# Dishwasher Motor 3 phase star, triple coil construction - how to run?

#### Tonyr1084

Joined Sep 24, 2015
7,454
OK, if that doesn't confuse you, I'm coming here with a new thread to keep things straight. On another thread I'm trying to figure out how to run a 3 wire air pump motor. See that thread for more info there. It's part of a pond project I want to undertake this year.

Part of what I'm doing and the reason for THIS thread is to figure out the best way to run a water pump for filtration of said pond. The motor is a three wire motor, one in which I have access to the star point (that's what I'm calling where all the coils are common). The three contacts, I'll call them "X", "Y" and "Z". When powering from a 12V SLA battery the motor will clock to one of three positions per set of contacts. That is to say that XY will rotate the motor to one of three positions. When powering XZ the motor will clock to the next position, and YZ will move it to yet a third position. The same thing occurs when I reverse the polarity, giving a total of six primary positions for a total of 18 positions total. Obvious to me is that when in one position and moving to the next then the next, when I reverse polarity it moves the same three steps further for the total of six positions. When the whole cycle repeats the next closest position for the motor to likely turn to is the seventh position. 7, 8, 9, 10, 11, 12. When the whole cycle is repeated for a third time the motor rotates again to the next set of six positions; 13, 14, 15, 16, 17 and 18. Once again, repeating the cycle starts the whole thing over again. I've drawn a diagram of what I believe how motor is constructed. DISCLAIMER: I'm no motor expert. Bear with me if I'm using incorrect terminology or wrong drafting models.

The whole intent of this thread is to learn how to drive this motor. It may be running on 24VDC, but so far I've tested it with 12VDC (SLA battery). I've seen YouTube video's, but with all things YT, I'm dubious of the outcome of repeating projects seen there. Your input is greatly appreciated.

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Joined Jul 18, 2013
27,601
Sounds like a BLDC or AC PM motor.
When ran with powering 2 windings at any one time, it is being commutated in the BLDC fashion, When three phases are used, it is AC 3ph mode.
The motor is either fitted with commutation position sensors, or a sensorless method is used such as phase detection feedback.
Both motors are essentially identical mechanically.

#### Tonyr1084

Joined Sep 24, 2015
7,454

Three individual contacts in the upper left corner. In the lower left corner are where all three sets of coils are common to each other. This is why I drew the triple star configuration in post #1. When I energize the listed configurations the motor will snap to one of three positions. If I energize Z with positive 12V and Y with the negative the pump will snap to either 0˚, 108˚ or 216˚ (as best as I can figure). If the mark on the impeller is closer to 108 degrees it will snap to that position and hold. Same is true of all listed configurations.

I want to figure out the easiest way to run this motor as close to design specs as possible, and no, I don't know what those are. Believe me when I say I'm no motor expert. That's why you're being asked for help. Looking at the motor I probably drew it incorrectly. For the X set of coils they are probably series wound and Not parallel. I'll modify the drawing and post it.

#### Tonyr1084

Joined Sep 24, 2015
7,454

Next set of tests I'll try X/Com (plus and minus),
then Y/Com (plus and minus),
then Z/Com (plus and minus),

#### Jon Chandler

Joined Jun 12, 2008
730
Despite your continued belief otherwise, pretty sure this is a BLDC motor, not a stepper motor.

#### Tonyr1084

Joined Sep 24, 2015
7,454
Again, I'm no motor expert!

The dishwasher pump has an electronics package that makes contact with the three contacts in the picture. Whatever it is - I want to run it. If this makes a difference: I can spin the motor and generate a voltage. Hence a permanent magnet is somewhere in there. Just flicking the impeller (will have to get the battery powered drill to spin it consistently) I'm seeing on my DVM 15V on the AC range.

Daughter needs tree help. Stepping away for a bit. Will be back.

#### Jon Chandler

Joined Jun 12, 2008
730
Search for a BLDC motor tutorial.

Joined Jul 18, 2013
27,601
The three sensors indicate commutation sensors (BLDC) also a PM rotor confirms it also.
You need to synchronize each sensor with its associated phase winding, normally this can be done easily with a double beam scope.
Edit:
I think i mistook the stator connections for sensors, IOW that is sensorless version.

