Fault diagnosis and protection of motors in coal shearer

Symmetrical components method is employed in analysis of the characteristic motor faults.Motor protection method is put forward based on detecting positive sequence,negative sequence and zero sequence current.And problems of lack of motor overload capacity in existing mining motor protection system,impact of dynamic current on stage and definite-time delay operation and inaccuracy of criterion phase failure protection are analyzed.The unbalanced faults protection and inverse-time overload protection,which can make protection time change with the current movement,are proposed.The above problems can be solved,and the reliability and intelligent of coal shearer are improved.

A novel predictive braking energy recovery strategy for electric vehicles considering motor thermal protection

Braking energy recovery(BER)aims to recover the vehicle's kinetic energy by coordinating the motor and mechanical braking torque to extend the driving range of the electric vehicle(EV).To achieve this goal,the motor/generator mode requires frequent switching and prolonged operation during driving.In this case,the motor temperature will unavoidably rise,potentially triggering motor thermal protection(MTP).Activating MTP increases the risk of motor component failure,and the EV typically disables the BER function.Thus,maximizing BER while reducing the risk of motor overheating is a challenging problem.To address this issue,this article proposes a predictive BER strategy with MTP using the non-smooth Pontryagin Minimum Principle(NSPMP)for EVs.Firstly,a Markov long short-term memory(MLSTM)model is designed to obtain future velocity information.Secondly,the BER problem with MTP in the studied EV is embedded in a model predictive control(MPC)framework.Then,under the MPC framework,the NSPMP strategy is proposed to resolve the problem of MTP.Finally,the performance of the proposed strategy is verified through simulation and a hardware-in-loop test.The results show that in two real-world driving cycles,compared to the rule-based strategy,the proposed strategy reduced power consumption by 1.24%and0.96%,respectively,and effectively limited motor temperature.Additionally,under global cycle conditions,this strategy demonstrated better MTP control performance compared to other benchmark strategies.

Protective effect of sodium valproate on motor neurons in the spinal cord following sciatic nerve injury in rats

BACKGROUND: Sodium valproate (VPA) is used to be an effective anti-epileptic drug. VPA possesses the characteristics of penetrating rapidly through the blood-brain barrier (BBB) and increasing levels of Bcl-2 and growth cone-associated protein (GAP) 43 in spinal cord. OBJECTIVE: To observe the effect of VPA on Bcl-2 expression and motor neuronal apoptosis in spinal cord of rats following sciatic nerve transection. DESIGN: Randomized controlled experiment. SETTING: Department of Hand Surgery and Microsurgery, Wuhan Puai Hospital. MATERIALS: A total of 30 male healthy SD rats of clean grade and with the body mass of 180-220 g were provided by Experimental Animal Center of Medical College of Wuhan University. Sodium Valproate Tablets were purchases from Hengrui Pharmaceutical Factory, Jiangsu. METHODS: The experiment was performed in the Central Laboratory of Wuhan Puai Hospital and Medical College of Wuhan University from February to May 2006. Totally 30 rats were randomly divided into two groups: treatment group (n =15) and model group (n =15). Longitudinal incision along backside of right hind limbs of rats was made to expose sciatic nerves, which were sharply transected 1 cm distal to the inferior margin of piriform muscle after nerve liberation under operation microscope to establish sciatic nerve injury rat models. Sodium Valproate Tablets were pulverized and diluted into 50 g/L suspension with saline. On the day of operation, the rats in the treatment group received 6 mL/kg VPA suspension by gastric perfusion, once a day, whereas model group received 10 mL/kg saline by gastric perfusion, once a day. L4-6 spinal cords were obtained at days 1, 4, 7, 14 and 28 after operation, respectively. Terminal deoxyribonucleotidyl transferase (TdT)-mediated dUTP-biotin nick end labeling (TUNEL) technique and immunohistochemical method (SP method) were used to detect absorbance (A) of neurons with positive Bcl-2 expression. Apoptotic rate of cells (number of apoptotic cells/total number of cells×100%) was calculated. MAIN OUTCOME MEASURES: A value of neurons with positive Bcl-2 expression and apoptotic rate in spinal cord of rats in the two groups. RESULTS: A total of 30 SD rats were involved in the result analysis. ①expression of positive Bcl-2 neurons: A value of positive Bcl-2 neurons were 0.71±0.02, 0.86±0.04, 1.02±0.06 at days 4, 7 and 14, respectively after operation in the treatment group, which were obviously higher than those in the model group (0.62±0.03, 0.71±0.05, 0.89±0.04, t = 3.10-4.50, P < 0.05). ②apoptotic result of motor neurons: Apoptotic rate of motor neurons in spinal cord was (6.91±0.89)% and (15.12±2.34)% at days 7 and 14 in the treatment group, which was significantly lower than those in the model group [(9.45±1.61)%, (19.35±0.92)%, t = 2.39, 3.03. P < 0.05]. CONCLUSION: VPA can increase expression of Bcl-2 in spinal cord and reduce neuronal apoptosis in rats following sciatic nerve injury, and has protective effect on motor neuron in spinal cord of rats.