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Are DC Motors Waterproof?

Are Dc Motors Waterproof

The waterproof problem has always troubled and hindered the use of DC motors in the wet and diving environment. If there is a waterproof motor, it will significantly expand its application area to meet the needs of particular users and bring great business opportunities to the market. Many applications such as windshield wipers and power windows still use brushed DC motors. But the question remains, are DC motors waterproof?

No, DC motors are not waterproof. The water can enter from the motor housing, end cap, output shaft, bearings, terminals, screw holes, and gaps in the component joints. Hence, the waterproof problem of DC motors restricts their use in underwater applications. 

In this article, we will discuss the waterproof behavior of brushed DC motors. Also, we’ll walk you through the method of making DC motors waterproof. 

 Let’s go!

Windshield Wipers

Why are DC Motors not Waterproof?

 

The ordinary Brushed DC motor in the market is not waterproof because their applications don’t need it.

If you are going to immerse the DC motor in water, the commutators will respond, resulting in a short circuit. So, a Brushed DC motor can’t run underwater. 

If you have to use a DC motor underwater, there are ways to waterproof them. But first, let’s discuss how water enters the DC motors. 

How Water Enters The DC Motors?

 

The water in Brushed DC motors enters through:

Motor Housing

 

If you look at the structure of motor housing in a brushed DC motor, you will find vent holes. 

These vent holes allow heat dissipation to keep heat within its optimal temperature limits. Yet, these vent holes also let the water enter the motor. 

Shaft End and Bearing Gap/Clearance

 

In a DC motor, a bearing under the end cap supports the end of a shaft. The gap or clearance between the shaft end and bearing will allow water to enter the motor. 

Screw Holes

 

For mounting purposes, there are screw holes in a DC motor. 

If exposed to water for a long period, water might enter through screw holes and affect the performance of your motor.

Rs 555sh Front View Prorich Motor

End Cap

 

A brushed DC motor has a plastic or metal end cap with two terminals and vent holes, allowing air to pass through for heat dissipation.

But, if you use it underwater, water may enter through the venting holes. 

Terminals

 

What happens when you run your motor underwater with terminals exposed?

Water enters into the insulation of the motor winding. It results in complete damage to the motor.

Gaps in the Joints of Component Assembly

 

The component assembly for a brushed DC motor includes a vented end cap and motor housings.

The gaps in the joints of the component assembly allow water to enter the motor. 

Rs 555sh Back View Prorich Motor

What Happens if the Water gets into the Motor?

 

The basic components of a brushed DC motor are;

  1. Stator
  2. Rotor/Armature
  3. Brushes
  4. Commutator

All the components are designed to use over water. Therefore, if the motor is exposed to moisture for a long time, the following damages may occur. 

  1. The insulation will fail, and the motor will produce heavy current.
  2. The heavy current produces heat. It damages the insulation of motor windings and creates a short circuit. As a result, the motor burns out soon.
  3. Stator and rotor materials are prone to corrosion and rusting in humid environments.

Brushed Motor Structure

How To Make a DC Motor Waterproof?

 

Brushed DC motors are not waterproof, and thus it’s challenging to make them 100% waterproof.

However, there are some common and effective methods to improve their waterproof performance.

Covering the Motor in Specialized Casing

 

Plastic Case

A practical method to waterproof your motor is covering it in a specialized casing. However, specialized cases are pretty expensive in the market.

Note: Specialized cases provide different levels of protection against moisture or liquids. Some cases may shield against minor water splashes. While some may provide outstanding underwater protection. 

Use Waterproof Shaft Seals

To make your DC motor waterproof, it is crucial to seal the moving parts such as the shaft and bearings. 
 

Waterproof shaft seals provide an enclosed area for the machine’s inner workings. It protects the water from entering the moving parts. 

You can use a stack of rubber rings joining a suitable tube on the outside. The rubber rings should be glued tightly to the case to protect against water. 

All in all, many waterproofing methods limit the airflow to the motor, impacting the performance. Thus, I do not recommend waterproofing your DC motor unless necessary. 

Tips to Run your DC Motors Underwater

 

If you want to run your motor underwater, here are some useful tips that will protect your motor from damage.

  1. Never run your motor in water with mineral content, just to avoid the electrical conductivity of the water.
  2. Be sure to choose a detachable motor, easy to clean later.
  3. I always recommend lubricating the bearings and brushes after dry-cleaning.

The Waterproof Performance of Brushed DC Motors in Clean Water

 

The DC motors perform differently when immersed in clean or dirty water. 

The brush of the motor might get affected when exposed to clean water. Water results in the wear and seat of the brushes and loss of functionality. 

Yet, clean water does not affect the commutator. 

The Waterproof Performance of Brushed DC Motors in Dirty Water

 

Under bad water conditions, the performance of a DC motor would face more challenges. 

Thus, dirty water would affect the commutators and brushes of the DC motor adversely. 

The roughness of dirty water affects the commutators the worst because they are soft parts compared to brushes. 

Therefore, when the DC motor is exposed to dirty water, I recommend replacing the entire commutator to keep the motor working. 

The Effect of Voltage on the Waterproof Performance of DC motors

 

Voltage is also an essential factor that affects the performance of DC motors. 

When running a motor at 15V or higher, water conducts current, and a sudden spark or silence from your motor is expected.

Thus, if you want to run your motor underwater, I will not advise operating the motor at 15V or higher. 

The impact of Waterproofing your Motor on Performance

 

If we compare the waterproof performance of Brushed DC motors to Brushless ones, it’s difficult to waterproof for obvious reasons.

The permanent magnet brushed motor uses armature windings on the rotor (the rotating part). And the stator uses fixed magnets. Thus, to drive current to armature windings, we need brushes.

The armature windings on the rotor generate heat, and it’s difficult to conduct the heat out of the motor. Now, this is where the problem arises. The brushed DC motor demands a good airflow to cool the coils. For this purpose, we use vent holes.

Motor Armature Winding

If vent holes are sealed or covered to make them waterproof, where will the heat go? 

The heat will transfer into the bearings. And it would be hazardous to your motor’s performance. 

Conclusion

 

DC motors are not 100% waterproof. You can transform them into water-resistant devices (to some extent). But they cannot be completely waterproof.

Follow the methods of waterproofing in this article to get the desired results

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