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Is the resistance in the start winding greater or less than the resistance in the run winding?
The resistance in the start winding is greater because it is longer and thinner and has the greatest resistance to current flow
Definition of a resistance-start induction run motor?
Resistance start-induction run motors are commonly known as split phase. They are only single phase motors. They have 2 sets of windings, the Start winding which is high resistance and low inductance made for thin wire, and the Run winding which is low resistance and high inductance made for thick wire. The 2 windings are set skewed about 30 degrees on a twist. This is to create the angular rotary motion, which is what a motor is all about. On start up both start and run windings are energised. Some form of switch disconnects the start winding when the motor is about 75% up to speed, and only the run winding remains in the circuit. There you have it.....
What motors is used in railway engines for traction?
dc series motor :A series-wound DC motor has a low resistance field and armature circuit. Because of this, when voltage is applied to it, the current is high. (Ohms Law: current = voltage/resistance). The advantage of high current is that the magnetic fields inside the motor are strong, producing high torque (turning force), so it is ideal for starting a train. The disadvantage is that the current flowing into the motor has to be limited, otherwise the supply could be overloaded and/or the motor and its cabling could be damaged.
Why dc series motor should start with load?
In DC Series Motors the field is in series with Armature. When the motor starts at no load, the armature current is very low and so is the field current. As the speed of DC Motor is inversely proportional to field current, the motor will try to shoot up to very high speed at no load and it can be dangerous for the motor itself and for this reason, any DC Motor should always be started on load.
Why would a dc motor show high amps no voltage and struggle to turn?
The current flowing in a dc motor is determined by (Applied voltage-Motor EMF) divided by armature resistance. The motor emf is a function of the field excitation of the motor and the speed at which the motor turns. When the motor starts, there can be no EMF because motor speed is 0 rpm. Therefore the motor will draw more current. But as the motor begins to speed up, if it has field excitation, it has to build up EMF and the current will drop. So : If the motor shows high amps and no voltage and struggles to turn the possible reasons are: 1. The motor has no excitation - The permanent magnets are weak or the field winding is faulty or the field is not being supplied. 2. The armature winding is faulty - it has shorted windings. This assumes your supply is healthy of course.
Why ac motor has low power factor?
because of high resistance in the load.
Why we connect high resistance in series to a motor?
Reduce current - reduce power.
How liquid rotor resistance operate?
Re: Liquid Rotor Starter A variant of the induction motor, is the slip ring, or wound rotor motor. The induction motor has a "squirrel cage" rotor which is in effect a short circuited winding in the rotor. The start and run characteristics are influenced by the resistance and inductance of the rotor circuit. One of the problems of the induction motor, is that the start current is very high (600 - 900%) and the start torque is relatively low (120 - 200%) compared to the start current drawn. The induction motor has a speed at which maximum torque is produced and this is very close to full speed. By altering the resistance in the rotor design, we can alter the speed at which maximum torque is produced. Below this speed, the current goes high and the torque goes down. Above this speed, the current drops with the torque. The wound rotor motor, has a winding on the rotor that is not short circuited, but is brought out to slip rings. This enables the effective rotor resistance to be altered. By varying the rotor resistance while the motor starts, we can cause the speed of maximum torque to shift from zero speed up to very close to full speed in a number of steps. The big advantage of this, is that the motor is able to provide a high start torque (around 200%) and a low start current (around 200%) from zero speed to full speed. This is very god for starting high inertia and difficult start loads on relatively weak supplies. The rotor resistors can be cast resistors, wound resistors, or liquid resistors. With standard resistors, the stages are switched in and out by contactors to alter the resistance. With liquid resistors, the resistance can be varied by varying the immersion of probes in the electrolyte. This can be achieved by raising and lowering the probes, or the liquid level.
High repetition resistance training Innervates high threshold motor units?
Does not innervate high threshold motor units and limits the potential for Type IIB muscle fiber hyper
Why shunt field resistance is high incase of dc shunt motor?
Back emf is proportional to the flux in the field winding.Flux in the field winding is proportional to the mmf in the winding.mmf = current passing through the winding * no of turns in the windingTo attain the required mmf we can use more current and less turns ( or ) less current and more turns .As the power loss in the field winding is considered it isPower loss = Square of voltage / resistanceAs the voltage is constant for a high resistance it is possible to have less losses. So we prefer for high shunt field resistance.As the field resistance is high current is less , so no of turns in the shunt field will be more to attain the required mmf.Answer'Shunt' is an archaic term for 'parallel', so the shunt winding is in parallel with the supply voltage which means its resistance must be relatively high to limit the current passing through it.Incidentally, the back-emf. is not proportional to the flux, but to the rate of change of flux.
What would be the shunt field current of your motor if the shunt field winding is excited by?
It could be anything, it depends on the design of the motor and whether it is a high-power or a low-power motor.
Why the armature rheostat of dc is motor kept at maximum resistance position?
It isn't. It is only kept at maximum resistance when the motor is not running. That is done to limit the starting current.
