Electric Hoist Power Wiring and Control System Guide
Electric Hoist Power Supply & Main Electrical Wiring The complete power path runs from the 380V/50Hz main supply through the main circuit breaker QF, fuse FU, control transformer TC (380V/220V), contactors KM1–KM4, thermal overload relay FR, and terminates at the motor junction box. The control circuit comprises the emergency stop button SB, limit switches SQ, remote receiver RX, intermediate relays KA, PLC controller, and related components. Main circuit conductors must be ≥2.5mm², control circuit conductors ≥1.5mm², and a PE grounding busbar connects all metal enclosures. Wiring complies with IEC 60204-1 and IEC 60947-1 standards.
The electrical control system of an electric hoist is a complete electrical chain from power input to motor operation, consisting of two main parts: the main circuit (power circuit) and the control circuit (signal circuit). The main circuit transmits electrical energy to drive the motor, while the control circuit receives operating commands and governs the on/off switching of the main circuit. A properly wired control system directly affects the operational reliability and electrical safety of the hoist. The following sections systematically outline the wiring methods for the hoist power supply and overall electrical system, covering main power wiring, control cabinet component layout, and wiring specifications for both main and control circuits, in accordance with IEC 60204-1 (Electrical Safety of Machinery), IEC 60947-1 (Low-Voltage Switchgear and Controlgear), and ISO 4301 (Crane Design Standard).
1. Main Power Wiring & Control Cabinet Layout
The main power supply for an electric hoist is typically drawn from the workshop power distribution cabinet using a three-phase five-wire system (TN-S): three phase conductors L1, L2, L3, plus a neutral conductor N and a protective earth conductor PE. The power cord size is determined by the hoist's total power: a 5t electric hoist (7.5kW hoisting motor + 1.5kW × 2 travel motors) has a total power of approximately 10.5kW, requiring a main circuit conductor cross-section of 4mm² copper-core wire and a 32A main circuit breaker QF. The standard component arrangement inside the electrical control cabinet is: main circuit breaker QF → fuse FU → contactors KM1–KM4 → thermal overload relay FR → terminal block XT → motor junction box.
Conductor Color Code Inside the Control Cabinet (IEC 60445): L1 phase — yellow, L2 phase — green, L3 phase — red, neutral N — blue, protective earth PE — yellow/green dual color, control circuit AC 220V — red or brown, DC control circuit 24V — blue with white marking. Conductor cross-sections: main circuit power lines ≥2.5mm² (4mm² recommended), control circuit ≥1.5mm² (2.5mm² recommended), signal/sensor circuits 0.5–1.0mm². All conductor ends must be terminated with cold-pressed wire ferrules (tubular ferrules recommended); never tighten stranded copper wires directly under screw terminals. Wire bundles inside the control cabinet should be secured with cable ties, and conductors from different circuits (main/control/signal) should be routed in separate layers to minimize electromagnetic interference.
2. Main Circuit Wiring
The main circuit is the power transmission path from the main supply to the motor. Standard wiring sequence: workshop distribution cabinet circuit breaker QF (3-pole, trip current selected based on motor power) → fuse FU (aM-type time-delay fuse link, rated current 1.5–2 times the motor's rated current) → contactor KM1 (hoisting) / KM2 (lowering) main contacts → thermal overload relay FR (heating element connected in series in the main circuit) → terminal block XT → motor junction box U1/V1/W1. On the load side, the output from KM1 and KM2 to the motor must have two phases swapped (see motor wiring section) to achieve forward/reverse rotation.
Thermal Overload Relay Setting: The FR trip current is set to 1.05–1.1 times the motor's rated current. For a 5t CD1-type electric hoist as an example (7.5kW hoisting motor, rated current approximately 15.5A), the FR setting should be 16–17A. The FR's normally closed auxiliary contact is wired in series in the control circuit — when the motor experiences overload, the FR trips, opening the normally closed contact and cutting off the contactor coil supply to stop the motor. The FR should be set to manual reset mode (requiring a manual press of the reset button before restarting), preventing automatic restart while the fault condition remains unresolved.
