Electrical Engineering Stack Exchange
Electrical Engineering Stack Exchange

Questions tagged [commutation]

33 questions
14
votes
4 answers

H-Bridge Fly-Back

Sorry if this question is a little long, but I though it prudent here to discuss the state-of-the art as I know it before asking the question. ISSUE When using an H-bridge to drive a bidirectional coil of a motor etc, I have always had my concerns…
Trevor_G
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1 answer

Universal AC Motor Brush Rotation Angle

Considering adding reversing capability to a Porter Cable 690LR (router) universal AC motor for use as a spindle motor. Yes, there are better alternatives but this is to finish someone else's wood-CNC project. 120 VAC, 60Hz, 11A, 27,500RPM,…
rdtsc
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1 answer

Problems of optimal commutation depending on number of pole

I am trying to design a three phase 4 pole motor, control with six-step. My problem appears when I draw the commutation to try to see how everything work. First, with a basic three phase 2 pole, there is no problemand the switching sequence seems…
Cyril
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2
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1 answer

trapezoidal bldc control oscilloscope artefacts

I am controlling a BLDC motor (24V, 125W) with this IFX007T board controlled by an STM32L412 MCU. The PWM frequency should be around 40kHz (I have 80MHz clock, counter period of 512-1 and prescaler of 4-1). I am using the hall sensors and a…
lazerlini
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2
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1 answer

BLDC motor drive: Requires an external push to start rotating

I am trying to drive a 23-pole pair(i.e. 46 poles) BLDC motor using an LV8139 pre-drive, the output of which is fed to drive the 3 half bridge MOSFETs. I managed to connect the correct phase sequence(out of the 6) between the motor and driver. The…
shwetank vishnu
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2
votes
1 answer

SSRs influenced by physical proximity?

This is part of a two-head EVSE. The two solid-state relays are used to drive contactors that supply high current power to the vehicles. I used to use a MOC3040 based triac circuit for this job, but decided to try SSRs to simplify things. First, the…
nsayer
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1 answer

LTspice diode commutation

I have modeled an ideal diode rectifier fed from a 230V/50Hz grid with a slim DC link capacitor and a constant power load (1kW) coupled with a small resistive load. For Cdc=14uF i get a phase input current that oscillates between 0A and 8A while it…
Nikos Vandoros
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2
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2 answers

Brushless DC motor problems at high velocities

For a project we use a brushless DC (BLDC) motor. Everything works fine until we tried to reach high velocities. I will first explain my setup, and than explain our problems using some graphs. Unfortunately I don't have enough points to put al my…
ProjectM
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1 answer

Confusion in magnetic neutral plane of DC machine

I was reading book Electric Machinery by Chapman and in topic 'Armature reaction ' It is written that "The magnetic neutral plane is defined as the plane within the machine where the velocity of the rotor wires is exactly parllel to magnetic flux…
user215805
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2 answers

Why do I need two PNP BJTs as a switch rather than only one?

As far as I know, the circuit into the read circle works as a switch. I would like you to help me to understand how does the circuit works as a switch and why I need something so complicated instead of a simple circuit with one BJT only. Also, why…
Stefano Fedele
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4 answers

How to make an audio 5.1 switch?

I'd like to make a 5.1 audio switch to enable my 5.1 audio system (+mic+headphones) to be available for any of the 4 computers it can be connected to. So I guess I would have : INPUT : 4 (computers) x 5 cables (x2 wires (stereo) ?) - 5 cables are 3…
Oliver
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1 answer

What is the effect of no-current periods in commutation on output power of a PM DC motor?

I have made a PM DC motor. This motor works on a unique magnetic circuit. This motor can work very well at different input levels. When it uses an input of 5.915 volts*3.5 Amperes=20.7025 Watts, its output is 8.85 watts. In this motor, 30% part of…
Umer Farooq
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2 answers

PMDC motor: how much is voltage reduced if the resistance produced by commutation system is eliminated?

I have made a PMDC motor. The resistance of the coils is 0.25 ohms. But the commutation system is very resistant. It adds more 0.85 ohms to the armature resistance. So, the total resistance becomes 1.1 ohms through the commutation system. The motor…
Umer Farooq
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1
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1 answer

Why do the polarities of the capacitor change while discharging?

I was going through the working of class D commutation and the article said: As soon as the capacitor completely discharges, its polarities will be reversed but due to the presence of diode the reverse discharge is not possible.  Why does the…
penguin99
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Is zero loss turn-off possible for thyristors?

Consider this very basic circuit: simulate this circuit – Schematic created using CircuitLab Don't mind the values - they don't matter, as this question is conceptual. Imagine that Vcomm is completely controllable, and ideal for the example's…
CaptainFantastic
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