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Questions tagged [back-emf]

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2 votes
3 answers
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Why inductor don't discharge completely even when the duty cycle is 50%?

1] My simple buck convertor circuit description I made this buck convertor on my breadboard- Falstad simulation The battery voltage is 12 V And the MOSFET is a N-channel enhancement mode MOSFET The ...
in.yssh's user avatar
  • 45
0 votes
1 answer
27 views

Supply voltage of BLDC motor increases during operation

I need some clarity on an issue I have been encountering with my BLDC motors.I am using 2 integrated driver BLDC motors to drive an RC truck sort of device, they run on 24v. For the most part it ...
Aman P's user avatar
  • 1
2 votes
1 answer
81 views

Back EMF & Efficiency of a BLDC Motor

So I've recently designed and built a 3 phase, coreless, brushless DC synchronous motor. I'm trying to estimate its efficiency but struggling to figure out the equations. Specifically, how back EMF is ...
persona679's user avatar
1 vote
2 answers
38 views

How to protect N-type mosfets in parallel againt back EMF of a transformer

I saw this schematic on a blog and I tried building it but always burns some of my mosfets. I am using the oscillating and driving part of this schematic with the exception of the battery charger part....
Kumah Andrews's user avatar
0 votes
3 answers
92 views

555 Timer for Motor Direction Control

I am building a circuit to control the direction of a DC motor using two 555 timers. The circuit diagram is given below. There will be a potentiometer and when it is turned to the rightmost position, ...
Kailash Kumaravel's user avatar
0 votes
1 answer
104 views

Debugging BLDC gate driver, unexpected back EMF waveform

I'm debugging an electronic speed controller I designed that uses a 3-phase gate driver, DRV8300DRGER, to control BLDC motors. The circuit is shown here (the 2 other phase aren't shown) with the ...
ken's user avatar
  • 31
2 votes
3 answers
115 views

What are the potentials at front and back of inductor when primary DC supply is disconnected in LR circuit?

I have been learning the basics of inductors in simple LR circuits with DC currents. I think I get most of it but I am a bit unclear about the secondary EMF produced by the inductor after the primary ...
steveOw's user avatar
  • 123
0 votes
1 answer
220 views

Relation between back emf and flux linkage

I've encountered a problem when trying to figure out my Electric Machine homework. In the homework's answer, it said that the back emf of a DC motor is equal to the speed of the motor times the flux ...
xinzhi Wei's user avatar
3 votes
1 answer
224 views

How to dissipate regenerative energy from a 400w brushless spindle motor connected to a 10-pound flywheel

I have a project where I have a 10-pound flywheel being spun up by a 48v 400w cnc spindle brushless motor at 5000 rpm, using a WS55-220S motor controller. As such, when the power to the motor stops ...
Tivity's user avatar
  • 161
0 votes
1 answer
290 views

How to find the back-EMF constant of BLDC motor from a motor technical data?

I have a BLDC motor with these info (please don't pay attention to the striped column): How from these info, how can I get the Back-emf constant ? Is it just 36V/4krpm = 9 V/krpm ? Thank you a lot.
Classy Fied's user avatar
0 votes
0 answers
46 views

Sensored Brushless DC Motor Back EMF Problem

I am working on the current control of a BLDC motor with a speed of 12000rpm. The current controller in the system is designed as PI. I give a reference value of 10A to control the motor and the ...
G. G's user avatar
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0 votes
0 answers
37 views

Sizing MOSFET VDS to account for Stepper Back EMF

I'm having difficulty conceptualizing how the Back EMF of a motor, stepper in this case, can damage an H-Bridge MOSFET if the Vds aren't sized correctly. My main issue is my understanding of how the ...
Lpaulson's user avatar
  • 305
0 votes
1 answer
117 views

Electric Shock off spinning motor

This large blower powering an inflatable structure has no on/off switch, requiring the actual power plug to be disconnected to power down the item. I frequently get a painful shock off the plug, and ...
MarktheSpark's user avatar
1 vote
1 answer
187 views

Circuit to measure back EMF around an H bridge

I want to design a circuit with an H-bridge to control a brushed DC motor. In order to control its speed, I want to measure the back-EMF of the motor and make a PID control loop in software. I do not ...
bask185's user avatar
  • 616
3 votes
3 answers
1k views

How can I clamp the voltage precisely from the back EMF of a brushed DC motor?

