1、 Clarify the core conclusion first
1. Directly driving a regular DC motor with AC power: Never use AC power directly as it may burn out
2. Direct drive of ordinary AC induction motor by DC power: completely unable to start, no torque, coil heating and burning out
The two cannot directly exchange power supply, but with the addition of a conversion circuit/device, they can be indirectly driven. Below are two categories to explain the principles and implementation solutions in detail.
2、 AC power → Drive DC motor (AC to DC)
Why can’t we directly apply AC power?
DC motors are divided into brushed permanent magnet DC, series excited DC, and parallel excited DC:
The armature coil is subjected to alternating current, causing the current to repeatedly switch between positive and negative directions, and the torque direction to reverse back and forth. The motor will only experience severe shaking and discontinuous rotation;
The commutator and brush are subjected to high alternating current, causing sparks to surge and significant copper loss in the coil, resulting in short-term overheating and burning of the winding.
Feasible usage plan (AC to DC)
Option 1: rectifier bridge (simplest, low voltage and low power)
AC 220V → Transformer voltage reduction → Single phase bridge rectification+electrolytic capacitor filtering → Stable DC, supplying power to DC motor.
Applicable: Small fans, small DC deceleration motors, 12/24V DC motors.
Option 2: Switching power adapter
Finished DC power supply (220V AC input, 12V/24V/48V DC output), directly connected to DC motor, stable voltage and current, high efficiency.
Plan 3: Controllable rectification speed regulation (high-power industrial DC motor)
Thyristor rectifier, adjustable DC voltage, realizing motor speed regulation, used for large series/separately excited DC motors.
Special exception: Series excited AC/DC dual-purpose motor (hand drill, vacuum cleaner)
The stator and armature of the series excited motor are connected in series, and both AC and DC can be converted without rectification.
Principle: During the positive and negative half cycles of communication, the stator magnetic field and armature current are synchronized and reversed, while the direction of torque remains unchanged.
Limitations: Extremely high speed, loud noise, and commutation sparks, cannot be used for ordinary permanent magnet DC motors.