3. Control Circuit Wiring
The control circuit is powered by the control transformer TC (380V/220V, capacity 100–300VA selected based on the number of circuits) providing 220V AC. Standard control circuit series sequence: TC secondary L → emergency stop button SB (normally closed) → power-off limit switch SQ1 (normally closed) → upper travel limit switch SQ2 (normally closed) → lower travel limit switch SQ3 (normally closed) → thermal overload relay FR (normally closed) → contactor KM coil → TC secondary N. Opening any contact in this series loop cuts off the control power supply. The coil of each directional contactor (KM1–KM4) is then connected in series with its corresponding control contact (pendant button or remote control relay output) at the front end.
Electrical Interlock Design: The normally closed auxiliary contacts of KM1 (hoisting) and KM2 (lowering) are wired in series in each other's coil circuits — when KM1 is energized, its normally closed contact opens the KM2 coil circuit, and vice versa. This ensures that even if both the hoisting and lowering buttons on the control grip are pressed simultaneously, only one contactor can be energized, preventing a phase-to-phase short circuit. Similarly, an interlock must be provided between KM3 (left travel) and KM4 (right travel). If a radio remote control is used in the control system, the relay output contacts of the remote receiver (typically rated 5–10A) can directly drive the contactor coils (coil current typically 0.1–0.5A), eliminating the need for additional intermediate relays.
4. Key Parameters for Power Wiring
| Parameter Item | 1~3tElectric Hoist | 5~10tElectric Hoist | 16~32tElectric Hoist |
|---|---|---|---|
| total power | 3~6kW | 10~15kW | 20~42kW |
| main circuit conductor | 2.5mm² | 4mm² | 6~10mm² |
| Circuit Breaker QFSetting | 16A 3P | 32A 3P | 63A 3P |
| Control Transformer Capacity | 100VA | 200VA | 300VA |
| Contactorrated current | 12A | 25A | 40~65A |
| control circuit Conductor | 1.5mm² | 1.5mm² | 2.5mm² |
| grounding wirecross-section Product | ≥2.5mm² | ≥4mm² | ≥6mm² |
| Protection Rating (IP)(Control Cabinet) | IP54 | IP54~IP55 | IP55~IP65 |
5. Power Wiring Data Card
| 380V Rated Supply Voltage Three-phase380V/50Hz TN-SSystem, L1Yellow/L2Green/L3Red/NBlue/PEYellow-Green (Green/Yellow) | ≥2.5mm² main circuitminimum Conductor main circuit conductorcross-section Product not less than2.5mm², control circuit Not less than1.5mm² | 1.05~1.1 FRSetting Coefficient Thermal Overload Relay Setting Current=Motorrated current×1.05~1.1, Recommendedmanual reset |
| 220V control circuit Voltage TCTransformer380V220VAscontrol circuit Power Supply, Capacity100~300VA | 2Layer Segregated routing of power and control cables main circuit Segregated routing from signal circuits, Spacing≥50mm Preventelectromagnetic interference | 100% factory Energization Testing Rate Kelude Heavy Industry Per unit Control Cabinetbefore delivery Perform100%Energizationfunctional test |
The above summarizes the wiring specifications for the power supply and overall electrical system of electric hoists. All Kelude electric hoist electrical control cabinets are designed and manufactured in accordance with the IEC 60204-32 standard, with segregated routing for main and control circuits. Each conductor is fitted with numbered ferrules at both ends for easy identification during future maintenance. Refer to the related article Electric Hoist Limit Switch Wiring Guide for details on safety protection device wiring.
