Short-Circuit-Rotor Electric Motor (Squirrel Cage, Induction Motor)
Asynchronous Electric Motors:
- Cheaperthan other motor types.
- Can be directly connected to electricity via a switch.
- Can be manufactured power up to 3500 kW.
- Do not require continuous maintenance. No need to change bearings of an asynchronous motor for 10 years under normal operating conditions.
- Operate at a constant speed under load.
- Their speed can be adjusted easily throughspeed control devices.
- No sparks during operation.
Because of this reasons above, this type of electric motor is one of the most common electric motor used in many applications. Asynchronous electric motors have protection classes such as IP54, IP55, IP56, IP66 and constructiontypes such as B3, B5, B14, B34 and B35. They have the advantage of being able to operate at any kind of mounting position.
However, the speed control of induction motors is more expensive and they are not suitablefor operations in any sensitive speed arrangement. It is more suitable to use servo motors or stepper motors instead of induction motors in this application areas.
Three phase asynchronous electric motors can be manufactured in range of 0.12 to 3500 kW. This type of motor is the most widely produced and available in the market. The following are examples of application areas that they can be used in: industry, pumps, pressure tanks, compressors, fans, elevators, cranes, conveyors, mills, turning machines, press machines, milling machine, sanding machine and hydraulic units.
Mono phase electric motors must be used where there is no three phase power supply systemdespite the better performance of three-phase electric motor.
The most common used mono phase electric motors are permanent split capacitor motors,start + permanent split capacitor motors and shaded pole electric motors.
Double capacitor or start+ permanent split capacitor mono phase motors are produced in range of 0.12 to 3 kW and they are used in cranes and compressors where high starting torque is needed. Permanent split capacitor mono phase motors can be produced in range of 0.12 to 3 kW and they are used in fans and pumps where no starting torque is needed.
Yaklaşık 50 W akadar üretilen gölge kutuplu asenkron motorlar ise küçük fan ve aspiratörlerde, çamaşır makinesi, bulaşık makinesi pompaları gibi kalkış momentine ihtiyaç duyulmayan yerlerde kullanılırlar. Rotoru Sargılı Asenkronkron Elektrik Motorları
Shaded pole asynchronous motors can be produced power up to 50 W and they are used in devices requiring low starting torque, such as electric fans, aspirators, small pumps orsmall household applications.
Ring asynchronous electric motors are used to start a high inertia load or a load that requires a very high starting torque.It is possible to reduce the starting current and increase the starting and breaking torque by using extra resistors.Limiting of the starting current and strengthens of the power supply system is not necessary.
Synchronous Electric Motors
Synchronous electric motors are especially useful in applications requiring precise speed that is independent of the load over the operating range of the motor.These designs are more complex and expensive than Short-Circuit-Rotor electric motors because of direct-current windings embedded in the rotor. Soft starters require special apparatuses. Synchronous electric motors are commonly used as generators.
DC Electric Motors
Advantages of DC electric motor include simple control of motor speed, precise powerful and smooth rotary movements. Electrical speed controller is simply designed to response to sudden changes in rotor speed and load.
If the motor often stops then starts, suddenly brakes and can be adjusted for speeds, DC motors up to power outputs of tens of megawatts are used. DC motors are preferred if the manufactured goods are sensitive to motor speed, position and systematic movement. DC motors are still widely used in automotive industry, collapsible bridges and cable cars. Development of inverter technology and decreasing prices of AC motors make AC motors advantageous against DC motors, but in automotive industry and small boats, where there is no AC current, DC motors are still preferable.
The main disadvantages of DC motors are; high costs, large frame size, increased operation and maintenance cost due to presence of collector and brushes. DC motors cannot operate in explosive and hazard conditions, like in gasoline pumping stations, due to sparking occur at brush. DC motors are completely closed. DC motor and motor environment are kept clean to prevent motor from potentially encountering any type of vapors, moisture and dust.
The universal motor is so named because it is a type of electric motor that can operate on both AC and DC power. Universal motors are produced in small power ratings between 1/500 HP and 2 HP. Universal motors are generally run at high speeds and can go up to 20000 rpm. Their high speed makes them useful for applications such as blenders, vacuum cleaners, hair dryers, sewing machines, portable sanding and grinding machines, washing machines and dishwashers where high speed is desirable.
A servo motor can be a DC or AC motor which must be equipped with some type of encoder and driver to provide positioning and speed feedback.So, an asynchronous motor paired with an encoder can also be called as a servomotor. Servo motors need feedback mechanism and driver. Their sensitivity depends on used encoder.They run at high speeds and response to commands from the driver with a short delay.
Moment of inertia of the servo motors is less than classical motors that's why they are produced in smaller sizes. Servo motors are used in applications where less power is needed such as automatic machine tools. Servo motors must have perfect characteristics for speed, torque, position and power. They are expensive because of embedded encoder and controller equipment.
One of most significant advantages of a stepper motor is its ability to be accurately controlled in an open loop system. They are suitable for operations in any sensitive speed arrangements and repetitive movement cycles.An encoder is not required and motor's driver is quite simple and inexpensive. Stepper motors with step angle of 0.36 degrees can be found easily in the market. Stepper motors operate at low speeds and produce more noise compared to servo motors. There are four main types of stepper motors: permanent magnet stepper, hybrid synchronous stepper, variable reluctance stepper and lavet type stepping motor.
All potential ignition sources are housed inside an enclosure which is designed with careful consideration of the strength of the materials without igniting the surrounding flammable gases or vapors by high surface temperatures or sparks.
There must be no risk of ignition by flames or sparks, so increased temperatures at the surface must be lower or equal than the gases or vapors in the surrounding.