I am going to be teaching a class that involves operating generators. I know my students will ask why one piece of equipment requires a 60 Hz generator and the other requires 400 Hz, while the voltage is the same for each generator. I am considering using food consumption as an analogy, where cheeseburger calories are the kWs and Hz are how many someone eats per hour. Maybe an office worker just needs 1 every few hours to work effectively, but an athlete needs one every hour to maintain themselves. Am I way off base? I'm not an engineer, just a guy who's gonna get asked why it matters.

 

I am going to be teaching a class that involves operating generators. I know my students will ask why one piece of equipment requires a 60 Hz generator and the other requires 400 Hz, while the voltage is the same for each generator. I am considering using food consumption as an analogy, where cheeseburger calories are the kWs and Hz are how many someone eats per hour. Maybe an office worker just needs 1 every few hours to work effectively, but an athlete needs one every hour to maintain themselves. Am I way off base? I'm not an engineer, just a guy who's gonna get asked why it matters.

Why don't you just tell them the facts and history of why instead of some bogus analogy.

It's not like this is a new subject that's never been asked before. How can you teach something you don't understand in detail first?

Just say, I don't know why.

https://forums.mikeholt.com/threads...-we-settle-on-60hz-and-not-say-400hz.2569300/

 

Why don't you just tell them the facts and history of why instead of some bogus analogy.

It's not like this is a new subject that's never been asked before. How can you teach something you don't understand in detail first?

Just say, I don't know why.

https://forums.mikeholt.com/threads...-we-settle-on-60hz-and-not-say-400hz.2569300/

I'm teaching them how to operate the equipment, the science behind why isn't the focus of the class. I'm interested in knowing why too, and an analogy (like the water pick analogy used for kWs and amps) is a good way to build a basic understanding. I have not been able to find any basic way to break down why the difference matters, hence why I asked here.

 

Don't give bad information to those that see you as a source of good information. It's the cardinal sin of teaching and a disservice to the students.

Don't try to be something you're not. Stick with teaching what you know. The why question is a endless pit for experts.

Just be honest.

 

Welcome to AAC.

The problem is, 400Hz is not "better" than 60Hz—it's different, and choosing between them depends on the application.

With 400Hz, anything magnetic—motors, transformers, &c—can be much smaller and lighter this is one of the reasons you find it on planes and ships. This means that 400Hz motors have a better power to weight ratio.

400Hz systems are also potentially faster than 60Hz, meaning they are better for high speed actuators and the like,

On the other hand, the higher frequency has its costs. Due to something called skin effect where the current travels on the outside of a conductor proportional to its frequency, to get the same current to a device will require larger cables. The practical length of cable runs is also reduced by eddy current losses. You can think of these as currents circulating in the wires and not getting put to use.

So, where its advantages are needed, 400Hz AC is a boon, but where it isn't needed, it is an extra cost that brings no benefit.

 

Don't give bad information to those the see you as a source of good information. It's the cardinal sin of teaching and a disservice to the students.

Don't try to be something you're not. Stick with teaching what you know. The why question is a endless pit for experts.

I dont want to be an expert in electrical generation. But being able to provide more than an "I don't know, because the instructions say so, for safety" would be great. Can you explain it in simple terms, why you'd need 400 Hz instead of the 50/60 standard?

 

Welcome to AAC.

The problem is, 400Hz is not "better" than 60Hz—it's different, and choosing between them depends on the application.

With 400Hz, anything magnetic—motors, transformers, &c—can be much smaller and lighter this is one of the reasons you find it on planes and ships. This means that 400Hz motors have a better power to weight ratio.

400Hz systems are also potentially faster than 60Hz, meaning they are better for high speed actuators and the like,

On the other hand, the higher frequency has its costs. Due to something called skin effect where the current travels on the outside of a conductor proportional to its frequency, to get the same current to a device will require larger cables. The practical length of cable runs is also reduced by eddy current losses. You can think of these as currents circulating in the wires and not getting put to use.

So, where its advantages are needed, 400Hz AC is a boon, but where it isn't needed, it is an extra cost that brings no benefit.

Easy for an expert to say. You now have 10 extra what and why questions to answer now , on words the generator students have heard just now but don't understand.

 

I dont want to be an expert in electrical generation. But being able to provide more than an "I don't know, because the instructions say so, for safety" would be great. Can you explain it in simple terms, why you'd need 400 Hz instead of the 50/60 standard?

