Creating a "flexible" appliance power scheme

[lindermat]

Hi all,
We make industrial equipment that our customers can order to run off different line voltages. Mainly

120V 60Hz
240V 60Hz (split phase)
208V 60Hz (single phase)
230V 50Hz (European)

My question is that there are parts of our product (like small .03HP motors) that will only run on 115V (nameplate rating) and some parts that can run on EITHER 120 OR 208/240 and others still that have a wide input and will run on anything from 90V to 240V. So, What should our power input be so that it is the most flexible to commonly available (in the US) outlet voltages.

My idea is to have four terminals (like a clothes dryer) two "hots" (L1 and L2) a neutral and a safety ground. Parts that need 208/240 can connect across the two hots and the stuff that needs 115V can connect from either hot to neutral. I think this is how a clothes dryer does it (parts of it run on 115V)

The only problem is that it REQUIRES a neutral. Correct me if I'm wrong, but "standard" 208V outlets don't have a neutral right? I'm concerned that our customers would be upset if they have to pull a neutral from a panel. I've seen 208V outlets with 4 connectors, but how common are those?

I don't want to add the cost and weight of a transformer if I don't have to.

Thanks,

Matt

P.S. For the European 230V version, I think the only option is a 1:1 transformer with a center tap on the secondary to use as a neutral.

 

[crutschow]

For power up to 1500W, 120V 60Hz is commonly used in the US (15A max.) for both household and industrial equipment.

 

[lindermat]

Carl,
Thanks, but some of our products use 20 amp NEMA plugs. For the 120V only versions, it's a pretty straight forward configuration, everything is the same. The problem is when 208/240 is used.
Matt

 

[KeepItSimpleStupid]

Before anyone can attempt to answer this question, one has to know the relative loads. Some thinks like 10 kW heaters running off 240 when the elements are 208. So, you have to change the elements.

Remember that 60 Hz stuff usually overheats at 50 Hz or has different perfomance. So 50/60 Hz nameplate labels should be used.

The US has 208 or 240 Volt power. 208 if the service is "Y" and 240 if it's a High leg Delta. 120 V 15A and 120 V 20 Amp are common.
When you have 208 or 240 V equipment, you have to run power to it anyway. It does happen, that in a move, one might change power sources. 208 V "Y" should be more common.

"Clothes dryer's are bad example".

Usually a control transformer which can be wired 240/115 primary is used for control applications and is usually an isolated source within the equipment enclosure.

 

[lindermat]

There are purely restive loads, and you are correct, when used at 208V they generate less heat, but we account for that.
We have had problems with 60Hz stuff overheating at 50Hz. Usually we reduce the voltage to 100V in that case.

Why are clothes dryers a bad example?

 

[blueroomelectronics]

For large appliances why bother with a universal design? Every country has it's own certification rules, plugs, etc. Fairly easy to drop in a new motor, coil & power cord on the line.

What product is this for?

 

[lindermat]

Just trying to reduce the number of parts in inventory and eliminate the need for a heavy expensive transformer.
They are so similar (component wise) that it would be nice if we had a "universal" scheme that could be wired as required for the country/voltage.

The products are environmental test chambers.

 

[BrownOut]

Some years ago, I made a 240V/120V extension cord that plugs into my dryer socket. I'd have to crack it open now to remember how I wired it.

 

[#12]

My (USA) power company promises to deliver 240V +/- 5% (and a rather accurate 60 Hz)
That means 120V +/- 5% on the wall outlets.
Just giving you some free information that has been checked out properly.

Clothes dryers are a "bad" example because they use the 240V for heaters and 120V for a light bulb, a timer, and sometimes the main motor. This is what I call a mixed load.

 

[Reloadron]

Just trying to reduce the number of parts in inventory and eliminate the need for a heavy expensive transformer.
They are so similar (component wise) that it would be nice if we had a "universal" scheme that could be wired as required for the country/voltage.

The products are environmental test chambers.

