DC motors can develop a constant torque over a wide speed range. For a DC motor : Torque is proportional to armature current – this means controlling torque requires simply controlling the motor DC current – easily achieved with a simple DC drive.
Do electric motors have constant torque?
So electric motor torque is not constant. There is a region of operation in conjunction with the controller and for certain load conditions which will give the appearance of constant torque.
How do you find the torque constant of a DC motor?
The Torque Constant defines the torque-current relationship of a motor and is in Nm/amp. The motor and torque constants are related by the formula Km = Kt(trap)/sqrt(R), where R is the phase-to-phase resistance of the winding.
Why do DC motors have more torque?
DC motors can provide a more constant torque over the speed range, and generally provide faster response to load changes that AC motors. Depending on the configuration of the coil connection (series versus parallel), different performance across load value for DC motors can be obtained.
How is torque maintained in a DC motor?
It has a rotor (consisting of the iron core, about which coils are wound) surrounded by radial permanent magnets on the stator. The current interacts with the B-field to produce a force by the motor effect. The forces on either side of the coils are in opposite directions, producing a torque which rotates the coils.
How do you increase the torque of a DC motor?
If the speed is to remain constant then the back-emf must also remain constant. Then the only way to increase torque is to increase the armature current and the only way to increase the armature current is to increase the supply voltage. This in effect is how a speed controller works.
Why do electric cars get instant torque?
As the electric current travels through the motor within a magnetic field, it generates a force. The more current applied, the more the motor will spin. … But at zero RPM, all of the electricity the motor creates from the time electric power is applied becomes instant torque—without any back EMF to reduce its output.
How do you find the constant torque?
To calculate the Torque Constant read the current draw at a given torque on the Typical Performance Characteristics graph. Now divide the torque by the current. To calculate the Motor Voltage Constant read the no-load speed (rpm) and convert it to radians per second.
How do you calculate the torque of an electric motor?
- Torque (lb.in) = 63,025 x Power (HP) / Speed (RPM)
- Power (HP) = Torque (lb.in) x Speed (RPM) / 63,025.
- Torque (N.m) = 9.5488 x Power (kW) / Speed (RPM)
- Power (kW) = Torque (N.m) x Speed (RPM) / 9.5488.
How much weight can a 12V DC motor lift?
Weight: 100 gm(Approx.) RPM: 100 Operating Voltage: 12V DC Gearbox: Attached Plastic (spur)Gearbox Shaft diameter: 6mm Shaft Length: 21 mm Torque: 1.2 Kg-cm. No-load current = 60 mA(Max) Load current = 300 mA(Max).
Which is more powerful AC or DC motor?
AC motors are generally considered to be more powerful than DC motors because they can generate higher torque by using a more powerful current. However, DC motors are typically more efficient and make better use of their input energy.
What are the disadvantages of DC motors?
Disadvantages of DC motors
- High initial cost.
- Increased operation and maintenance cost due to the presence of commutator and brush gear.
- Cannot operate in explosive and hazard conditions due to sparking occur at brush (risk in commutation failure)
How do you increase engine torque?
To increase the torque … that a bit harder. All you can do, electrically (as you can do it mechanically via gears), is to reduce the source impedance to maximise the current that can be delivered for a given stator impedance. Rewind it with more turns of thinner wire.
What is the source of the torque force in a DC motor?
By turning on and off coils in sequence, a rotating magnetic field can be created. These rotating magnetic fields interact with the magnetic fields of the magnets (permanent or electromagnets) in the stationary part of the motor (stator) to create a torque on the armature which causes it to rotate.
Which DC motor is preferred for constant speed?
Explanation: Rotary compressor generally demand constant speed operation throughout the load. Sometimes, DC machines are not able to produce constant speed throughout the process hence, synchronous machine is used. 4.
How do you reverse the rotation of a DC motor?
- The direction of a DC compound motor can be reversed by changing the polarity of the armature coil or the field coil.
- We can reverse the direction by simply reversing the armature leads. …
- Generally changing direction of field is easier, because it carries lesser current as compared to armature current.