Damper windings

The damper and field windings each produce an effect on accelerating torque. The resistance of the damper winding is usually selected to produce its maximum torque during the first part of the starting period and a field-discharge resistor is selected so that the field-circuit torque peaks near pull-in speed. 

A synchronous generator (and a synchronous motor) can be represented by many inductances and reactances to account for transformer-type induction, rotational induction, mutual coupling between windings, leakage and self-induction, magnetising and excitation induction and the effects of the pole-face damper windings. Extremely complex equivalent circuits have been developed for synchronous machines, see References 1 and 2 as examples. 

Most authors identity the various mutual inductances in each axis of (20.4) e.g. Mab, Maf, Makd and then assume them to be equal as, Md for the mutual inductances have been assumed to be unequal, particularly when two or more damper windings have been included in each axis, see References 6, 15 and 16. 

In addition the differential terms in (20.12) to (20.16) become zero and so do the currents in the damper windings. Hence by using suffix "ss the steady state version of (20.12) to (20.16) become ... 

Hence the machine with one damper winding on each axis is adequate for most practical sitnations, certainly for those in the oil indnstry. 

The following discussion applies to a synchronous machine that has one field and two damper windings. 

It is reasonable to regard the rotor windings as damper windings and use the notation of sub-transient reactances. Hence the following derived reactances and time constants are appropriate to induction machines. 

Action of the executor mechanism Mode damper wind to the person Circulation damper internal circulation Temperature damper cold end Wind amount the maximum Compressor enabled... 

Mode damper wind to the feet and defrost Circulation damper external circulation Temperature damper in the middle Wind amount small Compressor off... 

There is no permanent flux in this machine, hence, = 0. Further, assuming eddy currents in the rotor, modeled with one equivalent damper winding in each of both the d- and the -axes, results in the BG of Fig. 8.21, again with motor power flow convention. 

Salient-Pole Rotor with Damper Windings... 

The blower is designed to deliver 12 m3/min of air at 12 kPa guage pressure at 70°C. At 315°C this decreases to 6 kPa guage pressure. On the outlet of the blower is a manually controlled damper to regulate flow of air. Air is transported to the wind-box area via a pipe equipped with an orifice plate. 

The damper bars or winding act in a manner very similar to an induction motor and provide a breaking torque against the transient disturbances in shaft speed. To be effective the damper needs to have a steep torque versus shp characteristic in the region near synchronous speed. The equivalent impedance of the damper requires a low resistance and a high reactance. High conductivity copper bars are embedded into the pole face to provide a low reluctance path for the leakage flux. 

Insufficient hotair volume for defrosting 1. mode executor damaged 2. falling off of the drive rod 3. damper not in position 4. air vent blocked 5. inadequate heating supply 6. installation of wind tunnel not fit 7. circuit disconnected... 

The synchronous rotor carries the rotating independently excited field windings of the machine. For good control response, these must be fed with DC current via slip rings and these must be correctly sized for the low speeds and stall duties required by a hoist. The synchronous motor rotor will comprise of wound poles, pole bolting system, damper bars, slip rings/brush-less excitation and interconnections. 

The rating of a ventilator usually is in terms of linear exhaust velocity or air flow rate per square meter of ventilator area. This is a number supplied by the manufacturer. It depends strongly on temperatures and wind speed. A typical rate might give an upward air velocity of 15 m min. In addition to or instead of dampers in the ventilatorfs), the walls of the building are often supplied with adjustable louvers. 

Weather change could cause draft fluctuation. For example, when strong winds occur and cause draft fluctuation, the damper opening should be increased gradually to maintain flame stability. On the other hand, in windy weather, if the heater faces toward the wind with the highest static atmospheric pressure, this may result in a too high draft. In this case, the damper should be closed slightly. 

Taipei 101 in Taiwan is the world s second-tallest building. It is 101 stories (508 meters) tail, and its mass wind damper is a 660-metric ton metal sphere suspended like a pendulum between the eighty-seventh and ninety-second floors. If the building sways, the pendulum is driven in the opposite direction. This passively tuned mass wind damper reduces the building s lateral motion by more than half. Two six-metric-ton pendula are positioned in the tower to control its motion. 

Without a tuned mass damper, the top floors of very tall buildings can sway back-and-forth 30 centimeters or more in a strong wind, let alone an earthquake. 

In another civil engineering application, MR fluid dampers have been used to mitigate potentially damaging wind-induced cable vibrations in a cable-... 

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