# Tag Info

8

In a standard sensorless ESC, changing the throttle command to it changes its output PWM duty cycle, and so the mean voltage, delivered to the motor. Typically, 1mS corresponds to 0% or zero voltage, and 2mS corresponds to 100% or full voltage. The ESC continues to automatically commutate the motor as it turns, using zero voltage sensing on the un-energised ...

7

Does changing the throttle change the duration of the trapezoids? Not directly. The duration of the 'trapezoids' is determined by commutation, which is synchronized to the rotor position. The motor will rotate at the speed it wants to, determined by the applied voltage and torque load. The controller must respond to this by commutating at the same speed and ...

4

Not many brushless-DC motors have different d- and q-axis inductances; the only time you will find this is in a salient-pole PMSM (permanent magnet synchronous motor) with buried or interior permanent magnets. D-axis ("direct") refers to the component of the stator magnetic field that is in phase with the rotor magnetic field. Q-axis ("quadrature") refers to ...

4

Separation of functions. 1) The ESC sees the incoming servo pulses, and decodes their width to a value describing the desired speed (usually 0 to 100%). 2) This is translated to a desired PWM duty cycle (0 to 100%) at the PWM rate, which is unrelated to the trapezoidal motor drive waveforms, and usually much faster. 3) The details will vary between ...

4

The efficiency of a DC machine will be similar whether working as a motor or as a generator. Why not identical? Another way of expressing efficiency is the power loss of the machine. The main power losses are ... a) $I^2 R$ losses in the copper windings b) Wind resistance between rotor and stator, and friction in the bearings c) There will be a bunch of ...

3

The generating efficiency should be the same as motoring efficiency under the same operating conditions. It may be a little difficult to determine that the operating conditions are the same. When operating as a generator, some of the mechanical driving power goes directly to supply the mechanical losses of the generator. When the machine as acting as a ...

3

Motor/generators have a k1*V/f transfer function when coasting and when accelerating or braking have a force transfer function of k2*V/DCR. Since motors are designed to do work they may be >90% efficient but carry a lot on stored energy from the inertial load which can be far greater than the Joules stored in the motor itself. So the duty cycle of ...

2

In a modern AC motor drive such as depicted in that document, the input power supply passes through a full-wave bridge rectifier and is used to charge a high voltage DC capacitor bank from which the drive electronics then synthesize variable frequency and voltage 3-phase waveforms. Higher power industrial versions may rectify a 3-phase input, but the idea ...

2

In my experience (with my own FOC design) $\theta_{offset}$ errors primarily affect torque efficiency and bandwidth, and have a lesser or insignificant effect on vibration and audible noise. Small valued errors will result in 'lopsided' performance, where your motor spins faster in one direction than the other.

2

Tune kpq Tune kpd Tune kiq Tune kiq # typo... expecting to see kid Why do you feel the need to tune D and Q separately? D-component is non-torque producing current which manifests itself in the ABC reference frame as a phase shift. Why is this important? well it depends on whether you intentionally require D-component or not... If for ...

2

Some quick notes: I'm not certain from your description what exactly you're measuring (e.g. where is scope ground, where is scope probe) in the circuit. I think 5.15 is across the drain-source of Q2 (low-side MOS) Your GaN FET part number returns 0 hits on Google, and looks a bit more like an EPC device instead of Infineon. Maybe an EPC2014? I can't really ...

2

There are two magnetic fields, a stator field and a rotor field. Torque is developed due to the attraction and repulsion forces between the two fields. The energy is supplied through electric current in the stator field. The stator is designed so that its field does not cause the rotor field to deteriorate. If that field is allowed to become too strong, the ...

1

In a BLDC motor, the windings are concentrated on salient poles, so producing a voltage waveform that's more trapeziodal than sinusoidal. In a PMSM, the windings are distributed over several poles, so producing a voltage waveform that's more more sinusoidal. These differences mean that BLDC motors are slightly cheaper to produce, but may be slightly less ...

1

Regarding your first query you cannot just choose any curve you like to calculate mmf. The mmf here is due the conductor so you have to include it in the curve while applying ampere's circuital law to calculate mmf due to that conductor. And the 0 is all about chosen reference. Here the maximum of fundamental mmf waveform is chosen as 0 arbitrarily. If ...

1

The PM has to be magnetised in a such way that BEMF is sinusoidal. Therefore the flux density is not even on the whole surface area. This makes the difference when the magnet is passing over the slot gap. A minimal saliency is almost inevitable.

