Siemens WD14H421GB Washer-Dryer Doesn't Spin

[Andy Burns]

The engineer said my hotpoint washer/dryer (post indesit/ariston takeover) uses a 3-ph motor driven by a VFD.

[The Natural Philosopher]

almost the same. Its a very moot point as to when a multipole 3 phase motors ceases to be a 3 phase motor and becomes a stepper motor.

[Tweed]

My Miele washing machine, being Germanic, lights a ?hygiene? indicator if it has done too many low temperature washes without a hot wash. My old Bosch washer ended up getting black mould being imbedded in the door seal which would never shift. So with my Miele I now run it occasionally at 90 degrees C with a bottle of Aldi washing machine cleaner. The machine is as shiny and clean as the day it was purchased.

[Yellow]

On Thu, 23 May 2019 17:55:51 +0000 (UTC) Tweed [e-mail] posted:

Wiping the seal and rinsing the soap drawer, especially of fabric conditional, after every day's use pays dividends too.

My Bosch is 4 years old and sparkles for that 2 minutes of attention.

[Woody]

The hot wash does, to some extent at least, alleviate the 'black-spots-on-the-door-seal' problem, but not completely. HG do a mould remover which is very effective. There is also a powder product that you use to do an empty hot wash and it not only removes the black spots, it also shifts all that gunge that liquid washes at low temps produce (see my earlier.) Magic stuff but I can't remember the name of the **** stuff!

[Andrew]

So, a bit like rural broadband delivered by overhead lines, where the phone is never actually used. Ringing the landline number every so often, sends the ?60 volt ringing pulse down the line and helps to prevent cable joints going high-resistance.

[Woody]

Usually 50V 25Hz a.c.

[charles]

no. usually 33Hz and less that 100v. The safety elf doesn't like 240v,,

[Johnny B Good]

There's a very strong distinction between those two motor types. I believe what you may have had in mind was the very fine distinction between permanent magnet BLDC and three phase synchronous motors where the distinction *is* very much finer.

A three phase synchronous motor (regardless of pole pair number) when carefully designed, should ideally exhibit no 'cogging effect' as it is manually rotated. Perfection in this regard is hard to achieve so some cogging effect is still likely to be observed with such a test.

The endearing characteristic of a true three (or poly-phase) motor (whether of induction or synchronous type) is the constant torque output throughout each revolution once up to speed (no torque ripple).

Three phase motors designed to be driven directly from a 50 or 60 Hz supply run at just the one fixed speed which is fine for most industrial processes and those domestic applications where variable speed is not required (fan motors or pumps).

Of course, this leaves the issue of getting them up to speed on application of mains power which is solved by star to delta switching of the windings in large industrial machines along with current limiting resistors (smaller domestic sized machines forego the complexity of star to delta switching, relying on current limiting resistors alone).

Such starter gear complexity only has to deal with the relatively infrequent nought to 3000rpm speed changes, allowing the current limiting resistors used to be rated for a short term, non repetitive duty cycle.

Until semiconductors became available that could cost effectively use high frequency switching of the voltages and currents required to drive a high voltage DC to three phase variable voltage and frequency inverter, it hadn't been practical to use three phase motors for variable speed applications such as domestic washing machine drum drives.

Today, such VFD control modules and associated sub HP rated three phase multi-pole pair drum motors are becoming an ever more common feature of the modern domestic washing machine.

Whilst even today, after a decade or more since they first started to appear in high end white goods, they are still an expensive option. However, they're beginning to become more commonly featured in high end fridge freezers as ultra quiet, high efficiency surge free starting compressor motors (which is useful for anyone looking to provide power from a small emergency genset during a power blackout - what's not to like about a VFD motor, other than their rather high price premium?).

Getting back to the VFD three phase motor's close cousin, the permanent magnet (is there any other type?) BLDC motor driven by an ESC (electronic speed controller) from a DC supply, torque delivery in this class lacks the smoothness of a true three phase motor since only two of the three phase windings are actually being driven at any one time by the controller.

