The five electrical values that must match
Before a crane is quoted, record five values from the actual crane supply point: line-to-line voltage, frequency in Hz, number of phases, control voltage inside the panel, and whether a neutral conductor is available. A country name is not a specification. Two factories in the same city can have different transformer outputs and different voltage drop.
Also measure the voltage while the plant is operating, not only when it is idle. A nominal 400 V supply that falls below the motor's permitted range during a large press or welding load can create overheating, contactor chatter and failed starts.
380 V, 400 V, 415 V and 440 V are not interchangeable
These voltages are close, but the motor, brake, contactor coils and control transformer must still be rated for the supplied value. A motor may tolerate a modest voltage variation, but tolerance is not the same as being designed for that voltage. A 380 V motor run continuously at 440 V can overheat; a 440 V motor run at 380 V may lose starting and full-load torque.
Some motors are dual rated, for example 400/440 V, and some dual-voltage motors can be reconnected for two different winding voltages. This is only acceptable when the motor nameplate clearly permits it. Photograph the nameplate and the connection diagram instead of relying on memory.
50 Hz and 60 Hz change more than the number on the label
Motor synchronous speed is proportional to frequency. A motor designed for 50 Hz does not simply produce the same speed at 60 Hz. It may run about 20% faster, which changes hoist speed, brake wear, gearbox input speed and the time allowed for acceleration and stopping.
If the crane has a VFD, the rated voltage, base frequency, maximum frequency and motor insulation class must be configured together. Changing the inverter from 50 Hz to 60 Hz without checking the motor, gearbox and brake can create a machine that is faster but unsafe or overloaded. The correct solution may be a dual-frequency motor, a different gear ratio, a different pulley, or a carefully configured VFD.
Other components are affected, not only the main motor
The control transformer needs the correct primary taps. Contactor and relay coils must match the control voltage. The brake coil or brake rectifier must be rated for the actual supply. Indicator lamps, limit switches, anti-collision devices and radio controls may also depend on voltage and frequency.
For a VFD-controlled crane, confirm whether an input reactor, EMC filter or shielded motor cable is needed. These details matter on weak supplies, long cables, generators and installations where other sensitive equipment shares the same electrical room.
How to verify the site supply before ordering
Take a clear photograph of the crane feeder breaker and the motor nameplate, record the transformer capacity and cable size, then measure voltage and frequency with the plant running. If the crane will operate from a generator, state that at the quotation stage. Generator sizing, voltage regulation and starting current can change the required drive configuration.
A single-line diagram and a short video of the electrical room are more useful than the sentence “we use 380 V”. They let the supplier check phase configuration, earthing arrangement and available control supply before production begins.
Information to include in the crane RFQ
- Measured line-to-line voltage and frequency, with the plant running
- Number of phases and whether a neutral is available
- Required control voltage and preferred pendant or radio control
- Motor nameplate photograph if an existing motor or crane will be reused
- Transformer capacity, cable size and distance from the panel to the crane
- Whether power comes from the grid, a generator, or both
- Ambient temperature, altitude, indoor/outdoor location and corrosive atmosphere
- Required hoist, trolley and long-travel speeds
Once these values are fixed, the supplier can provide a compatible electrical package rather than a crane that has to be rebuilt at site.
Related reading
- Single-girder overhead cranes
- Double-girder overhead cranes
- Overhead-crane installation checklist
- Cranes for anodizing lines
Can a 380 V crane run on a 415 V supply?
Not safely as a general rule. It depends on the motor nameplate, permitted voltage tolerance, control transformer taps, brake rating and the actual measured voltage. The complete electrical package must be checked, not only the motor label.
Can a 50 Hz motor be used at 60 Hz?
Only after checking motor speed, insulation, bearings, gearbox, brake and driven machinery. The motor may run about 20% faster. A VFD can control the speed, but the motor and mechanical system must still be rated for the operating point.
Is the voltage printed on the quotation enough?
No. The quotation should also state frequency, phases, control voltage, motor rating, brake voltage and VFD input range. A crane quotation without those details is incomplete for export.
What if the factory has unstable voltage?
Record the voltage under load and tell the supplier. A voltage stabilizer, correctly rated transformer, VFD settings or a different motor winding may be required. Do not hide the fluctuation by using only the nameplate voltage.