Electric motor ratings

Simon and Andrew have pretty much nailed it except K is absolute temperature (Kelvin), the multiplier for thousands is k (lowercase).

Ahh, VAR's some early turbine aircraft actually had VAR meters so the flight engineer could ensure limits were not exceeded.

Robert G8RPI.

To Maurice Taylor I cannot to send you a PM. However, I'm unable to read off the lower numerals on your scope trace, was the duration of the surge current about 4.5 cycles of AC, then things settled down to normal running current.of 3.9 amps. Also, was you measuring the volts drop across a series resistor to obtain the trace.John

Andrew and Robert have (rightly) marked my work and found it wanting. Thank you both for your accuracy.

In fairness I was attempting to steer clear of explaining vector arithmetic!

Robert's comment on the upper or lower case k for kilo is interesting. I know he's right, though I (obstinately) disagree with him and quite possibly the rest of the scientific world. I'm old enough to remember the debate over whether kilo should be an upper case character because all the other multipliers are upper case - e.g. Mega, Giga etc. And the lower case qualifiers are all divisors - milli, micro etc. In my opinion the small k for kilo is an anomaly better resolved by accepting the coincidence with an upper case K for Kelvin and allowing the context to resolve the conflict.

The unit of absolute temperature should have been called a Thomson, though maybe that creates a conflict with the multiplier Tera.

Who said SI units were supposed to resolve all this?

Best rgds to all

Simon

Edit - I suppose, on reflection, my usage of the term multipliers and divisors is un-rigorous, as was my initial use of the phrase "reactive power" which is an oxy-moron.  I guess a better term for Mega, Giga etc is "positive exponents", whereas micro etc are negative exponent multipliers.  Ho hum.

Edited By Simon Williams 3 on 10/01/2020 17:07:46

Hi john fletcher1,I used a current clamp Pico model TA167 with a Picoscope model 4225.

The units on the bottom are milliseconds.The large part of the trace covers nearly 100mS ,about 4.5 cycles.The peak current after settling is 5.531A 3.9 A rms.Hope this helps .

Maurice

I know he's right, though I (obstinately) disagree with him and quite possibly the rest of the scientific world. I'm old enough to remember the debate over whether kilo should be an upper case character because all the other multipliers are upper case - e.g. Mega, Giga etc. And the lower case qualifiers are all divisors - milli, micro etc. In my opinion the small k for kilo is an anomaly better resolved by accepting the coincidence with an upper case K for Kelvin and allowing the context to resolve the conflict.

One must remember that kg is not a multiple - it is the basic unit of mass - so that is the reason for the lower case ‘k’. A carry-over from the previous systems perhaps? But I expect there was a quandary of adopting the gram as the basic unit of weight (there is a problem with mass and weight if both do not have have the same equivalent base unit). There was always (well, for a long time) a standard metre and kilogram in existence, as well as a lot of standards copied from those standards.

I remember several measurement systems over my time, one being the cgs system (centimetre gram second). They all had to make some compromise or have some idiosyncrasies within those systems.

Hence it is kg, not KG. Everything else falls into place quite well using upper and lower case multipliers. But I don’t think they will ever decimalise our normal time units.🙂

Edited By not done it yet on 10/01/2020 22:41:24

Digressing a bit but reading this just made me remember the 1st computer we built. I said I want a super machine so I can run Autocad. The biggest hard drive was 250 Megabites. Motherboard supported a huge 4 Mb of ram. with a 486DX processor. My god have things changed. Imagine back then being told that a few yrs down the line you could have a micro memory card no bigger than your little finger nail that would hold 1Tb & more. You would have got locked up for insanity. Can this advancement carry on at this rate. ????. To add. Motors are not that different now than back then. I know there are fancy dc drives & electronic control etc but the old 3 phase/ single phase motors are really unchanged.

a time and motion man has a watch that uses centiseconds, make it easy to add all the increment of a task together apparently.

Mike

I never said that k made sense just that it is the standard. That said there are actually grounds for using m as the thousanths multiplier that long predate SI and the Kelvin. The terms mil (1/1000" and milli have been used for centuries.

At least with k & K it is pretty obvious which is which. With m & M it may not be clear especially in electronics. A single design may use milliohms and Megohms, millihertz and Megahertz.

Robert G8RPI.