Tractorsport Flowbench Forum Archive

Posted: **Thu Apr 16, 2009 8:40 pm**

Tony,

Personally I'm not really chasing full automatic control, but more as you suggest automatic trim to maintain the pressure against fluctuations in voltage etc. as you mention, but also for steps in valve opening. With bench familiarity it will become obvious how many 100% motors need to be running with the variables.

I still consider universal vac motors in combination with a VFD experimental. I am thinking commutation would screw with the VFD diagnostics.

I've mentioned earlier using a pot controlled solid state relay to change vac motor speed. I'm presently checking out a couple low cost analog SSR options.

One option is a phase angle firing SSR with integral analog input claimed to be suitable for universal motors. These things come with 'headline ratings' up to 90Amps, and can be selected with one of 0-5V or 0-10v or 4-20ma input.

Another option is a $US60 card that screws on the input terminals of an instant switching SSR and operates them as phase control. The card is DIP switch settable for 0-5V, 0-10v, 4-20ma, 1-5v, 2-10v or potentiometer. There are myriad brands and sizes of the instant switching SSR's suitable for inductive loads. At around AU$70 for a 'headline 40A' SSR with heatsink, we have the power side control of about 25Amps conservatively worth of vac motors. These SSR's are availbe up to at least 150A headline, I'd only be guessing at prices for this rating.

I'm asking questions of the card manufacturer at the moment with the intention of getting one and trialling it as the most flexible option. The all in one SSR may work out the cheapest but also least flexible option.

Posted: **Thu Apr 16, 2009 8:46 pm**

Posted: **Fri Apr 17, 2009 10:28 am**

[color=#000000]John,

For simple discussion VFD do not like universal motors AT ALL, especially the constant torque type "Senseless Vector". I have tried this and

. For a simple solution not sure about reaction timing Payne Engineering

Posted: **Fri Apr 17, 2009 7:13 pm**

Posted: **Fri Apr 17, 2009 8:14 pm**

Gents,

400Hz induction motors are available, I haven't been able to lay my hands on the brochure I thought I had in my office.

I don't think replacing the universal motor on of a vacuum cleaner piece would be econimical.

If were not so far down the road of vaccum motors, I'd be looking at 400hz direct drive blowers as Tony suggests.

Posted: **Fri Apr 17, 2009 8:46 pm**

Did you ever sit in a plane listening to those 400hz motors run for a few hours?

I have :;):

My flowbench with a few motors running is a lot nicer than a screaming 400hz motor on a few hydraulic pumps and an inverter.

Posted: **Fri Apr 17, 2009 9:09 pm**

Just a quick look and not an extensive search turned up these motors:

Up to 12Kw and 18,000 rpm at 300 Hz

Yes Bruce, any very high rpm motor is going to howl a bit, it is not just the 400 Hz whistle, so much as the high rpm.
Even the hydraulic pumps in fork lifts that run on dc can kick up quite a respectable scream.

Posted: **Fri Apr 17, 2009 9:42 pm**

I still have the single blower project sitting here in the shop, someday I'll get back on it.

Posted: **Sat Apr 18, 2009 9:00 am**

Posted: **Sat Apr 18, 2009 6:39 pm**

Posted: **Tue May 05, 2009 12:46 am**

As mentioned earlier in this thread I've been working toward a solution for speed control of vac motors on my bench project.

This last week I have got my hands on an interface board and suitable solid state relays. Having rigged it up over the weekend it tested out OK for me.

The interface board comes from , and I chose 2 seconds soft start and the fast response options.

I bought Crydom D2450-10 solid state relays.

They were purchased through Fastron in Australia, along with heat sinks for the duty, but are readily available worldwide including some surplus joints.

Crydom also have a MCPC series part number that does not require the SSRMAN.

The MCPC is dearer than the D24 series and only has one input type as ordered. I liked the flexibility of the SSRMAN having nearly all of the typical input types on one module, its output voltage regulation and soft start capability.

I have tried a single SSRMAN driving four D2450-10 in series and 2 parallel pairs. In theory 2 parrallel sets of four in series should work.

I bought 4 SSR's so I could speed control all 12 motors in my bench if I wish. The SSRMAN and four D2450-10 SSR is cheaper than a MCPC setup of similar capacity.

Control ranged from 10VAC 1.2A with the motors just ticking over to 6.5A 229V flat out. Motors seemed happy but I haven't done any long term low speed running to check motor cooling at reduced speed. I doubt they will run that low in the completed bench due to the need to overcome pressure losses in the bench alone.

So for around $400AUD i can speed control about 80 amps worth of motors.

For 20 amps worth about $170AUD.

Be conservative with the load applied to the SSR / heat sink / ambient air combination and they are very reliable, get greedy and the smoke will come out.

Posted: **Tue May 05, 2009 1:42 am**

Well done John !!!

The power module combines all of the required features.
It has an SCR output (not triac, as most of these modules are).
So it will work very well with a highly inductive load such as vacuum motors. It also solves all the mains isolation and safety issues.

Just make absolutely sure you are buying this exact module. IT IS VERY SPECIAL
Many very similar looking modules sold on e-bay and elsewhere are entirely unsuitable. So make absolutely sure what you are getting is the correct part number. This is EXTREMELY important.

The Nuwave controller looks to be ideal as well.

This module is only the size of a match box, but it will generate a ferocious amount of heat.
A very large and efficient heat sink will be required if it is run at it's full rated current.
Or as John says, you will let the fairly expensive smoke out.

Again, great effort John at tracking down these parts.

Posted: **Wed May 06, 2009 6:23 pm**

[color=#000000]Any of the Crydom DXXXX-10 are suitable so long as the correct load current and voltage are selected for your motor load ambient conditions and supply voltage. I did find other brands had suitable modules but none were as readilly available.

Most SSR's are designed for resistive heating loads not inductive loads such as motors.

In industry for electric heating applicatoins nobody usually goes above 80% of the rated capacity. Many a switchboard fire has started from pushing SSR's too hard.

I have 20A per SSR. Rated capacity is about 30A at 50

Posted: **Wed May 06, 2009 11:38 pm**

Posted: **Thu May 07, 2009 2:19 am**

Tractorsport Flowbench Forum Archive

Digihelic controller - might suit some ones motor control needs