Inductive load
Inductive load
(OP)
What's an inductive load? Why should I care? What about impedance load?? Got a job to spec a variable transformer, but I"m all of a Mechanical engineer. I'm dealing with 115V to be transformed up(135V) and down (24v). Thanks..





RE: Inductive load
What does the load consists of ?
<nbucska@pcperipherals.com>
RE: Inductive load
RE: Inductive load
Now, what are you using the 24 volts for?
RE: Inductive load
RE: Inductive load
RE: Inductive load
One way of looking at inductive versus resistive loads is ...
On an inductive circuit current precedes voltage,
On resistive loads voltage precedes current.
That definition should warn you that an inductive load has the potential to strain an electrical system at the moment of energizing the circuit due to the voltage lag and high inrush current, whereas resistive loads do not produce that strain.
This high inrush feature of inductive loads therefore requires a different set of calculations and equipment to account for the starting surges, which is why the NEC has all those special rules for motors.
Richard Neff
pump@shadow.com
Richard Neff
Irrigation Craft
RE: Inductive load
RE: Inductive load
Most variable transformers are not isolated. In this application a 115/115 volt isolation transformer before the variable transformer is probably preferable.
Most variable transformer have a connection so that the output voltage can be higher than the input voltage. 115 volt input and 0 to 135 volt output is probably typical.
A WORD OF WARNING: Place a fuse or circuit breaker in the variable transformer output. Do not depend on a fuse or circuit break in the variable transformer input to protect the variable transformer or the load.
RE: Inductive load
For a resistor, current is in phase with voltage.
For a capacitor, current leads voltage, ie at swith on voltage collapses and current is high.
Bung
Life is non-linear...
RE: Inductive load
Please be careful with variable transformers and do not place isolation transformers or other inductive loads in the primary circuit. It is often forgotten that a variable transformer can also act as an auto transformer with a ratio of turns below the tap to the turns above the tap and under certain conditions this can produce several thousand volts on an open end or in other inductive circuits connected to the high end.
Hi Bung, the reason there is a high inrush current to an inductive load like a motor is because normal full load current (FLC) occurs when the back emf is established i.e when the motor has attained full speed. At zero speed the impedance is very low and in extreme cases the current can be some ten times greater than FLC.
Cheers,
G
RE: Inductive load
Using an isolation transformer after the variable transformer adds a fixed inductance, so that at low voltages, the regulation is worse, and short circuit current is less. It also allows the use of a series/parallel connection on the isolation transformer secondary allowing a greater range of voltages and currents.
Using the isolation transformer before the variable transformer makes the regulation better and short circuit currents higher at low voltages.
Whichever approach is used, don't forget the fuse or circuit breaker in the variable transformer output.
RE: Inductive load
Bung
Life is non-linear...