Q:I thought brushes were only for DC motors?

These are used in electric power tools, vacuum cleaners and hair dryers mostly. They are called universal motors, so named because they are AC/DC. These commutator motors go to a higher speed (for fans), and are more readily speed controlled where variable speed is needed. They are often series wound. The armature and the field are in series, so they go to a high speed with no load. Some AC motors of the past had a commutator start arrangement, particularly with refrigeration compressors. AC motors are becoming more capable of speed control with inverter style controllers. Generally they are limited to the AC supply frequency, for example a 2 pole motor (the fastest) can only go to 3000/3600rpm approx. for 50/60Hz.

Q:How does the battery of the electric car drive the AC motor?

The electric bicycle motor is made up of three pairs of coils, but that doesn't mean an AC motor.The controller controls the speed of the motor by adjusting the pulse width.

Q:Why does the current in an AC Induction motor start to go up when the voltage is dropped off?

Because the induction motor is a constant power device. If the voltage goes down, the current goes up to maintain constant power.

Q:How much does 15kw power AC power consume per hour?

15kw, which means 15kw power consumption per hour1kW = 1 degreesSo power consumption is 15 degrees per hour.

Q:What happens to a stator wound AC permanent magnet motor when the rotor is removed but still powered?

You will have an energised choke in one place and a rotor that is still spinning due to intertia but slowing down due to friction. With no rotor load the power consumption will go down. Probably. In real life the rotor would go out of control as you tried to disassemble the motor while working and it would shatter into little bits.

Q:I check with our supplier. they told me that we have to load on motor then only it will show correct rpm ( both low and high). what is the maximum load for this motor It is shoiwng 1.3 amp

DOES THE MOTOR HAVE A 2 SPEED switch, and what are you using it for? 1.3 amps has to be 120 volt. its probably a 2 speed motor without a switch. in that case it has to be under a load. if this helps you cant hear it change speeds, even under a load, i really need more info before i can help you. how are you checking the rpms? butch

Q:I bought a british warning siren made by Secomak, which has a motor rated for 240VAC/DC 3A @50Hz. I am confused on how to provide it power. Not only do I somehow have to provide it 240V (which would require at least a transformer given that US outlets are only 120V), but I've also been told US 240VAC power

The AC/DC rating indicates that the siren has a universal motor. That is essentially a DC motor with a commutator and brushes that is designed for use with either AC or DC. I believe that the starting current for a universal motor is less than for a regular AC motor. Even though one leg of UK 240 volts is grounded, I doubt that the frame of the siren is grounded. You can check that with a multimeter. At a minimum, you should have help from someone who knows how to use a multimeter. PS1 If I had the siren, I would probably connect it directly to a regular 120 volt outlet. If it has a universal motor, it should run at a lower speed, but not take too much current or anything. You should be able to check it out using just the two hot wires from a dryer outlet. You might be able to add a 15 or 20 amp 240 volt circuit to power it. A transformer large enough for it would be about half the size and weight of the motor. An auto-transformer would be a little smaller. With a rectifier and filter, you can get about 160 volts DC fro a 120 volt outlet. The motor will run a little faster at a given voltage with filtered DC, so 160 volts might be enough. PS2 I should have said that I doubt that the frame of the motor is connected to one of the power inputs. When you install the siren, you should connect the frame to the grounding conductor of the power system.

Q:I know AC motors have some advantages over DC in some applications, and the opposite is true in other applications. Most cars use DC motors when converted, but there was one professional model, The Sunrise by Solectra that had a huge range and highway speeds that used an AC motor. Why would that be the exception and not the rule?

DC motors will cost you a lot less in terms of control circuitry and the motors themselves. The new brushless DC motors are essentially AC motors with some control circuitry built in. It would also be easier to implement regenerative braking with DC motors. DC motors and their corresponding control circuitry are easy to find due to their use in forklifts. Unless you want something like the Tesla and have the corresponding budget, go with DC, the batteries are DC anyways so you save the energy loss of the inverter.

Q:thats an electric motor that can power your car...

The okorder Click on: EV AC MOTORS And on the bottom of that page, click PRICE LIST. It looks to me like 30kw will cost you $4,732.00. You'll need an AC power inverter, and a few assorted other things to make an electric car with it.

Q:Hello, I'm planning a project and I am going to need to control the rotational speed of an electric motor very accurately. Is there an easy way to do this? I was thinking about some sort of comparative op-amp but don't really understand.Also, I need the motor to be able to change speed very quickly, ie accelerate and decelerate to the required angular velocity. Is this quality the torque? Thanks

There are many types of electric motors and the answer will depend on what type you are talking about: DC motor, AC motor, stepping motor, synchronous motor, etc. A DC motor speed is controlled by the voltage applied. To control the speed accurately you would need some sort of sensor that would measure how fast it is going. I suggest that you look into stepping motors if you need to control the speed accurately.