° out of phase with each other.

     

    https://en.wikipedia.org/wiki/Two-phase_electric_power

    Grounding is a matter of safety, and not necessarily a part of the circuit. It is a 2 phase breaker.

    • 200 posts
    February 1, 2019 10:11 AM PST

    Dennis, I understand you as well, and I appreciate your post of Wikipedia article. But Terry's question is about the MOTOR, while the Wikipedia article is about 2-Phase power systems. Indeed they are very RARE.

    For most of Residential uses the system provided is Single-Phase ( 1_Hot + 1_Neutral = 110V ), but in our office (a relatively big building) we requested 3-Phase power system (120o separation: 3_Hots + 1_Neutral), also commonly available, and we installed 220V Air Conditioning equipment (motors for fans and compressors) using 2 OF 3 Phases (2 Hots = 220V). Other common equipment such as computers are 110V using 1_Hot+1_Neutral of the same 3-Phase system. 3-Phase systems are the most flexible system available and usually must be requested at power distribution company.

    Terry's question has a 230V motor, it must be a 2-Phase Motor, such kind of motor will work on the RARE 2-Phase system you found AND on (2 of) common 3-Phase system available mainly for Commercial/Business installations.


    This post was edited by Alex de Moura at February 1, 2019 10:13 AM PST
    • 141 posts
    February 1, 2019 10:52 AM PST

    Alex, what I am saying is his motor is not called 2 phases but rather single phase.  There are 2- hot conductors in single phase but they are not considered phases.  Just a technical difference

     

    I have hook up hundreds of motors that are 240v from a single phase panel.  It is just confusing when it is called 2 phase because it is not from a 2 phase system just from a single phase system

    • 200 posts
    February 1, 2019 11:19 AM PST

    Dennis, I DIDN"T say 240V Single-Phase motors don't exist, and I believe you when you say you have a lot of experience on such equipment.

    But, with all respect, if Terry's motor were a Single-Phase one ( 1_Hot[phase] + 1_Neutral ) - one of the wirings (RED OR BLACK) SHOULD BE THE NEUTRAL.

    NEUTRAL is NOT considered as HOT - in many instances NEUTRAL can be grounded, so it CANNOT BE HOT. Maybe, the confusion is here: NEUTRAL is part of active circuit together with a Phase, but it is a RETURN conductor, unlike the Phase conductors, the NEUTRAL does not present voltage with respect to ground, usually.

    Also, NEUTRAL CANNOT be broken by a Circuit Breaker for safety reasons, hence the installation in Terry's diagram is a 2-PHASE one (both RED and BLACK are Phases or Hots), no matter how the motor is (commercially or technically) called.

    • 141 posts
    February 1, 2019 12:54 PM PST

    Alex you are not understanding or perhaps there is a terminology difference where you are compared to me.  Single phase motors can have 2 hot wires as I stated a few times.  A single phase panel has 2 hot conductors and a neutral.  The voltage between the hots is 240V and the voltage between either hot wire and the neutral is 120V.  Thisis called a single phase system.  Our well pumps, electric ranges, a/c units, electric heat are all wired from a single phase panel in a residence and are 240v.  240 v has either 2 black wires or a black and a red.

     

    Even if wired from a 3 phase panel the motor that wires from only 2 of the hot conductors (240V or 208v) is considered a single phase motor.

     

    Look at the NEC at article 430 and go to the end of that section and look at Tables 430.248 - 430.250.

     

    Table 430-248 shows you single phase 240V motors.  Table 430 249 shows 2 phase motor chart but they are 4 wire and rare.

    Alex I think we may be having a language or terminology difference here.

     

    Below is what T. 430.248 says at the heading

    Table 430.248 Full-Load Currents in Amperes, Single-Phase Alternating-Current Motors
    The following values of full-load currents are for motors
    running at usual speeds and motors with normal torque
    characteristics. The voltages listed are rated motor voltages.
    The currents listed shall be permitted for system voltage ranges
    of 110 to 120 and 220 to 240 volts.

