basic principle of variable speed drives ?
831663
Variable voltage and frequency drives operate by first converting the incoming ac (typically 50 or 60Hz) into dc.  Then the drive controller uses this DC to generate an AC output that has the proper frequency to turn the motor at the desired speed.  The voltage output is varied depending on the amount of load on the motor.
1090847
I would just run it at 60 Hz. Output rpm will be 20% higher. \n\nAlternately, you could get a 400V VFD and set it's output to 50 Hz.
48905
There's a great article explaining thyristor operation and showing basic circuit diagrams here: http://www.ibiblio.org/obp/electricCircuits/Semi/SEMI_7.html\n\nThere was also a very good reference book called "SCR Manual Including Triacs and Other Thyristors" published by GE from the early 1960's into the late 1970's.  It's a highly prized source for many engineers, and you -may- be able to find one for sale, if you're lucky. (No, you can't have mine :-P )\n\nDo a Yahoo! search for "thyristor circuit diagram" and you'll get thousands of results. :)
572004
You mean VFD, Variable Frequency Drives. Also known as inverters. All the newer VFD's use a IGBT active power module device. The IGBT is mainly used in switching power supplies and motor control applications.\n\nAn example of use: Reliable IGBTs is a key enabler for electric vehicles and hybrid cars. Toyota's second generation hybrid Prius has a 50 kW IGBT inverter controlling two AC motor/generators connected to the DC battery pack.\n\nCheck out the following links:
846168
v1/v2 = n1/n2\n\nrefer to "Electric Machinary Fundamentals"\n by Chapman
607030
INTRODUCTION TO MOTOR, PULLEY AND BELT\nA motor is a prime mover means it provides power to mechanical system or machines. A motor converts electrical energy into mechanical energy which is transmitted by belt drive to perform some mechanical work. The armature (extension of the rotating part) of a motor is coupled with a shaft by a coupling (coupling is a device which connects two shafts so that if one is rotating, the other also rotates). From this shaft power is transmitted to a distant shaft by belt drive. Separate pulleys are present and keyed (means fixed with shaft so that both shaft and pulley rotate as a whole) to each of the driver and driven shaft and joined by a belt in such a way that if one pulley rotates the other also rotates.\n\nDRIVER AND DRIVEN PULLEY SPEEDS\nLet the driver pulley rotate at 'N1' rpm (revolution per minute) and the driven pulley rotate at 'N2' rpm. If the diameters of the respective pulleys be 'D1' metre and 'D2' metre respectively then we have the relation N1/N2 = D2/D1.\n\nBELT SPEED CALCULATION\nNow, we are in a position to start the belt speed calculation. The surface speed of the driver pulley is given by V1 = pi*D1*N1 metre/minute = pi*D1*N1/60 metre/second. In ideal condition i.e. if no slippage was present then the belt speed would have been equal to the surface speed of the driver pulley i.e. equal to 'V1'. But actually there is aways some slippage between the belt and pulley surface so the speed of the belt is always less than 'V1'. If this slip factor is 's' then the belt speed is (1-s)*V1 \n= pi*D1*N1*(1-s)/60 metre/second.
170254
Try these sites. Some have better explanations than others.\n\nSwitching and inverters: http://www.kpsec.freeuk.com/trancirc.htm\nAmplifiers: http://www.tpub.com/neets/book7/25c.htm\nLogic gates: http://hyperphysics.phy-astr.gsu.edu/hbase/electronic/trangate.html
679906
or is it maximun voltage?\n\nlike terminal velocity is maximum speed...
526931
Variable frequency drives provide for lower energy usage, and less wear and tear on the equipment, thus prolonging life. In addition, they may also provide power factor correction, and reduced electrical interference, if designed and installed properly.
604852
Here are a couple of web sites that approach this in different ways. \n\nhttp://www.circletrack.com/techarticles/84199/\n\nhttp://www.diracdelta.co.uk/science/source/e/n/engine%20excitation%20mechanisms/source.html\n\nHope these help.
1086026
You can get an idea on counting the discs on the insulator string and multiplying by 12kV/disc.\nAgain it is only a general rule of thumb and is not accurate.\n\nSource 50 years as an Electrical Engineer
173271
In the motor and VFD variable frequency drive industry, the standard speak is Amps, which is replacing HP old school.\n\nYou must realize that in an industry in which the typical 3phase power is based on 480VAC.\n\nThis means when someone is sizing a motor for a specific application they speak of the Amps need to perform the task.\n\nThe drives (VFD) which I work on are typically between 10amp up to 3000amp. Usually, 480Vac, sometimes 600Vac or 690Vac.\nA drive which is rated at 690Vac, 705amp is 600Vac, 800amp for the same drive.\n\nYou need to know both, HP and Amp for the machines which you are interested in. That means what is the typical voltage for the area. USA vs Canada vs UK vs Asia They are all different. \n\nKeep in mind Amps are Amps regardless where you are. Heavy wire sizing is crucial.