I believe what you need to do here is based on your target audience make your decisions. In North America and with a focus on residential consumers the power distribution to residential is just about always 240 VAC split phase 60 Hz. That is the average residential consumer. Large appliances like electric stoves, electric driers, and home electric heat take advantage of the 240 volt service. They may split that internally and use it as required but overall they require 240 VAC 60 Hz. service. The remainder of residential is 120 VAC 60 Hz derived from the 240 VAC split phase entry. Small appliances, home lighting, home electronics and the list goes on. The standards for residential power distribution within a residence is spelled out in the NEC (National Electric Code), however, individual states and cities may add to the NEC requirements and amend them as they see fit. The rules as to grounding etc. are pretty much spelled out in the NEC. The NFPA also figures into things (National Fire Prevention Act). All of that does not begin to include other safety ratings and approvals.

Next we enter commercial / Industrial power distribution which is another can of worms. This can vary greatly depending on the facility. However, it would likely be safe to say that distributions like 3 phase 4160, 480, 240 Delta are not common to a residence and that holds true for assorted WYE configured voltages.

This brings us back to who your target audience is and who you are marketing to.

Just My Take
Ron

 

[KeepItSimpleStupid]

Ron: ...and 208. 240 three phase is usually high leg delta. Light commercial may not have three phase and thus 240 single phase would be common there.

Dryers are a bad example" See Wiring a Clothes Dryer and Power Cord - 3-Wire and 4-Wire 240 Volt

The old dryer scheme (single phase 3-wire 240) was L1,L2 and Neutral to the panel. The outer case was permitted to connect to the Neutral at the dryer. It's grandfathered.

The new dryer scheme is (single phase 4-wire 240) or L1, L2, N and G.

An electric water heater would typically be wired with L1, L2 and Ground.

The environmental chamber we had used a dedicated 120 V outlet which has L, N and G. The circulating fan was 120 and the controls were 120. It was a small chamber. Could go from 200 to -80 C.

I can see reasons for keeping the circulator simple by using impeadence protected fans, BUT if you changed to a 3 phase brushless motor, you can easly detect a fan failure before the internal hi temp fuse melts. I failed to make the correct diagnosis and we ended up "Upgrading" the controller because of what looked like a short. The temperature limiter was installed wrong by a student and when it failed it shorted against the case.

With a 3 phase brushless motor for the circulator, you could detect failures before they did damage and use this as a selling point. I had the circulator not work because we were not PMing the oiler cups. My latest boss had a non-prevention or PM mentality and he micro managed to the point you couldn't even do it.

I remember one incident where two people worked more than 8 hours each over the weekend trying to solve a problem with sparking. I came in Monday morning and made a few tests and within 5 minutes, I had diagnosed an outlet with a bad ground. He failed to understand that using the right resources could save money.

He also would not let me repair the water interlock on a 30 KIlloGaus electromagnet because we "don't use it enough" and someone is always there.

 

[Reloadron]

Ron: ...and 208. 240 three phase is usually high leg delta. Light commercial may not have three phase and thus 240 single phase would be common there.

I agree, though I have never seen a 208 Delta in my travels. Since with 208 WYE any phase to neutral is 120. We bring in 4160 (actually older system bringing in 5 KV) and distribute 480 Delta with exception of some large pumps running 3 phase 4160. For my buildings we are adding a new sub this spring. The demand is ever growing. Mostly large heaters. Yes, light commercial or industrial does not generally have massive power distribution.

Before I drag this really off topic....

Anyway, I still think the OP needs to focus on who they are marketing to before all else. I have no clue what they manufacture or market?

Ron

 

[lindermat]

Ron,
I agree that the consumer homes and industrial are two different animals when it come to power feeds, but the problem is that we sell to both. Not necessarily consumer, but small university R&D labs, where all they have is a 120 wall outlet or 240 split phase. We also sell to larger manufacturers with the more industrial feeds (3 phase and 208) The example of a clothes dryer being a mixed load is similar to my situation. I think some of the motivation for changing the dryers to a 4-wire feed is so they would not need a transformer to get 120V to save on cost and weight (same as us) If it works for the dryer, we should be able to do it as well. My question is really on the industrial 208 side. Can we do the same thing? Since there are two hots and a neutral and from either hot to neutral is 120V I think it should work. As long as the hot-to-hot loads can work at 208 or 240 (they can since they are heaters, and at 208, they just produce slightly less heat)

Matt

 

[RMMM]

You dont need a transformer with the clothes dryer.