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#### Tonyr1084

Joined Sep 24, 2015
7,454
Just hooked the impeller to my drill and spun it at full speed. Saw 21VAC. On the scope I saw a beautiful sine wave. I don't see any sign of sensors. Bottom line, what I have (I think) is a 3 phase 24VAC motor. I said I THINK!

Double trace video - I can upload it to YT but I managed a screen grab where you can see one and a half traces with a ghost of a trace the camera didn't quite capture.

Each trace is of a different set of coils. Let me know if you want me to grab a single set of coils and their common point.

#### Tonyr1084

Joined Sep 24, 2015
7,454
WARNING! TURN THE VOLUME DOWN!

#### nsaspook

Joined Aug 27, 2009
11,746
Just hooked the impeller to my drill and spun it at full speed. Saw 21VAC. On the scope I saw a beautiful sine wave. I don't see any sign of sensors. Bottom line, what I have (I think) is a 3 phase 24VAC motor. I said I THINK!

Double trace video - I can upload it to YT but I managed a screen grab where you can see one and a half traces with a ghost of a trace the camera didn't quite capture.
View attachment 293905
Each trace is of a different set of coils. Let me know if you want me to grab a single set of coils and their common point.
The problem with the hacked three MOSFET YT driver video is that the star motor coils are being driven with DC pulses with the star point as the common or power connection. It works very inefficiently because the coils magnetic flux is not correctly aligned to the PM magnet flux during rotation..
What needed for a proper (still not optimized but much better) driver is a half-bridge per coil tap to send AC (+- DC swapping coil drive polarity) signals in BLDC correct sequence.

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#### Tonyr1084

Joined Sep 24, 2015
7,454
What needed for a proper (still not optimized but much better) driver is a half-bridge per coil tap to send AC (+- DC swapping coil drive polarity) signals in BLDC correct sequence.
Excellent video. Thanks.

You said a half bridge system. Is that what's shown in the video? Looks to me like a full wave driver. Correct me if I'm wrong.

As for hall effect sensors - there are none present.

On the original factory driver board there are six power transistors (or MOSFETS). Three are P12NK30Z and the others are GP10NP60SD and a very large 220µF 200V cap. As well as quite a bit of other controlling electronics. The OEM PCB has two power wires; don't know if they're AC or DC. Three grey control wires and I don't know how they're being controlled or what they're telling the OEM PCB. I can confiscate the transistors for a control board and make my own switcher, but therein I'm going to need a lot of help. I can imagine a counter that counts to 3 (0, 1, 2) and resets to 0 on the third output. Decade or Octal counter should do well enough. A 555 to drive the count and the transistors wired as shown in the video to prevent shoot-through.

You have a willing student here. And no, this is not a school project. I've been a member here for almost 8 years. Dang I'm getting old fast.

#### Jon Chandler

Joined Jun 12, 2008
730
You have a willing student here.
But not willing enough to read a tutorial on BLDC motors......

Joined Jul 18, 2013
27,601
There is a 8pin picmicro with s/w and development board designed for sensorless vector control of a BLDC motor , if needed, search for the pic10f320 on the picmicro site.

#### nsaspook

Joined Aug 27, 2009
11,746
Excellent video. Thanks.

You said a half bridge system. Is that what's shown in the video? Looks to me like a full wave driver. Correct me if I'm wrong.

As for hall effect sensors - there are none present.

On the original factory driver board there are six power transistors (or MOSFETS). Three are P12NK30Z and the others are GP10NP60SD and a very large 220µF 200V cap. As well as quite a bit of other controlling electronics. The OEM PCB has two power wires; don't know if they're AC or DC. Three grey control wires and I don't know how they're being controlled or what they're telling the OEM PCB. I can confiscate the transistors for a control board and make my own switcher, but therein I'm going to need a lot of help. I can imagine a counter that counts to 3 (0, 1, 2) and resets to 0 on the third output. Decade or Octal counter should do well enough. A 555 to drive the count and the transistors wired as shown in the video to prevent shoot-through.

You have a willing student here. And no, this is not a school project. I've been a member here for almost 8 years. Dang I'm getting old fast.
Yes, that's what's in the video. Each pole is connected to a half-bridge for six power transistors total and the cap is the DC link cap that supplies and stores energy for the motor. That sequencer supplies the correct sequence for firing each transistor and usually a means to detect and prevent (by delays and inhibits) destruction of transistor half-bridge pairs caused by shoot-thru.
No, you can't use a simple count up/down circuit. You need something, that at least, provides this sequence.

