We recently had some serious hijacking of the thread "Bauer Capitano II 480V 3 Phase to 240V Single Phase Help". We started going pretty deep down the rabbit hole of drives, phase inverters, soft starts and even PLCs. Somehow we missed the repeat cycle timers that are used to operate the automated condensate drains on the smaller Bauers. I'm starting a new thread here in hopes of putting this kind of useful information in a centralized location that can be found by browsing thread titles. I'm going to start with a few general assertions of mine & then let others fill in the holes in what I have posted. On the other thread, we had some robust sharing of information. Hopefully, that will continue.
My opening assertions are as follows:
Compressors tend to put a heavy load on an electric motor & the controls need to be up to snuff.
The most basic legitimate motor control is a manual motor starter, but sometimes people cheat & just use a panel breaker.
The second most basic motor control is a magnetic motor starter, which is basically comprised of a big relay that is called a contactor & a safety device that is called a thermal overload relay. On old nema type overload relays, you had to change "heaters" to change the set point for the over current trip. Modern IEC type overload relays usually have a dial that lets you make adjustments within a certain range of amps.
A more sophisticated type of motor control is called a variable frequency drive. These allow gentle starts, gentle stops, speed control & torque control, among other things. These are programmable. There are several different ways to control them. The really simple ones often have a speed dial & start/stop switches on the front panel. Some of these can take in single phase power & put out three phase power. Many can power a motor that runs on a lower voltage than the supply voltage. Some can power motors that run at higher than supply voltage, sometimes at full rated HP, most often at reduced HP. Very few can put out single phase power. The abilities of individual drives vary a lot. For running compressors, we are usually looking at some of the cheapest ones.
Three phase motors tend to give better performance & cheaper operation when three phase power is available. Unfortunately, sometimes we only have 1ph available.
When you need to make a 3 phase compressor run on a single phase, you have several options. They include:
Change the motor & rewire the control box
Install a Variable Frequency Drive that supports single phase primary power.
Install a static phase inverter
Install a rotary phase inverter
Each option has some advantages & disadvantages.
The automatic blow down version of a small compressor usually has a repeat cycle timer in it to control when the water gets blown out of the system. They are usually adjustable.
More complex systems, may have a Programmable Logic Controller installed in them. This allows many different inputs from things like temperature sensors, CO sensors, pressure transducers, over voltage and under voltage sensors, into a single control device. It also may provide messages about things like timing out maintenance intervals, or expected time to set pressure, via an operator interface panel. These devices are all programmable, but often programming is beyond the abilities of the end user who will operate the device.
I'm going to ask that we try something a little different than usual here, in the interest of concentrating useful information as much as possible. I'm going to ask that those who are experienced with controls, or who have done conversions before, please choose one of my assertions from above at a time & expound on it in as much detail as you are able. Please start by listing the assertion that you are commenting on. That way, if a person is looking for info on static phase inverters, they can just read all the replies that start with "static phase inverter".
Of course, if you see an important aspect of control systems that I failed to mention above, please do also chime in on that topic.
Of course, question from those who are looking for information are also encouraged.
Thanks,
the fish
My opening assertions are as follows:
Compressors tend to put a heavy load on an electric motor & the controls need to be up to snuff.
The most basic legitimate motor control is a manual motor starter, but sometimes people cheat & just use a panel breaker.
The second most basic motor control is a magnetic motor starter, which is basically comprised of a big relay that is called a contactor & a safety device that is called a thermal overload relay. On old nema type overload relays, you had to change "heaters" to change the set point for the over current trip. Modern IEC type overload relays usually have a dial that lets you make adjustments within a certain range of amps.
A more sophisticated type of motor control is called a variable frequency drive. These allow gentle starts, gentle stops, speed control & torque control, among other things. These are programmable. There are several different ways to control them. The really simple ones often have a speed dial & start/stop switches on the front panel. Some of these can take in single phase power & put out three phase power. Many can power a motor that runs on a lower voltage than the supply voltage. Some can power motors that run at higher than supply voltage, sometimes at full rated HP, most often at reduced HP. Very few can put out single phase power. The abilities of individual drives vary a lot. For running compressors, we are usually looking at some of the cheapest ones.
Three phase motors tend to give better performance & cheaper operation when three phase power is available. Unfortunately, sometimes we only have 1ph available.
When you need to make a 3 phase compressor run on a single phase, you have several options. They include:
Change the motor & rewire the control box
Install a Variable Frequency Drive that supports single phase primary power.
Install a static phase inverter
Install a rotary phase inverter
Each option has some advantages & disadvantages.
The automatic blow down version of a small compressor usually has a repeat cycle timer in it to control when the water gets blown out of the system. They are usually adjustable.
More complex systems, may have a Programmable Logic Controller installed in them. This allows many different inputs from things like temperature sensors, CO sensors, pressure transducers, over voltage and under voltage sensors, into a single control device. It also may provide messages about things like timing out maintenance intervals, or expected time to set pressure, via an operator interface panel. These devices are all programmable, but often programming is beyond the abilities of the end user who will operate the device.
I'm going to ask that we try something a little different than usual here, in the interest of concentrating useful information as much as possible. I'm going to ask that those who are experienced with controls, or who have done conversions before, please choose one of my assertions from above at a time & expound on it in as much detail as you are able. Please start by listing the assertion that you are commenting on. That way, if a person is looking for info on static phase inverters, they can just read all the replies that start with "static phase inverter".
Of course, if you see an important aspect of control systems that I failed to mention above, please do also chime in on that topic.
Of course, question from those who are looking for information are also encouraged.
Thanks,
the fish
