Motor lead connection diagrams

Motor connection diagrams are visual representations of the wire arrangements for various voltages, in the case where the motor is dual voltage, or for various speed characteristics, in the event where the motor is a multi-speed consequent pole or multi-speed separate winding motor. Dual voltage motor connection diagrams are the main topic of discussion in this lesson. I'll talk about multi-speed motors first, though. 

Most manufacturers offer dual voltage motors so that their goods can be used in industrial applications across several nations with varying electrical distribution voltages.

If you don't adhere to the motor connection schematic exactly as shown, it could have catastrophic consequences. A motor may be destroyed or, at the very least, perform poorly if it is improperly wired since the polarity of the magnetic field depends on the direction of the current.

 Always refer to the datasheet for the motor you are using. Do not take the motor connection diagram and terminal numbers as being universal just because they are shown in the lesson.

You must ascertain the proper connection diagram for a given motor of interest because thick, tangled jungle peculiarities occur, especially for older motors. 

The four popular three-phase alternating currents (AC) motor types—permanent magnet synchronous motors, electrical excited synchronous motors, squirrel cage induction motors, and wound round induction motors—typically have three, six, nine, or twelve leads where the stator, or stationary part of the motor, is concerned.

Electrical connections are made to the rotor, which rotates in electrically excited synchronous motors and wound rotor induction motors.

Permanent magnet synchronous motors and Squirrel cage induction motors will not have connections to the rotor. The rotor in the lesson will mostly be disregarded as we focus on the stator leads. Depending how the stator leads are connected determines;

1. The electrical configuration of the stator either Star or Delta, 
   
   
   
2. The resulting voltage and current each stator winding experiences  
3. The rotational direction of the rotating magnetic field produced by the stator 

Three and six lead motors

Three lead motors are often non-dual voltage motors since they are designed to operate on a single specified voltage and typically represent single winding per phase motors. A fixed Star or Delta configuration is included with every three-lead motor when purchased.

A six-lead motor, on the other hand, enables the user to choose whether the motor will be connected in a Star or Delta configuration. Direct measurement of the current through an individual winding in a three-lead Star configured motor is easy. However, voltage measurements of the individual windings are typically not possible at the central node of the three-phase lead Star configuration motor, which makes them challenging and intrusive. In a three-lead delta motor, it is simple to measure the line-to-line voltage across a single winding directly. For three lead Delta configuration motors, the current measurement of each individual winding is problematic and intrusive since the ammeter must be connected in series. Because it is difficult to calculate the direct electrical power consumption of three-lead motors in either a Star or a Delta configuration, a trick or two must be applied.

Line-to-line voltage and line-to-neutral voltage, as well as line current and winding current for a balance three-phase A.C loads, have a relationship that can be used to our advantage. For balance three phase A.C electrical loads like motors, the line-to-line voltage is square root three or 1.73 times greater than the line-to-neutral voltage.

For balanced three-phase A.C. electrical loads like motors, line current will be three times the square root, or 1.73 times, greater than the current through a winding with a delta configuration.

This mathematical ruse enables a technician to avoid intrusive and troublesome inspection by taking conveniently accessible line-to-line voltage and line current readings external to the motor, regardless of whether it is Star or Delta setup.

‎Due to the fact that three-lead, three-phase AC motors are prewired as either a Star or a Delta depending on the user's preference, manufacturers now offer six-lead motors that allow a motor to be configured in, either way, depending on the user's preference, rather than prewiring the motor in a fixed Star or Delta configuration. I've sketched the B winding with terminals two (2) and five (5), the C winding with terminals three (3) and six (6), and the A winding with terminals one (1) and four (4). (6). ‎

Six leads Star configured motor

If one wants to place this six leads motor into a star configuration terminals four (4), five (5), and six (6) are tied together forming a central junction of the Star, terminals one (1), two (2), and three (3) are left to be connected to three-phase A.C source where the direction of rotation is determined by the phase sequence. Terminals four (4), five (5) and six (6) form the central node of the Star are now accessible, a technician has direct access to the voltage across each winding without resorting to any mathematical trickery for power consumption calculation. 

The motor connection diagram might illustrate a six lead Star configuration using a diagram similar to this below:

Six leads Star configured motor

Six leads Delta configured motor

Terminals four (4) and two (2), terminals five (5) and three (3), and terminals six (6) and one (1) are connected in a triangle to make the Delta configuration for this six-lead motor. The three-phase AC source would be linked to corners [1, 6], [2, 4], and [3, 5], and the phase order would dictate the rotation's direction. The six-lead Delta arrangement motor now has access to both ends of all three windings, allowing a technician to measure the current via each winding directly without using any mathematical gimmicks. Below is an example of a motor connection schematic for a six-lead Delta design motor. 

