dje@datacube.UUCP (05/26/87)
Does anyone have experience with amplifiers driving inductive loads? I am building a small syncho system that needs to run off +12V DC. It currently uses a 400 Hz sine wave oscillator (Wien Bridge) followed by an automotive type amplifier chip (LM383) followed by a 1:4 step up transformer to get enough voltage to drive the synchros. Here's the problem. A synchros presents an inductive load. When a class A or AB amplifier drives an inductive load the current is maximum when load voltage is lowest (zero). This causes lots of power dissipation in the amplifier. This kills the batteries quickly and gets the amp *hot*. The synchros run cool as cukes. A high efficiency (switching) amplifier would be better. It only has to have reasonable performance at 400 Hz. But that sounds over- complicated. Know any simple circuits? How about a capacitor in series to create a resonant circuit? It would have to be fairly large and stable. Any drift in the L, C, or F would throw off resonance though. Any ideas? Theoretically driving an inductive load draws no power. I'll settle for less power. Dave Erickson ---------------------------------------------- ------ Datacube Inc. / /| 4 Dearborn Rd. ------ | Peabody, Ma 01960 || \| | ihnp4!datacube!dje || /|/ Human:(617)535-6644 ------ Fax: (617)535-5643
henkp@nikhefk.UUCP (Henk Peek) (05/29/87)
In article <100500010@datacube> dje@datacube.UUCP writes:
->Does anyone have experience with amplifiers driving inductive loads?
->I am building a small syncho system that needs to run off +12V DC.
->It currently uses a 400 Hz sine wave oscillator (Wien Bridge)
->followed by an automotive type amplifier chip (LM383) followed by a
->1:4 step up transformer to get enough voltage to drive the synchros.
->Here's the problem. A synchros presents an inductive load. When a
->class A or AB amplifier drives an inductive load the current is
->maximum when load voltage is lowest (zero). This causes lots of
->power dissipation in the amplifier. This kills the batteries quickly
->and gets the amp *hot*. The synchros run cool as cukes.
Put an capacitor parallel with your synchro. You can compensate your
inductieve load part and run with a very low dissipation in your
amplifier. :-) Drift of the resonant circuit does not change the
fase more then without capacitor. For the best result you must connect
the capacitor to the secundaire side of your step up transformer.
->How about a capacitor in series to create a resonant circuit? It
->would have to be fairly large and stable. Any drift in the L, C, or
->F would throw off resonance though.
Don't make a series resonant circuit: The voltage and the phase
are very difficult to controll.
henkp peek, henkp@nihefk ..!seismo!mcvax!nikhefk!henkp.UUCP