Types Induction Motor
Note that the major improvement in motor performance is made in the initial change from a capacitor-start to a two-value capacitor motor with a relatively low value of running capacitance. This initial design change also shows the shortest payback period.
The determination of the optimum two-value capacitor motor for a specific application requires a comparison of the motor costs and the energy consumptions of all such available motors. The efficiency improvement and energy savings of a specific product line of pool pump motors when the design was changed from capacitor-start motors to two-value capacitor motors are illustrated by Table 1.
Based on the same operating criterion used above, i. The permanent split capacitor motors, a single-phase induction motor, is defined as a capacitor motor with the same value of capacitance used for both starting and running operations. This type of motor is also referred to as a single-value capacitor motor. The application of this type of single-phase motor is normally limited to the direct drive of such loads as those of fans, blowers, or pumps that do not require normal or high starting torques.
Consequently, the major application of the permanent split capacitor motor has been to direct-driven fans and blowers. These motors are not suitable for belt-driven applications and are generally limited to the lower horsepower ratings.
The schematic diagram for a permanent split capacitor motor is shown in Fig. Note the absence of any starting switch. Since only the running capacitor which is of relative low value is connected in series with the auxiliary winding on starting, the starting torque is greatly reduced.
A typical speed-torque curve for a permanent split capacitor motor is shown in Fig. The running performance of this type of motor in terms of efficiency and power factor is the same as a two-value capacitor motor.
However, because of its low starting torque, its successful application requires close coordination between the motor manufacturer and the manufacturer of the driven equipment. A special version of the capacitor motor is used for multiple-speed fan drives.
This type of capacitor motor usually has a tapped main winding and a high-resistance rotor. The high-resistance rotor is used to improve stable speed operation and to increase the starting torque.
There are a number of versions and methods of winding motors. The most common design is the two-speed motor, which has three windings: For V power service, a common connection of the windings is called the T connection. Schematic diagrams for two-speed T-connected motors are shown in Figs.
For low-speed operation, the intermediate winding is connected in series with the main winding and with the auxiliary circuit as shown in Fig. Therefore, connect a capacitor, inductance coil or resistor to the starting winding in series make the current have a phase difference. In order to increase the starting torque on the connection, an autotransformer can be used to increase the single phase power supply voltage from v to V, shown in Figure 1.
General small motors are Y connection. For the Y-type three phase asynchronous motor, the capacitor C winding terminal connects to the autotransformer starting terminal.
If you want to change the shaft rotation direction, wire it as Figure 2. If you do not want to increase the voltage, the V power supply can use this too.
Because the original three phase V power supply voltage winding is now used for V power supply, the voltage is too low, so the torque is too low. Figure 3 wiring torque is too low. If you want to increase the torque, you can connect the phase-lock capacitor to the two-phase winding together in the coil and use this as the starting winding.
A single coil directly connected to the V power supply, see Figure 4. In Figure 3 and 4, if you need to change the shaft rotation direction, you can simply change the end-to-end direction of starting winding or working winding.
The value of the access resistor R Figure 7 on the starter winding should be closed to the stator winding phase resistance and should be able to withstand the starting current, which is 0. General working capacitor used in single phase power supply on the three phase asynchronous motor V: The starting capacitor can be selected according to the starting load, usually 1 to 4 times of the working capacitor. If require high starting torque, you can add a starting capacitor, and connected to the working capacitor.
When the starting is normal, disconnect the starting capacitor. There are many benefits in running three phase motor on single phase power supply, the rewinding work is easy. However, the general capacity of single phase power supply is too low, it has to withstand high starting current, so this method can be applied to 1kw motor or less only.
The single phase to 3 phase VFD is the best option for a 3 phase motor running on single phase power supply 1ph v, v, v , it will eliminate the inrush current during motor starting, make the motor run from zero speed to full speed smoothly, plus, the price is absolutely affordable. Impact of 60Hz 50Hz motor being used on 50Hz 60Hz power supply. You have no items in your shopping cart. Soft start can be achieved by adjusting the VFD's parameters, the starting time can be set to a few seconds or even tens.
Stepless speed regulation function to make the motor work at its best status. Each of the three single-phase windings consist of two coil windings. There are nine leads brought out externally from this type of stator winding. These leads, identified as leads 1 to 9, end in the terminal box of the motor. To mark the terminals, start at the upper left-hand terminal T1 and proceed in a clock wise direction in a spiral toward the center, marking each lead as indicated in the figure.
