- #1
How to determine the rating of a capacitor for a specific purpose?
In summary: You'll need to do some research and figure out what kind of gear reduction you need and try to find a motor with that type of gearing.In summary, the capacitor will help to control the current drawn from the battery by the motor, but you will need to research what gear reduction you need and find a motor with that rating.
- #2
NascentOxygen
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Hi arkaddas.
You don't connect a capacitor in series with a DC motor. It won't spin for very long if you do.
You don't connect a capacitor in series with a DC motor. It won't spin for very long if you do.
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- #3
Windadct
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Hello Ark... a schematic always helps - I just found another online tool Scheme It ( http://www.digikey.com/schemeit )
- #4
arkaddas
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There's a diode in parallel with the capacitor.
Actually I was searching for a way to increase the acceleration of the motor. According to me, the speed controller will determine that but my teammate insisted that capacitors are used to increase the acceleration of motors and he also found out a link that convinced me to give it a thought. I have attached the schematic.
Actually I was searching for a way to increase the acceleration of the motor. According to me, the speed controller will determine that but my teammate insisted that capacitors are used to increase the acceleration of motors and he also found out a link that convinced me to give it a thought. I have attached the schematic.
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- #5
Windadct
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How will you turn the motor on and off? I have a feeling the "diode" you show is not really what you are looking for, the capacitor seems to be more of a snubber (absorbing energy as the motor is turned on and off) and the "diode" a switch?
- #6
arkaddas
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I took the schematic from a presentation that was prepared by MIT students so I don't have doubts about it. However I cannot understand the function of this circuitry. Here's the link to the presentation :- http://web.mit.edu/first/kart/everpres.pdf
- #7
Windadct
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Well I certainly have doubts about the original schematic. The schematic now - is still really a block diagram and not complete enough to work with. This presentation is about using a Ultra-Cap for bulk energy storage in conjunction with batteries - since we are talking energy storage, typically the more the better, but you pay of it with size and weight. The later schematics - showing the switches for control, are closer but still not close to the whole system. If you look at the photos of their systems there is clearly a lot more going on than in the schematic you first posted.
Sizing the caps comes down to how much energy do you expect to store, in this case from regen braking, so the sizing is almost more of a mechanical calculation: Max Speed, Max Weight, inertia, total kinetic energy that needs to be regenerated back into the cap. They are using a different topology - series vs Parallel connections, and the controller needs to actively regulate the braking effect and current flow INTO the Ultra-Cap.
Also this motor is actively field controlled - another level of complexity - I would probably avoid on a cart.
Sizing the caps comes down to how much energy do you expect to store, in this case from regen braking, so the sizing is almost more of a mechanical calculation: Max Speed, Max Weight, inertia, total kinetic energy that needs to be regenerated back into the cap. They are using a different topology - series vs Parallel connections, and the controller needs to actively regulate the braking effect and current flow INTO the Ultra-Cap.
Also this motor is actively field controlled - another level of complexity - I would probably avoid on a cart.
- #8
arkaddas
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I see. Can you help me understand the real purpose of using the capacitors? I was planning to simply control the dc motor with a chopper circuit without introduction of capacitors but the problem that arises is quick drain of the battery.
I have another doubt. Will the motor consume more energy at higher speeds or at lower speeds? From the torque speed characteristics what I could understand is that torque will be less for high speeds so in my opinion power required should be less. But I'm still unsure about this conclusion.
I have another doubt. Will the motor consume more energy at higher speeds or at lower speeds? From the torque speed characteristics what I could understand is that torque will be less for high speeds so in my opinion power required should be less. But I'm still unsure about this conclusion.
- #9
NascentOxygen
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It the motor is driving a load which itself is harder to turn as it rotates faster, such as a fan or wheels, then higher speed demands higher power.
The purpose of the ultracap is to store regenerative energy during dynamic braking, then use that stored energy to assist the battery during powered drive. If your motor is not doing much braking, then the ultracap circuit won't be of any use.
The purpose of the ultracap is to store regenerative energy during dynamic braking, then use that stored energy to assist the battery during powered drive. If your motor is not doing much braking, then the ultracap circuit won't be of any use.
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- #10
arkaddas
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Thanks for the explanation about the ultracapacitor. It was really helpful. :)
- #11
arkaddas
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What can I do to accelerate the motor?
- #12
NascentOxygen
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Typical DC motors are very robust. You can often overdrive them (i.e., power them above their rated power) for a short time without ill effect, so long as you then run them at reduced drive so they can cool down.arkaddas said:
However, there is no magic for getting a continuous 20HP out of a 5HP motor.
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1. What is a capacitor and how does it work?
A capacitor is an electronic component that stores electrical energy in an electric field. It consists of two conductive plates separated by an insulating material, also known as a dielectric. When a voltage is applied across the plates, an electric field is created, causing one plate to accumulate positive charge and the other to accumulate negative charge. This creates a potential difference, or voltage, between the plates. Capacitors are commonly used to filter out unwanted frequencies in electronic circuits, store energy, and provide power supply stabilization.
2. How do I determine the capacitance value for a specific purpose?
The capacitance value of a capacitor is determined by the physical characteristics of the capacitor, such as the size of the plates, distance between the plates, and type of dielectric material. To determine the capacitance value needed for a specific purpose, you must first understand the requirements of your circuit or application. This includes considering the voltage and frequency requirements, as well as the desired capacitance range. You can then use a capacitance calculator or consult a datasheet to select a capacitor with the appropriate capacitance value.
3. What factors should I consider when choosing a capacitor for a specific purpose?
When choosing a capacitor for a specific purpose, there are several factors to consider. These include the capacitance value, voltage rating, frequency range, temperature range, and size of the capacitor. You should also consider the type of dielectric material, as different materials have different properties and are suitable for different applications. Additionally, you may need to consider the cost and availability of the capacitor.
4. How does the voltage rating of a capacitor affect its suitability for a specific purpose?
The voltage rating of a capacitor indicates the maximum voltage that the capacitor can safely withstand without breaking down. In other words, it is the maximum voltage that the capacitor can handle before it experiences a dielectric breakdown and becomes permanently damaged. When choosing a capacitor for a specific purpose, it is important to select one with a voltage rating that is equal to or higher than the maximum voltage that will be applied to the capacitor in your circuit or application.
5. Can I use a capacitor with a higher capacitance value for a specific purpose?
In some cases, using a capacitor with a higher capacitance value than what is required for a specific purpose may not cause any issues. However, it is important to note that a capacitor with a higher capacitance value may also have a larger physical size and higher cost. Additionally, using a capacitor with a much higher capacitance value than what is needed can cause problems in the circuit, such as slowing down the circuit's response time or causing excessive power draw. It is generally recommended to use a capacitor with the appropriate capacitance value for a specific purpose to ensure optimal performance and reliability.
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