Air conditioner questions

[Anarchist420]

Is the power circuitry used in most just mediocre or do most Air Conditioner makers go out of their way to make sure that they use last longing (at high temps) power circuitry that suppresses >= 99.8% of input ripple, that allow delivery of high instantaneous current, and that allow good line/input regulation?

Also, do most AC makers use power supplies with active PFC, do they use passive PFC, or something else?

Finally, what efficiency rating(s) would be considered poor? What would be considered mediocre and what would be considered good?

 

[sm625]

Most of the circuitry inside an AC is contained within the windings of the motor. There isnt much else to it. There isnt any PFC. There is no need for ripple rejection becuase it is an AC motor.

 

[Anarchist420]

Most of the circuitry inside an AC is contained within the windings of the motor. There isnt much else to it. There isnt any PFC. There is no need for ripple rejection becuase it is an AC motor.

Thanks Aren't some Air conditioners more efficient than others though?

Also, when you said "AC motor" did you mean "alternating current motor" or did you mean "air conditioning motor"?

 

[philipma1957]

ratings for an outside full home system 16 seer is high 10 seer is low and 13 seer is common. in your window type air conditioner 8 seer is low 10 seer is good. 12 seer is very good.

 

[Anarchist420]

ratings [...]

Thanks

 

[NeoPTLD]

Is the power circuitry used in most just mediocre or do most Air Conditioner makers go out of their way to make sure that they use last longing (at high temps) power circuitry that suppresses >= 99.8% of input ripple, that allow delivery of high instantaneous current, and that allow good line/input regulation?

Also, do most AC makers use power supplies with active PFC, do they use passive PFC, or something else?

Finally, what efficiency rating(s) would be considered poor? What would be considered mediocre and what would be considered good?

The respondents here are assuming USDM spec domestic brands.

Some A/Cs use power electronics, some don't. The type used in USA that integrates with ducted air handler system and outside condensing unit usually don't. They're antiquated and uses primitive on/off only control with passive components. The only electronics in American A/C systems is usually the thermostat. The basic design of US model A/Cs haven't changed in 40+ years.


Inverter drive models use BLDC motors in conjunction with VSD drive. Daikin, LG, Fujitsu, Mitsubishi Electric are some of them. Some like Mr. Slim uses active PFC on front-end. I would imagine that all of the units sold in Europe do as well to comply with EU initiatives.

Most of duct free ACs (condenser outside, evaporator unit inside only connected by refrigerant line and power cable) use power electronics driven compressor.

 

[soccerballtux]

Thanks Aren't some Air conditioners more efficient than others though?

Also, when you said "AC motor" did you mean "alternating current motor" or did you mean "air conditioning motor"?

Newer apt complexes have to install high efficiency AC units by legislation because there's no financial incentive for the apt complex to pay to save the environment.

In an attempt to cool refrigerant better at the high-pressure side (the big thing outside), higher efficiency units have more surface area to dissipate more heat. Dissipating more means the low-pressure side is cooler for a given cycle of pressurization/depressurization, which means more chill for your bill.

Of course if they still allowed Freon we'd have way more efficient units but that's bad for the Ozone, however I think there are alternatives that are just as good (and not as bad for environment).

That's about all I know.

 

[Modelworks]

Of course if they still allowed Freon we'd have way more efficient units but that's bad for the Ozone, however I think there are alternatives that are just as good (and not as bad for environment).

That's about all I know.

Propane is a very good refrigerant but it isn't used because of the fear of a leak.

 

[Mark R]

Is the power circuitry used in most just mediocre or do most Air Conditioner makers go out of their way to make sure that they use last longing (at high temps) power circuitry that suppresses >= 99.8% of input ripple, that allow delivery of high instantaneous current, and that allow good line/input regulation?

Also, do most AC makers use power supplies with active PFC, do they use passive PFC, or something else?

AC systems don't generally use DC power, so ripple is meaningless. Similarly, voltage regulation is not required for motor operation.

There are 2 main types of AC system:
1. Direct powered motors
2. Inverter drive

1.
In direct powered motors, the power supply is the grid. A switch connects grid power to the motor. Job done. The motor generally isn't affected by modest fluctuations in grid voltage, or voltage waveform problems, voltage spikes, etc.

Direct powered motors have a slightly inductive power factor (but this varies with load), as a result most AC systems include a capcitor to provide passive PFC. Active PFC is not needed for motors. Capacitors are all that are needed. They are cheap and very reliable. Active PFC is quite expensive.

When a direct powered motor starts it will take a very high instantaneous current (typically 50 - 100 A+). Because there is no power supply electronics, the grid just handles it, but you may notice the lights go dim during that instant. There are 3 problems, the voltage dip might upset inadequately designed electronics elsewhere in the building, the motor experiences a massive jerk at switch which causes excessive wear and stress, the electrical supply, wiring, etc. all get heavily stressed. Because of this, industrial AC systems in rural areas often have to install "restart prevention" or "anti-simultaneous start" systems, so that there is 5 minutes between each AC system kicking in, otherwise they risk overloading the power-company's equipment with too many current surges in too short a time (or annoying the neighbors with flickering lights).

2.
In inverter drive motors, mains AC is converted to high voltage DC, and then goes through a 3-phase inverter to power a 3 phase motor.

3 phase motors are more efficient than single phase motors, they are also smaller, quieter, cheaper and more efficient. Additionally, inverters allow precise control of motor voltage, speed, etc. This allows gentle starting, and allows motor speed and torque to be regulated to the cooling/heating requirement. This avoids cycling of the motor on and off, so more precise temperature regulation and higher efficiency as the system avoids over cooling/heating by running at full power.

The problem with inverters (and electronic power supplies in general) is they have a horrid power-factor, especially if single-phase mains supply (3-phase powered PSUs/inverters have much better power factor that rarely needs any correction at all). Single-phase inverter power factor is horrid, and as it's neither capacitative or inductive, it requires a complex correction system.

Usually this is done with passive PFC - a complex interconnection of multiple bulky, expensive inductors and capacitors. As bulk, weight and cost aren't so much of an issue as in consumer electronics. However, active PFC motor control systems are available. I don't know if any of these aPFC motor inverter systems are in HVAC; but I'm guessing if they aren't, they'll be there fairly soon, as manufacturers try to reduce the bulk of their units.

 

[Emulex]

so if you went all copper on the fins you could increase the efficiency of an a/c unit like cpu heatsink?

 

[NeoPTLD]

so if you went all copper on the fins you could increase the efficiency of an a/c unit like cpu heatsink?

Yes, but it would make them vulnerable to theft.

Newest trend is to use micro channel coil with corrugated fins. It would look more like a car radiator. This allows for better air flow. The coil itself would look like belt with many pipes going through it.

AC systems don't generally use DC power, so ripple is meaningless. Similarly, voltage regulation is not required for motor operation.

I think he meant harmonics. You're right that they don't normally operate off of DC power source, but many do operate from rectified power at equipment level. Most motor drives have active PFC front end to mitigate harmonics.

There are 2 main types of AC system:
1. Direct powered motors

These are mostly used in North American residential and light commercial.

2. Inverter drive

Direct powered motors have a slightly inductive power factor (but this varies with load), as a result most AC systems include a capcitor to provide passive PFC.

What is "most"? Where are you looking?

Many ductless units are BLDC inverter drive.

Three phase split line frequency units don't use equipment level PFC, though you may find a capacitor for starting the single phase blower motor.

Single phase induction motor units use capacitors to start and run the motor. They're not PFC capacitors, but I have some doubt that single phase induction represents the most units installed globally.