Soft Start For 3~ Dual Speed Motor

[Brad93]

I’m wanting to get a soft start for my geared head startrite drill. When you start it up it jumps straight to full speed and can make quite a crack from the gear train.

Thing is it’s a Dual Speed Motor. It is controlled by a big rotary switch in the face of the machine. I believe it once had forward and reverse on a foot pedal but that doesn’t make much sense to me.

So what I need is a control box, with start/stop, forward and reverse, with a soft starter wired through to the two speed knob on the front of the machine.

Is this possible?

 

[WorkshopChris]

I believe it once had forward and reverse on a foot pedal but that doesn’t make much sense to me.

Would it of been a feature to allow machine tapping?

What is the motor size?
https://www.automation24.co.uk/soft-starters

 

[Brad93]

0.96 / 1.4kW depending what speed it’s on.

 

[Brad93]

Data plate

 

[piman]

Hello Brad,

It shouldn't be much of a problem.

Her's a link to a few to let you see what there is:- https://uk.rs-online.com/web/c/auto...Term=soft start&applied-dimensions=4294701406

Alec

 

[Agroshield]

The speed selector knob is connected directly to the mains isolator and thence to the plug so you do not need to go inside the machine to connect any soft starter.

Would a standard 415v in 415v out VFD not do what you need for less money than a dedicated soft starter?

For utmost longevity, you might have to train yourself not to touch the drill's own speed selector while the VFD output is active. Otherwise you have to wire up an interlock such that operating the switch on the drill sends a stop signal to the VFD.

 

[Brad93]

The speed selector knob is connected directly to the mains isolator and thence to the plug so you do not need to go inside the machine to connect any soft starter.

Would a standard 415v in 415v out VFD not do what you need for less money than a dedicated soft starter?

For utmost longevity, you might have to train yourself not to touch the drill's own speed selector while the VFD output is active. Otherwise you have to wire up an interlock such that operating the switch on the drill sends a stop signal to the VFD.

A soft start can be had for about £120 from Siemens or ABB, don’t really want to spend £200-300 on a VFD, bit overkill on a drill with 20 speeds already.

 

[Brad93]

The speed selector knob is connected directly to the mains isolator and thence to the plug so you do not need to go inside the machine to connect any soft starter.

Would a standard 415v in 415v out VFD not do what you need for less money than a dedicated soft starter?

For utmost longevity, you might have to train yourself not to touch the drill's own speed selector while the VFD output is active. Otherwise you have to wire up an interlock such that operating the switch on the drill sends a stop signal to the VFD.

There is no mains isolator at the moment all I’ve got is a cable going in the back of the drill and high/low speed with off in between

 

[Spark plug]

Looking at the one of the Siemens starters in the above link, I thing what you would have to do is:

• fit the starter in series between the mains cable and the selector switch
• Install a start and stop button to control the starter
• Use the selector switch only to select the speed rather than start the machine also

Hopefully this makes sense, should be a fairly simple mod.

 

[daleyd]

I’ve never used a soft start with a 2 speed motor but used plenty on single speed stuff.

just wire your 3 phase in and out and have a start/stop signal. If it was something like a fan it would be common to also have a contactor in series to positively turn the motor off when not being used, but maybe overkill for a drill.

With a 2 speed motor I would look at something that could have 2 parameter sets as things like max currents would be different for each speed configuration but again for a drill with a relatively small motor it’s probably not necessary.

For the price difference though I’d be tempted to bung a vfd on it, much more control - but that’s just me

 

[Brad93]

I’ve never used a soft start with a 2 speed motor but used plenty on single speed stuff.

just wire your 3 phase in and out and have a start/stop signal. If it was something like a fan it would be common to also have a contactor in series to positively turn the motor off when not being used, but maybe overkill for a drill.

With a 2 speed motor I would look at something that could have 2 parameter sets as things like max currents would be different for each speed configuration but again for a drill with a relatively small motor it’s probably not necessary.

For the price difference though I’d be tempted to bung a vfd on it, much more control - but that’s just me

2hp on a drill is pretty powerful without going to a radial arm drill.

 

[daleyd]

2hp on a drill is pretty powerful without going to a radial arm drill.

Yeah, I was comparing to things like pump or fan motors which I usually deal with, not other drills... of your into 10kw and above then you would be wanting multiple parameter sets if you were going to connect it to multi speed motor - but for 2 Hp you could probably ignore the differences.

 

[Agroshield]

Use the selector switch only to select the speed rather than start the machine also

That is the challenge. To discipline yourself and any other user not to touch the selector switch when the soft starter is outputting anything.

Anything downstream of the soft starter, it will not know or care about.

There might be a way to hang a microswitch near the speed selector such that as it reaches or passes through its off position, that kills the output from the soft starter. It could be done externally using the selector switch knob itself to activate the microswitch but it would look ugly.

 

[Spark plug]

That is the challenge. To discipline yourself and any other user not to touch the selector switch when the soft starter is outputting anything.

Anything downstream of the soft starter, it will not know or care about.

There might be a way to hang a microswitch near the speed selector such that as it reaches or passes through its off position, that kills the output from the soft starter. It could be done externally using the selector switch knob itself to activate the microswitch but it would look ugly.

I belive there is an off position between the two speeds, probably you could interlock a no volt release with the off position to release the starter.

 

[Brad93]

I might get in touch with Newton Tesla or other such inverter/motor supplier to see if they can put together a solution.

 

[the snooper]

Would be any use to you putting varia

I might get in touch with Newton Tesla or other such inverter/motor supplier to see if they can put together a solution.

Cant you just add a speed controller so start off slow

 

[Brad93]

Would be any use to you putting varia

Cant you just add a speed controller so start off slow

No point. The main benefit of a VFD is for speed control and I have 20 known speeds from 30RPM up to 2400.
A VFD also isn’t the best idea on a twin speed motor nor one with such limited cooling as this one.

 

[Agroshield]

The main benefit of a VFD is for speed control and I have 20 known speeds...

I think the reason people are suggesting a VFD is that a used one could be a lot cheaper than a new soft starter, especially in 415v in and out as that will deter most home users.

Most VFDs can be programmed to operate just like the soft starter: no potentiometer needed, no speed control as such. Press 'start' and it ramps up from 0 Hz to 50 Hz in a time you set*. Press stop and it will coast down or ramp down or even brake to a halt.

You would have to read the manual for the soft starter to see if or how it implements reverse (mentioned as a requirement in your original post), whereas there is no VFD made that does not implement this feature.

Is it a Startrite EFI drill?

*If you want to get really advanced, you could have two ramps, one for slow speed and one for high speed. Again, would need a microswitch on the speed selector knob.

 

[Brad93]

I think the reason people are suggesting a VFD is that a used one could be a lot cheaper than a new soft starter, especially in 415v in and out as that will deter most home users.

Most VFDs can be programmed to operate just like the soft starter: no potentiometer needed, no speed control as such. Press 'start' and it ramps up from 0 Hz to 50 Hz in a time you set*. Press stop and it will coast down or ramp down or even brake to a halt.

You would have to read the manual for the soft starter to see if or how it implements reverse (mentioned as a requirement in your original post), whereas there is no VFD made that does not implement this feature.

Is it a Startrite EFI drill?

*If you want to get really advanced, you could have two ramps, one for slow speed and one for high speed. Again, would need a microswitch on the speed selector knob.

Yes it’s a Startrite EFI.

From my understanding not all VFD’s work with 2-speed motors.