Six leads Delta configured motor

In a three-phase AC system, keep in mind that the line-to-line voltage is always 1.73 times greater than the line-to-neutral voltage. In a six-lead motor arranged as a Star, each winding would experience lower voltage than it would in a six-lead motor configured as a Delta. A six-lead motor is actually a dual voltage motor because of the difference in line-to-neutral and line-to-line voltage. Six lead motors are typically utilized, however, it isn't for this reason. In a technique known as the Star (Wye) start delta run low voltage starter, the six lead motors' customizable Star or delta nature can be exploited to reduce inrush current.

Think about a motor starter that starts a motor in the Star configuration and then switches to the Delta configuration after a set amount of time or once the motor reaches a certain speed. Once a motor reaches a certain speed, counter electromotive force, also known as CEMF, will be greater, and the full line-to-line voltage can then be applied in a Delta configuration. When a motor is started in the Star configuration, each winding receives the smaller line to neutral voltage, and voltage being the cause of the current inrush current will lessen. The motor windings receive electricity in stages, preventing inrush current from unduly taxing the electrical supply system.

Nine (9) and twelve (12) lead motors

We enter the domain of true dual voltage motors when we reach nine and twelve motors. The basic guideline is high voltage series, low voltage parallel whether the windings are organized in a star or delta pattern. The two windings for a given phase are connected in series when a motor is to be operated at a high voltage. Each identical winding reduces the voltage by half and the current by half as a result. The two windings for a particular phase are connected in parallel when a motor is run at low voltage. Because electrical power consumption is the product of voltage and current, it is comparable for motors used in high- or low-voltage setups because each identical winding would drop the same amount of voltage while producing twice as much current. Although the current is reduced in the high voltage configuration, the voltage is higher. While voltage is lower in the low voltage configuration, the current is higher. Given the expense per foot of thicker gauge wire required to operate the lower voltage configuration, it appears that if given an option between a high voltage and a low current configuration, the high voltage version may be selected. In each setup, the amount of mechanical power delivered and the amount of electrical power consumed should be the same. A technician is not given the option to choose between Star or Delta configurations because nine lead motors are essentially an extension of the three lead motors. These motors often have windings that are pre-wired in a partial delta or a star pattern. To connect to a high- or low-voltage source, the remaining leads can be wired in series or parallel with pre-wired Star or partially wired delta. 

Nine-lead Star configured motor

Take a look at a nine-lead Star configuration motor. With windings, A2, B2, and C2, terminals seven (7), eight (8), and nine (9) create the prewired star. For a nine-lead motor, the center node is normally inaccessible. The two terminals of coil A1 are terminals one (1) and four (4). The two terminals of coil B1 are terminals two (2) and five (5). The two terminals of coil C1 are terminals three (3) and six (6).

Nine lead high voltage configure Star Motor

In a high voltage configuration, we need to create a series of configurations of windings. In this instance, terminals [4,7], [5, 8], and [6,9] are linked in a huge star shape, with each branch made up of a series of combinations of two windings. The term "big Star configurations" is occasionally used to describe high voltage series Star setups because of this. Terminals 1, 2, and 3 would receive phase voltages L1, L2, and L3, respectively.

The motor connection diagram might illustrate a nine lead high voltage Star using a diagram similar to this below:

Nine lead high voltage configure Star Motor

                                                                                                                                                                                                                                                                                                  

Nine lead low voltage configure Star motor

In a low voltage configuration, we need to create a parallel configuration, in this case, terminals four (4), five (5), and six (6) are tied together to form the central junction of another Star, then terminals[1&7], [2&8], and [3,&9] tied together. Phase voltages L1, L2, and L3 would be applied to terminals [1,7], [2,8], and [3, 9]. The motor connection diagram might illustrate a nine lead low voltage configuration Star motor using a diagram similar to this below:

Nine lead low voltage configure Star motor

It almost looks like two Star configurations are superimposed on top of one another in this low voltage parallel setup. The term "Star Star configurations" is occasionally used to refer to low voltage parallel Star configurations because of this. Note that you would typically need to connect the two middle connections for a completely balanced three-phase AC load, such as a motor.

Nine-lead Delta configured motor

In this instance, the pre-wired windings only partially complete Delta configurations. These partial Delta's can be placed in series for a high voltage configuration or placed in parallel with one another for a low voltage configuration. Winding A1 has terminals one and four, windings A2 has terminals seven and two, windings B1 has terminals two and five, windings B2 has terminals eight and three, winding C1 has terminals three and six, and windings C2 has terminals nine and one. 

Note terminals 1, 2, and 3. Access to both ends of a single winding is possible with a nine-lead Delta design motor. But take note that the manufacturer has already linked two windings together in each corner.

