All-digital AC variable-frequency speed control system (low voltage)

Variable-frequency speed control is an emerging automation technology that has developed in recent years. It achieves stepless speed regulation over a wide range for AC motors by varying the frequency of the controlled object. Our company has applied this technology to mining hoisting equipment.

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Mining electrical equipment

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Mine Hoist Fully Digital AC Variable-Frequency Speed Control System (High Voltage)

Product Overview

The fully digital AC variable-frequency speed control system (low-voltage) for mine hoists consists of a power supply cabinet, an inverter cabinet, a braking cabinet, a networked intelligent operator console, a human-machine interface, an encoder, and a PLC controller.

Product Model Designation Method

Use

The all-digital AC variable-frequency drive system (low voltage) is suitable for motor voltage ratings of 380V and 660V. It is primarily intended for non-explosion-proof applications both aboveground and underground, and is applicable to single-rope winding mine hoists (winches) and multi-rope friction hoists driven by AC variable-frequency motors. This system can be used with newly installed hoists (winches) as well as for retrofitting existing hoists (winches) with upgraded electrical control systems. It is also suitable for single-level and multi-level hoisting in main shafts and auxiliary shafts, as well as for single-layer and double-layer cage operations.

Features

1. The speed regulation is continuous and convenient, with a wide adjustment range, making it stepless and highly stable.

2. It achieves low-frequency, low-voltage soft start and soft stop, ensuring smoother operation with minimal mechanical impact and significantly extending the service life of the equipment. It also prevents derailment and track-off incidents.

3. The inrush current during startup and expansion is small, significantly reducing the impact on the power grid.

4. Compared to resistance-based speed control, this approach enhances system reliability and significantly improves the working environment for operators.

5. Successfully addressed regenerative power generation during deceleration of potential-energy loads, resulting in even more significant energy-saving effects.

6. High control accuracy and high operational reliability, virtually no maintenance workload, and reduced workload intensity for maintenance personnel.

Master control system

1. The control console adopts a workstation-style structure, integrating the functions of both the PUC control cabinet and the operator’s workstation. Apart from the necessary sensors for collecting signals such as position, speed, pressure, and current, as well as terminal actuators, all control circuits and operations are centrally located on the operator’s workstation. The operator can control the hoist’s operation by manipulating the control handles, switches, and buttons on the control console, and can promptly monitor the hoist’s operational status and parameters through indicator lights and the human-machine interface.

2. Two sets of programmable controllers are employed to achieve optimized control of the hoist’s operational characteristics, speed regulation, and various step-by-step protection functions. The system features multiple control functions, including trajectory-based speed setting, open-loop control, PID-based closed-loop speed control, various safety protections, automated start-up, and display of different operating states. A data exchange module is installed on the PLC, enabling readout of all CPI data from the entire PLC system.

3. Equipped with a safety circuit activation SMS notification function, available 24 hours a day. When the electrical control system’s safety circuit is activated, fault information will be sent to three pre-set SMS recipient numbers. A surge protector manufactured by a well-known domestic brand is used to enhance the system’s ability to withstand natural disasters.

4. The electronic control system is equipped with multi-functional redundant interfaces, including remote diagnostics, making it easy for users to connect and network-control additional automated devices.

5. Equipped with switches for automatic, semi-automatic, manual, and maintenance modes; features forward/reverse direction changeover switches; includes fault reset and power control buttons; has brake pump start/stop and changeover switches; features multi-function buttons for sliding pump start/stop and changeover; includes an automatic start confirmation button with direction memory function. It is equipped with a liquid-crystal industrial touch-screen display that shows the hoist’s operating status and records fault memories.

6. Configure the digital input module, analog input module, sensor interface module, and other such modules. Allocate 15% of the total budget for each application area.

Technical Parameters

Electrical Control Technical Parameters	Control	Control method		Space Voltage Vector Control Method
		Frequency setting resolution		Digital: 0.01 Hz (below 100 Hz) 0.1 Hz (below 100 Hz) Simulation: 0.5 Hz Output frequency range: 0-300 Hz
		Frequency accuracy		Digital: 0.01% of the maximum output frequency; Analog: 0.1% of the maximum output frequency
		V/F ratio		Linear: Square root, any V/F
		Overload capacity		Rated current: 150% for 1 minute; Rated current: 200% for 0.5 second (characteristic is directly proportional to time).
		Torque compensation		Manual torque compensation (0-20%) Automatic torque compensation
	Run	Input signal	Operating method	Keyboard/Terminal/RS485 Communication
			Frequency resolution	Simulation: 0-10V/4-20mA/Additional interface on the daughter board (0-10V, 4-20mA)
			Start signal	Digital: Keyboard/RS485 Communication
				Main story / Reverse
			Acceleration and Deceleration Time	0–6000 seconds: Acceleration and deceleration time is switchable.
				Deceleration mode: Linear S-shaped
			Emergency stop	Interrupt the inverter's output
			Inch movement	Slow-speed operation
			Fault reset	When the protection function is enabled, the fault state can be automatically reset.
		Output signal	Operating status	Frequency detection level, overload alarm, overvoltage, undervoltage, inverter overheating, running, stopping, constant speed
			Fault output	Contact output – AC 250V 1A, DC 30V 1A
			Analog output	Select from output frequency, output current, output voltage, and DC voltage (output voltage: 0–10V).
	Protection function	Run function		DC braking, frequency limitation, frequency hopping, slip compensation, reverse rotation protection
		Inverter protection		Overvoltage, undervoltage, overcurrent, blown fuse, ground fault, inverter failure, motor overheating, phase loss, overload protection, external fault 1.2, communication error, speed command loss, hardware failure, incorrect option, etc.
		Inverter alarm		Protection blocked, overload alarm, temperature sensor failure
		Power outage in an instant		Less than 15 milliseconds: Continuous operation
				Greater than 15 milliseconds: Automatic restart allowed
	Display	keyboard	Operating Information	Output frequency, output current, output voltage, set frequency, operating speed, DC voltage
			Error message	When operating in fault protection mode, 3 fault duration records are saved.
		Ambient temperature		-10℃ to 40℃
		Storage temperature		-20℃ to 65℃
		Environmental humidity		Maximum 90% RH (no condensation)
		Height/Vibration		Below 1000 m, below 5.9 m/s (=0.6 g)
		Application location		Non-corrosive gases, flammable gases, oil mist or dust, and others
	Cooling method			Forced air cooling