Coils are connected in series. The two coils of each single-phase winding are connected in series, ill shows the connections to permit operation from a volt, three-phase source. Coils are connected in parallel. If the lead identification of a 9-lead dual-voltage , 3-phase, Star connected motor have been destroyed, the electrician must re-identify them before connecting the motor to the line.
The following method may be used. First, identify the internally connected star point by checking for continuity between three of the leads as in ill 22 A. Then identify the three other sets of coils by continuity between two leads at a time ill 22 B. Assign T7, T8 and T9 to any of the three leads of the permanent star connected coils a. Apply the lower rated line voltage for the motor to T7, T8 and T9 and operate to check the direction of rotation. Disconnect line voltage and connect one of the undetermined coils to T Reconnect power, leaving the lines on T7, T8 and T9.
If the coil is correctly connected and is the proper coil, the voltage should be about 1. Be careful of line voltage. If the wrong coil is selected, the voltage differences between the loose end and the other two line leads will be uneven see ill 22 C.
When the readings are even and approximately 1. Perform the same tests with another coil connected to T Mark these leads T and T Perform the same test with the last coil connected to 19 to identify the 13 and 16 leads. The motor should operate in the same direction as before and operate quietly. Star or Wye connected motor; A Internal Star point lead marking; B coil group lead marking C Checking for proper coil lead markings on Wye connected, dual-voltage motor.
Another connection pattern for three-phase motors is the Delta connected motor. It is so named because the resulting schematic pattern looks like the Greek letter Delta delta symbol. A method of identifying and connecting these leads is necessary because it's different than the Star or Wye connected motor. Properly connecting the leads of a Delta connected, three-phase, dual-voltage motor presents a problem if the lead markings are destroyed.
Nine leads of a Delta connected, three-phase, dual-voltage motor. First, the electrician must determine if the motor is Delta connected or Star connected.
Both motors have nine leads if they are dual-voltage motors. However, the Delta-connected motor has three sets of three leads that have continuity and the Star-connected motor has only one set of three. To proceed, a sensitive ohmmeter is needed to find the middle of each group of three leads. The ohm values are low when using the dc power of an ohmmeter, so use care in identifying the center of each coil group.
Label the center of each group T1, T2 and T3 respectively. Connect the lower motor voltage rating using lines 1, 2, and 3 to T1, T4, and T9. The other coils will have induced voltage, so be careful not to touch the other loose leads to each other or to you!
Disconnect the power and connect the lead marked T4 to T7. Reconnect the power as before and read the voltage between T1 and T2. If the markings are correct the voltage should be about twice the applied line voltage.
If it reads about 1. If the voltage T1 to T2 then goes to , reconnect T9 to T7 thereby reversing both coils. When the voltage T1 to T2 equals twice the applied line voltage, mark the leads connected together as T4 from the T1 group connected to T7 of the T2 group. Now use the third coil group. Leave the lower line voltage connected to the first group as before. Test and connect the leads so that when T9 is connected to a lead of the third group, the T1-to-T2 voltage is twice the applied line voltage.
Mark the lead connected to T9 as T6 and the other end of the coil group as T8. If it does not, recheck the lead markings. Rotation should be the same as in the previous steps. Volt age is induced into other windings. Motor nameplates provide information vital to the proper selection and installation of the motor.
Most useful data given on the nameplate refers to the electrical characteristics of the motor. Given this information and using the National Electrical Code, the electrician can determine the conduit, wire, and starting and running protection sizes. The NEC gives minimum requirements. The design and performance data given on the nameplate is useful to maintenance personnel. The information is vital for the fast and proper replacement of the motor, if necessary.
For a better understanding of the motor, typical information found on motor nameplates is described as follows ill This is the individual number assigned to the motor, similar to a social security number for a person.
It is kept on file by the manufacturer. The motor will operate safely if it's run at the rated horsepower times the service factor, maximum. Common ser vice- factors are 1. It is recommended that the motor not be run continuously in the service factor range.
This may shorten the life expectancy of the insulation system. Amperes means the current drawn from the line when the motor is operating at rated voltage and frequency at the fully rated nameplate horsepower. Performance will be altered if it's operated at other frequencies. This means the motor can operate at full load for the specified period.
The motor should then be stopped and allowed to cool before starting again. This is used to determine starting equipment and protection for the motor. A code letter table is found in the National Electrical Code.