1

You are correct ! Burried magnet change the permitivity distribution inside the rotor. Thus depending on the arrangement of the magnets, asymetrising its direct and quadratic inductances. Look at this post: Explanation of Lq, Ld and how it relates to motor inductance And this paper (if you can): https://doi.org/10.1109/emobility.2010.5668074

1

Please note that PMSM stays for Permanent Magnet Synchronous Machine, which means that stator flux has to be in synchronism with rotor flux, therefore the frequency is the same. Only the phase angle may vary, but not the frequency.

1

For a simple motor with a two-pole armature, if $\theta_A$ is the armature angle, and $\theta_S$ is the stator's electrical angle, and a motor with a sinusoidal back-EMF, then the torque is going to be $k_T I \sin \theta_A - \theta_S$, where $k_T$ is the motor torque constant and $I$ is the armature current intensity. So if the motor is turning a ...

1

The maximum ringing of a mismatched driver depends on the series L/R ratio which is maximum when R is lowest in the ON state R=RdsOn + DCR You must define your goals for current, temp. Rise, and settling time to avoid shoot-thru or the margin to that failure mode from dead-time. then a solution may be chosen. There are tradeoffs between ringing, ...

1

Both {BLDC, PSMS} have PM on rotor, but the difference is the distribution of stator windings. BLDC's are cheaper, better slightly more transient torque, when you do not need any precise position control unless you have a position encoder feedback then other specs determine which is better like EMI, THD, current crest factor, but generally any Sine wave ...

1

PMSM and BLDC are almost identical, except the one outputs sine wave back EMF while the other trapezoidal back EMF, respectively. VESC is a more broad abbrevation for a moto speed control. A BLDC usally uses six-step commutation technique with the use of hall feedback sensors, or it can be sensorless with the help of back EMF sensing. At each time only two ...

1

If you have your $i_d$ and $i_q$ currents, you can perform the inverse Parks-transformation (thus you obtain the $i_\alpha$ and $i_\beta$ currents) and subsequently the inverse Clarke-transformation. Then you have the three sinusoidal currents $i_a$, $i_b$, and $i_c$, which have the same amplitude and a phase difference of 120° to each other. ...

1

In normal specified use, the permanent magnets in a PM motor retain 100% of their field. There are several ways to reduce the field of the magnets, all involve abusing the motor beyond its specifications. The first is to deliver excess current. The current in the armature generates a field in a direction that opposes the field of the permanent magnets. ...

1

I guess, your motor has rotor of uniform shape and have glued permanent magnets. There is a certain problem detecting the rotor position for the sensorless method, as it is takes the advantage of the reluctance paths of the internal PMSM (I-PMSM) which has a "buried" permanent magnet in the stack laminations. Your motor is probably SM-SMPM which has surface ...

1

Usually the microcontroller need to communicate with the outside world (beyond the VFD output stage), so you need RS-485, USB, analog input 0-10V, LED or LCD display, membrane keyboard and other things connected to the microcontroller. It's also useful for EMC reasons (susceptibility in particular) to have the micro at ground potential (at least for AC). ...

1

It is rather hard to think of such a system without carving out a shaft position/velocity estimator as a separate concept whose properties you can adjust independently of the other components. The estimator would update the position/velocity estimate each time you update the control loop. The inputs to the estimator are passage of time (e.g. control loop ...

1

can FOC even work for BLDC without an encoder but just with Hall sensors? You have an encoder, it just doesn't have very high resolution. But how to increase it? Once you know how fast the rotor is spinning (time between Hall sensor signal changes) you can predict intermediate angles. If motor speed is changing then the prediction will be off, but you ...

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You do not need to solve the set of equations to linealize them. You can read more about it in here: https://en.wikipedia.org/wiki/Linear_approximation https://en.wikipedia.org/wiki/Linearization

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Yes, but only if the controller allows it. Stall current is usually much higher than normal operating current, so the controller may limit startup current to avoid blowing things up. Yes. Speed is directly proportional to voltage. Yes (if you ignore 'iron' losses, which are usually a small proportion of total power consumption). Maximum power output is ...

1

No, as long the driver can supply the rated current, the torque is the same. The resistance is pure loss, the current regulator has to apply more voltage, since the back EMF voltage at zero speed is zero, then it should be no problem to supply the rated current at start (n=0). Yes, as the V_BEMF rises when motor is turning there is no longer possible to ...

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