The short answer
The motors and electrical controls of a tube mill line and its entry-section equipment are selected for the buyer's grid, so state your voltage and frequency at the inquiry stage. China's domestic standard is 380 V / 50 Hz. Common export supplies include 415 V / 50 Hz, 440 V / 60 Hz, 460 V / 60 Hz and 480 V / 60 Hz. Taking our entry-section equipment (uncoilers, leveling machines, shear & butt welders and spiral accumulators) as the example: the power circuit is selected for your voltage and frequency; the control circuit is normally 220 V AC, and on 415–440 V supplies it is normally stepped down to 220 V by a control transformer; push buttons, relays, solenoid valves, sensors and PLC inputs work at 24 V DC.
Other supplies, such as 400 V / 50 Hz or 380 V / 60 Hz, can be discussed — send the exact figures. The electrical solution for the whole line, including the main mill drive, is confirmed by our engineers for each project and written into the technical proposal.
Common supplies at a glance
Industrial supplies can differ between regions and even between sites in the same country. Use the figures from your own plant supply, not a country table.
- 380 V / 50 Hz: standard supply in China.
- 415 V / 50 Hz: a common 50 Hz export supply; on entry-section equipment, a control transformer normally provides the 220 V control circuit.
- 440 V / 60 Hz: a common 60 Hz export supply; on entry-section equipment, a control transformer normally provides the 220 V control circuit.
- 460 V / 60 Hz and 480 V / 60 Hz: common 60 Hz export supplies; how the control supply is derived is decided in the project's electrical design.
- Other supplies (for example 400 V / 50 Hz or 380 V / 60 Hz): send the exact figures with your inquiry and our engineers confirm the solution.
Three voltage levels inside the electrical system
Take the electrical system of our entry-section equipment — uncoilers, leveling machines, shear & butt welders and spiral accumulators — as an example. It works at three levels:
- Power: the three-phase grid supply feeds the motors through circuit breakers or motor protection switches, then either contactors (direct start, forward and reverse) or variable-frequency drives (speed control).
- Control: 220 V AC, taken from one phase and neutral or from a control transformer. It feeds the switching power supply, cabinet fans and other AC devices.
- Signals and operator devices: 24 V DC from a switching power supply, for push buttons, relays, solenoid valves, indicator lamps, proximity switches and PLC inputs. In current designs, all operator and signal devices work at 24 V DC.
What has to be checked when the supply changes
The power circuit — motors, drives, circuit breakers, contactors and other power components — is selected for your voltage and frequency. The control circuit is normally 220 V AC at the grid frequency: on a 60 Hz supply it also runs at 60 Hz, so AC control parts such as AC-coil contactors and cabinet fans are checked for frequency as well. How the 220 V control supply is derived is decided in the project's electrical design. Operator and signal devices work at 24 V DC.
If your electrical specification requires a different control voltage, this is confirmed for each project.
The control transformer and the neutral conductor
On a 380 V system with a neutral conductor, the 220 V control supply can be taken between one phase and neutral. On 415–440 V supplies, our entry-section equipment normally has a control transformer that steps the control circuit down to 220 V. For other voltages, the choice depends on the supply voltage, whether a neutral is available and your electrical specification, and is made in the project's electrical design.
This is why your inquiry should state not only voltage and frequency, but also whether the supply includes a neutral conductor.
Why 50 Hz and 60 Hz are not interchangeable
Matching the voltage is not enough. Motors, drives and other electrical equipment also have to be selected and set for the frequency at the site where the line will run.
Do not assume that equipment built for a 50 Hz grid can simply be connected to a 60 Hz grid, or the other way round. State the frequency in your inquiry so the configuration is right from the start.
A common mix-up: “440 V” on the DC main motor
The forming and sizing mill uses a DC main motor with a DC speed controller as standard; an AC variable-frequency drive is available on request. The 440 V printed on the nameplate of the DC main motor is its rated armature voltage, not the grid voltage. A line supplied at 380 V / 50 Hz can still carry a main motor marked 440 V. A plant with a 440 V / 60 Hz grid is a separate matter, and it must be stated in the inquiry.
Brands, PLCs and electrical specifications
Brands of motors, drives and electrical components can follow your specification. If your plant has its own electrical specification, send the document with your inquiry. We can configure to it; which requirements can be met is confirmed in the quotation and technical proposal.
Control methods differ by machine. The fully automatic shear & butt welder is PLC-controlled through its whole cycle. Spiral accumulator storage and feeding use variable-frequency speed control. If you have requirements for the PLC, component brands or operator-panel language, state them in your inquiry so we can confirm in the proposal what can be supplied.
What to state in your inquiry
- Supply voltage (line-to-line) and frequency.
- Number of phases, and whether a neutral conductor is available.
- Required brands for motors, drives, PLC and electrical components, if any.
- Your plant's electrical specification, if you have one.
- Language requirements for the operator panel and labels.
- DC drive (standard) or AC variable-frequency drive for the main mill.
Frequently asked questions
- Can the line be configured for 440 V / 60 Hz? Motors and electrical controls can be configured for 440 V / 60 Hz. On entry-section equipment, the control cabinets normally use a control transformer to step the control circuit down to 220 V. The electrical solution for the whole line, including the main mill drive, is confirmed by our engineers for each project.
- Our grid is 60 Hz. Can we use equipment built for 50 Hz? Do not assume so. Motors, drives and other electrical equipment must be checked and selected for the actual frequency, so state it in your inquiry.
- Is the 440 V on the motor nameplate our grid voltage? No. On the DC main motor, 440 V is the rated armature voltage, which is a different thing from the grid voltage.
- Can you use our preferred electrical brands? Yes. List the required brands in your inquiry.
- Does the supply voltage affect the quotation? Motors and controls are configured for your grid, and a different configuration means a different quotation. Prices are customized by configuration and quoted individually.
About this article
Prepared by the InGen Engineering Team. This is a general technical guide, not an electrical design for any project. Supply voltage, control method and components are confirmed in the project's technical proposal and technical agreement.