46
votes
Accepted
Why does the current carrying capability of a cable increase with temperature
You're looking at it from the wrong direction.
The more current you put through a cable, the hotter it gets. Push too much current through, and the insulation starts to deteriorate. Wire insulation, ...
- 20k
20
votes
Why does the current carrying capability of a cable increase with temperature
Those aren't increases in capacity at higher ambient temperatures, the temperatures are the ratings for the cable.
So if the cable, terminations and equipment in your system are rated for 90 degrees, ...
- 27.8k
11
votes
what are the implications of using a 45kW ACS580 ABB VSD on a 22kw induction motor?
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 ...
- 174k
11
votes
Need help identifying component with 'T4 G4' markings
It's likely a Diodes Inc. BAV16W or 1N4148W fast switching diode in a SOD123 package.
The following marking information is shown in the datasheet.
The horizontal T4...
- 70.7k
10
votes
Why do variable frequency drives (VFDs) need so much information?
The number of poles tells the VFD the divider between electrical and mechanical speed. For example, a two-pole motor runs a bit below 60 RPS at 60Hz, but a four-pole motor only at 30RPS.
The nominal ...
- 14.4k
9
votes
Accepted
Why do variable frequency drives (VFDs) need so much information?
If the VFD is trying to do speed control and doesn't have an external speed sensor it has to try to sense the speed electrically. But electrical speed is not mechanical speed. Running one complete ...
- 57.3k
8
votes
what are the implications of using a 45kW ACS580 ABB VSD on a 22kw induction motor?
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 ...
- 99
8
votes
Why does the current carrying capability of a cable increase with temperature
That's not right. DC resistance of a conductor actually rises with temperature, which means at higher temperatures you will lose more power into heat in the cabling, which will heat it up even more.
...
- 172k
7
votes
Tesla Car "maximum torque at 0 RPM" - is this correct?
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 ...
- 174k
7
votes
Accepted
Can I run a VFD off a generator?
Two different pump salesmen have told me that running a VFD off a generator might hurt the VFD.
It's not that simple. But I can understand why the saleman says it.
It often causes problems because ...
- 24k
6
votes
Accepted
How to calculate RPM using frequency
If a motor has two poles it will rotate once per mains cycle. At 50 Hz this will be 50 x 60 = 3000 RPM.
If a motor has four poles it will rotate half a revolution per mains cycle. At 50 Hz this will ...
- 180k
6
votes
Accepted
Are there safe ways to run an induction motor rated for 50/60 Hz at a lower frequency?
An induction motor (when run at a lower speed) should have the RMS voltage reduced as frequency gets below a certain threshold. This is to stop the magnetics saturating at low frequencies. Saturation ...
- 473k
6
votes
Powering a 3 phase 230VAC motor with 28 12V batteries wired in ceries
Wow. You have multiple problems.
A '12V' lead-acid battery can have 2.2V/cell (or more) = 13.2V at the end of a recharge cycle. 13.2 x 28 = 370Vdc, so you're over the maximum input. Whilst the ...
- 4,223
6
votes
How many times of a frequency of a PWM can properly generate a sine wave to drive a motor?
In my experience as a post-doctoral researcher in motor drives, 10x fundamental frequency is generally accepted as a minimum PWM frequency. I searched the literature to find precedents for this when ...
5
votes
Accepted
Can I use a VFD to send power of a specific frequency to a frequency meter?
You can get stereo sounds synthesized in Audacity (free) and sweep each channel then playback with a PA and stepup XFMR using a stepdown wallwort.
I 've never seen these ABB historic instruments but I ...
- 148k
5
votes
Can a Variable Frequency Drive convert standard wall outlet (120V/15A/single phase) to ~220V 3 phase?
There are VFDs that will accept 115V single phase input and give you a 230V 3 phase output. They use what is called a "voltage doubler" front-end rectifier, meaning they rectify the 115VAC to approx. ...
- 3,740
5
votes
How can I convert ±10 V input to 0-10 V w/ run/stop/reverse signals?
Here is essentially @Carl's idea using a small number of inexpensive components. Up to you to convert the +/-11V signals into something your controller will accept. Below about +/-120mV (1.2% of full ...
4
votes
Accepted
Is it possible to connect a phase control relay to an inverter (VFD)?
No, this is not recommended. The output of a VFD is not suitable of any electronics except the motor, you can't even measure it with your multimeter without putting it in a special low-z (low pass ...
- 24k
4
votes
Accepted
Mega2560 master on RS485 bus stops communicating with VFD when I add another RS485 module
You (or whoever made this dubious module) have erroneously wired the transmit enable pin with a pullup resistor. Without code configuring a corresponding MCU pin as an output and driving it low, that ...
- 33.6k
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