Table of Contents
The above equation (1) shows that the rotor speed N bears a constant relationship with the field poles and the frequency of the generated voltage in the armature winding. A machine that runs at synchronous speed is called a synchronous machine.Synchronous Speed. Number of Poles Synchronous Speed NS in r.p.m 2 3000 4 1500 6 1000 8 750.
What is the difference between rotor speed and synchronous speed?
Induction motor with squirrel cage rotor has two different speeds. The synchronous speed refers to the stator rotating magnetic field, which depends on the number of poles and frequency. The other speed is the rotor’s. The rotor speed will be always slower than the stator speed, we call it slip.
What do you call the difference between the synchronous speed and the actual rotor speed in an AC motor?
The rotor will always rotate slower than the magnetic field of the stator and is playing a constant game of catch up. This produces the torque to get an AC motor running. The difference between the synchronous speeds of the stator (3600 and 1800 rpm) and the actual operating speed is called slip.
What is synchronous speed?
Synchronous speed is a significant parameter for the rotating magnetic field-type AC motor. It is determined by the frequency and the number of magnetic poles. A collective name for the motors that run at the synchronous speed is the synchronous motor.
What is synchronous speed for a 2 pole 60hz AC machine?
A 2-pole (pair of N-S poles) alternator will generate a 60 Hz sine wave when rotated at 3600 rpm (revolutions per minute). The 3600 rpm corresponds to 60 revolutions per second. A similar 2-pole permanent magnet synchronous motor will also rotate at 3600 rpm.
What is slip speed?
The speed at which the induction motor work is known as the slip speed. The difference between the synchronous speed and the actual speed of the rotor is known as the slip speed. In other words, the slip speed shows the relative speed of the rotor concerning the speed of the field.
How do you measure rotor speed?
3 Answers. The synchronous speed of the rotor in RPM N = 120f/P where f is the frequency of the stator current and P is the number of poles. The operating speed No = N – Ns where Ns is the slip speed. The frequency of the rotor current fr = Ns x P/120, so fr = 0 if the slip is zero.
What two factors determine synchronous speed?
The synchronous speed of an AC motor is determined by the frequency of the source and the number of poles.
Why rotor speed is always less than synchronous speed?
The actual rotor speed is always less than synchronous speed so as to produce current in the rotor bars. Two terms are used to define relative motion between rotor and rmf. One of them is slip speed. Slip speed is defined as the difference between synchronous speed and rotor speed.
Why is it called synchronous speed?
The synchronous speed is the speed of the revolution of the magnetic field in the stator winding of the motor. Thus, an AC machine in which the rotor moved at a speed and built a constant relationship between the frequency of the voltage in the armature winding and the number of poles is called a Synchronous Machine.
What is slip formula?
If the revolving magnetic flux’s synchronous speed & the speed of rotor are Ns & Nr in the motor, then the speed among them can be equivalent to (Ns – Nr). So, slip can be determined as. S = (Ns – Nr) / Ns.
What is the slip?
Slip is the differentiation between synchronous and asynchronous speed. The difference between the synchronous speed of the electric motor magnetic field, and the shaft rotating speed is slip – measured in RPM or frequency. Slip increases with increasing load – providing a greater torque.
What RPM does a 2 pole rotor produce 60Hz?
As per the above formula, a 2-pole generator producing an output frequency of 60 Hz has an engine speed of 3,600 rpm.
What happens if 60Hz motor is driven at 50Hz?
It will run with following problems for a 50Hz motor running on 60Hz: The core loss will increase and cause over heating of core. As the core loss will increase, the Power Factor of motor will reduce. The motor speed will be higher, so shaft load will increase.
Can a 60Hz motor run on 50Hz?
For a generic answer: yes you can, IF: you reduce the voltage by 50/60, the equipment doesn’t care, you don’t care about potentially overheating the motor, the process/load can tolerate the lower speed/torque, etc.
What is full load slip?
The slip corresponding to full load speed of th motor is called full load slip. Example 1 : A 4 pole, 3 phase induction motor is supplied from Hz supply. Determine its synchronous speed. On full load, its speed is observed to be 1410 r.p.m. calculate its full load slip.
Can slip be negative?
If the rotor of an induction machine rotates above synchronous speed, slip is negative, as are torque, mechanical output power and air gap power. i.e. the machine is operating as a generator. Rotational losses are 2450W.
What happens when slip is zero?
Zero slip means that rotor speed is equal to synchronous speed. If rotor is rotating at synchronous speed in the direction of rotating magnetic field the, there will be no flux cutting action, no emf in the rotor conductors, no current in rotor bar conductor and hence no development of electromagnetic torque.
What is a rotor speed?
Rotor spinning Rotor speeds typically lie in the 120–210 m/s range, but mostly between 150 and 190 m/s, with a tendency to be higher with a smaller rotor diameter [6]. Currently the smallest rotor diameter used industrially is 28 mm with rotor speed up to 150,000 rpm, though some machines can reach 160,000 rpm.
How do you calculate full load rotor speed?
Explanation: Speed of the rotor field w.r.t. rotor structure = 120*rotor frequency/Poles = 120*2/4 = 60 rpm = 6.28 rad/s. 9. A three phase, 50 Hz induction motor has a full load speed of 1440 rpm.
What is rotor frequency?
i.e., Rotor current frequency = Fractional slip x Supply frequency (i) When the rotor is at standstill or stationary (i.e., s = 1), the frequency of rotor current is the same as that of supply frequency (f’ = sf = 1× f = f).
