Two-speed motors with inverters (again)

timleech · 2009-03-20T22:18:41+00:00

OK, harking back to an older thread, I've now got a 3hp, 415 in & out3-phase inverter (Siemens Micromaster 420) to run the head motor on mymill.The motor is 2-speed, 2700/1420, 3 / 2 hp.Should Ia) run it permanently on the high speed settingb) retain the 2-speed switching?Would the inverter be seriously 'confused' by two different loadswithout resetting the parameters?That I suppose will really depend on how the setup will behave atmotor speeds below the existing 1420If I retain the 2-speed switching, is it vital not to switch speedswhen the inverter is on?with the present belt-change system the top spindle speed is about4880 rpm, I can't see myself wanting to push it much above that evenif that was a good idea.ThanksTimL

T

timleech 17 years ago

I've got one of those Commander drives, the right size for this motor, but it's 240V. It would be great to be able to alter the motor wiring to use that ;-) The basic Siemens instructions seem wonderfully vague, the drive I have has no control panel & basic operation is possible using the usual pot & switch plus a couple of dip switches. I'm going to have to get a panel for it, I think, they do one with a serial port which might be the best bet as well as being the cheapest. I have a single phase Micromaster Vector on my lathe but it's a completely different kettle of fish from this one.

This is copied from the manual and lists the Control Modes available if you have the panel:-

4.4 Control modes (P1300)

All control modes of the MICROMASTER 420 are based on a V/Hz control. The following different control variants are provided to suit different types of application: =01 Linear V/f control, P1300 =3D 0 Can be used for variable and constant torque applications, such as conveyors and positive displacement pumps. =01 Linear V/f control with Flux Current Control (FCC) P1300 =3D 1 This control mode can be used to improve the efficiency and dynamic response of the motor. =01 Quadratic V/f control P1300 =3D 2 This mode can be used for variable torque loads, such as fans and pumps. =01 Multi-point V/f control P1300 =3D 3 For information regarding this mode of operation, please consult the MM420 Reference Manual.

There's a very long list of settable parameters, if you have the right panel, but a quick skim through doesn't immediately throw up any which would allow storage of more than one set of motor parameters. I may well be missing something, it's not my forte.

Many thanks

Tim

Vote

B

Bob Minchin 17 years ago

Tim,

I've played with a few micro-master controllers and I think you can store more than 1 set of parameters in some of the operator panels. I've certainly used a BOP to move parameters from one converter to another but I can't remember if it asks for a file location which would imply storing more than one set of params. The other way as you say would be to use the serial interface and a laptop. I've got some Siemens software CDs somewhere...... I'll see if I can find them and see if there is anything useful there.

Bob

Vote

R

Rob Wilson 17 years ago

Hi, Actually yes using some software to set unit up is normally a lot easier, but I thing Siemens kit aint that user friendly; that's certainly true of their PLC's. Certainly not as good as the Control Techniques stuff. We had stuff like CT-Soft (which I also had involvement with as I was a Windows programmer in another life) which made commisioning a lot easier. From what Bob says there is a Siemens flavoured version so try that out.

From what you say the Siemens think it straight V to F. You will need some boost to keep the motor going, or rather delivering torque, at very low revs if you want some torque out of it, but beware it'll get very hot unless it's got a separate blower due to the I^2*R losses in the windings. Don't forget torque is prop to current, so it'll be running at nearly full current (if you need that kind of torque) at nearly a standstill. Because you're running a machine off it it might not be too important as you will be running fairly quickly, but I thought I should mention it.

Sincerely,

Rob.

Vote

T

timleech 17 years ago

I've ordered a PC interface kit today, I started the wiring over the w/ e & might try to finish it this pm, feeling a bit under the weather but might cope with an hour or two of pottering in the shop.

I don't envisage going down to extremely low speeds, but obviously I'll have to watch the temperatures.

I'll report progress when there is some.

Many thanks Tim

Vote

D

duttondock 17 years ago

All up and running now, using the 'FCC' option which seemed the most appropriate. I haven't done much with it yet as I've had the feed gearbox apart, I still need to play with the ramp times and the DC injection braking seems pretty ineffectual compared with other inverters that I've used but the proof will come when I do some real work with it. It does seem to function OK on both motor speed settings, but I'm not sure how much the lower speed setting will get used. The default minimum frequency on the inverter is 0Hz, which had me confused for a moment when everything was switched on and nothing happened!

Thanks to all

Tim

Vote