From time to time someone will say
From time to time someone will say
(OP)
From time to time someone will say something like this about car components like 12 V DC air compressors and industrial devices driven by 120 VAC induction motors
"Use right size cables, if there is voltage drop in the cables the compressor will take the same power and compensate loss of voltage by taking more amps."
Is there any truth to such a statement ?
"Use right size cables, if there is voltage drop in the cables the compressor will take the same power and compensate loss of voltage by taking more amps."
Is there any truth to such a statement ?





RE: From time to time someone will say
As demonstrated recently by a family member who connected an ice cream freezer to a truck battery via an inverter.
With 8 gage battery cables, the compressor refused to start.
With 4 gage battery cables, the compressor started right up and ran happily.
Mike Halloran
Pembroke Pines, FL, USA
RE: From time to time someone will say
Current draw is determined by the degree that generated back emf is less than applied forward emf and, internal resistance... any external condition that causes generated back emf to drop e.g. applied load, applied voltage influence, will cause current draw to increase. The "motor effective circuit" diagram in the reference below illustrates this relationship visually.
http://www.4qd.co.uk/docs/back-emf-internal-resist...
Perhaps the simplest explanation is that a motor (as an energy transformation device) takes electrical power input in the form of voltage and current. If the applied voltage drops, and the motor is expected to drive the same load (rotational speed and torque), current must increase.. conservation of energy.
RE: From time to time someone will say
The speed of an AC induction motor is controlled by the applied frequency. If you reduce the voltage it will not slow down but will draw more current to increase torque in order to try to maintain speed.
https://www.youtube.com/watch?v=LtJoJBUSe28
RE: From time to time someone will say
TTFN
I can do absolutely anything. I'm an expert!
FAQ731-376: Eng-Tips.com Forum Policies forum1529: Translation Assistance for Engineers
RE: From time to time someone will say
Within a certain operating window, AC motors will run very close to a fixed speed (speed varies by 2-3%). So, you also get a fixed load speed, meaning the load is taking a fixed mechanical power from the motor shaft. The motor input power has to balance with the mechanical power so if you drop the voltage a bit then the current will go up a bit. But, drop the voltage too much and it all goes to crap because the motor just stalls and the load quits using any shaft power.
RE: From time to time someone will say
RE: From time to time someone will say
Cheers
Greg Locock
New here? Try reading these, they might help FAQ731-376: Eng-Tips.com Forum Policies http://eng-tips.com/market.cfm?
RE: From time to time someone will say