The MC33932 chips are DC bridge (where you typically use a full-bridge) motor drivers chips being used in the half-bridge configuration for 3-phase power generation.
https://www.nxp.com/docs/en/data-sheet/MC33932.pdf

The PIC32MK controller handles the sequencing and PWM to generate polyphase sinusoidal power waveforms for motors and other devices.

Joined Jul 18, 2013
27,601
Much material on Microchip forum, code included. sensored ans sensorless.

#### Tonyr1084

Joined Sep 24, 2015
7,454
Despite your continued belief otherwise, pretty sure this is a BLDC motor, not a stepper motor.
Again, I'm no motor expert!
Search for a BLDC motor tutorial.
You have a willing student here.
But not willing enough to read a tutorial on BLDC motors......
Three posts by you Jon Chandler and you expect me to become a professor on the subject in a mere few hours ? ? ? I DO have a life other than sitting in my basement trying to understand BLDC's. OK? Now you can throw a party. I said "BLDC". "/

#### Jon Chandler

Joined Jun 12, 2008
730
No, I expect nothing of the sort. Several people have suggested you have a BLDC motor, which would be common in a washing machine, dish washer or wherever you got the motor, but you seem to be stuck on the idea that it's a stepper motor or 3 phase AC motor.

But you do you and I'll STFU.

#### Tonyr1084

Joined Sep 24, 2015
7,454
you seem to be stuck on the idea that it's a stepper motor or 3 phase AC motor.
You're right. I AM stuck. It's a strange animal to me. Whatever it is I want to understand it. Some have said it's a BLDC with hall effect sensors. I balked at that because it doesn't have any hall effect sensors. I'm not balking at the idea of it being brushless. What has taken me some time to understand is that the motors I AM familiar with that ARE BLDC, small, like the type that drive the main hard drive in a computer or some other precision setting device. I've known stepper motors to be lacking brushes, but they have very specific indentured locations where they like to rest. The steppers I've played with in passing have had many "bumps" to it when rotating the shaft. On the order of 24 to 48. I assume (rightfully or wrongfully - I don't know) there are likely stepper motors with even higher numbers. I may even be wrong about the 48, it's just been so darn long since I played with one.

What I DO know about a stepper motor is that it can be precisely stepped to a given rotation and stopped. With gearing it can be even more precise. There's steppers in some printers I've pulled apart. Don't recall exactly, but I think the ink carriage is stepper driven. Or maybe it's the paper. I don't know! I'm not afraid of those three words. When I don't know something I take it as a matter of pride when I can admit there's things I don't know. Some people just can't say those words. Not directing that at you, just saying that I want you to listen when I say "I don't know." So if I call it an Aardvark - obviously I'm wrong. I'm not afraid of being wrong either.

Anyway, I WILL get around to looking up some tutorials on BLDC's. Would have been helpful if you had linked at least one.

I'm an old school guy. I want to take a chip and make it do something. Not an attiny or some other µP. I don't know how to code, I don't have things to use for coding, Coding is strange to me, I even kind of fear it. I am what I am.

#### nsaspook

Joined Aug 27, 2009
11,746
A BLDC is a PMSM 3-phase AC motor. Each type is designed internally to optimize the performance from the expected drive waveform. It's not a stepper motor.
https://www.motioncontroltips.com/faq-whats-the-difference-between-bldc-and-synchronous-ac-motors/
What’s the difference between BLDC and synchronous AC motors?
The short answer is: brushless DC (BLDC) and synchronous AC motors are similar in construction and operation. Some manufacturers and experts even group them together as similar technologies, in the category of “permanent magnet synchronous motors.” Their key difference, however, lies in the stator coil windings and resulting back-EMF waveform of each motor. This gives them distinct performance characteristics and dictates separate drive techniques for each.

Similarities in construction
Despite the specificities of their names, BLDC and synchronous AC motors are both brushless, and both run at synchronous speeds. Brushless means that they rely on electronics (typically Hall-effect sensors), rather than mechanical brushes, to control current to the windings. And synchronous means that their rotor and stator magnetic fields rotate at the same frequency, or with synchronous speed.