new aussie member with a few Q's

[FPV_GTp]

Try Melbourne Machinery in Clayton South on 03 9548 2000


speed controller AC motor three phase

Kwatts ............................ Price
0.75 kw ............................ $ 300-00 single phase in / three phase out

2.2 kw ............................ $ 550-00 single phase in / three phase out

3.7 kw ............................ $ 900-00

7.5 kw ............................ $ 1370-00

11 kw ............................ $ 1840-00

from memory GST is applicable also

Not cheap at all

cheers

[Tony]

Have to agree, Melbourne Machinery is definitely the place to go.

I bought my own 7.5Kw VFD from there, as well as various motors and much other stuff over the years.

Ask for Michael Roche, I know him well. He is a great guy.

A big three phase industrial centrifugal blower, and a VFD will do everything you want, including fully automatic control of test pressure. It will be quiet, efficient, be a joy to use, and work reliably without problems for decades.

[jsa]

The prices I mentioned are inc GST and what I would sell to my building automation customers for. The PID option would be a little more. They are Control Techniques brand made by Emerson, distributed by IPD Group (Alsthom offshoot).

I get discounts off list for many drive brands and can help Aussie forum members out with drives by passing on the discount.

PM me if you know what you want and need a price.

Beware the 1 phase in 3 phase out will only be 240V 3 phase out not 415V. Requires an induction motor that is wound for 240V delta / 415V star, reverse of the norm.

Yeah Tony, I know you were talking about variacs for vac motors, just wanted to make it clear to all, as we were also covering induction motors in the posts.

I agree an induction motor and blower is a better way than vac motors. Vac motors being single phase work out well for connection to everyday power points. A 1in/3out VFD on an induction will only allow up to about a 2.2kw motor on a 10A power point.

[FPV_GTp]

Hi jsa ( John ) , where are you located again ?

Just heading of to do some fishing snapper are in the bay early once again this year


cheers

[FPV_GTp]

Hi , for the guys using vac motors single phase AC and need some for of a speed controller maybe this could do the trick


MSC500A Controller
The MSC500A Controller has a rotational on/off switch and provides: one switched, uncontrolled output, and one switched output which is controlled electronically to provide stepless speed control for single phase PSC motors, or shaded pole motors, in fan applications.




[quote]

[jsa]

[jsa]

[FPV_GTp]

Hi jsa , now Brisbane is the SUNNY state beautiful area , Sunny one day perfect the next , well we do get some nice weather down in Melbourne also LOL

What line of work are you involved in jsa ?


Endless learning curve , seems like I'm back at school, pity I ragged classes , " You Can't Teach An Old Dog New Tricks !!!!! " You have to admit the internet is like a University at your finger tips. From flow benches to electric motor design and how they work too electronics VSD's and VFD's my brain is really hurting now.




[quote] Q. What's the difference between a variable frequency drive (vfd) and a variable speed drive (vsd)?

A. A variable frequency drive (VFD) refers to AC drives only and a variable speed drive (VSD) refers to either AC Drives or DC Drives.
VFD's vary the speed of an AC motor by varying the frequency to the motor. VSD's referring to DC motors vary the speed by varying the voltage to the motor [quote]

[jsa]

[FPV_GTp]

What's Inside Your Central Vacuum?

for those guys who are worried about heating up the air as it passes throw the electric motor there are other options in air source . The things you learn about vacuum cleaner motors.


There are also three types of motors to choose, flow-thru, peripheral by-pass, and tangential bypass. Which motor is used depends on what the manufacturer is trying to achieve.

The Flow-Thru Motor

Inexpensive, these motors are generally used in conventional canister vacuums or upright vacuum cleaners with the larger more powerful versions used in a central vacuum.

Aside from being less expensive they also make a central vacuum sound quieter since there isn't a cooling fan spinning at speeds in excess of 20,000 RPM. This motor uses vacuumed air to cool itself by passing vacuumed air over the armature. It is critical then that care be taken to insure air is filtered and clean to prolong the life of this motor.

Often you will see this type of motor in less expensive systems or you may find them used in a dual motor situation whereby two lesser powered motors are used together to create a more power system. We will talk about that later.


The Peripheral By-Pass Motor

Again typically less expensive then a tangential type motor, these motors actually employ a cooling fan on top of the motor which blows fresh clean air over the armature and exhausts it peripherally through vents on the side of the motor.