Power Wiring Technical Notes
"An electric hoist control cabinet may look simple — a few contactors and a thermal overload relay — but the wiring quality you see on site varies enormously. The most common issue is inconsistent conductor colors: some use red wire for neutral, black for ground, leaving maintenance technicians unable to trust the color coding at all. GB/T 7947-2010 specifies conductor colors clearly: L1 yellow, L2 green, L3 red, N blue, PE yellow-green. Kelude affixes a color-coded wiring diagram inside every control cabinet door, showing the destination and terminal number of each conductor, so both installation and future troubleshooting can be done quickly."
6. FAQ: Electric Hoist Electrical System Wiring
Q: What cross-section should the electric hoist power cable be?
A: The power cable cross-section is selected based on total power. For 1–3t electric hoists (total power 3–6kW), 2.5mm² copper-core wire with a 16A circuit breaker is recommended. For 5–10t hoists (total power 10–15kW), use 4mm² copper-core wire with a 32A breaker. For 16–32t hoists (total power 20–42kW), 6–10mm² copper-core wire with a 63A breaker is recommended. These figures apply to the main circuit power conductors; the control circuit uniformly uses 1.5–2.5mm². The power cable is a five-core type (3 phases + neutral + ground), such as YZW 4×4mm²+1×2.5mm² rubber-sheathed flexible cable. If the cable run exceeds 50m, step up one cross-section size to compensate for voltage drop.
Q: What layout sequence is required for components inside the hoist control cabinet?
A: Per IEC 60204-32, components inside the control cabinet should be arranged following the power flow principle of "top to bottom, left to right." The standard sequence is: Top row — main circuit breaker QF, fuse FU, control transformer TC. Second row — main contactors KM1–KM4. Third row — thermal overload relays FR, terminal block XT. Fourth row — intermediate relays KA, wireless receiver RX/PLC controller, 24V switching power supply. The PE grounding copper busbar is mounted at the very bottom. Maintain a minimum spacing of 50mm between rows for heat dissipation and wiring access. Conductors of different voltage levels (380V main circuit / 220V control circuit / 24V signal circuit) must be routed in separate wire ducts, with at least 50mm separation.
Q: Is grounding important for an electric hoist? What happens if it's not grounded?
A: Absolutely critical. The metal enclosures of the electric hoist (motor housing, control cabinet body, pendant housing) must be reliably grounded. Without proper grounding: if the motor winding insulation fails or a conductor is damaged, the enclosure becomes live, and an operator touching it will receive an electric shock. IEC 60204-32 explicitly requires protective grounding of all metal enclosures of electrical equipment, with a grounding resistance of ≤4Ω. The grounding conductor cross-section must be no less than 50% of the main circuit conductor (if the main circuit is 4mm², the ground wire must be ≥2.5mm²). Use dedicated yellow-green insulated wire for grounding, connected to the PE copper busbar, which is then tied to the workshop grounding grid. Important: the neutral (N) and ground (PE) conductors must never be interchanged or shorted together inside the control cabinet.
Q: What items should be checked during daily inspection of the hoist electrical system?
A: Per TSG Q7016-2016, daily inspection of the electric hoist electrical system should include at least: ① Check the main circuit breaker QF and fuse FU for abnormal heating (use infrared thermometry; temperature rise must not exceed 40K). ② Check for abnormal noise or vibration when contactor KM picks up (replace contacts if wear exceeds 60% of original thickness). ③ Verify the manual test button on thermal overload relay FR operates correctly. ④ Check for loose connections at terminal blocks inside the control cabinet (tighten each with a screwdriver). ⑤ Verify grounding connections are secure (visual inspection plus pull test). ⑥ Inspect the cable outer sheath for damage or aging (pay special attention to cable entry points and bend areas). Perform an Insulation Resistance Test every six months (500V Megohmmeter; main circuit to ground ≥1MΩ, control circuit to ground ≥0.5MΩ).
Refer to the related article Electric Hoist Motor Wiring Guide for details on connecting the contactors and motor in the main circuit.