Explain, no, tell yes. The information post above is a example of telling.

 

Easy for an expert to say. You now have 10 extra what and why questions to answer now , on words the generator students have heard just now but don't understand.

He doesn't have to say more. If there are questions, he needs to have a resource to point them at. The summary does provide enough information to understand there is a distinction and it is not just "400Hz better".

 

Welcome to AAC.

The problem is, 400Hz is not "better" than 60Hz—it's different, and choosing between them depends on the application.

With 400Hz, anything magnetic—motors, transformers, &c—can be much smaller and lighter this is one of the reasons you find it on planes and ships. This means that 400Hz motors have a better power to weight ratio.

400Hz systems are also potentially faster than 60Hz, meaning they are better for high speed actuators and the like,

On the other hand, the higher frequency has its costs. Due to something called skin effect where the current travels on the outside of a conductor proportional to its frequency, to get the same current to a device will require larger cables. The practical length of cable runs is also reduced by eddy current losses. You can think of these as currents circulating in the wires and not getting put to use.

So, where its advantages are needed, 400Hz AC is a boon, but where it isn't needed, it is an extra cost that brings no benefit.

Thank you! This helps my own understanding of the subject. I don't need an analogy when you break it down like this.

 

He doesn't have to say more. If there are questions, he needs to have a resource to point them at. The summary does provide enough information to understand there is a distinction and it is not just "400Hz better".

Just as I told the OP, tell don't explain.

 

Don’t give analogies. Teach it as it is.
There is a reason and history for using 400 Hz. Look it up.

 

Thank you! This helps my own understanding of the subject. I don't need an analogy when you break it down like this.

I hope it does to some extent but please don't try to explain, just use correct references when asked questions, don't try to adlib.

 

Thank you! This helps my own understanding of the subject. I don't need an analogy when you break it down like this.

Find some sources you can offer that have more information if they want to pursue it.

 

Just as I told the OP, tell don't explain.

I didnt want to explain in depth, I just need to give them a basic explanation as to why they are using generators that are basically the same in everything but Hz. The why is important to students, even if it's just the basics. Telling them that the 400 Hz generator is powering a lot of moving parts and will fry the components of something that only needs 50/60 Hz is better than telling them "I don't know, just don't mix them up".

 

I didnt want to explain, I just need to give them a basic explanation as to why they are using generators that are basically the same in everything but Hz. The why is important to students, even if it's just the basics. Telling them that the 400 Hz generator is powering a lot of moving parts and will fry the components of something that only needs 50/60 Hz is better than telling them "I don't know, just don't mix them up".

Sure, create a handout for the beginning of class with this type of information and then say, it's out of the scope of your class of generator operators.

Leave the rest to those qualified to teach it.

 

I know my students will ask why one piece of equipment requires a 60 Hz generator and the other requires 400 Hz, while the voltage is the same for each generator

I am often asked about frequency, why fast. I make power supplies that operate at 60khz or 600khz. (switching power)

 

Find some sources you can offer that have more information if they want to pursue it.

Nothing else in the course they are in will relate to this topic, but it is a commonly asked question and they will need to know there is a difference once they get on the job. I hope they will remember this bit of knowledge you provided.

 

Nothing else in the course they are in will relate to this topic, but it is a commonly asked question and they will need to know there is a difference once they get on the job. I hope they will remember this bit of knowledge you provided.

If they need the information to operate the equipment, then you should be required to be qualified to teach it. Saying or handing out information does not qualify you to teach it if they really need know there is a difference on the job as a matter of getting a job done correctly. Decide, and act in the students best interest and yours long term.

 

If they need the information to operate the equipment, then you should be required to be qualified to teach it. Saying or handing out information does not qualify you to teach it if they really need know there is a difference on the job as a matter of getting a job done correctly. Decide, and act in the students best interest and yours long term.

You've been really great at giving unhelpful, condescending bits of advice. Do you expect a driving instructor to know the history and inner workings of an internal combustion engine before telling his class not to put diesel in a gas car? I can't give you the full details of why, but my students will typically have access to a 400 Hz generator that is bolted on to one system, and an additional system that has the same voltage requirements but does not always have the 60 Hz generator required to run it. Some one who does NOT KNOW why my students can't use the generator they already have will ask them to use it to run the 60 Hz equipment. I want my students to be prepared to quickly explain why it is not possible, and understand that they will need to request a 60 Hz generator instead.