Generally more powerful then their Flow-thru cousins these motors should be more reliable since clean fresh air is being use to cool the armature. Care should be considered in the exhaust of this unit which is dirty and heated.


The Tangential By-Pass Motor

This style is the most commonly used motor in the central vacuum industry. While more expensive then it's cousins, the implementation of a tangential exhaust ensures all heated and dirty exhaust is removed from the motor chamber and expelled thus maximizing longevity

Available sizes are usually 5.7" Diameter and 7.2" Diameter; the latter generally producing more power at the same or lower RPM.

[FPV_GTp]

Just which one will suit ones application depends on a lot of variables.

The 0 to 10 volt signal output controller will be available on the air source to maintain automatic speed control of the pumping/suction source that will be a awesome feature controlling and maintaining a constant pressure to leave hands free for other work mmmmmm.



fully digital variable speed drive for controlling low power single phase AC motors. Single Phase-in / Single Phase-out. The E2 is


230Vac Motor Speed Controller Modules - adjust the speed of 230Vac single-phase induction motors as used in power drills, vacuum cleaners, etc. Speed adjustment is controlled using a Triac output and a potentiometer mounted on the board.


Variable Frequency AC Fan Speed Control drive -

Fan speed controller

Single-phase AC drive MINIMOTOR -



Pump Express > Pump Controllers and Switches -http://www.pumpexpress.co.uk/acatalog/pump_controllers_switches_pump_express_19.html

jsa you will have to be our tech-man

cheers

[jsa]

[Tony]

Agree 100% John.

Single phase induction motors are not really suitable for very slow speed operation, they will not run smoothly, and have great difficulty starting up. Three phase motors with a proper VFD are far superior for very wide variable speed operation.

There are really only two motor choices for a flow bench.

Either the very high rpm brush type universal ac/dc motors used in vacuum cleaners (and most power tools). These things always scream, and wear out fairly quickly, and are fairly susceptible to overheating.

All you need to do to speed control these, is to vary the motor voltage. Fairly simple.

For running a large industrial high horsepower blower, or a supercharger in your flow bench, a three phase induction motor is the ideal choice. These have no brushes to wear out, they are silent, available everywhere at low cost, and they will not overheat in our application.

But speed controlling them is complicated, because both the motor voltage and frequency need to both be varied together to control motor speed.
This requires a proper Variable Frequency Drive.
But the initial high cost of the VFD is the only disadvantage.
The blower and motor themselves should be pretty low cost, much cheaper than vacuum motors for similar air capacity.

[Moriniman]

I've just started building my bench and been thinking about motor control.

Phase angle control is electrically quite noisy and I'd rather not have interference with my digital manometers. Most vacuum cleaner motors are of the 'universal' type and will run on DC. It's then possible to use a simply PWM controller.

A quick Google search found;

[Tony]

The basic idea is certainly sound, but there are a few pitfalls for the unwary when experimenting with these types of motor control circuits.

Triacs can sometimes have great difficulty turning off at the zero crossings with highly inductive loads. This can cause erratic operation at certain phase angles and motor loads. By far the better way is to use back to back SCRs rather than a Triac, if at all possible. It will be far less temperamental.

The IGBT circuit is even better still, but it has one significant vulnerability to failure.

The mains supply voltage often carries very fast high voltage spikes. These originate throughout the whole power distribution network, and especially from lightning strikes inducing voltages into overhead transmission lines.

These voltage spikes can easily reach several thousand volts, but only for microseconds, and do not effect most mains operated equipment. Now something like a Triac or SCR will just turn hard on for half a cycle through dv/dt switching of the gate. In effect, in turning on, it protects itself from high voltages. But an IGBT will not do this. A 600 volt rated device will be destroyed by the very first mains borne voltage spike significantly over 600 volts.

If using an IGBT, make damned sure you have transient voltage suppression, preferably right across the IGBT itself. And maybe a second suppressor right across the incoming mains supply.

All the circuits in that application note are directly connected to the mains supply which can be pretty lethal. I much prefer to isolate the drive to the power control device, either with an opto isolator, or pulse transformer.

The microprocessor, or any control potentiometer is then safely isolated from the mains voltage. It also means you can use test equipment to monitor voltages and waveforms, without killing either the test equipment or yourself.