What Does A Motorcycle Rectifier Do?

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What is a Motorcycle Rectifier?


A motorcycle rectifier, also known as a motorcycle voltage regulator, is a part of the charging system that supplies the motorcycle with the electrical current it demands, ensuring it is at the correct voltage and has the correct type of power.


A rectifier is an electronic device that converts AC power into DC power. Motorcycles typically have an alternator that generates AC voltage, but the electrical system of a bike requires DC voltage to function properly.


The rectifier also keeps this DC power output within a specific range. If the voltage exceeds safe levels, this excess power runs the risk of damaging the battery or other electrical components.



Two main types of rectifiers are fitted into most motorcycles. Each requires a different type of voltage regulator rectifier.


Permanent Magnet Rotor Alternator (PMR): This type has permanent magnets that revolve around the engine. Some of these have two output wires (single phase), but most have three (three phase).

Field Control Type (FCT): Instead of fixed magnets, this type has a ‘field’ or ‘exciter’ coil. Once supplied with power from the regulator, this coil becomes magnetized.


How Does A Rectifier Work In A Motorcycle?

So how does the rectifier make sure things are functioning correctly? Rectifiers have a sensing mechanism to measure the output voltage, and it references this with a predetermined reference voltage. The rectifier will make sure the voltage never gets too far from this predetermined point. So it's constantly working to keep the voltage stable.


A rectifier works to regulate the voltage of the motorcycle and convert AC power to DC power in order not to damage any components with incompatible AC power.

It's important to note that rectifiers do not produce power; this comes from the stator coil within the alternator. The alternator is what produces the AC power.

Most rectifiers use a three-stage method that links the three wires to the stator and regulator rectifier. There are single-phase systems that employ two wires rather than three. The regulator rectifier first converts the AC power into a burst of DC power, then normalizes the DC power to ensure that it does not exceed roughly 14 volts. The DC voltage is then sent to the battery and used to power the electronics of the motorcycle.



How Do I Know If I am Having Trouble With My Rectifier?

There are several signs to know if you are having trouble with your rectifier. One of these is output voltage fluctuations. The voltage should ideally be smooth and constant, so if you notice significant fluctuations or instability, it could be a sign of rectifier malfunction.

Another sign is excessive ripple voltage. While some ripple is expected in rectified DC output, an unusually high ripple voltage can indicate a problem with the rectifier. This may be from failed or faulty diodes in the rectifier bridge or issues with the smoothing capacitor.

Other problem signs are overheating, no output or low voltage output, and the circuit's protection mechanisms constantly triggering.


Will A Motorcycle Run Without A Rectifier?

So will a motorcycle even run without a rectifier? Typically it won't, especially if it's equipped with an electrical system that relies on a battery and requires DC voltage to operate.

Motorcycles generally need a DC voltage to function correctly. Without a functioning rectifier, the battery won't receive the proper charging voltage, leading to a discharged or weak battery over time.



A motorcycle requires a rectifier. It is one of the key components in regulating the power within the motorcycle while also overseeing the conversion of AC power from the alternator to DC power, allowing the battery to charge and power important components including the lights, starter motor, and dashboard. If you have problems with your regulator rectifier, you can come to our store. DISELMART has the answers you're looking for – and the products, too!


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