The method for reversing an electric motor depends entirely on the type of motor you’re working with. For the most common type, a brushed DC motor, you simply swap the two power leads. Other motor types require different approaches, from swapping phase wires to reprogramming a controller. Here’s how reversal works for each major motor type.
Brushed DC Motors: Swap the Two Leads
Brushed DC motors are the simplest to reverse. They have two wires (positive and negative), and swapping them reverses the direction of spin without causing damage. This works because reversing the polarity flips the direction of current through the armature, which flips the magnetic force that turns the shaft.
One caveat: some brushed motors have brush assemblies optimized for one direction of rotation. These motors will technically spin in reverse, but the brushes may wear faster or make poor contact, reducing performance and lifespan. If you’re planning permanent bidirectional use, check the motor’s datasheet to confirm it’s rated for both directions.
Using a DPDT Switch for Easy Reversal
If you need to switch directions on the fly, a Double-Pole Double-Throw (DPDT) switch is the standard hardware solution. The switch has six terminals arranged in two rows of three: top, common, and bottom on each side. Wire the motor to the two common tabs. Then wire the power supply to the top and bottom tabs in an “X” pattern, so that the positive terminal connects to the top on one side and the bottom on the other, with the negative terminal mirrored. Flipping the switch toggles which polarity reaches each motor lead, reversing rotation instantly.
Three-Phase Induction Motors
Three-phase motors, the workhorses of industrial equipment, reverse by swapping any two of their three power leads. The three leads are typically labeled U, V, and W (or A, B, and C). Swapping U and V, or V and W, or U and W all achieve the same result: the rotating magnetic field inside the motor spins in the opposite direction, and the rotor follows.
The procedure is straightforward but requires care:
- Disconnect and lock out the power source before touching any wiring.
- Identify the three motor leads at the terminal box.
- Swap any two leads at their connection points.
- Reconnect power and test. The motor should now spin in the opposite direction.
Some motors have a rotation direction diagram on their nameplate indicating which specific leads to swap. If yours does, follow that guidance. If the motor doesn’t rotate in the desired direction after your first swap, try a different pair.
Brushless DC Motors (BLDC)
Brushless DC motors don’t connect directly to a power supply. They run through an Electronic Speed Controller (ESC), which is essentially a small computer that sends precisely timed pulses of current through three phase wires to spin the motor. The ESC controls direction by changing the order it fires those phases.
For a permanent reversal, you can swap any two of the three wires between the motor and the ESC. This is the physical equivalent of what the ESC does electronically when it reverses direction.
For on-the-fly reversal, you need an ESC that supports bidirectional operation. Not all do. RC airplane ESCs, for example, are designed for single-direction use only, since a propeller never needs to spin backward in flight. RC car ESCs, on the other hand, are built for forward and reverse operation. If you need software-controlled reversal, make sure both your ESC and motor are rated for it. Car-style ESCs that support reverse typically require a motor with a position sensor so the controller knows the rotor’s exact position at zero and low speeds.
Universal Motors
Universal motors (found in many power tools, vacuum cleaners, and small appliances) can run on both AC and DC power. They have two internal circuits: the armature winding and the field winding, connected in series. Reversing the motor requires changing the polarity of one of these windings, but not both.
If you swap the connections on just the armature winding, the motor reverses. If you swap just the field winding connections, the motor also reverses. But if you reverse both at the same time, the two changes cancel out and the motor continues spinning in the original direction. This is why simply flipping the plug in the wall outlet doesn’t reverse a universal motor: that reverses current through both windings simultaneously.
In practice, this means you need access to the internal winding connections, which are sometimes brought out to separate terminals and sometimes buried inside the motor housing. If the motor wasn’t designed for user-reversible operation, this can require disassembly.
Single-Phase Induction Motors
Single-phase motors (common in household appliances, fans, and shop equipment) use two windings: a main winding and a start winding. The start winding, often paired with a capacitor, creates a phase-shifted magnetic field that gives the motor its initial push in one direction. To reverse rotation, you reverse the polarity of the start winding by swapping the connections at either end of it.
This only works if the motor’s internal wiring is accessible. You need at least three wires coming out of the motor (or four, if both windings are fully separated). If the start and main windings are tied together internally with only two external wires, you can’t reverse the motor without opening it up and re-soldering connections.
When the two windings have different resistances, which is common, the motor may run with slightly different characteristics in reverse. Some single-phase motors reverse the entire start circuit, including the capacitor and centrifugal switch, while others only reverse the winding itself. Check for a wiring diagram on the motor’s nameplate or inside the junction box cover.
Stepper Motors
Stepper motors move in discrete steps rather than spinning continuously, and they’re always controlled by a driver circuit. Reversing a stepper motor means reversing the sequence of electrical pulses sent to its coils. The driver handles this through software or logic inputs, typically a single “direction” pin that you set high or low.
At the hardware level, bipolar stepper motors (the most common type) use H-bridge circuits to control current direction through each winding. An H-bridge has four switches arranged in a diamond pattern. Closing one diagonal pair sends current one way through the winding; closing the opposite pair sends it the other way. The driver sequences these switches to step the motor forward or backward. You don’t need to rewire anything. Just change the direction signal going to the driver.
Motors That Can’t Be Reversed
Shaded-pole motors are the notable exception. These small, inexpensive AC motors (found in bathroom exhaust fans, small desk fans, and some appliances) use copper rings physically embedded around part of each pole to create the phase shift that starts rotation. Because the shading rings are part of the motor’s fixed construction, the direction of rotation is set at the factory and cannot be changed electrically.
The only workaround, if you absolutely need the characteristics of a shaded-pole motor but in the opposite direction, is to mount a second motor oriented to spin the opposite way and switch between them. It’s an awkward solution, which is why shaded-pole motors are typically only used in applications where one direction is all that’s needed.
Choosing the Right Approach
If you’re looking at a motor and aren’t sure what type it is, start with the number of wires. Two wires almost always means a brushed DC motor: just swap them. Three wires going to a controller suggest a brushless DC or three-phase motor. Four or more wires coming out of the motor body point to a stepper or a single-phase motor with accessible windings.
For any reversal involving AC mains voltage, work with the power completely disconnected and locked out. For DC projects where you want convenient switching, a DPDT switch or an H-bridge motor driver board gives you clean, reliable direction control without rewiring anything each time.