     

     

     

    • 27 posts
    February 1, 2019 1:41 PM PST

    The diagram shows two hot lines. it means 2 ph. voltage L-L will not be same as L-reference ground or neutral point.

    • 141 posts
    February 1, 2019 1:50 PM PST

    Again there does not need to be a neutral in the circuit to be called single phase.  It is a double pole circuit on a single phase system.  DP breaker is used but the transformer is a single phase trany.  I don't know what else to say.  The only thing I can guess is that we call this single phase and you call it 2- phase.  

    • 141 posts
    February 1, 2019 1:52 PM PST

    120 / 240V Single Phase 3 Wire (1P3W)

    240V Single Phase Power Sketch

    120/240V 1 Phase 3 Wire

    In the US, 240V Power is provided to homes and small buildings as a 120/240V 1P3W power circuit. It provides 120V for light loads (lights, TV, etc.) and 240V for medium loads (Water Heaters, AC Compressors, etc.).

    MAXIMUM POWER – In a single phase power circuit maximum power is calculated as the voltage times the current. If we assume it’s a 200A power circuit then the maximum deliverable power is 200 x 240 as follows

    • Current (Amps): 200A
    • Voltage (Volts): 240V
    • Maximum Single Phase Power
      • 48 KVA Kilovolt Amps or
      • 48 KW Kilowatts
    • 200 posts
    February 1, 2019 2:10 PM PST
    A bit unfair: i am in restaurant having a brunner (breakfast+lunch+dinner) in a meeting, replying in a phone this interesting debate...

    Any that is I can agree with you, Dennis:
    "there is a terminology difference "

    And what I strongly disagree, no matter terminology:

    " Single phase motors can have 2 hot" - I am sorry Dennis, but 2_HOTS=2-PHASE no matter what, no matter terminology. Use a 220V Single-Phase motor in a 220V 2-Phase installation, such motors have different windings, motor can run, but it's not a good Engineering Practice, same as parallel grounding cable in other topic. It can be done but...

    "single phase panel has 2 hot conductors and a neutral" - yes we have a problem in terminology: 2_HOTS (different between them, 220V between 2 Hots) means 2-PHASE in all companies and countries I had worked for...

    " 2 phase motor chart but they are 4 wire and rare." - as I said before all the Air Conditioning equipment we had installed are 2-wire, 2-phase, 220V very common, the other option we had is 2-wire, Single-phase, 110V equipment.

    I don't know what to say more on this debate, but I suppose we cannot have the assumption that Terry's motor is a Single-phase in a 2-Phase installation (2-Phase CB, and that is it) just because one of the Members work under a different terminology from the rest. It is a difficult situation to solve.
    • 27 posts
    February 1, 2019 2:21 PM PST
    Dennis Alwon said:

    Again there does not need to be a neutral in the circuit to be called single phase.  It is a double pole circuit on a single phase system.  DP breaker is used but the transformer is a single phase trany.  I don't know what else to say.  The only thing I can guess is that we call this single phase and you call it 2- phase.  

    Double pole circuit on a single phase  system is not possible but if you say single phase with double pole, it is possible. 

    • 27 posts
    February 1, 2019 2:47 PM PST
    Dennis Alwon said:

    120 / 240V Single Phase 3 Wire (1P3W)

    240V Single Phase Power Sketch

    120/240V 1 Phase 3 Wire

     

    This diagram is different from my first post diagram. I quoted the below text from this diagram. This diagram describes correctly difference between 2 phase and single phase. 

    • Low power loads (lights, TV, etc.) powered using either either of (2) 120V power circuits

    This is statement is correct. This diagram shows 2 ph and 1 ph. same like in a 3 phase system which we can take 1 phase with the help of neutral. 

    • High power loads (Water Heaters, AC Compressors) powered using (1) 240V power circuit"

    This statement is also correct and describes 2 phase system connection.

