# Tag Info

83

Fans of that type have induction motors with two windings with a capacitor in series with one of the windings. For every individual motor design there is a certain capacitor value that allows the motor to develop maximum torque and operate at the maximum corresponding speed. Smaller capacitor values are used to reduce the torque so that the load overcomes ...

29

With frequency control, there is not just one torque curve, but an infinite number of curves, one for every operating frequency. The voltage needs to be proportional to frequency. If the voltage is carefully regulated using a mathematical model of the motor with motor operating voltage, current and power factor information, the torque curve can be made to ...

27

The compressor compresses coolant on one side of a closed loop. If you shut off the compressor, you still have the load side of the closed loop full of pressurized coolant. That pressurized coolant makes it much more difficult to start the motor. A motor starting at 0 RPMs will want to draw large amounts of current. With an added load to the motor (...

18

The capacitor symbol inside it may be a clue; the block next to it is one way of representing a resistor, and the staggered lines above it suggest there are three. Given this, I suspect it's three R-C snubbers, wired in delta, to reduce noise and switching transients on the 3 phase supply. This IS a guess, but there's not much else it could be. Component ...

16

From All About Circuits: Brushless DC motors are similar to AC synchronous motors. The major difference is that synchronous motors develop a sinusoidal back EMF, as compared to a rectangular, or trapezoidal, back EMF for brushless DC motors. Both have stator created rotating magnetic fields producing torque in a magnetic rotor. Construction wise, ...

16

The magnetic field of the stator, rotating faster than the physical speed of the rotor passes through the rotor conductors. That induces current in the rotor. Current in the rotor generates a magnetic field in the rotor that rotates at the same speed as the stator magnetic field, but lagging in position. That creates rotor torque. At synchronous speed, the ...

13

I'm a little late in answering this question and I can't yet reply directly to embedded.kyle above, but I wanted to correct a little misinformation given above. My expertise is motors, not controls, BTW. 1) "Universal motors" are entirely different than BLDC or induction motors. Universal motors have wound stators and armatures and have brushes. Just ...

13

But, I am going to pay for only real power? Isn't it right? So why do I want power factor to be high? If you are a small user you will only pay for real power. Your poor power factor will make little difference to the electrical grid. It is not worthwhile for the power company to meter you for the reactive power (kVArh). If you are a large user and your ...

13

It may be intentionally designed to force the fan on "high" for it to spin up before allowing it to drop back down to "low" The amount of power needed to overcome the static rolling resistance can be higher than what is output to maintain the "low" speed, thus it could end up stalling and not moving or only wiggling back and forth on a "low" setting

13

simulate this circuit – Schematic created using CircuitLab Figure 1. Two connection methods. The windings on your motor can take 220 V between their terminals. On a 220 V 3-phase supply you connect as shown in Figure 1b. On a 380 V 3-phase supply you connect as shown in Figure 1a. Note that in each case the voltage across each winding is 220 V ...

13

Air has a much higher reluctance (the magnetic equivalent of resistance) than the magnetic materials used in the motor. The smaller the air gap is, the lower that reluctance, and thus the higher the magnetic flux (which is the magnetic analog of current), allowing the motor to work more efficiently and at a higher power. Smaller air gaps also minimize ...

12

The answers regarding built-up pressure are correct, but there's another aspect which hasn't yet been mentioned. In order for an induction motor to produce torque, it must have within it a magnetic field which is rotating at a particular speed (called the synchronous speed). Assume a particular motor is set up to run at a synchronous speed of 600rpm from ...

12

The back EMF is generated in the wire that makes up the coils of the motor. When a wire is swept sideways thru a magnetic field, a voltage is generated along the length of the wire. Spin the motor with just a voltmeter connected, and you will see it make a voltage. So yes, the resistance and the back EMF are actually distributed along the wire in the coil....

12

It certainly can rotate at synchronous speed, or even faster. But electric power is communicated to the rotor by induction. Effectively, the rotor is the secondary winding of a transformer, which is driven by a frequency equal to the slip speed. So, at synchronous speed, that frequency is zero, and no power is communicated to the rotor. So, to rotate at ...

11

It means the ACS580 will run nice and cool. The motor will only take the power it wants. If it has programmable current limits, you may want to halve the default settings, to help protect the motor if it became overloaded, though the primary protection for this would be a thermal trip on the motor itself.

