How to use inverter to control slip ring motor

How to use inverter to control slip ring motor

The speed control of the slip ring motor can be realized by using a frequency converter. The frequency converter is a device that can adjust the frequency and voltage of the input power supply and supply the adjusted output power to the motor. By changing the output frequency and voltage of the frequency converter, the speed and torque of the motor can be adjusted and controlled.

Here are some steps to control a slip ring motor using a frequency converter:

Confirm the rated voltage and rated current of the slip-ring motor, and the rated output power and rated output current of the inverter.

Connect the input of the inverter to the grid and the output of the inverter to the power terminals of the slip ring motor.

Connect the control signal of the inverter to the control terminal of the slip ring motor, so that the speed, direction, start and stop of the slip ring motor can be controlled.

Set the motor's rated current, voltage, frequency, speed and other parameters on the inverter's control panel. In this process, it is necessary to make corresponding adjustments based on the actual situation of the slip ring motor.

In actual use, the motor can be monitored and adjusted in real time through the control panel of the inverter to ensure stable operation of the motor.

It should be noted that using a frequency converter to control a slip ring motor requires professional technical knowledge and experience to avoid damage to the motor due to improper operation. At the same time, the appropriate frequency converter and slip ring motor combination should be selected according to actual needs to achieve the best control effect.

The difference between slip ring motor and ordinary motor

There are some differences between slip ring motors and ordinary motors (i.e. fixed rotor motors) in structure and working principle. The following is a specific comparison in several aspects:

Rotor structure: The rotor of an ordinary motor is a fixed structure and will not rotate with the change of current. The rotor of a slip ring motor is a rotating structure with a set of rotatable brushes and coils on the rotor. By constantly changing the contact points of the brushes, the current can continue to flow in the rotor coil, thereby generating an electromotive force on the rotor and driving the rotor to rotate continuously.

Starting method: Ordinary motors usually use direct starting method, that is, the motor is directly connected to the power supply and the start and stop of the motor are controlled by the switch. However, slip ring motors usually need to use additional starting devices or starting methods when starting, such as star-delta starting, transformer starting, soft starter or inverter, etc.

Power range: The power range of ordinary motors is usually wide, ranging from a few watts to several thousand kilowatts. Slip ring motors are usually used in the medium power range, ranging from tens of kilowatts to several thousand kilowatts.

Control method: Ordinary motors usually use direct control, that is, the start and stop and speed of the motor are controlled by switches. However, the control of slip ring motors usually requires more complex control systems, such as PID control, vector control, magnetic field oriented control, etc.

Application scope: Ordinary motors are widely used in various fields, such as home appliances, machinery manufacturing, electric power industry, etc. Slip ring motors are usually used in some special applications, such as lifting equipment, machine tools, metallurgical equipment, etc.

Slip ring motor rotor six wire connection

The six-wire connection of the slip-ring motor rotor is usually called the "six-wire method", which means that the three sets of windings on the motor rotor are connected to three independent wires respectively, and a pair of slip rings and brushes are connected at both ends of each set of windings to form six wires. This wiring method is suitable for the rotor of a three-phase slip-ring asynchronous motor.

Specifically, the wiring method of the six-wire method is as follows:

Label the three sets of windings on the motor rotor as A, B, and C, and connect the two ends of each set of windings to three independent wires.

A pair of slip rings and brushes are connected at both ends of each winding, numbered 1 and 2. The slip rings are usually made of brass or copper, and the brushes are made of graphite or carbon.

Connect the brushes at both ends of the A-phase slip ring to wires 1 and 2 respectively; connect the brushes at both ends of the B-phase slip ring to wires 3 and 4 respectively; connect the brushes at both ends of the C-phase slip ring to wires 5 and 6 respectively.

The advantage of the six-wire method is that it can provide a larger starting torque and a lower starting current, which is suitable for some occasions with heavy loads and difficult starting. However, the wiring of the six-wire method is relatively complicated, requiring special slip rings and brushes, and the cost is relatively high. In addition, the six-wire method also has some disadvantages, such as the starting current is still large and the speed fluctuation is large. Therefore, some applications usually use other slip ring motor wiring methods, such as the three-wire method, the double winding method, etc.