Table of Contents
- 1 How do you find the rotor resistance of a slip ring induction motor?
- 2 Why is resistance used in slip ring motor?
- 3 How many slip rings are there in a slip ring induction motor?
- 4 How do the resistor banks connected to the slip rings effect the wound rotor induction motor during starting?
- 5 How is slip of Ship calculated?
- 6 How do you calculate the rotor resistance of a motor?
- 7 Can a VFD motor run without resistors?
How do you find the rotor resistance of a slip ring induction motor?
What is a Slip Ring Induction Motor?
- Definition: A slip ring induction motor is referred to as an asynchronous motor as the speed at which it operates is not equal to the synchronous speed of a rotor.
- r = Smax.
- r+R= (Smax)’.
- R = r(S’ max/Smax – 1) —— (iii)
- R = r. (
- R = r. (
- R = 9.
- 1).
What is the formula for calculation of rotor resistance?
Example 5.3
Step no. | Total rotor circuit resistance RΩ | Resistance between steps Ω |
---|---|---|
3 | R23 = β · R22 = 0.676 × 0.435 = 0.294 | 0.294 – 0.199 = 0.095 |
4 | R24 = β · R23 = 0.676 × 0.294 = 0.199 | 0.199 – 0.135 = 0.064 |
5 | R25 = β · R24 = 0.676 × 0.199 = 0.135 | 0.135 – 0.09 = 0.045 |
6 | R2 = 0.09 = 0.09 | 0.09 – 0 = 0.090 |
Why is resistance used in slip ring motor?
The slip rings in a wound rotor motor form a secondary, external circuit. Inserting resistance to this circuit allows the motor to produce very high torque at start-up, which is necessary for moving loads with high inertia.
How do you control the speed of a slip ring induction motor?
There are two mechanisms to control speed, the first is through rotor rheostat control and the second is through cascade control. The objective of speed control can be achieved through the rheostat which in the first place is used to induce resistance in the system and set up the starting phase for motor slip ring.
How many slip rings are there in a slip ring induction motor?
three slip rings
A wound rotor motor uses three slip rings, typically made of high-quality phosphor bronze, mounted on the shaft with brushes resting on them. Each slip ring is connected to one of the three phases of rotor windings.
What is slip power recovery method of speed control of slip ring induction motor?
The slip energy recovery method provides the speed control of a slip ring induction motor below its synchronous speed. A portion of rotor AC power (slip power) is converted into DC by a diode bridge. The smoothing reactor is provided to smoothen the rectified current.
How do the resistor banks connected to the slip rings effect the wound rotor induction motor during starting?
A wound-rotor motor, also known as slip ring-rotor motor, is a type of induction motor where the rotor windings are connected through slip rings to external resistance. During start-up the resistors reduce the field strength at the stator. As a result the inrush current is reduced.
How is slip of a motor calculated?
Slip speed is the speed difference between the Synchronous speed and Rotor speed. Slip speed = Synchronous speed – Rotor speed = Ns -N. Slip, s = (Ns – N) / Ns.
How is slip of Ship calculated?
Soln: Slip (percent) = Engine distance – ship’s distance/ Engine’s distance X 100. Engine distance = Pitch X RPM X 60 X 24 / 1852.
What is an slip ring motor?
Slip ring motors are normally used where additional torque is required to overcome the inertia of the load. The rotor is normally connected over a 3 stage resistor bank. It goes through the three, (sometimes 4), stages. Once the inertia of the load is overcome the rotor is shorted and at that time it is running like an induction motor.
How do you calculate the rotor resistance of a motor?
Pick the number of steps and then calculate the resistor needed to bring the motor to the maximum speed for each step. The EASA Technical Manual has a section on calculating the rotor resistors to start a motor. The basics are to take the secondary phase voltage and divide by phase current to calculate the total rotor resistance.
How do you find the power dissipation of a resistor?
P = I × V A simple use of these is finding the power rating required for resistors. In this case, enter any two of the following values: the voltage across the resistor, the current through the resistor, or its resistance in ohms to find the power dissipation in watts. This is the minimum power rating you can use on your resistor.
Can a VFD motor run without resistors?
A VFD will run the motor from Zero to full speed but without the resistor banks, the torque will be reduced. In some instances such as centrifugal pumps where the resistors are used to hold the motor at a slower speed but where the added torque is required you should do some engineering.