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What causes runaway in a DC series motor?
It happens when the shunt field coil is open circuited so no current flows in it and thus it produces no magnetic field. It also requires that there be no or very little load on the shaft. In this instance the armature will spin much faster than design speed and can even fly apart.
What is runaway condition?
Thermal runaway occurs in situations where an increase in temperature changes the conditions in a way that causes a further increase in temperature, often leading to a destructive result. It is a kind of uncontrolled positive feedback.
What two DC motors can go into runaway?
With no mechanical load on the series motor, the current is low, the counter-Electro motive force produced by the field winding is weak, and so the armature must turn faster to produce sufficient counter-EMF to balance the supply voltage. The motor can be damaged by overspeed. This is called a runaway condition.
How do you test a DC fan motor?
Check to make sure the DC motor’s rotor can turn with no impediments. Switch the voltmeter to “Ohms”. Attach one end of the red lead wires to the DC motor and run the DC motor’s red wire to the battery. Attach the clip of the black lead wire to the DC motor and run the black motor wire to the battery.
How do you control a runaway reaction?
A runaway reaction, if caught early, can sometimes be halted by adding chemicals to cancel the effect of the catalyst. Common measures include neutralization, quenching with water or other diluent, or dumping the contents into another vessel which contains a quench liquid.
What is runaway in DC motor?
Can a series wound DC motor be run without a load?
This is a consequence of wiring the field winding in series with the armature, and is the most concerning disadvantage of these motors. For this reason, these motors should never be run with no load attached to them, under any circumstances, and should always be loaded.
How did the shunt wound DC motor get its name?
Series Wound DC Motor or DC Series Motor. A series wound DC motor like in the case of shunt wound DC motor or compound wound DC motor falls under the category of self-excited DC motors, and it gets its name from the fact that the field winding in this case is connected internally in series to the armature winding.
Why are DC series coils wound with fewer turns?
The field coils of DC series motor are wound with relatively fewer turns as the current through the field is its armature current and hence for required mmf less numbers of turns are required. The wire is heavier, as the diameter is considerable increased to provide minimum electrical resistance to the flow of full armature current.
What is the torque of a series wound motor?
As in this case relatively higher current flows through the heavy series field winding with thicker diameter, the electromagnetic torque produced here is much higher than normal. This high electromagnetic torque produces motor speed, strong enough to lift heavy load overcoming its initial inertial of rest.