What Determines Synchronous Speed in a Squirrel Cage Motor?
What determines synchronous speed in a squirrel-cage motor? This article discusses synchronous speed, Normal pull-out torque, Standardized speed-torque characteristics, and Class of insulation of squirrel cage motors. This information is useful for designing motors for specific applications. It also helps you determine what squirrel cage motors can do for you. Here are some general guidelines. When selecting a motor for your needs, always choose a model with NEMA standard frames.
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synchronous speed of rotating electromagnetic field
A squirrel cage motor makes use of the synchronous speed of the rotating electromagnetic field (EMF) in order to maximize the efficiency of the mechanical motion produced by the machine. This EMF is generated by the bars of the rotor as a result of the current flowing through the stator. The stator usually contains windings of wire carrying AC current. The direction of the current changes in sync with the sinusoidal curve of the wires, and the resulting EMF follows these oscillations. The opposing voltage induced by the rotating EMF pushes the rotor around and produces rotation.
The synchronous speed of the rotating electromagnetic field in a squirrel cage motor is 1800 rpm. The torque developed by the motor is the start-up torque, which is the peak torque applied to the rotor. The rotor field angle increases with increasing load torque. At a certain torque, the rotor field angle is 90deg or more. If the load torque applied exceeds this value, the motor stalls.
Class of insulation in a squirrel cage motor
The class of insulation in a squirrel cage motor is the insulating material in the windings of the motor stator. This classification is based on the International Electrotechnical Commission (IEC) standards and is expressed as a letter corresponding to the motor’s temperature and service factor. It also indicates the upper limit of the insulation application area. Another key feature of the insulation system of the motor is the protection class, expressed as IP. The IP classification is in accordance with the IEC 60034-5 standard.
The class of insulation in a squirrel cage motor that affects its synchronous speed also has an impact on its maximum ambient temperature. It lists the maximum temperature that the motor can withstand, either continuously or intermittently. A continuous duty rating is necessary when the motor is running full load 24 hours a day. Intermediate duty allows the motor to run full load for a specific period of time before it must be stopped. Similarly, the ambient temperature identifies the maximum air temperature that can be tolerated for the motor’s operation. A phase entry rating also indicates how many voltage phases the motor can operate at.
Normal pull-out torque
The synchronous speed of a squirrel cage motor depends on normal pull-out torque. A squirrel cage motor operates at a steady state of torque and speed at a base operating point. The motor reaches this steady state by undergoing a transient start-up. This is typically visualized with a torque-speed curve. This curve describes the operating conditions of the motor.
The normal pull-out torque is the maximum torque that the motor can sustain at synchronous speed for one minute. For electric motors with unity or 0.8 leading power factor, the torque is between 150 and 200 percent. The normal pull-out torque, however, is not always the same. The synchronous speed and torque curve are different at various operating points, and the two may not be directly related.
The normal pull-out torque of a squirrel cage motor depends on the number of poles. If the poles are doubled, the synchronous speed is reduced to half. However, this method may not be ideal for many applications. This type of motor has a magnetic field that rotates 180 degrees in space for an electrical sine wave. The normal pull-out torque of a squirrel cage motor is determined by the normal pull-out torque.
Standardized speed-torque characteristics
Despite the low cost of squirrel cage motors, they are still prone to a variety of problems, including improper start-up, low torque, and excessively high starting current. In this article, we’ll explore some of the most common issues associated with direct online starting, and provide solutions for avoiding these problems. We’ll also cover how to properly apply the motor to avoid damage.
The rotor of a squirrel cage motor consists of a conductive cylinder that is mounted on a shaft. The internals of the motor contain longitudinal conductive bars made of copper or aluminium that are connected to one another through shorting rings. The similarity to the shape of a squirrel cage inspired the name “squirrel cage” for the rotor.
The standardized speed-torque characteristics of a squirrel cage motor can help determine the proper motor for a specific application. These characteristics are based on a number of factors, including the starting torque. The starting torque is the torque generated when power is applied to the motor at rest and used to accelerate a load. It is represented on the torque-speed curve. This metric is important because it can be confusing when choosing the proper motor for your application.
What is the primary reason for the difference between the synchronous speed and the actual speed of a squirrel cage induction motor?
Answer: The difference is due to the rotating magnetic field of the stator winding interacting with the stationary rotor winding which induces a voltage in the rotor winding.
The induced voltage in the rotor winding causes a current to flow which in turn creates a magnetic field.
The interaction between the rotating magnetic field of the stator and the magnetic field of the rotor causes the rotor to rotate.
Why is the synchronous speed of a squirrel cage induction motor lower than the synchronous speed of a comparable synchronous motor?
Answer: The difference is due to the rotating magnetic field of the stator winding interacting with the stationary rotor winding which induces a voltage in the rotor winding.
The induced voltage in the rotor winding causes a current to flow which in turn creates a magnetic field.
The interaction between the rotating magnetic field of the stator and the magnetic field of the rotor causes the rotor to rotate.
How does the number of poles affect the synchronous speed of a squirrel cage induction motor?
Answer: The synchronous speed of a squirrel cage induction motor is directly proportional to the number of poles.
What is the relationship between the frequency of the AC power supply and the synchronous speed of a squirrel cage induction motor?
Answer: The synchronous speed of a squirrel cage induction motor is directly proportional to the frequency of the AC power supply.
What is the relationship between the slip speed and the synchronous speed of a squirrel cage induction motor?
Answer: The slip speed is the difference between the synchronous speed and the actual speed of the motor.
What is the synchronous speed of a squirrel cage induction motor if the AC power supply is 60 Hz and the motor has 4 poles?
Answer: The synchronous speed would be 1200 RPM.
What is the synchronous speed of a squirrel cage induction motor if the AC power supply is 50 Hz and the motor has 2 poles?
Answer: The synchronous speed would be 1000 RPM.
What is the synchronous speed of a squirrel cage induction motor if the AC power supply is 60 Hz and the motor has 8 poles?
Answer: The synchronous speed would be 600 RPM.
What is the synchronous speed of a squirrel cage induction motor if the AC power supply is 50 Hz and the motor has 4 poles?
Answer: The synchronous speed would be 800 RPM.
What is the synchronous speed of a squirrel cage induction motor if the AC power supply is 60 Hz and the motor has 6 poles?
Answer: The synchronous speed would be 1000 RPM.
What is the synchronous speed of a squirrel cage induction motor if the AC power supply is 50 Hz and the motor has 8 poles?
Answer: The synchronous speed would be 400 RPM.
What is the synchronous speed of a squirrel cage induction motor if the AC power supply is 60 Hz and the motor has 10 poles?
Answer: The synchronous speed would be 600 RPM.
What is the synchronous speed of a squirrel cage induction motor if the AC power supply is 50 Hz and the motor has 6 poles?
Answer: The synchronous speed would be 600 RPM.
What is the synchronous speed of a squirrel cage induction motor if the AC power supply is 60 Hz and the motor has 12 poles?
Answer: The synchronous speed would be 500 RPM.
What is the synchronous speed of a squirrel cage induction motor if the AC power supply is 50 Hz and the motor has 10 poles?
Answer: The synchronous speed would be 500 RPM.
Jessica Watson is a PHD holder from the University of Washington. She studied behavior and interaction between squirrels and has presented her research in several wildlife conferences including TWS Annual Conference in Winnipeg.
