Did you know that there are two methods used to brake a motor? One of these methods is DC injection braking and it was invented as a safer alternative to conventional friction braking.
We have put together this guide to teach you all the ins and outs of DC injection braking.
Table of Contents
What Is DC Injection Braking?
DC injection braking is when direct current (DC) is used to brake. The current is applied to the movement of an AC motor once there is no more voltage. This is a very effective and efficient way to brake most AC motors out there.
You will have a very quick and smooth braking action even if you are dealing with high speed and high loads. Whenever you remove the AC voltage the motor will be able to coast to a standstill after some time because there is no induced field to keep the motor rotating.
A fixed magnetic field is created when a DC current is applied to the motor windings. Then the rotor that is working to align this stationary field produces braking action. The higher the DC current is the stronger the braking force is.
Some typical places that you can find this braking system are in machine tools, safety brakes, circular saws, large flywheel applications, and high inertia loads.
Differences Between DC Injection and Dynamic Braking
One of the major differences between these two braking methods is that DC injection braking needs very minimal maintenance because the working units do not have to touch in order to produce braking results. With dynamic braking, the braking action lessens as the motor speed goes down. This means that a motor is never able to come to a complete stop when you are using dynamic braking units.
Difference Between Friction Braking and DC Injection
A perfect example of friction braking is a bike braking. Most bikes rely on friction braking which is why if you ever raced someone on a bike when you were younger, you probably relied on a sharp turn, a hill, or another external method to help slow you down.
When you squeeze the levers next to the handlebars it engages rubber pads that are on either side of the bike’s tires and then the friction from the pads pressing the tires will slowly bring the bike to a stop. Friction brakes on a motor are similar in that they require a specific method to help stop the motor and how long the complete stop takes all depends on the inertia applied.
A DC injection braking system can be integrated into the motor control circuitry which allows small electric motors that are AC powered to stop much faster than friction brakes.
You can easily mount these brakes in a remote and convenient location vs friction brakes that have to be mounted within the rotor area in order for them to work. DC brakes can even go into the motor drive circuitry so that it will not be necessary for a human operator to control the braking unit.
Long Term Solution
As mentioned earlier DC injection brakes can be installed in order to stop an AC motor safely and rapidly. There are options for adjustable braking as well with closed-loop current control.
The great thing about DC injection brakes is that they do not wear because they are not exposed to any friction when you are braking. This also means that high levels of torque can be delivered in order to stop the motor. DC injection brakes can be installed away from the rotor or from the motor switchgear.
Advantages
There are quite a few advantages when opting for DC injection braking such as a much shorter stop time. This equates to increasing production rate in machine tools and in high inertia loads. Another advantage is that they are easy to install.
A third advantage is that they increase a person’s safety protection on hazardous machines. There is also less motor heating because of its auto-stop capability. You also have an adjustable braking torque that matches the load size along with the required stop time.
One last advantage worth mentioning is that there is less wear and tear of mechanical parts because stopping is a lot softer and smoother.
Can It Damage Motors?
The one word answer is – yes. The good news is that there are ways to avoid damaging any motors. One way to damage the motor is if the DC injection braking is applied for too long when stopping or slowing down the motor.
In order to avoid the heat damage this causes, is to make sure that your braking system is using a zero-speed sensor. This sensor will shut the DC braking current to off once the rotor is at a complete stop.
Another way the motor can be damaged is with a surge current. A surge current can be avoided by using a fixed time delay mechanism to control when the DC current is applied to the motor.
Feeling Like a DC Injection Pro?
Now that we went over everything there is to know about DC injection braking you can make an informed decision on which is the best braking system for your specific needs. Once you are sure of what will help you brake quickest and safest then you want to buy them from a place that you can trust.
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