You run L1 to the 120v stuff and you run L1 and L2 to the motor and/or heating coils.

No transformer needed.

208v is a different beast. There is no way that I can think of, that you will be able to share a scheme without having a transformer.

you could use a multi-tapped transformer to accept 120, 208 or 240. Thats gonna reduce your parts count, but gonna be pricey for a 20A+ version.

 

[RMMM]

Actually, you should look into Q-mark hanging heaters.

It has been a few years since I have installed them, but they only had 1 version for all supplies (at the same Hz)

When I installed it, I had to move 2 wires to go from split phase 240 to 3 phase 208.

It was just 2 wires... no transformer.. and they were 19kW heaters.

Heating elements/thermostat controls and fan motor.. So "mixed" load.

Check them out. I think Granger in the US sells them as Q-Mark, or Dayton. They are the "creme" colored cases with brown louvers. Im sure you have seen them in hundreds of warehouses and industrial buildings.

 

[4pyros]

I think some of the motivation for changing the dryers to a 4-wire feed is so they would not need a transformer to get 120V to save on cost and weight (same as us)

The 4th wire is the return for 110 volt stuff but you can only do that up to a certain percentage of the total load. In a clothes dryer the 110 V load is vary small. If you put to much load on just one leg of the 220VAC then you will have to over rate the whole input. You can use SMPS with universal inputs and universal motors but thay will cust a lot more than fixed voltage stuff. Andy

 

[BrownOut]

If you put to much load on just one leg of the 220VAC then you will have to over rate the hole input. Andy

Did you mean, the "whole" input?

 

[4pyros]

Fixed, Brownout

 

[KeepItSimpleStupid]

Remember to look at buck/boost transformers for your systems too to get the 208/240 in line. Buck/boost transformers are cheaper.

Get away from 120 60 Hz altogether. Design with 50/60 Hz stuff or with motors consider DC.

 

[Reloadron]

Originally older clothes dryers using split phase 220 VAC used a three prong 220 volt plug. Newer units were required to go to a 4 prong 220 volt plug. The change was not driven by a design change of the appliance but the NEC code.

Newer homes are now being equipped with 4-prong dryer cord plugs. This is the new standard and is required under Article 550.16(A)(2) of the National Electrical Code (NEC) 2008. Connections of electrical clothes dryers shall be made with a 4-conductor cord and 3-pole, 4-wire, grounding-type plugs or by Type AC cable.

The above quote was taken from here:

Electric Dryer Cords And Plugs - How To Convert Electric Clothes Dryer 3-Prong To 4-Prong Cords

The article describes how to modify old to new.

Article 550.16(A)(2) of the National Electrical Code (NEC) 2008 reads as follows:

(2) Connections of Ranges and Clothes Dryers. Connections of ranges and clothes dryers with 120/240-volt, 3-wire ratings shall be made with 4-conductor cord and 3-pole, 4-wire, grounding-type plugs or by Type AC cable, Type MC cable, or conductors enclosed in flexible metal conduit.

Now as was pointed out, in a 208 volt 3 phase wye configuration phase to any other phase is 208 volts, any phase to neutral is 120 volts. The reason that most residential clothes dryers (and other 220 volt appliances) use 120 volt motors and electronics is for that reason. The higher voltage of 208 or 240 is used only to drive the heating elements in most cases.

The load is marked on the device and the wire gauge used needs to support the load. Additionally the circuit breaker(s) need to be rated for the load.

Thus, companies manufacturing for export to the US should design their products in accordance with NEC standards.

Actually appliances like dryers don't even include a cord anymore. They have a small rear panel with a terminal block. Installing (and buying) the cord has been outsourced. To the customer!

Ron