     

    But motor's diagram has no neutral and only two hot lines, it means 2 phase. Are you agree on this?

    • 141 posts
    February 1, 2019 3:23 PM PST

    No, I don't agree.  Again I believe your country calls this 2 phase but technically that is incorrect as it has 2 hots but they are derived from one phase being 180° out of phase.  That's how we see it. 

    When you say that your motor is 2 phases that makes one believe it is from a 2- phase system which would be 4 or 5 wires.  There is a difference in this terminology is all that I am trying to say.  2 phase is a different system.

    You may be using 2 phases of a 3 phase system but that is not called a 2 phase motor and it is wired to 2 phases, however that would still be considered a single phase motor even at 240v-- no neutral involved.  The charts in the nec show this explicitly in T. 430-248-250

     

    Again I think we just have a different name for the same thing.

    • 200 posts
    February 1, 2019 4:09 PM PST
    "your country calls this 2 phase but technically that is incorrect as it has 2 hots but they are derived from one phase being 180° out of phase" - Dennis, please I usually I don't use any reference to "my country" since I rarely work with Electrical/Electronics/Automation in my own country. The companies I worked for are most international ones (including US ones) using international standards and nomenclature. But I don't like technical debates won by resume size.

    None of countries I worked in, including mine, have 2-phase systems. In Africa, Asia, North America, South America - on sea or land - the service are provided as Single-Phase or 3-Phase, only.

    I heard about 2-phase power services, but you are the first Engineer/Technician talking about it openly in a forum. I am not aware of any place using this service widely.

    However, any equipment in the countries I worked in are usually provided on 110V for Single-phase service ( ONLY) or 220V for 2-phase service or 220V Single-phase service, most for Residential use, not Industrial installation.

    Of course, there are many regions including in my country with Single-phase 220V ( 1_Hot + 1_Neutral ) - usually countryside or distant towns, they can use 220V 2-phase equipment in this situation alright, but Industrial sites usually select 2-phase systems.

    But again this is NOT the case of Terry's motor - a CB for 2-phase supply.

    Besides your disagreement, I am not aware of any equipment, panel or whatever with 2-phases (separated by 180o) or 2 OF 3 Phases (separated by 120o) and still called "Single-phase".

    The CB in Terry's diagram is clear: 2 phases, so 2-phase motor.
    • 200 posts
    February 1, 2019 4:17 PM PST
    "using 2 phases of a 3 phase system but that is not called a 2 phase motor and it is wired to 2 phases, however that would still be considered a single phase motor even at 240v-- no neutral involved"

    Now the sentence above I can agree with you about terminology differences as you consider if "NEUTRAL is not involved" it is called "Single-phase". It is possible the terminology is different in many places and countries. That is OK for me now this debate and I understand what you saying.
    This post was edited by Alex de Moura at February 1, 2019 4:22 PM PST
    • 141 posts
    February 1, 2019 7:03 PM PST

    Here is my confusion... You say no one talks about 2 phase and the system is rare (I agree, I never have seen one) but  then you say the motor is 2 phase.... do you see my problem.  To summarize you say there are no 2 phase systems but the motor is 2 phase.  Calling it 2 phase makes me think of the rare 2 phase system.  

     

    If you have a 3 phase system then yes it uses 2 of the 3 phases but IMO that is not called 2 phase.  I understand that it is technically incorrect to see it as single phase when installed to a 3 phase system but when you install 2 hots to a motor on a single phase system it is not 2 phases.

     

    Maybe the thread below will help explain it better

     

    If you are interested read this thread and maybe they will explain it better than I can.

     

    https://forums.mikeholt.com/showthread.php?t=192670&highlight=single+phase+180


    This post was edited by Dennis Alwon at February 1, 2019 7:12 PM PST
    • 27 posts
    February 1, 2019 11:53 PM PST
    Dennis Alwon said:

    No, I don't agree.  Again I believe your country calls this 2 phase but technically that is incorrect as it has 2 hots but they are derived from one phase being 180° out of phase That's how we see it. 

