Motor stall – In electric motor understanding for both AC or DC, we will meet torque, where torque is the ability of the motor to maintain its inertia force.
Stalling is when the motor stops rotating because the load torque is greater than motor torque or breakdown torque characteristics. In a simple explanation, motor stall means the electric motor is overloaded and the motor can’t produce more torque to keep rotating.
Stall current is the current drawn at maximum value when the motor is producing maximum torque but the motor is unable to rotate. It is either because it can’t accelerate further or malfunction.
The explanation above is quite enough for us to understand why motor stall and what stall current. To understand it better, let’s observe the explanation below.
What is Motor Stall
When we check the dictionary, the stall or stalling is occured when the motor stops rotating even if the voltage applied to the terminal is sufficient to energize the motor. This occurs if the required torque for the load is more than the maximum generated torque by the motor (breakdown torque). When this occurs, the motor still absorbs the maximum power but produces zero speed.
DC Motor Torque-Speed Curve Characteristics
Motors are designed to rotate a connected load. The more load we connect to the motor, the lower its rotating speed. If we increase the load even further beyond its overload point, the motor’s speed decreases further until it stalls. The motor will always slip when it is stalling. There is no generated EMF (Electromotive Force) and the power consumption is on maximum level.
Why the Motor Stall
After we read the explanation above, it should be sufficient for us to analyze why our motor stall. Of course there are electrical and mechanical causes for stalling of a motor.
- Electrical: the voltage phase is missing or disconnected. It can be one or two phases disconnected for a three phase motor, or voltage source disconnected for a single phase motor.
- Mechanical: the rotor is jammed, overloaded, or the load is unable to move.
What is Stall Current
Stall current is the current drawn by the motor when it is in a stalling condition. On the other words, the current which motor draws when the rotor is locked or unable to move. The motor draws the maximum current from the source proportional to the rotor’s resistance. If this continues, the motor will get overheat and cause damage to the windings.
What is Stall Torque
Stall torque is the torque when the motor shaft (or rotor) is not rotating. The limit of torque causes the motor to rotate slower or even makes it stop rotating.
Stall torque is a torque produced by a motor or other mechanical device when the motor’s rotational speed is zero. Every mechanical device can still produce torque when stalled.
Electric motor keeps producing torque when it is stalled. But we must take care of it because even if the motor is not rotating, it still draws maximum current. If we leave it stalling, the motor will overheat and damage the windings.