Heidelberg Cylinder - Single Phase Question

We recently picked up a Heidelberg KS Cylinder.

I’m curious what the consensus is as to how I should power the thing with single-phase.

Would you use a VFD, or just replace the motor with a 1ph model?

If the vote is for VFD, what rating?

Thank you.

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I believe the KS comes equipped with a 4kw (approx. 5.5hp). Most motors you’ll find in this range are going to be three phase or very pricey single phase motors. The VFDs will also get more expensive as you get into this size. If it were me I’d probably go with the VFD and get one rated for 7.5hp or so—I think they jump from 5hp to 7.5hp.

Hope this helps.


I got a rotary phase coverter to power my 220 3-phase KS. It is efficient, but very noisy when there is no load and is installed in the basement. If it was right in the pressroom I’d have hearing loss from it.

Hmm. The other option is to have 3phase installed to the building. Over the long run that would make the most sense, I guess. How reliable are these VFDs?

I keep wavering on what I should do. For example, if I spent the money on the VFD and it died, I would have been better off investing in running proper power to the building.


How long do you plan on being in the building? It sounds like you’ve looked into having the utility company do a 3-phase run into your space. If that’s the case and it’s only a bit more than a VFD then I’d definitely do the 3-phase drop.

However, if it is double the cost of the VFD and you won’t be there for a substantial time (5 years or more) then I’d stick with the VFD. They are reliable as long as you get a reputable brand from a trusted vendor (I’d recommend TECO drives which you can purchase from Dealers Electric).

Hope this helps,

I got the rotary phase converter because the closest three phase service was many blocks away, no way PG&E would extend it for a small customer. If service is accessible, it is more efficient than any converter.
I had a smaller rotary converter for a Kelly press with smaller hp motor. No problems there.
The original Heidelberg motor is well-made, no problems in 25 years, and it was 25 years old when I got it. Think that would be true from anything bought new today?

Thanks for the advice.

We don’t have plans to leave the building — it is working out well. I was discussing it with my neighbor, who recently had 3-phase power installed in his shop. He said the city electric utility ran it from the pole for no charge , and his costs to install the meter box and breaker panel were about $3,000.

So the question becomes, $3,000ish for getting proper juice, $500-$1000ish for the VFD, or $500-$1000 for a 1phase motor that may or may not be as good as the original Heidelberg motor.

Long-term, having 3phase power to the building would increase the property value I suppose, the motors would be more efficient to operate, and I would have flexibility to add more 3phase machinery. Seems like avoiding the phase-conversion mess would make the most sense.

Installation costs might be minor if the electric utility has “minimum” usage charges for billing on a monthly basis for a second meter and 3-phase. You might check that out with your neighbor or the utility before committing to it. It may be different if the service is already in your neighborhood.

Comparing 3,000 to 1,000 I’d be tempted to get the VFD and call it a day. John is right… some utilities have minimum billing requirements for second meters and three-phase runs.

The nice thing about a VFD is that you can, if you need to, take it with you when you move to a different space.

I suppose it’s six of one, half-dozen of the other…


On the other hand, having three-phase service will allow installation of other three-phase equipment, where a new VFD must be bought and configured for every new motor.
My rotary phase converter powers two different presses, but not at the same time. I have to go into the basement and throw a switch to transfer power .

To parallel imp and others

To satisfy my own curiosity, what is the overall efficiency of the rotary converter? If 4 kW is coming out, how many kW is going in from the single-phase supply? Is your single-phase input at 110 volts or 220?

I traced a (domestic) problem by counting the revolutions of the electricity meter and deduced that the electricity-overload safety device had down-graded, it was rated at 8 amps, but had degraded to less than 7.5, which was the load it was connected to. Replacing the overcurrent safety device cured the problem, but led me to check the appliance that was connected on that circuit, and (fortunately) to replace it under advantageous circumstances.

Australia’s electricity supply is mostly under semi-government control, and I doubt a heavy load would be allowed on single-phase, though that attitude is being modified in recent years.

There should be plenty of electrical engineers in USA with the necessary understanding to solve this question of what is the best way, considering economic and safety and reliability factors.


I have a KSBA running with a rotary phase converter, and that has worked great. Do not change the motor to single phase! The press has a large electrical box, it’s not like a Windmill where all you have to do is switch out the motor. The electrical on the cylinder presses is set up so the motor starts at a lower speed and then shifts to full speed once the press gets moving. If you switch to a single phase motor, the motor will be under a lot of stress every time you start and stop the press. Or, you would need to have the press professionally converted to single-phase, which would be ridiculously expensive.

Rlomascolo - That’s good advice! I didn’t know that! I was looking at 7.5 HP 1phase motors.

The electric utility here is run by the city. It seems to be against city code to run 1phase motors of 1 hp or more. The electrical inspector didn’t say anything when inspecting our presses, and I regularly use a 5hp 1phase motor on my paper cutter. The city engineers haven’t come knocking, so I suppose it isn’t bothering them too much.

If I can’t swap the motor, the options change to rotary phase converter, VFD, or installing 3phase.

It’s right out there on the street, we own the building, all my neighbors have it, and I have a 3phase Challenge 305 sitting in the corner unused for lack of power. It seems like the only rational choice is to forget the phase conversion nonsense and just get the real deal. I just wish I had $3,000…



I didn’t realize you owned the building. In that case, by all means, get the 3 phase run in. It’ll be a bit more pricey than the phase conversion, but as stated above you’ll be able to run the cylinder AND cutter without a headache/hassle.

Keep us posted.


Another thing to think about and ask your power company Ryan is if there is 3phase on the pole. If it is not ran in your area or on the pole that will be big bucks cause the power company wont run just for one person!

I would go for getting 3phase into your building, I have it in mine and its so much nicer. 3phase runs lower amps so the coast is less.

This has been a great discussion, and I really appreciate all of the great feedback. I’m going to get a few quotes from electricians and talk to the city about getting 3 phase run to the building.

The power is definitely on the pole. The building is a storefront at sidewalk level, so it’s right out front.

I’ll report back to this thread as I learn more, so others can benefit from the experience.

Awesome, good luck! let us know.

So, it’s been quite a long time but I finally hooked up the Heidelberg KS Cylinder press to single phase using a VFD.

I took out the soft-start components and it fit inside nicely, once I took the face plate off of the VFD. I used an Ebay Huanyang 7.5kw model, which was only $265 delivered. The default soft-start program seems to work fine in place of the original components. The original microswitch switch was suitable to start the VFD when you slide the control lever to Run.

Behind the Heidelberg face plate, there is a solenoid connected to the missed-sheet trip apparatus. Can anyone explain the purpose of this solenoid? It was not wired correctly when I got it. It seems the purpose is to disable the missed-sheet trip when the motor is not running.

As a test, I hooked it to a relay, and set the VFD to trigger it in Run state. Power goes on, solenoid pulls up, and the trip components work. I’m having trouble understanding the point of it, though. Why would you have to disable the missed-sheet when the motor is off?