Obviously, this is no great detriment in their typical usage or else they wouldn't be so widely deployed as high efficiency alternatives to the classic DC brushed motor used in battery powered cordless drills, screwdrivers, chainsaws and drone prop motors.

In the latter case, this allows each of the three windings to provide a back emf zero crossing signal in turn to drive the commutation switching circuit in the 'sensorless' ESCs used with drone propeller motors.

This 'sensorless' technique whilst fine with propeller or fan loads, isn't suited to BLDC motors driving gross mechanical loads such as drills and starter motors since it relies on the motor to actually be spinning to generate the commutation sensing signal, the timing of which is critical to the smooth and efficient operation of such motors.

To achieve the starting reliability and smooth running of a traditional DC brushed motor, a BLDC motor's controller requires an accurate mechanically synchronised signal independent of speed which works even when at a standstill (startup or stalled by the load).

With the more traditional design of BLDC motor, this is achieved by the extra complication of a trio of Hall Effect sensors, precisely aligned for maximum efficiency during their manufacture, making them more expensive.

However of late, AMS have produced a neat alternative solution[1] which can trivially be retrofitted to any three phase alternator whether permanent magnet type such as used by emergency inverter gensets or separately excited as in an IC powered vehicle's alternator, neatly converting them into a BLDC motor (a lightweight solution to upgrading a pull cord only start emergency inverter genset to electric start for one instance).

Although the BLDC motor has a 'cogging' characteristic more akin to that of a stepper motor, the difference in this case is that it's an undesirable side effect best minimised by design whilst in the stepper motor case it's a desirable effect best maximised by design. Also, the major difference between the two motor types is that stepper motors are normally a two phase design and the BLDC motor is always a three phase one, more akin to that of a traditional three phase AC motor.

[1] For the more curious amongst you, there's an in depth article covering the subject of BLDC control at this web address:-

HTH & HAND! :-)

[Woody]

Sorry Charles, wrong.

In the UK in the days of Strowger the ringing frequency was 17Hz but when Crossbar and electronics came into the arena it went to 25Hz where it stays to this day. Voltage is nominally 50Vac but it is quite normal for this to be as high as 70V - indeed that is the voltage offered by most VoIP ATA units.

[Woody]

Hmmm. In that case why does the motor of our Miele washer do 15000rpm when spinning?

[Bob Eager]

It is in fact nominally 70v for ISDN lines.

[Vir Campestris]

Why can't the manufacturing process include a calibration step for the actual location of the sensors?

In fact the controller ought to be able to self calibrate as soon as the drum is spinning at any reasonable speed.

Andy

[Vir Campestris]

It probably doesn't. Did you mean 1,500 rather than 15,000?

Andy

[The Natural Philosopher]

Lets see,

50v. Less than 100V. Check 25Hz well not far of 33Hz. Check

In fact in the UK its 20Hz and 90V RMS.

[Andy Burns]

BT SIN 351 says 20 to 26Hz at 40 to 100V

[tabbypurr]

I don't know any belt drive WM motor that does 1500rpm. 15k is more typical.

NT

[Woody]

No, confirmed from the senior tech who came to replace the belt under warranty that it does 15000rpm - probably why it whistles. I would believe it as well given the motor pulley is only about 3in across (if that) but the drum pulley must be well over a foot and the machine will spin at 1600rpm.

[The Natural Philosopher]

15,000 RPM is fairly low for small electric motors.

Some of the ones dentists use are over 100k.

In model planes, 15,000 wont even get a ducted fan out of bed.

And yes we are talking horsepower level motors

[Steve Walker]

It is quite typical of a washing machine for the motor to have no pulley and instead just have multi-v grooves machined into the motor shaft - about 1/2" to 3/4" diameter.

The pulley on the back of the drum is typically about 18" diameter.

Using the larger drive shaft size, the ratio is: 18":3/4" which equals 24:1.

With a spin speed of 1600rpm, that means a motor speed of 38400 rpm.

SteveW