How does work the motor ? with dc 24 volts or ac voltage

Because of the very high voltage on the output of the Inverter drive, I do not want to be responsible for your injury or death from you servicing this machine without proper training.

Bosch is not very good about putting manuals or other documentation online for older products, so I'll have to give you generic advice.

Some electric motors have optional voltage connections. If your motor has this feature, there will be a box or removable plate on the motor with 110 Volt and 220 Volt connections inside. You would need to replace the line cord with a 220 Volt cord having the correct plug for the location you plan to use the mixer, and connect the motor "hot" wire to the 220 V connection in the motor junction box instead of the 110 V connection (the neutral wire goes to the same neutral).

If there is no such option available on the motor, you would also have to replace the motor with a 220 Volt version. Check the labeling on the speed control (inside the mixer) to be sure it is rated for 240 VAC, and check the power label by the power cord. If the label gives a single range of input voltages spanning both 110 VAC and 220 VAC (e.g., "Input 97 V- 265 V") then you only need to change the plug. Unless the electrical parts are all rated for 240 VAC or higher, conversion is not safe.

Some products (especially desktop computers) have a recessed switch on the back that lets you select either 115 VAC or 230 VAC input power. If you have this on the mixer, all you have to do is use a small tool to push it to the other position.

An alternative is to get a 230 VAC - 115 VAC transformer or inverter rated for at least 800 Volt-Amps and wire it with a 230 Volt plug on the primary side and a 115 Volt socket on the secondary side; then you can just plug in your unmodified mixer to this. If you cannot find a box like this, you can buy a "control transformer" from an industrial equipment supplier and put it in a suitable metal box. I recommend including a power switch and a 4 Amp dual-element fuse or breaker on the primary side circuit; you don't want somebody burning up the transformer with a 1200 Watt microwave oven or griddle.

There is a transformer sold for US travelers that should work just fine.

http://www.amazon.com/VOLTAGE-CONVERTER-PRODUCTS-COUNTRIES-SM-1875/dp/B000W91XBO/ref=pd_sbs_a_5

You cannot wire a three phase motor for single phase and you cannot wire a single phase motor for three phase. If you have a three phase dual voltage motor your options are 220 or 440 volts. If you have a single phase dual voltage motor your options are 120 or 240 volts. A 208 volt Hobart motor will only function correctly on 208 volts and is not dual voltage.

The answer is clearly in the starting circuit which doesn't have too many parts, but depends on the type of starting circuit your mixer uses (electronic or mechanical start switch). I'm assuming your mixer isn't very old, as the old units used brushed motors which did not have starting circuits.

The parts of the starting circuit are the motor start winding, the start capacitor and the start switch (probably electronic in your case which is a small silver box with four wire terminals on it). The capacitor should be tested with a multimeter after verifying it's not holding a charge (check with multimeter set to DC Volts, mixer unplugged, should read zero volts).
Start winding should be tested with the meter to measure ohms. Locate the wires leading to the motor (hopefully only three wires) and you should get a reading for all three combinations of measurements (wire 1-to-wire 2, 2-to-3, 1-to-3) if meter indicates open on any of these, motor stator is bad(this is pretty rare and quite expensive).
Electronic start switches are not very simple to test, but if the capacitor and motor test out OK with the meter, and all the wiring is intact (look closely for loose wires, burned wires, poorly crimped terminals, etc.) then it must be the start switch.

An ohm is a measurement of electrical resistance to dc current flow which obeys Ohms Law E=IR where E is voltage, I is current and R is resistance in ohms.

a Henry is a unit of inductance in which an induced electromotive force of one volt is produced when the current is varied at the rate of one ampere per second. This is an AC measurement.

How do you convert three oranges to apples???

Here is how your speed control works:

Speed Control
The speed control of the mixer is attained through the use of a governor assembly mounted at the rear of the control plate assembly.
The electrical circuit is made and broken by the action of the fly ball governor revolving against the control plate.
When the switch lever is moved to an ON position, the position of the control plate with respect to the governor is changed by the action of the switch lever.
Thus, when the control plate is set close to the governor, a relatively low speed of the motor causes the governor to make or break the mixer’s electrical circuit through the control plate.
When the control plate is set farther away, a greater motor speed is required before the governor starts breaking the circuit.
The action of the governor is such that the speed of the motor will remain constant for a given setting of the control plate within certain loads.
After certain loads have been exceeded, the speed of the motor will drop to meet the torque requirements of the given load.
Speed is controlled by the governor and the control plate in conjunction with the phase control.

TRIAC RMS VOLTAGE
BOTH CONTACTS OPEN - 40 VOLTS
ONE CONTACT OPEN - 80 VOLTS
BOTH CONTACTS CLOSED - FULL VOLTAGE
NOTE: The triac regulates the power the motor sees depending on control board contacts.
A device called a triac is a part of the phase control circuit.
This device determines the amount of power the motor sees dependent upon the condition of the control board contacts.
If both contacts are open, about 40 volts RMS is applied to the motor and about 80 volts is applied when either contact is closed and the other is open.
When both contacts are closed, the triac is full on; consequently, full power is applied to the motor. In this way, the speed is controlled.
If the mixer motor begins to run too fast for a
particular speed setting, one or both contacts open, which cuts back on the voltage the motor sees, thus slowing it up.
If the motor operation becomes too slow, one or both contacts will close, applying the needed voltage to the motor to sufficiently increase motor speed.
This is always accomplished through the triac.
The control plate contacts control the triac, and in turn, controls the amount of power supplied to the motor.

The control Plate for your mixer is PN
W10119326
http://www.marbeck.com/mixers_kitchenaid_parts.html

If your not good with tools / meters or tedious repairs do NOT attempt this yourself.
The service manual for your mixer can be found here
http://www.f-ems.com/download/DownLoad.aspx?DocsID=082009012917

and is:
LIT4177310-C

Why not use a transformer?

http://www.amazon.com/VOLTAGE-CONVERTER-PRODUCTS-COUNTRIES-SM-1875/dp/B000W91XBO/ref=pd_sbs_a_5

i want to buy a kitchen aid

and i was wondering about the voltage since i'm in Qatar


and i found this answer , Hope its useful

http://www.110220volts.com/Merchant2/merchant.mvc?Screen=PROD&Product_Code=750-WATT&Category_Code=DownVoltageTransformer

The 0.1 microfarad can be safely replaced with a 275 VAC 0.1mF mains capacitor. You can remove the clip that held the old electrolytic capacitor by sliding the old capacitor out and squeeezing the metal clip so that it disengages with the plastic base. The load resistor is 450 Ohm 15W or 20W wirewound. There is a 56 ohm resistor in series with the capacitor which helps smooth the speed change and reduces wear on the contacts. A 2W wirewound resistor works best. (It is worth removing the contacts and removing any pitting or carbon build up with fime emery paper). I have repaired about 20 speed controls sucessfully with these components.