On a standard ZLP630 suspended platform hoist, the brake is a DC electromagnetic brake, while the motor is AC-powered. Therefore, a brake rectifier is installed to convert AC voltage into DC voltage for the brake coil.In most Chinese-made ZLP630 hoists (LTD6.3), the rectifier receives 380V AC from the motor circuit and outputs approximately 99V DC to energize the brake coil. Similar industrial brake rectifiers commonly produce about 0.45 × the AC voltage when using half-wave rectification.
| System Power Supply | Rectifier AC Input | Rectifier DC Output | Rectifier Type | Common Application |
| 380V–415V 3-Phase | 220V AC | 99V / 103V DC | Half-Wave (e.g., RY-99) | Standard International |
| 380V–415V 3-Phase | 380V–415V AC | 170V / 190V DC | Half-Wave (e.g., RY-170) | Specialized Heavy Duty |
| 220V 3-Phase | 220V AC | 198V / 207V DC | Full-Wave | Americas / Japan |
Standard ZLP630 Brake Rectifier Voltage Specifications： What Your Multimeter Should Show)
The Standard 380V Box (Most Common Globally)
This is the default setup for most international construction sites. The control box draws a single-phase and a neutral wire (220V AC) to power the rectifier.
- Rectifier Input (AC): 220V
- Rectifier Output (DC): 99V to 103V (powers the brake coil)
The Line-to-Line 380V Box (No Neutral Line)
Some heavy-duty or specialized international boxes run the rectifier across two hot phases directly, bypassing the need for a neutral wire.
- Rectifier Input (AC): 380V to 415V
- Rectifier Output (DC): 170V to 190V
The 220V 3-Phase Box (Americas / Alternative Grids)
Common in regions like North/South America or Japan, running on a 220V three-phase grid.
- Rectifier Input (AC): 220V
- Rectifier Output (DC): 198V to 207V (Note: This uses a full-wave rectifier, which is why the voltage doesn’t drop).
The LTD63 Hoist (ZLP630) vs LTD80 Hoist (ZLP800) Crucial Safety Warning
The ZLP630 rectifier may not all be 99V direct current. For example, LTD8.0 (ZLP800) has a direct current range of 99V to 110V.
- LTD63 (ZLP630): Built for a 1.5 kW motor, featuring a smaller brake disc assembly and lower spring tension suited for a 630 kg load capacity.
- LTD80 (ZLP800): Built for a heavier 1.8 kW or 2.2 kW motor. It requires a significantly larger electromagnetic coil, a wider friction disc, and much higher mechanical spring torque to safely hold the extra weight.
While the voltage and the rectifiers are completely interchangeable, the mechanical brake components are NOT.Never install an LTD63 brake coil or friction pad onto an LTD80 motor. Even though the 99V DC rectifier will power it up and release the brake perfectly fine during an empty test, the mechanical braking torque will be insufficient under a true 800 kg working load, risking catastrophic platform slippage.
| Component Check | LTD63 Hoist (ZLP630) | LTD80 Hoist (ZLP800) | On-Site Reality |
| Motor Power | 1.5 kW | 1.8 kW or 2.2 kW | Check the motor nameplate to verify the hoist model. |
| Black Rectifier Block | Universal (Usually RY-99) | Universal (Usually RY-99) | Yes, the rectifier blocks are interchangeable. |
| Mechanical Brake Assembly | Smaller size, lighter spring | Larger size, heavy-duty spring | NEVER swap these parts. |
If your job site or rental fleet utilizes both ZLP630 (LTD63 hoist) and ZLP800 (LTD80 hoist) platforms, pay close attention:
“The LTD80 hoist is built to pull a much heavier load (800 kg). Because the electrical voltage is exactly the same (99V DC), an LTD63 brake assembly will fit and release perfectly during an empty test run on an LTD80 motor. However, once the platform is loaded with workers and tools, the smaller brake pad cannot hold the massive mechanical torque. The platform will slip out of control down the wire rope, creating a catastrophic safety hazard.”
3-Step Brake Troubleshooting Checklist
When the motor is “humming loudly but the platform won’t move up (brakes locked)” or “the platform slips down slightly after releasing the button (delayed braking)”, follow these steps:
Step 1: Check the Rectifier Output Voltage
- Press and hold the UP button on the pendant control. Measure the DC output terminals on the rectifier.
- If it reads 0V or just a few volts, the rectifier is fried or shorted. Replace the rectifier block immediately.
Step 2: Check the Coil Resistance
- Turn off the power, disconnect the two wires going from the rectifier to the motor brake tail, and measure the resistance of the brake coil wires using the $\Omega$ (Ohms) setting on your multimeter.
- If the multimeter reads 0 (short circuit) or $\infty$ / OL (open circuit), the electromagnetic coil inside the motor brake is burnt out. You must replace the entire brake coil assembly.
Step 3: Check for “Fast Braking” Wiring
- If the platform takes a split second to stop after you let go of the button, look at the wiring diagram inside the box.
- Bad Wiring: The rectifier AC input is just wired to the back of the contactor. When power cuts, the residual magnetism in the coil takes time to dissipate, causing a dangerous braking delay.
- Correct Wiring: The rectifier must use a DC fast-braking loop. This means the DC output line runs through an auxiliary normally-open (NO) contact on the main contactor, cutting the DC power instantly the moment the button is released.
How to Measure the Rectifier Output?
Using a multimeter:
- Set the meter to DC voltage.
- Place the probes on the two wires leading to the brake coil.
- Start the hoist.
- A healthy ZLP630 rectifier should read approximately: 99–110 VDC
If the reading is:
- 0 VDC → rectifier may be damaged.
- Much lower than 90 VDC → diode failure or insufficient input voltage.
- Higher than 120 VDC → wrong rectifier specification.
