Timeline for How exactly does the inductor in an LC filter reduce motor noise?
Current License: CC BY-SA 4.0
12 events
| when toggle format | what | by | license | comment | |
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| Dec 8, 2021 at 18:35 | answer | added | Jasen Слава Україні | timeline score: -2 | |
| Dec 8, 2021 at 16:34 | comment | added | Drewster | @Andyaka added... | |
| Dec 8, 2021 at 15:03 | history | edited | Drewster | CC BY-SA 4.0 |
added 266 characters in body
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| Dec 8, 2021 at 8:07 | comment | added | Andy aka | Schematic please. | |
| Dec 8, 2021 at 5:32 | comment | added | Kartman | @Drewster, i fixed up the ‘inductor’ on the source - shorter and fatter tracks. If you suspect the pcb, then modify it by adding wires or capacitors across the suspect tracks. Having no gate stopper resistor would make the issue worse. If you had problems when adding a 1Ohm gate stopper, then that suggests you have other problems. 1Ohm should add a few nanoseconds to the switching time of the mosfet. If the circuit is that sensitive, then there’s other issues methinks. Substitute a resistive load instead of the motor and see if the observed issues change. | |
| Dec 8, 2021 at 3:51 | comment | added | D.A.S. | The driver source impedance will have Coss capacitance with low RdsOn but R rises quickly when the driver goes into CC mode which performs better. You need to specify the driver and settings, otherwise your question gets lost in the "noise". Everything needs an impedance spec. to model it from DCM to CCM to Voltage source and fix it from diff LPF to CM choke to cable type and snubber type. Got it? The diff chokes need to be more like 1% of motor inductance and RdsOn same~ 1% of motor DCR. My guess DCR is 0.5 ohm | |
| Dec 8, 2021 at 3:02 | comment | added | Drewster | @Kartman yes this is being done with a spectrum analyzer. What specifically did you change on your low side FET? This isn't a board I laid out, so there's a lot I would do differently... | |
| Dec 8, 2021 at 2:56 | comment | added | Kartman | I had a similar problem with a low side mosfet switch. Due to the inductance of the source wiring, i’d get bursts of around 70MHz when it turned on. So have a close look at your current paths and view every wire as an inductor. An inch or so is all that is needed. Make yourself a little sniffer loop as a probe for your scope and go sniffing. The results might surprise you. Having a spectrum analyser makes it easier. | |
| Dec 8, 2021 at 2:43 | comment | added | D.A.S. | Link motor specs and load current limits along with cable type and scope 10:1 probe gnd length SVP, for a better answer! | |
| Dec 8, 2021 at 2:35 | answer | added | D.A.S. | timeline score: 1 | |
| Dec 8, 2021 at 2:32 | answer | added | R Dent | timeline score: 0 | |
| Dec 8, 2021 at 2:22 | history | asked | Drewster | CC BY-SA 4.0 |