10

(Assuming you are talking about an induction motor) Such a motor will have six terminals - i.e. start and end points of all three windings available, which you should connect as star or delta. The terminals are arranged to allow you to do this easily. The motor is rated to tolerate 230V RMS across points U1-W1, U2-W2 and U3-W3. If you connect it in in star ...

10

If the rotor is spun at synchronous speed there would be zero induction and hence zero torque produced. What you see is slip and that slip creates enough induction which leads to enough torque to overcome residual friction and losses when no proper mechanical load is connected. Just in case you didn’t understand the zero induction idea; if the rotor ...

9

I'm understanding this question to mean that you're trying to run a three-phase motor off a single-phase line. If you're trying to run the motor directly off the AC line, the phase angles involved will make it difficult to get the motor started, which is part of the reason three-phase exists in the first place. Single-phase motors usually have motor start ...

9

The motor will try to run 20% faster than the unit is designed to run. Increasing the fan speed by 20% will theoretically increase the load torque by 44% and the load power by 73%. The compressor part of the load will theoretically increase by 20% torque and power. Operating the motor at 220 volts on 60 Hz will theoretically reduce the motor's torque ...

8

You're spending more money than you need to. If you have one "Lying around" no problem, but if we double rate every component and have to buy the equipment your wasting money.For example, If your motor only needs to do 10kw of work why would you use a 22kw motor? inefficient, also if you have a constant load on the motor just use the VFD for starting i.e. ...

8

What UPS inverter is used? If it is a model that does not produce a "proper" sinewave signal then this distorted sinewave can be the issue. Cheap inverters just use "hard" switching and a transformer to turn the battery power into something that looks like mains power. This hard switching means that the sinewave isn't very "clean". This means that it ...

7

An induction motor never spins at synchronous speed. A motor spinning at constant speed must be producing enough accelerating torque to overcome the decelerating torque of the load. Since an induction motor must slip to provide torque, the full-load speed will always be less than synchronous speed. Even an un-loaded motor with nothing on the shaft still ...

7

For an AC machine, the air gap flux is proportional to voltage and inversely proportional to frequency. (Note that $\frac{V}{Hz}$ can be converted to $\frac{V}{rad/sec}$ which is equivalent to $V\cdot s$, or Volt-seconds. $1 V\cdot s$ is equivalent to 1 Weber, which is the unit for magnetic flux.) So, if you maintain a constant ratio of voltage ...

7

The circuit I believe you're looking for is something like this: (please excuse the odd symbols for the switch & motor ...) simulate this circuit – Schematic created using CircuitLab With the switch in the Low seting, only C1 is connected in the circuit. When the switch is set to Medium or High, either C2 or C3 will be connected in parallel with ...

7

The wording of your question implies that you are asking about an induction motor that has a capacitor that remains connected to the auxiliary winding while the motor is running. That type of motor is called a permanent split capacitor (PSC) motor. The following is based on that assumption. Changing the capacitor value changes the amplitude and phase shift ...

7

That curve is for constant frequency excitation. If you are accelerating a motor, you know it's going to be for a very short time, so you can thermally overload it. If you want more torque from standstill on an induction motor drive, then you can use a lower drive frequency than the max. I'm sure Elon has thought of both things.

7

The spring mechanism appears to be part of a centrifugal switch arrangement, which would be crucial to getting the motor started. Trying to start the motor without it would result in no rotation and excessive current draw.

7

The nominal VFD kW rating is the maximum motor kW rating. The VFD kW rating may need to be higher than the motor kW rating in various situations. The VFD output current rating must also be equal or greater than the motor full-load current rating. Some motors, such as those with more than 4 poles, may have a higher than typical current rating. The nominal kW ...

7

Not just fans A lot of devices are designed this way. It almost seems standard, even though I agree it is counter-intuitive. For example, in my kitchen I have: Cooktop hood fan/light - fan goes from Off to High to Low (continuous except for switch Off) Cooktop hood fan/light - light goes from Off to High to Low (discrete settings) Cooktop gas burners - ...

6

I needed a 6 uF replacement and only found a used 5 uF and a used 1.25 uF. With the help of several answers, I decided to only install the 5 uF capacitor. The motor started fine on its own. Having assembled the pump with its pumping "blades" (extra mass) and the outer case it still started fine in my workshop. Then I re-installed the 1-inch hose and the ...

Only top voted, non community-wiki answers of a minimum length are eligible