I am using DRV8412DDWR in a medical product, where we are driving two DC motors (graphite brushed) bidirectional using PWM. In our application, we have to suddenly stop the motor. When we do that, we ...
Nice Guy's user avatar
2 votes
3 answers
188 views

Bulk capacitor sizing to protect H bridge during motional EMF

I'd like to drive a 30 V motor with this H bridge driver and an Arduino. The problem is that on top of working in forward motoring and reverse motoring conditions, it will also work in forward braking ...
Guillaume D's user avatar
1 vote
2 answers
68 views

Voltage behaviour in battery-powered vehicle when motors regenerate

I am wondering how the voltage in a battery powered vehicle will behave in case its BLDC motors are acting as generators (i.e. while decelerating). In a system powered with a DC/DC converter for ...
l.voe's user avatar
  • 52
1 vote
4 answers
554 views

If you put a polarized capacitor parallel with a coil, can you leave the flyback diode out

I want to set a relay when an object passes an IR sensor. The IR sensor controls the NPN transistor which powers the relay coil. It may be that the passing object has some holes which allow the IR ...
bask185's user avatar
  • 616
0 votes
0 answers
62 views

Troubleshooting a force feedback wheel with a DC motor that resets when blocked from rotating in a specific direction

I am troubleshooting a electronic force feedback steering wheel (Fanatec Porsche 911 Turbo S Wheel) that uses a DC motor for force feedback. The wheel restarts every time force feedback is activated, ...
Roy Meijer's user avatar
0 votes
3 answers
190 views

About the I1N1 = I2N2 equation

I have a silly question about this equation which is very frequently used in ideal transformer relations. If I draw the electrical equivalent circuit of the core, then the MMFs of 2 coils N1I1 would ...
Aniket sen's user avatar
1 vote
1 answer
146 views

Is back-EMF an issue in a push-pull converter when both driving transistors are off?

For reference, I am talking about a conventional push-pull converter topology as discussed e.g. in this question. Wikipedia has the following to say about transistor timing in the push-pull converter (...
tobalt's user avatar
  • 22.5k
2 votes
1 answer
1k views

BLDC back-EMF zero-crossing detection using comparators: resistor confusion

I am building a sensorless BLDC driver development board using an RP2040 chip and I plan on detecting the back-EMF using comparators. After reading quite a bit about the BLDC phases and methods to ...
vm1988's user avatar
  • 59
1 vote
1 answer
255 views

Does Back EMF change according to stator current in SM?

The concept of Back EMF always confuses me in Synchronous Machines. If I have a synchronous machine and I manually rotate at "x" rpm, do I get the same back EMF as when I excite the stator ...
Zelreedy's user avatar
1 vote
2 answers
323 views

Free wheeling (back EMF) diode for latching relay

I'm designing a circuit to drive a single coil latching relay. This uses two MOSFETs, arranged so current flows one way through the relay coil to switch it on, and then the other MOSFET activates to ...
David Moorhouse's user avatar
0 votes
2 answers
211 views

Understanding back EMF current in DC

I am trying to make a kicker solenoid. My circuit is: 12 V battery connected to DC step-up booster 300 V diode A10A. The diode is rated for 10 A and 1000 V. thyristor BTW69-1200 with external ...
Tito's user avatar
  • 465
8 votes
4 answers
2k views

Switching inductive loads without flyback diodes

I came across a commercial design which switches coils using N-channel MOSFETs (two in one MOSFET in a SOIC package). It surprised me a bit that there were no flyback diodes in parallel to the coils. ...
bask185's user avatar
  • 616
1 vote
1 answer
693 views

H-bridge back EMF

I've built a H-bridge circuit to control a brushed DC motor. A schematic of the H-bridge is shown below: When designing the H-bridge I didn't add any diodes in parallel to the MOSFETs as I had ...
Andrew Lees's user avatar
0 votes
0 answers
99 views

Coil abrupt discharge BEMF amplitude

My goal it to understand and attain the highest voltage possible for an amateur experiment. Can't find specs on BEMF properties, only that it's a "dangerous spike" on the instant a switch ...
juanmf's user avatar
  • 135
0 votes
0 answers
124 views

Circuit protection from voltage spike

In order to suppress the voltage spike getting from an AC single phase motor (it is an exhaust type fan connected to 10 A relay) can somebody please guide me to select a proper protection device. To ...
KOmkar 's user avatar
0 votes
1 answer
437 views

EveryCircuit-Simulator Specific shortcomings

Just sent this to EveryCircuit ...
juanmf's user avatar
  • 135
1 vote
1 answer
845 views

How to get the back EMF graph of my BLDC motor in an oscilloscope?

I have a BLDC motor and its controller. How can I see its back EMF graph using an oscilloscope provided I can see the phase-to-phase voltage graph?
Vijay Anand. R's user avatar
3 votes
3 answers
3k views

How pick/calculate flyback diode current value?

Say I have a design that switches a 5A coil using a MOSFET. In order to protect the MOSFET, I place a flyback diode parallel over the coil. If the coil is switched off, a back EMF current will flow ...
bask185's user avatar
  • 616
1 vote
1 answer
509 views

Why use only one comparator for back-EMF (ESC build)

I’m working on an esc project. I’ve got the motor spinning by just using a timer to switch the phases on and off. Now I’m trying to include circuitry for BEMF reading. I was watching a video from ...
BigChungus443's user avatar
4 votes
1 answer
335 views

4-20mA ADC, HV DC measurement & DC/DC PSUs schematic validation [closed]

Hello i am designing a small Li-ion battery charger based on an custom generator which produces 36v DC output and i have designed a PCB that controls the whole procedure and logs the measured data to ...
geocheats2's user avatar
1 vote
1 answer
321 views

Will a flyback diode damage my battery due to back EMF?

