How does a synchronous motor start without a starting device?
2 Answers
In general, synchronous motors require a starting device to bring them up to synchronous speed before they can run in synchronization with the power supply. The starting device is typically used to overcome the initial inertia and bring the motor to the synchronous speed, which is determined by the frequency of the power supply and the number of poles in the motor.
However, there are some specific scenarios where a synchronous motor can start without a starting device. This is possible under certain conditions:
Inherent Self-Starting Capability: Some synchronous motors are designed with inherent self-starting capabilities. These motors have a special rotor design or are designed with a small amount of saliency (variation in pole strength) in the rotor, which allows them to start without a starting device. The motor will still need an initial external torque to get moving, but once it reaches a certain speed, it can synchronize with the power supply and continue to run without additional assistance.
Assistance from Load or Auxiliary Motor: In certain applications, the load connected to the synchronous motor or an auxiliary motor can provide the initial torque needed for the motor to start rotating. Once the motor picks up speed, it can synchronize with the power supply and continue to run in synchronism.
Reduced Mechanical Load: If the mechanical load on the synchronous motor is very light, it might be possible for the motor to start without a starting device. The initial torque required to overcome inertia and start rotation may be small enough to be provided by the available power supply.
It's important to note that these scenarios are not common for most synchronous motors, and the majority of synchronous motors in practical applications require a starting device. The starting device is essential for ensuring reliable and controlled motor starting, especially when the motor has a significant mechanical load to overcome. The starting device can be a variety of methods, including a pony motor, a wound rotor with resistors, or electronic starting systems.
Before attempting to start a synchronous motor without a starting device, it is crucial to refer to the manufacturer's specifications and recommendations to ensure that the motor is capable of such a start-up method and that it won't cause damage to the motor or the connected system. In most industrial applications, synchronous motors are started using appropriate starting devices to ensure smooth and reliable operation.
However, there are some specific scenarios where a synchronous motor can start without a starting device. This is possible under certain conditions:
Inherent Self-Starting Capability: Some synchronous motors are designed with inherent self-starting capabilities. These motors have a special rotor design or are designed with a small amount of saliency (variation in pole strength) in the rotor, which allows them to start without a starting device. The motor will still need an initial external torque to get moving, but once it reaches a certain speed, it can synchronize with the power supply and continue to run without additional assistance.
Assistance from Load or Auxiliary Motor: In certain applications, the load connected to the synchronous motor or an auxiliary motor can provide the initial torque needed for the motor to start rotating. Once the motor picks up speed, it can synchronize with the power supply and continue to run in synchronism.
Reduced Mechanical Load: If the mechanical load on the synchronous motor is very light, it might be possible for the motor to start without a starting device. The initial torque required to overcome inertia and start rotation may be small enough to be provided by the available power supply.
It's important to note that these scenarios are not common for most synchronous motors, and the majority of synchronous motors in practical applications require a starting device. The starting device is essential for ensuring reliable and controlled motor starting, especially when the motor has a significant mechanical load to overcome. The starting device can be a variety of methods, including a pony motor, a wound rotor with resistors, or electronic starting systems.
Before attempting to start a synchronous motor without a starting device, it is crucial to refer to the manufacturer's specifications and recommendations to ensure that the motor is capable of such a start-up method and that it won't cause damage to the motor or the connected system. In most industrial applications, synchronous motors are started using appropriate starting devices to ensure smooth and reliable operation.
A synchronous motor is a type of AC (alternating current) motor that runs at a constant speed, synchronizing its rotational speed with the frequency of the power supply. Unlike induction motors, synchronous motors do not inherently have the ability to start on their own without some external assistance due to their design characteristics.
Synchronous motors are typically used in applications where a constant and precise speed is required, such as in power generation, industrial processes, and precision timing systems.
To start a synchronous motor, a starting device is generally required. The two common methods used to start a synchronous motor are:
Starting with a "pony motor": In this method, a small induction motor (commonly known as a "pony motor") is used to initially bring the synchronous motor to a near-synchronous speed. Once the synchronous motor reaches a speed close to synchronous speed, it is synchronized with the power supply by gradually connecting it to the power source using a switch or a mechanical coupling. After synchronization, the synchronous motor remains locked in step with the power supply's frequency.
Using an external starting device: Another way to start a synchronous motor is by using external starting devices such as a variable frequency drive (VFD) or a static frequency converter. These devices can generate an adjustable frequency that allows the synchronous motor to start and gradually reach synchronous speed. Once the motor is synchronized, the frequency is adjusted to match the power supply frequency, and the motor continues to run at a constant speed.
It's important to note that synchronous motors are not self-starting like induction motors, which can develop a rotating magnetic field on their own. As a result, synchronous motors require additional methods or devices to bring them up to speed and synchronize them with the power supply. Once synchronized, the synchronous motor can maintain its speed and provide constant and precise rotational motion, making them suitable for various industrial and power generation applications.
Synchronous motors are typically used in applications where a constant and precise speed is required, such as in power generation, industrial processes, and precision timing systems.
To start a synchronous motor, a starting device is generally required. The two common methods used to start a synchronous motor are:
Starting with a "pony motor": In this method, a small induction motor (commonly known as a "pony motor") is used to initially bring the synchronous motor to a near-synchronous speed. Once the synchronous motor reaches a speed close to synchronous speed, it is synchronized with the power supply by gradually connecting it to the power source using a switch or a mechanical coupling. After synchronization, the synchronous motor remains locked in step with the power supply's frequency.
Using an external starting device: Another way to start a synchronous motor is by using external starting devices such as a variable frequency drive (VFD) or a static frequency converter. These devices can generate an adjustable frequency that allows the synchronous motor to start and gradually reach synchronous speed. Once the motor is synchronized, the frequency is adjusted to match the power supply frequency, and the motor continues to run at a constant speed.
It's important to note that synchronous motors are not self-starting like induction motors, which can develop a rotating magnetic field on their own. As a result, synchronous motors require additional methods or devices to bring them up to speed and synchronize them with the power supply. Once synchronized, the synchronous motor can maintain its speed and provide constant and precise rotational motion, making them suitable for various industrial and power generation applications.