Application of Powtran Technology’s PI500 Series Inverters in Electric Hoists
2019-08-20
Preface
An electric hoist is a specialized lifting device installed on overhead cranes and gantry cranes. It features a compact size, light weight, simple operation, and ease of use, making it suitable for applications in industrial and mining enterprises, warehouses, docks, and other similar locations. Each electric hoist is equipped with two motors—one for controlling the main hook and the other for controlling the trolley movement. Typically, two variable-frequency drives are used to independently control the start, stop, and speed adjustment of these motors.
1. The main hook hoisting motor is a squirrel-cage asynchronous motor with a conical rotor and high starting torque, eliminating the need for an external brake. The motor’s duty cycle is 25%.
2. Ordinary three-phase asynchronous motors are typically used for driving.
Principle
The stator inner cavity and the rotor exterior of the conical rotor motor both have a conical shape. A conical braking ring is embedded in the fan’s braking wheel, while a stationary braking ring is mounted on the rear end cover. When the stator is energized, it generates a rotating magnetic field, which simultaneously produces an axial magnetic attraction force. This axial force causes the rotor to move axially and compress the spring, thereby separating the conical ring on the fan’s braking wheel from the stationary braking ring. As a result, the rotor begins to rotate. Once the stator is de-energized, the axial magnetic attraction force vanishes, and under the action of the spring, the rotor—along with the fan’s braking wheel—returns to its original position, bringing the moving and stationary braking rings into contact. This contact creates a frictional torque that immediately brings the motor to a stop.
On-site conditions and technical requirements
1. The on-site equipment is equipped with an electric hoist, featuring a main hook motor rated at 4.5 kW and a traveling motor rated at 0.64 kW.
2. On-site, one inverter is required to control two motors separately.
Gourd walking cart motor
Gourd main hook motor
1. One PI500 7R5G3 frequency converter (with dedicated software) is used on-site to control two motors.
2. KM1/KM2 are used to switch between two motors.
3. K4 (DI4) is used to switch between two sets of motor parameters: when closed, it switches to the traveling motor parameters; when open, it switches to the main hook parameters.
4. On-site VFD is equipped with a braking resistor of 75 ohms/780W.
Picture inside the cabinet
Product features:
The Pintech PI500 series inverters feature the following notable characteristics:
·Small starting current, high torque, and no impact on the power grid;
·The speed control system features fast dynamic response, low losses, and high efficiency.
·Easy installation and commissioning of equipment;
·Reduce noise and lower motor temperature rise to protect the motor;
· Built-in braking unit, compatible with external braking resistors, making it ideal for applications involving frequent braking.
·There are control parameters specifically designed for conical motors, eliminating the need to add additional equipment.
·The output terminal of the inverter can be connected to a contactor for switching purposes.
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