I am following this example of a sensored BLDC motor. This post assumes conventional current flow. I am trying to understand how the diodes in this circuit protects the rest of my circuit from back ...
Trev347's user avatar
  • 1,072
1 vote
1 answer
198 views

Will primary flux & secondary flux (back MMF) in a transformer attract or repel each other?

I couldn't find it on google or may be I am not using the right keywords, if my terminologies are not sounding accurate, please bear with me, I am beginner in electrical engineering. When the primary ...
Yogie's user avatar
  • 129
1 vote
2 answers
318 views

Why does the signal and power supply in my custom ESC breadboard become so noisy when the motor is rotating?

I am building a custom ESC to drive my BLDC motor. The motor spins in open loop and I want to debug the back-EMF detection circuit, but as soon as the motor spins, the signal line of the MCU (MCU uses ...
Edmond's user avatar
  • 23
1 vote
1 answer
281 views

DC Motor Design Question - Bypassing Back-EMF

I'm not gonna lie - I don't have enough knowledge about EMF and Back EMF so I need you guys. My friend will soon build a DC motor for me but I currently have no idea what design will produce high ...
lidorov19's user avatar
0 votes
1 answer
158 views

Question - LC Tank - Resonance , Duty Cycle , Back EMF

I was wondering about that for some time now but didn't have the time to try it myself , maybe some of you guys will help me out with this question : What happens when LC Tank is operated in its ...
lidorov19's user avatar
1 vote
0 answers
74 views

If I use a DC motor as a generator, would the output current be AC or DC [duplicate]

I am thinking of using a DC motor as a generator for a toy, but I am unsure if I need to do a full wave rectification if the output current is AC.
TheRavenSpectre's user avatar
0 votes
0 answers
89 views

Feedback from a 100 W laser power supply

I built a 100 W laser cutter from scratch using a controller from a small laser cutter I had before (Open Builds Blackbox 4x). It worked with no problems, but I'm going from a 7 W laser to a 100 W ...
Michael Suits's user avatar
0 votes
1 answer
773 views

Why does slow decay decelerate a motor faster than fast decay does in a H Bridge?

I understand how the terms slow decay and fast decay relate to current rather than angular acceleration, but I am currently having a lot of trouble understanding why slow decay decelerates the motor ...
Jayson Meribe's user avatar
7 votes
4 answers
2k views

Do I need back EMF protection for a small brushless cooling fan?

I am designing a PCB, and I want to add cooling to the project. To accomplish this I have added a connector for small (40mm x 40mm) brushless cooling fan that will draw off an existing 12V supply from ...
flimsy's user avatar
  • 362
0 votes
0 answers
60 views

What could be the cause of a limit in the voltage supplied to a capacitor?

Recently I built a very basic 2-stage coil gun for a school project. Each coil was powered by an electrolytic capacitor. In order to charge the capacitor, the coil connected to an IGBT (insulated-gate ...
Tristan Brown's user avatar
0 votes
2 answers
4k views

How to calculate torque constant and back EMF constant of a BLDC motor?

I have a BLDC motor to run for a fan. The parameters are as follows: Electrical frequency measured: 61.936 Hz Pole pairs: 8 Line voltage measured: 70.365 V RMS Line voltage peak: 99.51113732 ...
sukhbir1996's user avatar
0 votes
2 answers
1k views

Confused about back EMF protection in maglock circuit

Straight upfront...electrical engineering is not my forte. However, I am trying to help a client with a particular issue and I'm hoping this community can provide some invaluable insight. They have a ...
RMR's user avatar
  • 1
4 votes
3 answers
1k views

Weird speed issues with brushed DC motors in parallel?

So I have a simple system where I want to run eight large DC brushed motors (for wheels) in parallel, which should give them all the same voltage, and they should independently change rpm depending on ...
MCA's user avatar
  • 49
1 vote
1 answer
379 views

Back-EMF Concepts (Confusion)

I am trying to understand the current and EMF relationships in a brushless motor. Can someone tell me if this explanation is correct? Specifically, I'm interested in what is happening as the rotor ...
mrbean's user avatar
  • 812
7 votes
4 answers
963 views

Fast coil decay

I have circuit where I need to fire electromagnetic actuator fast. If I need to go faster strike I need to increase voltage. But what about freewheeling inductor energy. In circuit A the energy is &...
eSlavko's user avatar
  • 171
0 votes
1 answer
180 views

Why is one of my MCU (Bluepill) digital pins broken/not working?

Sorry for the noob question. I'm working on an ESC circuit, first I want to work on a very simple ESC circuit without Back-EMF detection like in this video https://www.youtube.com/watch?v=kAaknXe_JSk&...
Ujanderas's user avatar