10-05-2014, 09:09 PM
Hi,
Over the years I've been asked many times questions about connecting a 3 phase motor for low voltage supply with some of the motors having no identification plates. (Nameplates).
I worked at Brook Motors for 24 years but do not have any electrical training nor certificates covering electrical training so only add these notes from personal experiences only and will not in any way whatsoever be held responsible should any accident occur. Working with mains electricity can kill through a simple mistake so I urge any novice reading these notes and looking at the sketches not to take any risks however slight the risk may be.
This information is meant to give very basic information on how to connect a 3 phase motor either in High voltage (Star) or Low Voltage (Delta) general 3 phase connection diagrams being widely available by browsing the web. However this assumes the motor is already set up for connection so I'll start right at the beginning.
Very old 3 phase motors will possibly only have three visible leads coming out of the coils in the stator. 3 phase motors have three separate coils which are hidden out of sight within the motor; the part we are interested in is the terminal or junction box where access to the motor connections is available by removing the terminal box lid (ISOLATE FROM THE SUPPLY BEFORE REMOVING LID IF THE MOTOR IS ALREADY CONNECTED)
Assuming the motor is on the bench therefore safe (disconnected from the supply) and is indeed a 3 phase motor remove the terminal box lid. If you have a modernish motor then hopefully there will be a plastic block staring at you this block having six connections. If the six connections are present then the motor can be connected in either Star or Delta. If only three connections are seen then I would advise a novice to source another motor because many old 3 phase motors intended only for star connection has the star point buried in the windings and trying to dig this star point out to gain access to the three leads will possibly render the motor useless and unsafe.
Lets start with a 3 phase motor having 6 leads but non of the leads are connected in any way just being "floating". The motor has 3 coils so these leads will be in 3 pairs the ends of each pair being one coil; the pairs now need to be identified and marked which is quite easy once you know how. Using a multi-meter on Ohms setting select any two leads and take a resistance reading; no reading? hold on to one lead but then select another lead until a reading is obtained; the order of the lead pairs is unimportant at this stage. Once two leads are identified as a complete coil then mark these one end U1 the other end U2 this is the first coil; repeat the procedure marking the second coil leads V1 and V2; this leaves two final leads which are marked W1 and W2. If it is found that a pair of leads is left which does not show a reading then its likely the motor is useless having an open circuit coil.
If a multi-meter is not available then a simple test lamp and battery can be used or even a battery and buzzer as long as continuity through each coil can be determined. Now all six leads are identified as U1-U2 / V1-V2 and W1-W2. This might all sound very complicated to a novice but in reality identifying the leads takes little time and once done the rest is just a matter of following the sketches as to connecting either in Star or Delta.
If the motor runs in the wrong direction simply swap two of the supply leads (Disconnect from supply first) and the motor will then reverse.
Brook motors are fitted with plastic connection blocks these having six connections (nuts). Also will be seen are what are called links these being strips of metal copper or brass which are used for connecting pairs of terminals; the sketches show how these three links are connected for either Star or Delta connection; in order not to lose a link connecting in star two links are placed together one on top of the other so that should the motor need connecting in Delta the link is available.
Most of the above information is readily available on the web but sorting out the motor leads if they are not connected I've not seen on the web only finding this out by looking over someone's shoulder whilst he sorted a motor out for me; I'm nosy and a quick learner.
I hope this information is of use but I repeat I'm not qualified in electrical work. All connections need to be well made and secure and above all safe before applying power; ENSURE A SOUND EARTH CONNECTION TO THE MOTOR WHICH IS SO IMPORTANT!!!
Kind regards, Col.
Over the years I've been asked many times questions about connecting a 3 phase motor for low voltage supply with some of the motors having no identification plates. (Nameplates).
I worked at Brook Motors for 24 years but do not have any electrical training nor certificates covering electrical training so only add these notes from personal experiences only and will not in any way whatsoever be held responsible should any accident occur. Working with mains electricity can kill through a simple mistake so I urge any novice reading these notes and looking at the sketches not to take any risks however slight the risk may be.
This information is meant to give very basic information on how to connect a 3 phase motor either in High voltage (Star) or Low Voltage (Delta) general 3 phase connection diagrams being widely available by browsing the web. However this assumes the motor is already set up for connection so I'll start right at the beginning.
Very old 3 phase motors will possibly only have three visible leads coming out of the coils in the stator. 3 phase motors have three separate coils which are hidden out of sight within the motor; the part we are interested in is the terminal or junction box where access to the motor connections is available by removing the terminal box lid (ISOLATE FROM THE SUPPLY BEFORE REMOVING LID IF THE MOTOR IS ALREADY CONNECTED)
Assuming the motor is on the bench therefore safe (disconnected from the supply) and is indeed a 3 phase motor remove the terminal box lid. If you have a modernish motor then hopefully there will be a plastic block staring at you this block having six connections. If the six connections are present then the motor can be connected in either Star or Delta. If only three connections are seen then I would advise a novice to source another motor because many old 3 phase motors intended only for star connection has the star point buried in the windings and trying to dig this star point out to gain access to the three leads will possibly render the motor useless and unsafe.
Lets start with a 3 phase motor having 6 leads but non of the leads are connected in any way just being "floating". The motor has 3 coils so these leads will be in 3 pairs the ends of each pair being one coil; the pairs now need to be identified and marked which is quite easy once you know how. Using a multi-meter on Ohms setting select any two leads and take a resistance reading; no reading? hold on to one lead but then select another lead until a reading is obtained; the order of the lead pairs is unimportant at this stage. Once two leads are identified as a complete coil then mark these one end U1 the other end U2 this is the first coil; repeat the procedure marking the second coil leads V1 and V2; this leaves two final leads which are marked W1 and W2. If it is found that a pair of leads is left which does not show a reading then its likely the motor is useless having an open circuit coil.
If a multi-meter is not available then a simple test lamp and battery can be used or even a battery and buzzer as long as continuity through each coil can be determined. Now all six leads are identified as U1-U2 / V1-V2 and W1-W2. This might all sound very complicated to a novice but in reality identifying the leads takes little time and once done the rest is just a matter of following the sketches as to connecting either in Star or Delta.
If the motor runs in the wrong direction simply swap two of the supply leads (Disconnect from supply first) and the motor will then reverse.
Brook motors are fitted with plastic connection blocks these having six connections (nuts). Also will be seen are what are called links these being strips of metal copper or brass which are used for connecting pairs of terminals; the sketches show how these three links are connected for either Star or Delta connection; in order not to lose a link connecting in star two links are placed together one on top of the other so that should the motor need connecting in Delta the link is available.
Most of the above information is readily available on the web but sorting out the motor leads if they are not connected I've not seen on the web only finding this out by looking over someone's shoulder whilst he sorted a motor out for me; I'm nosy and a quick learner.
I hope this information is of use but I repeat I'm not qualified in electrical work. All connections need to be well made and secure and above all safe before applying power; ENSURE A SOUND EARTH CONNECTION TO THE MOTOR WHICH IS SO IMPORTANT!!!
Kind regards, Col.
Happiness is a wreck of a cabinet to restore.