     

     

     

    again, you are talking about 180 degree and 1 phase. Lets do explanation another way, if you take the ampere meter, and measure live current on both legs? Is there same current flow on both legs, for instance 25A one leg and 25A second leg? if so, it is 2 phase. You can call it only 1 ph, 230V, if you measure voltage between neutral to phase 230V, do you have this?

    • 141 posts
    February 2, 2019 2:44 AM PST

    I totally get what you are saying Terry but in the US we don't have neutral to hot at 240v, it does not exist.  I assume because of the issue with a 2 phase system this side of the pond calls it single phase- 

    If I has a single phase panel- 2 hots and a neutral and we installed a motor like you show above would you call that 2 phase even if it comes from a single phase panel?  This would be called single phase 240V because it comes from a single phase panel.  So when the same motor is wired with 2 phases of a 3 phase system the name stuck and although it is basically incorrect it is still called 240 single phase in the US.  

    So, when you posted the question originally I could only answer it based on what we call it here.  I understand that on your side of the pond you call it 2 phase.  My confusion was I thought you meant a 2 phase system and that is where the confusion originated at.

     

    Your question also was misleading when you said why is there not 5 wire.  I assume you meant 4 current carrying conductor's and a ground which is called a 2 phase system

    We are good we just have different names for the same thing.

    BTW, I am not an engineer.  I am just an electrical contractor and really I am not good at the technical end or theory.  I did learn something as I never thought about why we call it single phase when coming from a 3 phase panel.  Because on a single phase system there is 2 conductors that are hot but they originate from the same place and you still get 240v.

     

    Thank you for this interesting discussion

     

     

     

     

     

    • 3 posts
    February 2, 2019 3:32 AM PST

    Hi everyone,

    current perspective this system is called Single Phase but voltage perspective 2 phase.

    The current is flowing same as single phase either by leg 1 or leg 2 but not at the same time but the voltage point remain the same 240V. This causes to increase power at the end consumer.

    In other countries the 2 phase legs means current is flowing at the same direction at a time but with this system it is not.


    This post was edited by Gregg Mallick at February 2, 2019 3:32 AM PST
    • 200 posts
    February 2, 2019 10:48 AM PST
    Terry, right now I'm inclined to agree with Dennis that the motor is Single-Phase. My intention is to edit my response by changing from "2-Phase Motor" to "Single-Phase Motor in a 230V 2-Phase Installation".

    I believe that Dennis' last few sentences reminded me that many countries distribute 110V Single-phase through the main cities, and 220V Single-phase in countryside and less developed regions due to distances.

    In such countries, with both 110V and 220V Single-phase, motors and other equipment are available at both voltages. In regions with 110V Single-phase it is also offered the 3-phase service (220V between phases).

    In this way the equipment and motors for Residence and Commerce usage are manufactured in versions of 110V and 220V, but both Single-phase.

    Residents of cities with 110V have the option (usual option offered to Commerce and Businesses) to request the 3-phase system from the Power Company and install 220V Single-phase motors and equipment connecting to two phases to obtain the required 220V. That is the case of your diagram, a 230V Single-phase motor installed in 2-Phase branch of a (probable) 3-Phase service. That is also the case of our office here. I will not discuss the efficiency of such configuration as required in Industry, it is not the case here.

    The residents of countryside with 220V Single-phase service must install the SAME 220V Single-phase motor or equipment, but connecting to Phase+Neutral.

    So, it is the very SAME 220V/230V Single-phase motor or equipment, it can run in both available configurations: 220V/230V Single-phase service or 220V/230V 2-Phase branch.

    Sorry for that, my excessive service at Industry made me away from the most common motors, equipment and services available for the simple population of many countries including mine.

    I would like to receive your acknowledgement on this, preferably your agreement, before I post or edit my previous reply. Regards.


    This post was edited by Alex de Moura at February 2, 2019 10:53 AM PST