Nine lead high voltage configure Delta Motor

When these windings are wired in series or in a high voltage configuration, four is connected to seven, five to eight, and six to nine. It forms a very huge Delta in this example, with each corner to corner from one to two, two to three, and three to one consisting of two windings in sequence. Big Delta is another name for this series of high-voltage setups. L1, L2, and L3 phase voltages would be applied to terminals one, two, and three. The motor connection diagram for a nine-lead high-voltage Delta motor may depict this setup using the diagrams below:

Nine lead high voltage configure Delta Motor

Nine lead low voltage configure Delta Motor

In this instance terminals one, six, and seven are joined together, forming the upper corner of the parallel delta. Terminals two, eight, and four create the delta's right corner, whereas terminals nine, three, and five forms the delta's left corner. When the three partial Deltas are squeezed together, winding A1 is parallel to A2, winding B1 is parallel to B2, and winding C1 is parallel to C2. The Delta Delta connection is another name for the parallel low voltage setup. L1, L2, and L3 phase voltages would be applied to terminals [1, 6, 7], [2, 8, 4], and [3, 9, 5].

A motor connection diagram displaying a nine lead low voltage Delta may depict this setup using a diagram similar to this:

Nine lead low voltage configure Delta Motor

Twelve-lead Star configured motor

This motor is the most flexible, as it can be configured for use with high or low voltage in either a Star or Delta configuration. In this case, both terminals have two windings per phase and are accessible, making a total of 12 terminations available. Winding A1 has terminals 1 and 4, winding A2 has terminals 7 and 10, winding B1 has terminals 2 and 5, winding B2 has terminals 8, and 11, winding C1 has terminals 3 and 6, and winding C2 has terminals 9 and 12.

Twelve lead  high voltage Star configured motor

In this configuration, terminals 10, 11, and 12 are linked together to form the Star's central node, terminals four and seven are linked together to connect winding A1 and A2, terminals five and eight are linked together to connect winding B1 and B2, and terminals six and nine are linked together to connect winding C1 and C2. L1, L2, and L3 phases would be applied to terminals one, two, and three, where the phase sequence determined the rotational direction. The motor connection diagram for a 12-lead high voltage Star configured motor may show this configuration using the diagram below.

Twelve lead  high voltage Star configured motor

Twelve lead low voltage Star configured motor

By connecting terminals four, five, and six, the parallel low voltage configuration forms one Star. Then, by connecting terminals 10, 11, and 12, another Star is formed. By connecting terminals one and seven, two and eight, and three and nine, two Stars are connected in parallel. L1, L2, and L3 phase voltages would be applied to terminals [1,7], [2,8], and [3,9] where the phase sequence determined the rotational direction. The diagram below may be used to illustrate a 12-lead low voltage Star configurated motor.

Twelve lead low voltage Star configured motor

Twelve lead high voltage Delta configured motor

The series high voltage configuration connects terminals four and seven, connecting windings A1 and A2, terminals five and eight, connecting windings B1 and B2, terminals six and nine, connecting windings C1 and C2, then one is connected to 12 forming the top corner of the series Delta, two is connected to 10 forming the right corner of the series Delta, and three is connected to 11 forming the left corner of the series Delta. L1, L2, and L3 phase voltages will be applied to terminals [1,12], [2,10], and [3,11] where the phase sequence determines the rotational direction. A motor connection diagram illustrating a 12-lead high voltage Delta configuration might look like this.

Twelve lead high voltage Delta configured motor

Twelve lead low voltage Delta configured motor

In the parallel low voltage configuration terminals [1&7] and [4&10] are tied together, connecting windings A1 and A2 in parallel. Then terminals [2&8] and [5&11] are tied together, parallelizing windings B1 and B2, then terminals [3&9] and [6&12] are tied together, parallelizing windings C1 and C2, then the 1,7 group is joined with the 6,12 group, forming the top corner of the parallel Delta, and the 2,8 group is joined with a 4, 10 group, forming the right corner of the parallel Delta. Finally, the 3,9 group is joined with the 5,11 group to form the parallel Delta's left corner. Phase voltages L1, L2 and L3 will be applied to group [1,7,6,12], [2,8,4,10], and [3,9,5,11] where phase sequence determines direction of rotation. A motor connection diagram illustrating a 12-lead low voltage Delta configuration might look something like this.

Twelve lead low voltage Delta configured motor

Dual speed motors

The rotational speed of the rotating magnetic field is changed by changing the number of active pole pairs in the stator, which is known as synchronous speed. The various configurations for dual-speed motors change the number of pole pairs in the starter in one of two ways: consequent pole, which means you get rid of some pole pairs by sending current in the opposite direction, or separate winding, which means there are different windings that you can connect or disconnect to change the number of pole pairs per phase. These configuration changes only affect speed and have no bearing on the high or low-voltage operation. I'm not spending much time on dual-speed motors because you're unlikely to come across them unless you're working on really old equipment. Dual-speed motors have a noticeable difference between high and low speeds and have been largely replaced by a power electronics device known as a motor drive, which varies the excitation frequency, thereby directly influencing rotational speed. Varying the excitation frequency rather than the number of pole pairs per phase allows for finer tuning of rotational speed while requiring no physical changes to the motor.

Conclusion 

In conclusion, we examine three, six, nine, and twelve lead motor connection diagrams, dual voltage motors, Star and Delta configurations, and briefly discuss multi-speed motors using consequent pole and separate winding method.  

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