Why do stepper motors need drivers?

by:V&T Technologies     2020-01-29
Why do stepping motors need to add drivers many industrial control friends and PLC automation practitioners know stepping motors, but some PLC beginners do not understand why stepping motors need to add a stepping driver, instead of directly inserting the power supply like a normal motor, you can use it. Today, let's learn about the stepper driver. The structure of the stepping driver: the stepping driver can be divided into two parts: one is a ring distributor and the other is power amplification. Ring Distributor: if three kinds of signals are received: pulse signal, direction signal and offline signal. Then the pulse signal is distributed to control the conduction of the corresponding transistor of the power amplifier, and then the coil of the stepping motor is charged. From here we can see that if the stepping motor is to operate, then the pulse must be input. If there is no pulse, the stepping motor will not move, therefore, we need a driver to energize the windings of the stepping motor in turn. Direction signal: to control the phase sequence of AB power-on, A-B clockwise, B- A anticlockwise off-line signal: When the stepping motor stops, AB coil has A phase to get electricity. The function of getting electricity locks the rotor so that the rotor cannot move. When the rotor needs to be moved, it is necessary to give off-line signals so that the AB phase winding is completely cut off and the rotor is in a free rotation state. Connection between stepping motor, stepping driver and PLC: stepping driver must first be externally connected with DC power supply 24 ~ 28 V, one end should be connected to the stepping motor, and the other end should be used as the input signal, that is, the control signal. The structure of the stepping motor receiving external signals is photoelectric isolation, such: the pulse signal of PLC is sent to the driver. We want the PLC to generate pulse, which can be generated only by continuously connecting and closing Y0. When Y0 is on, current flows in from CP, through current limiting resistor, diode, and then through CP- , And then return to the negative end of the power supply through the COM end, thus forming a loop. In this way, the light emitting diode will be turned on, the transistor will be turned on, and a high level 1 will be generated. If it is turned off, a low level 0 will be generated. In this way, when Y0 is continuously on and off, and through this circuit, pulses can be sent from external devices to drivers. Then the ring distributor receives the pulse and distributes the pulse signal. Control the winding of the stepping motor to power in turn. Therefore, the stepping motor must have pulses when rotating. If there is no pulse, the stepping motor will be in a stopped state. The same is true for directional signals and decoupling signals. Step drive devices related to subdivision step drive settings related to subdivision, what is Subdivision? In order to improve the precision of stepping motor control, the current stepping driver has the function of subdivision. The so-called subdivision is to reduce the step angle by the circuit in the driver. For example, the stepping driver is set to 5 subdivisions, assuming the original step angle is 1. 8 °Then set to 5 subdivision, the step angle is 0. 36 °. That is to say, if you can finish one step, you need to take 5 steps after setting it to subdivision. Matters needing attention when setting subdivision: 1. Under normal circumstances, subdivision cannot be set too large, because under the condition that the control pulse frequency is unchanged, the subdivision is larger, the slower the motor speed is, and the output torque of the motor decreases. 2. The pulse frequency of driving stepping motor should not be too high, generally not exceeding 2 KHz, otherwise the torque output by the motor will decrease rapidly. Subdivision table of stepping motor driver: the subdivision table of general stepping motor can be directly seen on the driver. TAG stepper motor to add driver
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