cuky2000 mentions that 'ln', in my equation above, should be 'log10' and he is correct.
In IEEE 142-2007, it's shown as 'in'; I slipped the 'ln' in.
IEEE does a good job on their standards don't they.
IEEE Std 142-2007 "Grounding....Power Systems" has two equations [ 2.3a & 2.3b] that help define the thermal boundary for wire insulation protection based on I^2t, the initial wire temp, final temp, and wire xsect area. The equation 2.3a is I^2t/A = 0.0297ln[(Max Temp + 234)/(Initial Temp +...
I'm investigating using the subject PLC to control a wastewater treatment process. I'm planning on 20 digital I/O and 16 analog I/O and I'm trying to estimate the memory needed. The AB selection guide gives a memory of 4000 bytes needed per controller task, but I'm not clear on what constitutes...
To davidbeach,
You are correct that power doesn't change as you cross thru the starter. However, you can't use full voltage on the source side in the calculation. The "effective" value of that portion of the voltage waveform that's being "utilized" by the motor while the solid state devices are...
Thanks to JRaef, for a fundamental explanation. I was beginning to doubt my own understanding of electrical theory,since so many knowledgeable people were disagreeing with me.
The hardest thing to overcome is the concept that full voltage on the line side times the current passing thru to the...
I agree there might be some slight difference in the line and motor, but that difference is not defined by Input V*I = Output V*I.
It's easy to show how a conversion device like a transformer changes voltage and current on either side of the device and that Input V*I = Output V*I, but a solid...
I'm in a disagreement with an Engineer with a major electrical equipment manufacturer over the basics of a thyristor controlled soft starter. I am trying to calculate the voltage drop profile on the supply system during starting.
The Engineer's analysis shows the initial starting voltage at...
Response to dpc,
The utlity source impedance would be a component of Z1+Z2, but not Z0 as there is no current flowing in the ground loop on the primary side since the transformer is delta on the primary. In case of a bolted fault Zf would be zero.
A local company has approached my client with an offer to install a "device" that increases power factor to reduce KWH consumption thereby reducing utility cost. They claim that PF improvement lowers current, which is true, but that it also lowers KWH usage by the same percentage which is not...
I'd like to add to DPC's comment, which is correct. In the case of a bolted single line to ground fault on the secondary of a delta-wye transformer, which equals
3xE/(Z1+Z2+Z0), Z0 only includes the impedance from the transformer to the fault. Primary side Z0 isn't reflected thru to the...
I'm interested in getting the names of manufacturers of Supervisory Control and Data Acquisition (SCADA) equipment/systems for utility type electrical power distribution systems.
Can anyone help?
mc5w,
I respectfully disagree with your first sentence, if the wye is ungrounded. Read what "dpc" said, in essence, if current can't flow in the primary, it can't flow in the secondary. Circulating currents in the delta are all in phase. That means the wye side currents would be in phase, which...
mc5w,
What you're proposing may be correct, but that's not what I asked for. This is not something I'm planning to do, it's something that's already been done and I'm analizing it.
Several manufacturers recommend that a three phase delta-delta transformer, with the 240V secondary center tapped to serve lighting or other 120V loads, should have the 120 volt load limited to only 5% of the kva rating of the transformer because of the resulting loading caused by circulating...
With a delta-delta connection, there exists an unbalanced voltage on the secondary that results in a 'net' voltage around the secondary delta 'loop'. Normally the three phase voltages would 'sum' to zero. This 'drives' the circulating current, which is supported by the delta connected primary --...