1025865
It's a homework question...am I right?  It's cool, you need help just the same, why not give some?\n\n1. Volatile memory (RAM)\n2. Non-volatile memory (hard drive, disk drive, CD-ROM...)\n3. Power supply\n\n(your turn) :-)
973437
You should use pulse width modulation (PWM).  PWM is essentially an on-off sequence in time, like a square wave alternating between 0 and 1.\n\nClearly full voltage will give you maximum speed.  This happens when the voltage is always on.  Now, suppose you only wanted to go half the maximum speed.  You could send a a square wave with 50% duty cycle (on half the time and off half the time) at high enough frequency that the motor will spin at a constant 50% maximum speed.  The motor is like a lowpass filter and therefore, a square wave at high enough frequency will produce a steady response without oscillation.\n\nIf you want the motor to go slower, say, at 25% maximum velocity then send a pulse that is on 25% of the time and off 75% of the time.\n\nIn reality, if you want 25% speed you may have to send something like a 27% duty cycle because of the time delay between commanding 'on' and the system actually turning 'on'.  In this application, though, I don't think you will have this porblem.
892848
One of the most frequently used is E=IR    ;E =voltage    I=current   R= resistance. U can change this every way depending on the unknown.\n    Good luck
914458
i=C(dV/dt)\n\nwhere\n i= the instanious current through the cap\nC= the cap siz in farads\ndV= the change in voltage\ndt= the change in time\n\nI use this equation in my op-amp class where were are doing PWM power supplies and motor drivers right now.
731158
"A good AC drive technician understands the operation of the variable speed drive and the functions of its components.\nAn outstanding AC drive technician also understands the effects of the load on the drive and the effects of the drive on the load."\n...James Shumberg\n\nExactly what is an AC drive? The word "drive" is used loosely in the industry. It seems that people involved primarily in the world of gear boxes and pulleys refer to any collection of mechanical and electro-mechanical components, which when connected together will move a load, as a "drive". When speaking to these people, an AC drive may be considered by them as the variable frequency inverter and motor combination. It may even include the motor's pulley - I am not sure.\n\nPeople in the electrical field and electrical suppliers usually refer to a variable frequency inverter unit alone, or an SCR power module alone (when discussing DC drives) as the "drive" and the motor as the "motor".\n\nManufacturers of variable frequency drives (VFD) used to refer to the drive as just that, a "variable frequency drive". More manufacturers are referring to their drive as an "adjustable speed AC drive". To make matters worse when a motor is included in the package it may be referred to as an "adjustable speed AC drive system".\n\nA variable frequency drive is an adjustable speed drive. Adjustable speed drives include all types; mechanical and electrical. Now is it clear? Don't worry about it. It's not clear to anyone. As you read on, when I refer to the "drive" I  am referring to the variable frequency inverter alone.\n\n\nA little about AC drives\nThe main power components of an AC drive, have to be able to supply the required level of current and voltage in a form the motor can use. The controls have to be able to provide the user with necessary adjustments such as minimum and maximum speed settings, so that the drive can be adapted to the user's process. Spare parts have to be available and the repair manual has to be readable. It's nice if the drive can shut itself down when detecting either an internal or an external problem. It's also nice if  the drive components are all packaged in a single enclosure to aid in installation but that's about it. \n\nThe paradox facing drive manufacturers today is that as they make their drives easier to use,  the amount of training with which they must provide their users increases. This is because as drives become easier to use they are purchased more and more by people of less and less technical capability. As less technical people get involved in drive purchases the number of misapplications goes way up. I call this phenomenon the "dumb trap". (When manufactures discover this phenomenon they simultaneously discover how dumb they've been. Some have not yet discovered it.)\n\nAmbiguous Motor Theory \nThe real action in an AC variable frequency drive system is in the motor. This is really where it all happens.\nTo be an AC drive application Wizard (which is several levels higher then Guru) one must understand how motors use electric power. It is essential. I cannot emphasize the importance of this.\n\nAll loads moved by electric motors are really moved by magnetism. The purpose of every component in a motor is to help harness, control, and use magnetic force. When applying an AC drive system it helps to remember you are actually applying magnets to move a load. To move a load fast does not require more magnets, you just move the magnets fast. To move a heavier load or to decrease acceleration time (accelerate faster) more magnets (more torque) are needed. This is the basis for all motor applications.